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7-1-1.
National Weather Service Aviation Products
a.
Weather service to aviation is a joint effort of the
National Weather Service (NWS), the Federal Aviation
Administration (FAA), the military weather services, and
other aviation oriented groups and individuals. The NWS
maintains an extensive surface, upper air, and radar weather
observing program; a nationwide aviation weather forecasting
service; and provides limited pilot briefing service
(interpretational). The majority of pilot weather briefings
are provided by FAA personnel at Flight Service Stations
(AFSSs/FSSs). Aviation routine weather reports (METAR) are
taken manually by NWS, FAA, contractors, or supplemental
observers. METAR reports are also provided by Automated
Weather Observing System (AWOS) and Automated Surface
Observing System (ASOS).
REFERENCE-
AIM, Para
7-1-12,
Weather Observing Programs.
b.
Aerodrome forecasts are prepared by approximately 100
Weather Forecast Offices (WFOs). These offices prepare and
distribute approximately 525 aerodrome forecasts 4
times daily for specific airports in the 50 States, Puerto
Rico, the Caribbean and Pacific Islands. These forecasts are
valid for 24 hours and amended as required. WFOs
prepare over 300 route forecasts and 39 synopses for
Transcribed Weather Broadcasts (TWEB), and briefing
purposes. The route forecasts are issued 4 times
daily, each forecast is valid for 12 hours. A centralized
aviation forecast program originating from the Aviation
Weather Center (AWC) in Kansas City was implemented in
October 1995. In the conterminous U.S., all Inflight
Advisories Significant Meteorological Information (SIGMETs),
Convective SIGMETs, and Airmen's Meteorological Information
(AIRMETs) and all Area Forecasts (FAs) (6 areas) are now
issued by AWC. FAs are prepared 3 times a day in the
conterminous U.S. and Alaska (4 times in Hawaii), and
amended as required. Inflight Advisories are issued only
when conditions warrant. Winds aloft forecasts are provided
for 176 locations in the 48 contiguous States
and 21 locations in Alaska for flight planning
purposes. (Winds aloft forecasts for Hawaii are prepared
locally.) All the aviation weather forecasts are given wide
distribution through the Weather Message Switching Center
Replacement (WMSCR) in Atlanta, Georgia, and Salt Lake City,
Utah.
REFERENCE-
AIM, Para
7-1-6,
Inflight Aviation Weather Advisories.
c.
Weather element values may be expressed by using
different measurement systems depending on several factors,
such as whether the weather products will be used by the
general public, aviation interests, international services,
or a combination of these users.
FIG 7-1-1 provides conversion
tables for the most used weather elements that will be
encountered by pilots.
7-1-2.
FAA Weather Services
a.
The FAA maintains a nationwide network of Automated
Flight Service Stations (AFSSs/FSSs) to serve the weather
needs of pilots. In addition, NWS meteorologists are
assigned to most ARTCCs as part of the Center Weather
Service Unit (CWSU). They provide Center Weather Advisories
(CWAs) and gather weather information to support the needs
of the FAA and other users of the system.
b.
The primary source of preflight weather briefings is an
individual briefing obtained from a briefer at the AFSS/FSS.
These briefings, which are tailored to your specific flight,
are available 24 hours a day through the use of the toll
free number (1-800-WX BRIEF). Numbers for these services can
be found in the Airport/Facility Directory (A/FD) under "FAA
and NWS Telephone Numbers" section. They may also be listed
in the U.S. Government section of your local telephone
directory under Department of Transportation, Federal
Aviation Administration, or Department of Commerce, National
Weather Service. NWS pilot weather briefers do not provide
aeronautical information (NOTAMs, flow control advisories,
etc.) nor do they accept flight plans.
REFERENCE-
AIM, Para
7-1-4,
Preflight Briefing, explains the types of preflight
briefings available and the information contained in
each.
FIG
7-1-1
Weather Elements Conversion Tables
c.
Other Sources of Weather Information
1.
Telephone Information Briefing Service (TIBS) (AFSS);
and in Alaska, Transcribed Weather Broadcast (TWEB)
locations, and telephone access to the TWEB (TEL-TWEB)
provide continuously updated recorded weather information
for short or local flights. Separate paragraphs in this
section give additional information regarding these
services.
REFERENCE-
AIM, Telephone Information Briefing Service (TIBS),
Paragraph 7-1-8.
AIM, Transcribed Weather Broadcast (TWEB) (Alaska Only),
Paragraph 7-1-9.
2.
Weather and aeronautical information are also available
from numerous private industry sources on an individual or
contract pay basis. Information on how to obtain this
service should be available from local pilot organizations.
3.
The Direct User Access Terminal System (DUATS) can
be accessed by pilots with a current medical certificate
toll-free in the 48 contiguous States via personal
computer. Pilots can receive alpha-numeric preflight weather
data and file domestic VFR and IFR flight plans. The
following are the contract DUATS vendors:
GTE Federal Systems
15000 Conference Center Drive
Chantilly, VA 22021-3808
Computer Modem Access Number: For filing flight plans and
obtaining weather briefings:
(800) 767-9989
For customer service: (800) 345-3828
Data Transformation Corporation
108-D Greentree Road
Turnersville, NJ 08012
Computer Modem Access Number: For filing flight plans and
obtaining weather briefings:
(800) 245-3828
For customer service: (800) 243-3828
d.
Inflight weather information is available from any FSS
within radio range. The common frequency for all AFSSs is
122.2. Discrete frequencies for individual stations are
listed in the A/FD.
1.
Information on In-Flight Weather broadcasts.
REFERENCE-
AIM, Inflight Weather Broadcasts, Paragraph
7-1-10.
2.
En Route Flight Advisory Service (EFAS) is provided to
serve the nonroutine weather needs of pilots in flight.
REFERENCE-
AIM, En Route Flight Advisory Service (EFAS), Paragraph
7-1-5,
gives details on this service.
7-1-3.
Use of Aviation Weather Products
a.
Air carriers and operators certificated under the
provisions of 14 CFR Part 119 are required to use the
aeronautical weather information systems defined in the
Operations Specifications issued to that certificate holder
by the FAA. These systems may utilize basic FAA/National
Weather Service (NWS) weather services, contractor- or
operator-proprietary weather services and/or Enhanced
Weather Information System (EWINS) when approved in the
Operations Specifications. As an integral part of this
system approval, the procedures for collecting, producing
and disseminating aeronautical weather information, as well
as the crew member and dispatcher training to support the
use of system weather products, must be accepted or
approved.
b.
Operators not certificated under the provisions of 14
CFR Part 119 are encouraged to use FAA/NWS products through
Flight Service Stations, Direct User Access Terminal System
(DUATS), and/or Flight Information Services Data Link
(FISDL).
c.
The suite of available aviation weather product types is
expanding, with the development of new sensor systems,
algorithms and forecast models. The FAA and NWS, supported
by the National Center for Atmospheric Research and the
Forecast Systems Laboratory, develop and implement new
aviation weather product types through a comprehensive
process known as the Aviation Weather Technology Transfer
process. This process ensures that user needs and technical
readiness requirements are met before experimental products
mature to operational application.
d.
The FAA, in conjunction with the NWS, established the
Aviation Weather Technology Transfer (AWTT) Board so that
newly developed aviation weather products meet regulatory
requirements and enhance safety. The AWTT is charged with
managing and accelerating the transfer of these products
into operational use. Members of the AWTT Board include
mid-level managers from the FAA and NWS who are responsible
for various aspects of the development and use of aviation
weather products (e.g., aviation weather R & D,
transition of weather products from R & D to operational
use, etc.).
e.
The AWTT is a management-review and decision-making
process that applies criteria to weather products at various
development stages (decision stages, i.e., "D-stages"). The
D-stages are composed of the following:
1.
(D1) Sponsorship of user needs.
2.
(D2) R & D and controlled testing.
3.
(D3) Experimental application.
4.
(D4) Operational application.
f.
Weather products maturing into the D3 experimental stage
of the AWTT process are often made available to the public
on the Aviation Weather Center's Experimental Aviation
Digital Data Service (ADDS) website at:
http://weather.aero/. The intent is to allow public
access to this information in order to obtain feedback for
product development and improvement. However, it is
important to note that weather products displayed on this
site are experimental, and although they may appear to be
fully operational products, they are subject to change
without notification and may not be used for any
flight related decisions. At the D4 stage, the FAA approves
a weather product for operational use by end users (with
restrictions, if necessary), and the product is made
available to the public via long-line circuit, satellite,
and/or other means of communication.
g.
Pilots and operators should be aware that weather
services provided by entities other than FAA, NWS or their
contractors (such as the DUATS and FISDL providers) may not
meet FAA/NWS quality control standards. Hence, operators and
pilots contemplating using such services should request
and/or review an appropriate description of services and
provider disclosure. This should include, but is not limited
to, the type of weather product (e.g., current weather or
forecast weather), the currency of the product (i.e.,
product issue and valid times), and the relevance of the
product. Pilots and operators should be cautious when using
unfamiliar products, or products not supported by FAA/NWS
technical specifications.
NOTE-
When in doubt, consult with a FAA Flight Service Station
Specialist.
h.
In addition, pilots and operators should be aware there
are weather services and products available from government
organizations beyond the scope of the AWTT process mentioned
earlier in this section. For example, governmental agencies
such as the NWS, the Aviation Weather Center (AWC), and the
National Center for Atmospheric Research (NCAR) display
weather "model data" and "experimental" products which
require training and/or expertise to properly interpret and
use. These products are developmental prototypes that are
subject to ongoing research and can change without notice.
Therefore, some data on display by government organizations,
or government data on display by independent organizations
may be unsuitable for flight planning purposes. Operators
and pilots contemplating using such services should request
and/or review an appropriate description of services and
provider disclosure. This should include, but is not limited
to, the type of weather product (e.g., current weather or
forecast weather), the currency of the product (i.e.,
product issue and valid times), and the relevance of the
product. Pilots and operators should be cautious when using
unfamiliar weather products.
NOTE-
When in doubt, consult with a FAA Flight Service Station
Specialist.
i.
The development of new weather products coupled with
increased access to these products via the public Internet,
created confusion within the aviation community regarding
the relationship between regulatory requirements and new
weather products. Consequently, FAA differentiates between
those weather products that may be utilized to comply with
regulatory requirements and those that may only be used to
improve situational awareness. To clarify the proper use of
aviation weather products to meet the requirements of 14
CFR, FAA defines weather products as follows:
1.
Primary Weather Product. An aviation weather product
that meets all the regulatory requirements and safety needs
for use in making flight related, aviation weather
decisions.
2.
Supplementary Weather Product. An aviation weather
product that may be used for enhanced situational awareness.
If utilized, a supplementary weather product must only be
used in conjunction with one or more primary weather
product. In addition, the FAA may further restrict the use
of supplementary aviation weather products through
limitations described in the product label.
NOTE-
An aviation weather product produced by the Federal
Government and managed by the AWTT is classified a primary
weather product unless designated a supplementary weather
product by the FAA.
j.
In developing the definitions of primary and
supplementary weather products, it is not the intent of FAA
to change or increase the regulatory burden on the user.
Rather, the definitions are meant to eliminate confusion by
differentiating between weather products that may be
utilized to meet regulatory requirements and other weather
products that may only be used to improve situational
awareness.
k.
All flight-related, aviation weather decisions must be
based on primary weather products. Supplementary weather
products augment the primary products by providing
additional weather information but may not be used as
stand-alone weather products to meet aviation weather
regulatory requirements or without the relevant primary
products. When discrepancies exist between primary and
supplementary weather products describing the same weather
phenomena, users must base flight-related decisions on the
primary weather product. Furthermore, multiple primary
products may be necessary to meet all aviation weather
regulatory requirements.
l.
The development of enhanced communications capabilities,
most notably the Internet, has allowed pilots access to an
ever-increasing range of weather service providers and
proprietary products. The FAA has identified three distinct
types of weather information available to pilots and
operators.
1.
Observations. Raw weather data collected by some type of
sensor suite including surface and airborne observations,
radar, lightning, satellite imagery, and profilers.
2.
Analysis. Enhanced depiction and/or interpretation of
observed weather data.
3.
Forecasts. Predictions of the development and/or
movement of weather phenomena based on meteorological
observations and various mathematical models.
m.
Not all sources of aviation weather information are able
to provide all three types of weather information. The FAA
has determined that operators and pilots may utilize the
following approved sources of aviation weather information:
1.
Federal Government. The FAA and NWS collect raw weather
data, analyze the observations, and produce forecasts. The
FAA and NWS disseminate meteorological observations,
analyses, and forecasts through a variety of systems. In
addition, the Federal Government is the only approval
authority for sources of weather observations; for example,
contract towers and airport operators may be approved by the
Federal Government to provide weather observations.
2.
Enhanced Weather Information System (EWINS). An EWINS is
an FAA approved, proprietary system for tracking,
evaluating, reporting, and forecasting the presence or lack
of adverse weather phenomena. An EWINS is authorized to
produce flight movement forecasts, adverse weather phenomena
forecasts, and other meteorological advisories. For more
detailed information regarding EWINS, see the Aviation
Weather Services Advisory Circular 00-45 and the Air
Transportation Operations Inspector's Handbook 8400.10.
3.
Commercial Weather Information Providers. In general,
commercial providers produce proprietary weather products
based on NWS/FAA products with formatting and layout
modifications but no material changes to the weather
information itself. This is also referred to as
"repackaging." In addition, commercial providers may produce
analyses, forecasts, and other proprietary weather products
that substantially alter the information contained in
government-produced products. However, those proprietary
weather products that substantially alter
government-produced weather products or information, may
only be approved for use by 14 CFR Part 121 and Part 135
certificate holders if the commercial provider is EWINS
qualified.
NOTE-
Commercial weather information providers contracted by FAA
to provide weather observations, analyses, and forecasts
(e.g., contract towers) are included in the Federal
Government category of approved sources by virtue of
maintaining required technical and quality assurance
standards under Federal Government oversight.
n.
As a point of clarification, Advisory Circular 00-62,
Internet Communications of Aviation Weather and NOTAMS,
describes the process for a weather information provider to
become a Qualified Internet Communications Provider (QICP)
and only applies to 14 CFR Part 121 and Part 135
certificate holders. Therefore, pilots conducting operations
under 14 CFR Part 91 may access weather products via the
public Internet.
7-1-4.
Preflight Briefing
a.
Flight Service Stations (AFSSs/FSSs) are the primary
source for obtaining preflight briefings and inflight
weather information. Flight Service Specialists are
qualified and certificated by the NWS as Pilot Weather
Briefers. They are not authorized to make original
forecasts, but are authorized to translate and interpret
available forecasts and reports directly into terms
describing the weather conditions which you can expect along
your flight route and at your destination. Available
aviation weather reports, forecasts and aviation weather
charts are displayed at each AFSS/FSS, for pilot use. Pilots
should feel free to use these self briefing displays where
available, or to ask for a briefing or assistance from the
specialist on duty. Three basic types of preflight briefings
are available to serve your specific needs. These are:
Standard Briefing, Abbreviated Briefing, and Outlook
Briefing. You should specify to the briefer the type of
briefing you want, along with your appropriate background
information. This will enable the briefer to tailor the
information to your intended flight. The following
paragraphs describe the types of briefings available and the
information provided in each briefing.
REFERENCE-
AIM, Preflight Preparation, Paragraph
5-1-1, for
items that are required.
b.
Standard Briefing. You should request a Standard
Briefing any time you are planning a flight and you have not
received a previous briefing or have not received
preliminary information through mass dissemination media;
e.g., TIBS, TWEB (Alaska only), etc. International data may
be inaccurate or incomplete. If you are planning a flight
outside of U.S. controlled airspace, the briefer will advise
you to check data as soon as practical after entering
foreign airspace, unless you advise that you have the
international cautionary advisory. The briefer will
automatically provide the following information in the
sequence listed, except as noted, when it is applicable to
your proposed flight.
1.
Adverse Conditions. Significant meteorological and
aeronautical information that might influence the pilot to
alter the proposed flight; e.g., hazardous weather
conditions, airport closures, air traffic delays, etc.
2. VFR
Flight Not Recommended. When VFR flight is proposed and
sky conditions or visibilities are present or forecast,
surface or aloft, that in the briefer's judgment would make
flight under visual flight rules doubtful, the briefer will
describe the conditions, affected locations, and use the
phrase "VFR flight not recommended." This
recommendation is advisory in nature. The final decision as
to whether the flight can be conducted safely rests solely
with the pilot.
3.
Synopsis. A brief statement describing the type,
location and movement of weather systems and/or air masses
which might affect the proposed flight.
NOTE-
These first 3 elements of a briefing may be combined in any
order when the briefer believes it will help to more clearly
describe conditions.
4.
Current Conditions. Reported weather conditions
applicable to the flight will be summarized from all
available sources; e.g., METARs/ SPECIs, PIREPs, RAREPs.
This element will be omitted if the proposed time of
departure is beyond 2 hours, unless the information is
specifically requested by the pilot.
5. En
Route Forecast. Forecast en route conditions for the
proposed route are summarized in logical order; i.e.,
departure/climbout, en route, and descent. (Heights are MSL,
unless the contractions "AGL" or "CIG" are denoted
indicating that heights are above ground.)
6.
Destination Forecast. The destination forecast for the
planned ETA. Any significant changes within 1 hour before
and after the planned arrival are included.
7.
Winds Aloft. Forecast winds aloft will be provided using
degrees of the compass. The briefer will interpolate wind
directions and speeds between levels and stations as
necessary to provide expected conditions at planned
altitudes. (Heights are MSL.) Temperature information will
be provided on request.
8.
Notices to Airmen (NOTAMs).
(a)
Available NOTAM (D) information pertinent to the
proposed flight.
(b)
NOTAM (L) information pertinent to the departure and/or
local area, if available, and pertinent FDC NOTAMs within
approximately 400 miles of the FSS providing the briefing.
AFSS facilities will provide FDC NOTAMs for the entire route
of flight.
(c)
FSS briefers do not provide FDC NOTAM information for
special instrument approach procedures unless specifically
asked. Pilots authorized by the FAA to use special
instrument approach procedures must specifically request FDC
NOTAM information for these procedures.
NOTE-
NOTAM information may be combined with current conditions
when the briefer believes it is logical to do so.
NOTE-
NOTAM (D) information and FDC NOTAMs which have been
published in the Notices to Airmen Publication are not
included in pilot briefings unless a review of this
publication is specifically requested by the pilot. For
complete flight information you are urged to review the
printed NOTAMs in the Notices to Airmen Publication and the
A/FD in addition to obtaining a briefing.
9. ATC
Delays. Any known ATC delays and flow control advisories
which might affect the proposed flight.
10.
Pilots may obtain the following from AFSS/FSS briefers upon
request:
(a)
Information on Special Use Airspace (SUA), SUA related
airspace and Military Training Routes (MTRs) activity within
the flight plan area and a 100 NM extension around the
flight plan area.
NOTE-
1. SUA and related airspace includes the
following types of airspace: Alert Area, Military Operations
Area (MOA), Prohibited Area, Restricted Area, Refueling
Anchor, Warning Area and Air Traffic Control Assigned
Airspace (ATCAA). MTR data includes the following types of
airspace: IFR Military Training Route (IR), VFR Military
Training Route (VR), Slow Training Route (SR) and
Aerial Refueling Track (AR).
2.
Pilots are encouraged to request updated information
from ATC facilities while in flight.
(b)
A review of the Notices to Airmen Publication for
pertinent NOTAMs and Special Notices.
(c)
Approximate density altitude data.
(d)
Information regarding such items as air traffic services
and rules, customs/immigration procedures, ADIZ rules,
search and rescue, etc.
(e)
LORAN-C NOTAMs, available military NOTAMs, and runway
friction measurement value NOTAMs.
(f)
GPS RAIM availability for 1 hour before to 1 hour after
ETA or a time specified by the pilot.
(g)
Other assistance as required.
c.
Abbreviated Briefing. Request an Abbreviated Briefing
when you need information to supplement mass disseminated
data, update a previous briefing, or when you need only one
or two specific items. Provide the briefer with appropriate
background information, the time you received the previous
information, and/or the specific items needed. You should
indicate the source of the information already received so
that the briefer can limit the briefing to the information
that you have not received, and/or appreciable changes in
meteorological/aeronautical conditions since your previous
briefing. To the extent possible, the briefer will provide
the information in the sequence shown for a Standard
Briefing. If you request only one or two specific items, the
briefer will advise you if adverse conditions are present or
forecast. (Adverse conditions contain both meteorological
and/or aeronautical information.) Details on these
conditions will be provided at your request. International
data may be inaccurate or incomplete. If you are planning a
flight outside of U.S. controlled airspace, the briefer will
advise you to check data as soon as practical after entering
foreign airspace, unless you advise that you have the
international cautionary advisory.
d.
Outlook Briefing. You should request an Outlook Briefing
whenever your proposed time of departure is six or more
hours from the time of the briefing. The briefer will
provide available forecast data applicable to the proposed
flight. This type of briefing is provided for planning
purposes only. You should obtain a Standard or Abbreviated
Briefing prior to departure in order to obtain such items as
adverse conditions, current conditions, updated forecasts,
winds aloft and NOTAMs, etc.
e.
When filing a flight plan only, you will be asked
if you require the latest information on adverse conditions
pertinent to the route of flight.
f.
Inflight Briefing. You are encouraged to obtain your
preflight briefing by telephone or in person before
departure. In those cases where you need to obtain a
preflight briefing or an update to a previous briefing by
radio, you should contact the nearest AFSS/FSS to obtain
this information. After communications have been
established, advise the specialist of the type briefing you
require and provide appropriate background information. You
will be provided information as specified in the above
paragraphs, depending on the type briefing requested. In
addition, the specialist will recommend shifting to the
Flight Watch frequency when conditions along the intended
route indicate that it would be advantageous to do so.
g.
Following any briefing, feel free to ask for any
information that you or the briefer may have missed or are
not understood. This way, the briefer is able to present the
information in a logical sequence, and lessens the chance of
important items being overlooked.
7-1-5.
En Route Flight Advisory Service (EFAS)
a.
EFAS is a service specifically designed to provide en
route aircraft with timely and meaningful weather advisories
pertinent to the type of flight intended, route of flight,
and altitude. In conjunction with this service, EFAS is also
a central collection and distribution point for pilot
reported weather information. EFAS is provided by specially
trained specialists in selected AFSSs controlling multiple
Remote Communications Outlets covering a large geographical
area and is normally available throughout the conterminous
U.S. and Puerto Rico from 6 a.m. to 10 p.m. EFAS
provides communications capabilities for aircraft flying at
5,000 feet above ground level to 17,500 feet MSL on a common
frequency of 122.0 MHz. Discrete EFAS frequencies have
been established to ensure communications coverage from
18,000 through 45,000 MSL serving in each specific ARTCC
area. These discrete frequencies may be used below 18,000
feet when coverage permits reliable communication.
NOTE-
When an EFAS outlet is located in a time zone different from
the zone in which the flight watch control station is
located, the availability of service may be plus or minus
one hour from the normal operating hours.
b.
In some regions of the contiguous U.S., especially those
that are mountainous, it is necessary to be above 5000 feet
AGL in order to be at an altitude where the EFAS frequency,
122.0 MHz, is available. Pilots should take this into
account when flight planning. Other AFSS communication
frequencies may be available at lower altitudes. See
FIG
7-1-2.
c.
Contact flight watch by using the name of the ARTCC
facility identification serving the area of your location,
followed by your aircraft identification, and the name of
the nearest VOR to your position. The specialist needs to
know this approximate location to select the most
appropriate transmitter/receiver outlet for communications
coverage.
EXAMPLE-
Cleveland Flight Watch, Cessna One Two Three Four Kilo,
Mansfield V-O-R, over.
d.
Charts depicting the location of the flight watch
control stations (parent facility) and the outlets they use
are contained in the A/FD. If you do not know in which
flight watch area you are flying, initiate contact by using
the words "Flight Watch," your aircraft identification, and
the name of the nearest VOR. The facility will respond using
the name of the flight watch facility.
EXAMPLE-
Flight Watch, Cessna One Two Three Four Kilo, Mansfield V-O-R,
over.
e.
AFSSs that provide En Route Flight Advisory Service are
listed regionally in the A/FDs.
f.
EFAS is not intended to be used for filing or closing
flight plans, position reporting, getting complete preflight
briefings, or obtaining random weather reports and
forecasts. En route flight advisories are tailored to the
phase of flight that begins after climb-out and ends with
descent to land. Immediate destination weather and terminal
aerodrome forecasts will be provided on request. Pilots
requesting information not within the scope of flight watch
will be advised of the appropriate AFSS/FSS frequency to
obtain the information. Pilot participation is essential to
the success of EFAS by providing a continuous exchange of
information on weather, winds, turbulence, flight
visibility, icing, etc., between pilots and flight watch
specialists. Pilots are encouraged to report good weather as
well as bad, and to confirm expected conditions as well as
unexpected to EFAS facilities.
7-1-6.
Inflight Aviation Weather Advisories
a.
Background
1.
Inflight Aviation Weather Advisories are forecasts to
advise en route aircraft of development of potentially
hazardous weather. All inflight aviation weather advisories
in the conterminous U.S. are issued by the Aviation Weather
Center (AWC) in Kansas City, Missouri. The Weather Forecast
Office (WFO) in Honolulu issues advisories for the
Hawaiian Islands. In Alaska, the Alaska Aviation Weather
Unit (AAWU) issues inflight aviation weather advisories. All
heights are referenced MSL, except in the case of ceilings
(CIG) which indicate AGL.
2.
There are three types of inflight aviation weather
advisories: the Significant Meteorological Information
(SIGMET), the Convective SIGMET and the Airmen's
Meteorological Information (AIRMET). All of these advisories
use the same location identifiers (either VORs, airports, or
well-known geographic areas) to describe the hazardous
weather areas. See FIG
7-1-3 and FIG
7-1-4. Graphics with improved
clarity can be found in Advisory Circular AC 00-45E,
Aviation Weather Services, which is available on the
following web site: http://www.faa.gov.
3.
Two other weather products supplement these Inflight
Aviation Weather Advisories:
(a)
The Severe Weather Watch Bulletins (WWs), (with
associated Alert Messages) (AWW), and
(b)
The Center Weather Advisories (CWAs).
FIG
7-1-2
EFAS Radio Coverage Areas
NOTE-
EFAS radio coverage at 5000 feet AGL. The shaded areas
depict limited coverage areas in which altitudes above 5000
feet AGL would be required to contact EFAS.
FIG
7-1-3
Inflight Advisory Plotting Chart
FIG
7-1-4
Geographical Areas and Terrain Features
FIG
7-1-5
Aviation Area Forecasts
FA Locations - Contiguous United States
b.
SIGMET (WS)/AIRMET (WA)
SIGMETs/AIRMETs
are issued corresponding to the Area Forecast (FA) areas
described in FIG
7-1-5, FIG
7-1-6 and FIG
7-1-7. The maximum forecast
period is 4 hours for SIGMETs and 6 hours for AIRMETs. Both
advisories are considered "widespread" because they must be
either affecting or be forecasted to affect an area of at
least 3,000 square miles at any one time. However, if
the total area to be affected during the forecast period is
very large, it could be that in actuality only a small
portion of this total area would be affected at any one
time.
FIG
7-1-6
Alaska Area Forecast Sectors
FIG
7-1-7
Hawaii Area Forecast Locations
c.
SIGMET (WS)
1.
A SIGMET advises of nonconvective weather that is
potentially hazardous to all aircraft. SIGMETs are
unscheduled products that are valid for 4 hours. However,
conditions that are associated with hurricanes are valid for
6 hours. Unscheduled updates and corrections are issued as
necessary. In the conterminous U.S., SIGMETs are issued when
the following phenomena occur or are expected to occur:
(a)
Severe icing not associated with thunderstorms.
(b)
Severe or extreme turbulence or clear air turbulence
(CAT) not associated with thunderstorms.
(c)
Dust storms or sandstorms lowering surface or inflight
visibilities to below 3 miles.
(d)
Volcanic ash.
2.
In Alaska and Hawaii, SIGMETs are also issued for:
(a)
Tornadoes.
(b)
Lines of thunderstorms.
(c)
Embedded thunderstorms.
(d)
Hail greater than or equal to 3/4
inch in diameter.
3.
SIGMETs are identified by an alphabetic designator from
November through Yankee excluding Sierra and Tango. (Sierra,
Tango, and Zulu are reserved for AIRMETs.) The first
issuance of a SIGMET will be labeled as UWS (Urgent Weather
SIGMET). Subsequent issuances are at the forecaster's
discretion. Issuance for the same phenomenon will be
sequentially numbered, using the original designator until
the phenomenon ends. For example, the first issuance in the
Chicago (CHI) FA area for phenomenon moving from the Salt
Lake City (SLC) FA area will be SIGMET Papa 3, if the
previous two issuances, Papa 1 and Papa 2, had been in the
SLC FA area. Note that no two different phenomena across the
country can have the same alphabetic designator at the same
time.
EXAMPLE-
Example of a SIGMET:
BOSR WS 050600
SIGMET
ROMEO 2 VALID UNTIL 051000
ME NH VT
FROM CAR TO YSJ TO CON TO MPV TO CAR
MOD TO OCNL SEV TURB BLW 080 EXP DUE TO STG NWLY FLOW. CONDS
CONTG BYD
1000Z.
d.
Convective SIGMET (WST)
1.
Convective SIGMETs are issued in the conterminous U.S.
for any of the following:
(a)
Severe thunderstorm due to:
(1)
Surface winds greater than or equal to 50 knots.
(2)
Hail at the surface greater than or equal to
3/4 inches in diameter.
(3)
Tornadoes.
(b)
Embedded thunderstorms.
(c)
A line of thunderstorms.
(d)
Thunderstorms producing precipitation greater than or
equal to heavy precipitation affecting 40 percent or more of
an area at least 3,000 square miles.
2.
Any convective SIGMET implies severe or greater
turbulence, severe icing, and low-level wind shear. A
convective SIGMET may be issued for any convective situation
that the forecaster feels is hazardous to all categories of
aircraft.
3.
Convective SIGMET bulletins are issued for the western
(W), central (C), and eastern (E) United States. (Convective
SIGMETs are not issued for Alaska or Hawaii.) The areas are
separated at 87 and 107 degrees west longitude with
sufficient overlap to cover most cases when the phenomenon
crosses the boundaries. Bulletins are issued hourly at H+55.
Special bulletins are issued at any time as required and
updated at H+55. If no criteria meeting convective SIGMET
requirements are observed or forecasted, the message
"CONVECTIVE SIGMET... NONE" will be issued for each area at
H+55. Individual convective SIGMETs for each area (W, C, E)
are numbered sequentially from number one each day,
beginning at 00Z. A convective SIGMET for a continuing
phenomenon will be reissued every hour at H+55 with a new
number. The text of the bulletin consists of either an
observation and a forecast or just a forecast. The forecast
is valid for up to 2 hours.
EXAMPLE-
Example of a Convective SIGMET:
MKCC WST 251655
CONVECTIVE
SIGMET 54C
VALID UNTIL 1855Z
WI IL
FROM 30E MSN-40ESE DBQ
DMSHG LINE TS 15 NM WIDE MOV FROM 30025KT. TOPS TO FL450.
WIND GUSTS TO 50 KT POSS.
CONVECTIVE SIGMET 55C
VALID UNTIL 1855Z
WI IA
FROM 30NNW MSN-30SSE MCW
DVLPG LINE TS 10 NM WIDE MOV FROM 30015KT. TOPS TO
FL300.
CONVECTIVE SIGMET 56C
VALID UNTIL 1855Z
MT ND SD MN IA MI
LINE TS 15 NM WIDE MOV FROM 27020KT. TOPS TO FL380.
OUTLOOK VALID 151855-252255
FROM 60NW ISN-INL-TVC-SBN-BRL-FSD-BIL-60NW
ISN
IR STLT IMGRY SHOWS CNVTV CLD TOP TEMPS OVER SRN WI HAVE
BEEN WARMING STEADILY INDCG A WKNG TREND. THIS ALSO
REFLECTED BY LTST RADAR AND LTNG DATA. WKNG TREND OF PRESENT
LN MAY CONT...HWVR NEW DVLPMT IS PSBL ALG OUTFLOW BDRY
AND/OR OVR NE IA/SW WI BHD CURRENT ACT.
A SCND TS IS CONTG TO MOV EWD THRU ERN MT WITH NEW DVLPMT
OCRG OVR CNTRL ND. MT ACT IS MOVG TWD MORE FVRBL AMS OVR THE
WRN DAKS WHERE DWPTS ARE IN THE UPR 60S WITH LIFTED INDEX
VALUES TO MS 6. TS EXPD TO INCR IN COVERAGE AND INTSTY DURG
AFTN HRS.
WST ISSUANCES EXPD TO BE RQRD THRUT AFTN HRS WITH INCRG
PTNTL FOR STGR CELLS TO CONTAIN LRG HAIL AND PSBLY DMGG SFC
WNDS.
e.
International SIGMET
1.
Some NWS offices have been designated by the ICAO as
Meteorological Watch Offices (MWOs). These offices are
responsible for issuing International SIGMETs for designated
areas that include Alaska, Hawaii, portions of the Atlantic
and Pacific Oceans, and the Gulf of Mexico.
2.
The offices which issue International SIGMETs are:
(a)
The AWC in Kansas City, Missouri.
(b)
The AAWU in Anchorage, Alaska.
(c)
The WFO in Honolulu, Hawaii.
(d)
The WFO on Guam Island in the Pacific Ocean.
3.
These SIGMETs are considered "widespread" because they
must be either affecting or be forecasted to affect an area
of at least 3,000 square miles at any one time. The
International SIGMET is issued for 12 hours for volcanic ash
events, 6 hours for hurricanes and tropical storms, and 4
hours for all other events. Like the domestic SIGMETs,
International SIGMETs are also identified by an alphabetic
designator from Alpha through Mike and are numbered
sequentially until that weather phenomenon ends. The
criteria for an International SIGMET are:
(a)
Thunderstorms occurring in lines, embedded in clouds, or
in large areas producing tornadoes or large hail.
(b)
Tropical cyclones.
(c)
Severe icing.
(d)
Severe or extreme turbulence.
(e)
Dust storms and sandstorms lowering visibilities to less
than 3 miles.
(f)
Volcanic ash.
EXAMPLE-
Example of an International SIGMET:
WSNT06 KKCI 022014
SIGA0F
KZMA KZNY TJZS SIGMET FOXTROT 3 VALID 022015/030015 KKCI-
MIAMI OCEANIC FIR NEW YORK OCEANIC FIR SAN JUAN FIR FRQ TS
WI AREA BOUNDED BY 2711N6807W 2156N6654W 2220N7040W
2602N7208W 2711N6807W. TOPS TO FL470. MOV NE 15KT. WKN.
BASED ON SAT AND LTG OBS.
MOSHER
f.
AIRMET (WA)
1.
AIRMETs (WAs) are advisories of significant weather
phenomena but describe conditions at intensities lower than
those which require the issuance of SIGMETs. AIRMETs are
intended for dissemination to all pilots in the preflight
and en route phase of flight to enhance safety. AIRMET
Bulletins are issued on a scheduled basis every 6 hours
beginning at 0145 UTC during Central Daylight Time and at
0245 UTC during Central Standard Time. Unscheduled updates
and corrections are issued as necessary. Each AIRMET
Bulletin contains any current AIRMETs in effect and an
outlook for conditions expected after the AIRMET valid
period. AIRMETs contain details about IFR, extensive
mountain obscuration, turbulence, strong surface winds,
icing, and freezing levels.
2.
There are three AIRMETs: Sierra, Tango, and Zulu. After
the first issuance each day, scheduled or unscheduled
bulletins are numbered sequentially for easier
identification.
(a)
AIRMET Sierra describes IFR conditions and/or extensive
mountain obscurations.
(b)
AIRMET Tango describes moderate turbulence, sustained
surface winds of 30 knots or greater, and/or nonconvective
low-level wind shear.
(c)
AIRMET Zulu describes moderate icing and provides
freezing level heights.
EXAMPLE-
Example of AIRMET Sierra issued for the Chicago FA
area:
CHIS WA 121345
AIRMET SIERRA UPDT 3 FOR IFR AND MTN OBSCN VALID UNTIL
122000.
AIRMET IFR...SD NE MN IA MO WI LM MI IL IN KY
FROM 70NW RAP TO 50W RWF TO 50W MSN TO GRB TO MBS TO FWA TO
CVG TO HNN TO TRI TO ARG TO 40SSW BRL TO OMA TO BFF TO 70NW
RAP
OCNL CIG BLW 010/VIS BLW 3SM FG/BR. CONDS ENDG 15Z-17Z.
AIRMET MTN OBSCN...KY TN
FROM HNN TO TRI TO CHA TO LOZ TO HNN
MTNS OCNL OBSC CLDS/PCPN/BR. CONDS ENDG TN PTN AREA 18Z-
20Z..CONTG KY BYD 20Z..ENDG 02Z.
EXAMPLE-
Example of AIRMET Tango issued for the Salt Lake
City FA area:
SLCT WA 121345
AIRMET TANGO UPDT 2 FOR TURB VALID UNTIL 122000.
AIRMET TURB...NV UT CO AZ NM
FROM LKV TO CHE TO ELP TO 60S TUS TO YUM TO EED TO RNO TO
LKV OCNL MOD TURB BLW FL180 DUE TO MOD SWLY/WLY WNDS. CONDS
CONTG BYD 20Z THRU 02Z.
AIRMET TURB...NV WA OR CA CSTL WTRS
FROM BLI TO REO TO BTY TO DAG TO SBA TO 120W FOT TO 120W TOU
TO BLI
OCNL MOD TURB BTWN FL180 AND FL400 DUE TO WNDSHR ASSOCD WITH
JTSTR. CONDS CONTG BYD 20Z THRU 02Z.
EXAMPLE-
Example
of AIRMET Zulu issued for the San Francisco FA
area:
SFOZ WA
121345
AIRMET ZULU UPDT 2 FOR ICE AND FRZLVL VALID UNTIL
122000.
AIRMET ICE...WA OR ID MT NV UT
FROM YQL TO SLC TO WMC TO LKV TO PDT TO YDC TO YQL
LGT OCNL MOD RIME/MXD ICGICIP BTWN FRZLVL AND FL220. FRZLVL
080-120. CONDS CONTG BYD 20Z THRU 02Z.
AIRMET ICE...WA OR
FROM YDC TO PDT TO LKV TO 80W MFR TO ONP TO TOU TO YDC
LGT OCNL MOD RIME/MXD ICGICIP BTWN FRZLVL AND FL180. FRZLVL
060-080. CONDS CONTG BYD 20Z THRU 02Z.
FRZLVL...WA...060 CSTLN SLPG 100 XTRM E.
OR...060-070 CASCDS WWD. 070-095 RMNDR.
NRN CA...060-100 N OF A 30N FOT-40N RNO LN SLPG 100-110
RMNDR.
g.
Severe Weather Watch Bulletins (WWs) and Alert Messages
(AWWs)
1.
WWs define areas of possible severe thunderstorms or
tornado activity. The bulletins are issued by the Storm
Prediction Center (SPC) in Norman, OK. WWs are unscheduled
and are issued as required.
2.
A severe thunderstorm watch describes areas of expected
severe thunderstorms. (Severe thunderstorm criteria are
3/4-inch hail or larger and/or wind
gusts of 50 knots [58 mph] or greater.)
3.
A tornado watch describes areas where the threat of
tornadoes exists.
4.
In order to alert the WFOs, CWSUs, FSSs, and other
users, a preliminary notification of a watch called the
Alert Severe Weather Watch bulletin (AWW) is sent before the
WW. (WFOs know this product as a SAW).
EXAMPLE-
Example of an AWW:
MKC AWW 011734
WW 75
TORNADO TX OK AR 011800Z-020000Z
AXIS..80 STATUTE MILES EAST AND WEST OF A LINE..60ESE
DAL/DALLAS TX/ - 30 NW ARG/ WALNUT RIDGE AR/
..AVIATION COORDS.. 70NM E/W /58W GGG - 25NW ARG/
HAIL SURFACE AND ALOFT..1 3/4 INCHES.
WIND GUSTS..70 KNOTS. MAX TOPS TO 450. MEAN WIND VECTOR
24045.
5.
Soon after the AWW goes out, the actual watch bulletin
itself is issued. A WW is in the following format:
(a)
Type of severe weather watch, watch area, valid time
period, type of severe weather possible, watch axis, meaning
of a watch, and a statement that persons should be on the
lookout for severe weather.
(b)
Other watch information; i.e., references to previous
watches.
(c)
Phenomena, intensities, hail size, wind speed (knots),
maximum cumulonimbus (CB) tops, and estimated cell movement
(mean wind vector).
(d)
Cause of severe weather.
(e)
Information on updating Convective Outlook (AC)
products.
EXAMPLE-
Example of a WW:
BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 381
STORM PREDICTION CENTER NORMAN OK
556 PM CDT MON JUN 2 1997
THE STORM PREDICTON CENTER HAS ISSUED A TORNADO WATCH FOR
PORTIONS OF NORTHEAST NEW MEXICO TEXAS PANHANDLE
EFFECTIVE THIS MONDAY NIGHT AND TUESDAY MORNING FROM 630 PM
UNTIL MIDNIGHT CDT.
TORNADOES...HAIL TO 2 3/4 INCHES IN
DIAMETER...THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS
LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS ALONG AND 60 STATUTE MILES NORTH
AND SOUTH OF A LINE FROM 50 MILES SOUTHWEST OF RATON NEW
MEXICO TO 50 MILES EAST OF AMARILLO TEXAS.
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE
FOR TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE
WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT
FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER
STATEMENTS AND POSSIBLE WARNINGS.
OTHER WATCH INFORMATION...CONTINUE... WW 378...WW
379...WW 380
DISCUSSION...THUNDERSTORMS ARE INCREASING OVER NE NM IN
MOIST SOUTHEASTERLY UPSLOPE FLOW. OUTFLOW BOUNDARY EXTENDS
EASTWARD INTO THE TEXAS PANHANDLE AND EXPECT STORMS TO MOVE
ESE ALONG AND NORTH OF THE BOUNDARY ON THE N EDGE OF THE
CAP. VEERING WINDS WITH HEIGHT ALONG WITH INCREASGING MID
LVL FLOW INDICATE A THREAT FOR SUPERCELLS.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH
HAIL SURFACE AND ALOFT TO 2 3/4
INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN
STORM MOTION VECTOR 28025.
6.
Status reports are issued as needed to show progress of
storms and to delineate areas no longer under the threat of
severe storm activity. Cancellation bulletins are issued
when it becomes evident that no severe weather will develop
or that storms have subsided and are no longer severe.
7.
When tornadoes or severe thunderstorms have developed,
the local WFO office will issue the warnings covering those
areas.
h.
Center Weather Advisories (CWAs)
1.
CWAs are unscheduled inflight, flow control, air
traffic, and air crew advisory. By nature of its short lead
time, the CWA is not a flight planning product. It is
generally a nowcast for conditions beginning within the next
two hours. CWAs will be issued:
(a)
As a supplement to an existing SIGMET, Convective SIGMET
or AIRMET.
(b)
When an Inflight Advisory has not been issued but
observed or expected weather conditions meet SIGMET/AIRMET
criteria based on current pilot reports and reinforced by
other sources of information about existing
meteorological conditions.
(c)
When observed or developing weather conditions do not
meet SIGMET, Convective SIGMET, or AIRMET criteria; e.g., in
terms of intensity or area coverage, but current pilot
reports or other weather information sources indicate that
existing or anticipated meteorological phenomena will
adversely affect the safe flow of air traffic within the
ARTCC area of responsibility.
2.
The following example is a CWA issued from the Kansas
City, Missouri, ARTCC. The "3" after ZKC in the first line
denotes this CWA has been issued for the third weather
phenomena to occur for the day. The "301" in the second line
denotes the phenomena number again (3) and the issuance
number (01) for this phenomena. The CWA was issued at 2140Z
and is valid until 2340Z.
EXAMPLE-
ZKC3 CWA 032140
ZKC CWA 301 VALID UNTIL 032340
ISOLD SVR TSTM over KCOU MOVG SWWD 10 KTS ETC.
7-1-7.
Categorical Outlooks
a.
Categorical outlook terms, describing general ceiling
and visibility conditions for advanced planning purposes are
used only in area forecasts and are defined as follows:
1. LIFR
(Low IFR). Ceiling less than 500 feet and/or visibility
less than 1 mile.
2. IFR.
Ceiling 500 to less than 1,000 feet and/or visibility 1
to less than 3 miles.
3. MVFR
(Marginal VFR). Ceiling 1,000 to 3,000 feet and/or
visibility 3 to 5 miles inclusive.
4. VFR.
Ceiling greater than 3,000 feet and visibility greater
than 5 miles; includes sky clear.
b.
The cause of LIFR, IFR, or MVFR is indicated by either
ceiling or visibility restrictions or both. The contraction
"CIG" and/or weather and obstruction to vision symbols are
used. If winds or gusts of 25 knots or greater are forecast
for the outlook period, the word "WIND" is also included for
all categories including VFR.
EXAMPLE-
1. LIFR CIG-low IFR due to low ceiling.
2.
IFR FG-IFR due to visibility restricted by fog.
3.
MVFR CIG HZ FU-marginal VFR due to both ceiling and
visibility restricted by haze and smoke.
4.
IFR CIG RA WIND-IFR due to both low ceiling and
visibility restricted by rain; wind expected to be 25 knots
or greater.
7-1-8.
Telephone Information Briefing Service (TIBS)
a.
TIBS, provided by automated flight service stations
(AFSSs) is a continuous recording of meteorological and
aeronautical information, available by telephone. Each AFSS
provides at least four route and/or area briefings. In
addition, airspace procedures and special announcements (if
applicable) concerning aviation interests may also be
available. Depending on user demand, other items may be
provided; i.e., METAR observations, terminal aerodrome
forecasts, wind/temperatures aloft forecasts, etc.
b.
TIBS is not intended to substitute for
specialist-provided preflight briefings. It is, however,
recommended for use as a preliminary briefing, and often
will be valuable in helping you to make a "go or no go"
decision.
c.
TIBS is provided by Automated Flight Service Stations
(AFSSs) and provides continuous telephone recordings of
meteorological and/or aeronautical information.
Specifically, TIBS provides area and/or route briefings,
airspace procedures, and special announcements (if
applicable) concerning aviation interests.
d.
Depending on user demand, other items may be provided;
i.e., surface observations, terminal forecasts,
winds/temperatures aloft forecasts, etc. A TOUCH-TONE™
telephone is necessary to fully utilize the TIBS program.
e.
Pilots are encouraged to avail themselves of this
service. TIBS locations are found at AFSS sites and can be
accessed by use of 1-800-WX BRIEF toll free number.
7-1-9.
Transcribed Weather Broadcast (TWEB) (Alaska Only)
Equipment
is provided in Alaska by which meteorological and
aeronautical data are recorded on tapes and broadcast
continuously over selected L/MF and VOR facilities.
Broadcasts are made from a series of individual tape
recordings, and changes, as they occur, are transcribed onto
the tapes. The information provided varies depending on the
type equipment available. Generally, the broadcast contains
a summary of adverse conditions, surface weather
observations, pilot weather reports, and a density altitude
statement (if applicable). At the discretion of the
broadcast facility, recordings may also include a synopsis,
winds aloft forecast, en route and terminal forecast data,
and radar reports. At selected locations, telephone access
to the TWEB has been provided (TEL-TWEB). Telephone numbers
for this service are found in the Supplement Alaska A/FD.
These broadcasts are made available primarily for preflight
and inflight planning, and as such, should not be considered
as a substitute for specialist-provided preflight briefings.
7-1-10.
Inflight Weather Broadcasts
a.
Weather Advisory Broadcasts. ARTCCs broadcast a Severe
Weather Forecast Alert (AWW), Convective SIGMET, SIGMET, or
CWA alert once on all frequencies, except emergency, when
any part of the area described is within 150 miles of the
airspace under their jurisdiction. These broadcasts contain
SIGMET or CWA (identification) and a brief description of
the weather activity and general area affected.
EXAMPLE-
1. Attention all aircraft, SIGMET Delta Three,
from Myton to Tuba City to Milford, severe turbulence and
severe clear icing below one zero thousand feet. Expected to
continue beyond zero three zero zero zulu.
2.
Attention all aircraft, convective SIGMET Two Seven
Eastern. From the vicinity of Elmira to Phillipsburg.
Scattered embedded thunderstorms moving east at one zero
knots. A few intense level five cells, maximum tops four
five zero.
3.
Attention all aircraft, Kansas City Center weather
advisory one zero three. Numerous reports of moderate to
severe icing from eight to niner thousand feet in a three
zero mile radius of St. Louis. Light or negative icing
reported from four thousand to one two thousand feet
remainder of Kansas City Center area.
NOTE-
Terminal control facilities have the option to limit the
AWW, convective SIGMET, SIGMET, or CWA broadcast as follows:
local control and approach control positions may opt to
broadcast SIGMET or CWA alerts only when any part of the
area described is within 50 miles of the airspace under
their jurisdiction.
b.
Hazardous Inflight Weather Advisory Service (HIWAS).
This is a continuous broadcast of inflight weather
advisories including summarized AWW, SIGMETs, Convective
SIGMETs, CWAs, AIRMETs, and urgent PIREPs. HIWAS has been
adopted as a national program and will be implemented
throughout the conterminous U.S. as resources permit. In
those areas where HIWAS is commissioned, ARTCC, Terminal
ATC, and AFSS/FSS facilities have discontinued the broadcast
of inflight advisories as described in the preceding
paragraph. HIWAS is an additional source of hazardous
weather information which makes these data available on a
continuous basis. It is not, however, a replacement for
preflight or inflight briefings or real-time weather updates
from Flight Watch (EFAS). As HIWAS is implemented in
individual center areas, the commissioning will be
advertised in the Notices to Airmen Publication.
1.
Where HIWAS has been implemented, a HIWAS alert will be
broadcast on all except emergency frequencies once upon
receipt by ARTCC and terminal facilities, which will include
an alert announcement, frequency instruction, number, and
type of advisory updated; e.g., AWW, SIGMET, Convective
SIGMET, or CWA.
EXAMPLE-
Attention
all aircraft. Hazardous weather information (SIGMET,
Convective SIGMET, AIRMET, Urgent Pilot Weather Report
(UUA), or Center Weather Advisory (CWA), Number or Numbers)
for (geographical area) available on HIWAS, Flight Watch, or
Flight Service frequencies.
2.
In HIWAS ARTCC areas, AFSS/FSSs will broadcast a HIWAS
update announcement once on all except emergency frequencies
upon completion of recording an update to the HIWAS
broadcast. Included in the broadcast will be the type of
advisory updated; e.g., AWW, SIGMET, Convective SIGMET, CWA,
etc.
EXAMPLE-
Attention all aircraft. Hazardous weather information for
(geographical area) available from Flight Watch or Flight
Service.
3.
HIWAS availability is shown on IFR Enroute Low Altitude
Charts and VFR Sectional Charts. The symbol depiction is
identified in the chart legend.
7-1-11.
Flight Information Services (FIS)
a. FIS.
Aviation weather and other operational information may
be displayed in the cockpit through the use of FIS. FIS
systems are of two basic types: Broadcast only systems
(called FIS-B) and two-way request/reply systems. Broadcast
system components include a ground- or space-based
transmitter, an aircraft receiver, and a portable or
installed cockpit display device. Two-way systems utilize
transmitter/receivers at both the ground- or space-based
site and the aircraft.
1.
Broadcast FIS (i.e., FIS-B) allows the pilot to
passively collect weather and other operational data and to
display that data at the appropriate time. In addition to
textual weather products such as Aviation Routine Weather
Reports (METARs)/ Aviation Selected Special Weather Reports
(SPECIs) and Terminal Area Forecasts (TAFs), graphical
weather products such as radar composite/mosaic images,
temporary flight restricted airspace and other NOTAMs may be
provided to the cockpit. Two-way FIS services permit the
pilot to make specific weather and other operational
information requests for cockpit display. A FIS service
provider will then prepare a reply in response to that
specific request and transmit the product to that specific
aircraft.
2.
FIS services are available from four types of service
providers:
(a)
A private sector FIS provider operating under service
agreement with the FAA using broadcast data link over VHF
aeronautical spectrum and whose products have been reviewed
and accepted by the FAA prior to transmission. (Products and
services are defined under subparagraph c.)
(b)
Through an FAA operated service using a broadcast data
link on the ADS-B UAT network. (Products and services are
defined under subparagraph d.)
(c)
Private sector FIS providers operating under customer
contracts using aeronautical spectrum.
(d)
Private sector FIS providers operating under customer
contract using methods other than aeronautical spectrum,
including Internet data-to-the-cockpit service providers.
3.
FIS is a method of receiving aviation weather and other
operational data in the cockpit that augments traditional
pilot voice communication with FAA's Flight Service Stations
(FSSs), ATC facilities, or Airline Operations Control
Centers (AOCCs). FIS is not intended to replace traditional
pilot and controller/flight service specialist/aircraft
dispatcher pre-flight briefings or inflight voice
communications. FIS; however, can provide textual and
graphical background information that can help abbreviate
and improve the usefulness of such communications. FIS
enhances pilot situational awareness and improves safety.
4.
To ensure airman compliance with Federal Aviation
Regulations, manufacturer's operating manuals should remind
airmen to contact ATC controllers, FSS specialists, operator
dispatchers, or airline operations control centers for
general and mission critical aviation weather information
and/or NAS status conditions (such as NOTAMs, Special Use
Airspace status, and other government flight information).
If FIS products are systemically modified (for example, are
displayed as abbreviated plain text and/or graphical
depictions), the modification process and limitations of the
resultant product should be clearly described in the
vendor's user guidance.
b.
Operational Use of FIS. Regardless of the type of FIS
system being used, several factors must be considered when
using FIS:
1.
Before using FIS for inflight operations, pilots and
other flight crewmembers should become familiar with the
operation of the FIS system to be used, the airborne
equipment to be used, including its system architecture,
airborne system components, coverage service volume and
other limitations of the particular system, modes of
operation and indications of various system failures. Users
should also be familiar with the specific content and format
of the services available from the FIS provider(s). Sources
of information that may provide this specific guidance
include manufacturer's manuals, training programs and
reference guides.
2.
FIS should not serve as the sole source of aviation
weather and other operational information. ATC, AFSSs and,
if applicable, AOCC VHF/HF voice remain as a redundant
method of communicating aviation weather, NOTAMs, and other
operational information to aircraft in flight. FIS augments
these traditional ATC/FSS/AOCC services and, for some
products, offers the advantage of being displayed as
graphical information. By using FIS for orientation, the
usefulness of information received from conventional means
may be enhanced. For example, FIS may alert the pilot to
specific areas of concern that will more accurately focus
requests made to FSS or AOCC for inflight updates or similar
queries made to ATC.
3.
The airspace and aeronautical environment is constantly
changing. These changes occur quickly and without warning.
Critical operational decisions should be based on use of the
most current and appropriate data available. When
differences exist between FIS and information obtained by
voice communication with ATC, FSS, and/or AOCC (if
applicable), pilots are cautioned to use the most recent
data from the most authoritative source.
4.
FIS aviation weather products (e.g., graphical
ground-based radar precipitation depictions) are not
appropriate for tactical avoidance of severe weather such as
negotiating a path through a weather hazard area. FIS
supports strategic weather decision making such as route
selection to avoid a weather hazard area in its entirety.
The misuse of information beyond its applicability may place
the pilot and aircraft in jeopardy. In addition, FIS should
never be used in lieu of an individual pre-flight weather
and flight planning briefing.
5.
FIS NOTAM products, including Temporary Flight
Restriction (TFR) information, are advisory-use information
and are intended for situational awareness purposes only.
Cockpit displays of this information are not appropriate for
tactical navigation - pilots should stay clear of any
geographic area displayed as a TFR NOTAM. Pilots should
contact FSSs and/or ATC while en route to obtain updated
information and to verify the cockpit display of NOTAM
information.
6.
FIS supports better pilot decision making by increasing
situational awareness. Better decision-making is based on
using information from a variety of sources. In addition to
FIS, pilots should take advantage of other weather/NAS
status sources, including, briefings from Flight Service
Stations, FAA's en route "Flight Watch" service, data from
other air traffic control facilities, airline operation
control centers, pilot reports, as well as their own
observations.
c.
FAA FISDL (VHF) Service. The FAA's FISDL (VHF datalink)
system is a VHF Data Link (VDL) Mode 2 implementation that
provides pilots and flight crews of properly equipped
aircraft with a cockpit display of certain aviation weather
and flight operational information. This information may be
displayed in both textual and graphical formats. The system
is operated under a service agreement with the FAA, using
broadcast data link on VHF aeronautical spectrum on two 25
KHz spaced frequencies (136.450 and 136.475 MHz). The FAA
FISDL (VHF) service is designed to provide coverage
throughout the continental U.S. from 5,000 feet AGL to
17,500 feet MSL, except in areas where this is not feasible
due to mountainous terrain. Aircraft operating near
transmitter sites may receive useable FISDL signals at
altitudes lower than 5,000 feet AGL, including on the
surface in some locations, depending on transmitter/aircraft
line of sight geometry. Aircraft operating above 17,500 feet
MSL may also receive useable FISDL signals under certain
circumstances.
1.
FAA FISDL (VHF) service provides, free of charge, the
following basic text products:
(a)
Aviation Routine Weather Reports (METARs).
(b)
Aviation Selected Special Weather Reports (SPECIs).
(c)
Terminal Area Forecasts (TAFs), and their amendments.
(d)
Significant Meteorological Information (SIGMETs).
(e)
Convective SIGMETs.
(f)
Airman's Meteorological Information (AIRMETs).
(g)
Pilot Reports (both urgent and routine) (PIREPs); and,
(h)
Severe Weather Forecast Alerts and Warnings (AWWs/WW)
issued by the NOAA Storm Prediction Center (SPC).
2.
The format and coding of these text products are
described in Advisory Circular AC-00-45, Aviation Weather
Services, and paragraph 7-1-30,
Key to Aerodrome Forecast (TAF) and Aviation Routine Weather
Report (METAR).
3.
Additional products, called "Value-Added Products," are
also available from the vendor on a paid subscription basis.
Details concerning the content, format, symbology and cost
of these products may be obtained from the vendor.
d.
FAA's Flight Information Service-Broadcast (FIS-B) Service.
FIS-B is a ground broadcast service provided through the
FAA's Universal Access Transceiver (UAT) "ADS-B Broadcast
Services" network. The UAT network is an ADS-B data link
that operates on 978 MHz. The FAA FIS-B system provides
pilots and flight crews of properly equipped aircraft with a
cockpit display of certain aviation weather and flight
operational information. The FAA's FIS-B service is being
introduced in certain regional implementations within the
NAS (e.g., in Alaska and in other areas of implementation).
1.
FAA's UAT FIS-B provides the initial products listed
below with additional products planned for future
implementation. FIS-B reception is line of sight and can be
expected within 200 NM (nominal range) of each ground
transmitting site. The following services are provided free
of charge.
(a)
Text: Aviation Routine Weather Reports (METARs).
(b)
Text: Special Aviation Reports (SPECIs).
(c)
Text: Terminal Area Forecasts (TAFs), and their
amendments.
(d)
Graphic: NEXRAD precipitation maps.
2.
The format and coding of the above text weather-related
products are described in Advisory Circular AC-00-45,
Aviation Weather Services, and paragraph
7-1-30, Key to Aerodrome
Forecast (TAF) and Aviation Routine Weather Report (METAR).
3.
Details concerning the content, format, and symbology of
the various data link products provided may be obtained from
the specific avionics manufacturer.
e.
Non-FAA FISDL Systems. Several commercial vendors also
provide customers with FIS data over both the aeronautical
spectrum and on other frequencies using a variety of data
link protocols. In some cases, the vendors provide only the
communications system that carries customer messages, such
as the Aircraft Communications Addressing and Reporting
System (ACARS) used by many air carrier and other operators.
1.
Operators using non-FAA FIS data for inflight weather
and other operational information should ensure that the
products used conform to FAA/NWS standards. Specifically,
aviation weather and NAS status information should meet the
following criteria:
(a)
The products should be either FAA/NWS "accepted"
aviation weather reports or products, or based on FAA/NWS
accepted aviation weather reports or products. If products
are used which do not meet this criteria, they should be so
identified. The operator must determine the applicability of
such products to their particular flight operations.
(b)
In the case of a weather product which is the result of
the application of a process which alters the form, function
or content of the base FAA/NWS accepted weather product(s),
that process, and any limitations to the application of the
resultant product, should be described in the vendor's user
guidance material.
2.
An example would be a NEXRAD radar composite/mosaic map,
which has been modified by changing the scaling resolution.
The methodology of assigning reflectivity values to the
resultant image components should be described in the
vendor's guidance material to ensure that the user can
accurately interpret the displayed data.
7-1-12.
Weather Observing Programs
a.
Manual Observations. With only a few exceptions, these
reports are from airport locations staffed by FAA or NWS
personnel who manually observe, perform calculations, and
enter these observations into the (WMSCR) communication
system. The format and coding of these observations are
contained in paragraph
7-1-30, Key to Aviation
Routine Weather Report (METAR) and Aerodrome Forecasts
(TAF).
b.
Automated Weather Observing System (AWOS).
1.
Automated weather reporting systems are increasingly
being installed at airports. These systems consist of
various sensors, a processor, a computer-generated voice
subsystem, and a transmitter to broadcast local,
minute-by-minute weather data directly to the pilot.
NOTE-
When the barometric pressure exceeds 31.00 inches Hg., see
paragraph
7-2-2, Procedures, for
the altimeter setting procedures.
2.
The AWOS observations will include the prefix "AUTO" to
indicate that the data are derived from an automated system.
Some AWOS locations will be augmented by certified observers
who will provide weather and obstruction to vision
information in the remarks of the report when the reported
visibility is less than 7 miles. These sites, along with the
hours of augmentation, are to be published in the A/FD.
Augmentation is identified in the observation as "OBSERVER
WEATHER." The AWOS wind speed, direction and gusts,
temperature, dew point, and altimeter setting are exactly
the same as for manual observations. The AWOS will also
report density altitude when it exceeds the field elevation
by more than 1,000 feet. The reported visibility is derived
from a sensor near the touchdown of the primary instrument
runway. The visibility sensor output is converted to a
visibility value using a 10-minute harmonic average. The
reported sky condition/ceiling is derived from the
ceilometer located next to the visibility sensor. The AWOS
algorithm integrates the last 30 minutes of ceilometer data
to derive cloud layers and heights. This output may also
differ from the observer sky condition in that the AWOS is
totally dependent upon the cloud advection over the sensor
site.
3.
These real-time systems are operationally classified
into four basic levels:
(a)
AWOS-A only reports altimeter setting;
NOTE-
Any other information is advisory only.
(b)
AWOS-l usually reports altimeter setting, wind data,
temperature, dew point, and density altitude;
(c)
AWOS-2 provides the information provided by AWOS-l plus
visibility; and
(d)
AWOS-3 provides the information provided by AWOS-2 plus
cloud/ceiling data.
4.
The information is transmitted over a discrete VHF radio
frequency or the voice portion of a local NAVAID. AWOS
transmissions on a discrete VHF radio frequency are
engineered to be receivable to a maximum of 25 NM from the
AWOS site and a maximum altitude of 10,000 feet AGL. At many
locations, AWOS signals may be received on the surface of
the airport, but local conditions may limit the maximum AWOS
reception distance and/or altitude. The system transmits a
20 to 30 second weather message updated each minute. Pilots
should monitor the designated frequency for the automated
weather broadcast. A description of the broadcast is
contained in subparagraph c. There is no two-way
communication capability. Most AWOS sites also have a
dial-up capability so that the minute-by-minute weather
messages can be accessed via telephone.
5.
AWOS information (system level, frequency, phone number,
etc.) concerning specific locations is published, as the
systems become operational, in the A/FD, and where
applicable, on published Instrument Approach Procedures.
Selected individual systems may be incorporated into
nationwide data collection and dissemination networks in the
future.
c. AWOS
Broadcasts. Computer-generated voice is used in AWOS to
automate the broadcast of the minute-by-minute weather
observations. In addition, some systems are configured to
permit the addition of an operator-generated voice message;
e.g., weather remarks following the automated parameters.
The phraseology used generally follows that used for other
weather broadcasts. Following are explanations and examples
of the exceptions.
1.
Location and Time. The location/name and the phrase
"AUTOMATED WEATHER OBSERVATION," followed by the time are
announced.
(a)
If the airport's specific location is included in the
airport's name, the airport's name is announced.
EXAMPLE-
"Bremerton National Airport automated weather observation,
one four five six zulu;"
"Ravenswood
Jackson County Airport automated weather observation, one
four five six zulu."
(b)
If the airport's specific location is not included in
the airport's name, the location is announced followed by
the airport's name.
EXAMPLE-
"Sault Ste. Marie, Chippewa County International Airport
automated weather observation;"
"Sandusky, Cowley Field automated weather observation."
(c)
The word "TEST" is added following "OBSERVATION" when
the system is not in commissioned status.
EXAMPLE-
"Bremerton National Airport automated weather observation
test, one four five six zulu."
(d)
The phrase "TEMPORARILY INOPERATIVE" is added when the
system is inoperative.
EXAMPLE-
"Bremerton National Airport automated weather observing
system temporarily inoperative."
2.
Visibility.
(a)
The lowest reportable visibility value in AWOS is "less
than 1/4." It is announced as
"VISIBILITY LESS THAN ONE QUARTER."
(b)
A sensor for determining visibility is not included in
some AWOS. In these systems, visibility is not announced.
"VISIBILITY MISSING" is announced only if the system is
configured with a visibility sensor and visibility
information is not available.
3.
Weather. In the future, some AWOSs are to be configured
to determine the occurrence of precipitation. However, the
type and intensity may not always be determined. In these
systems, the word "PRECIPITATION" will be announced if
precipitation is occurring, but the type and intensity are
not determined.
4.
Ceiling and Sky Cover.
(a)
Ceiling is announced as either "CEILING" or "INDEFINITE
CEILING." With the exception of indefinite ceilings, all
automated ceiling heights are measured.
EXAMPLE-
"Bremerton National Airport automated weather observation,
one four five six zulu. Ceiling two thousand overcast;"
"Bremerton National Airport automated weather observation,
one four five six zulu. Indefinite ceiling two hundred,
sky obscured."
(b)
The word "Clear" is not used in AWOS due to limitations
in the height ranges of the sensors. No clouds detected is
announced as "NO CLOUDS BELOW XXX" or, in newer systems as
"CLEAR BELOW XXX" (where XXX is the range limit of the
sensor).
EXAMPLE-
"No clouds below one two thousand."
"Clear below one two thousand."
(c)
A sensor for determining ceiling and sky cover is not
included in some AWOS. In these systems, ceiling and sky
cover are not announced. "SKY CONDITION MISSING" is
announced only if the system is configured with a ceilometer
and the ceiling and sky cover information is not available.
5.
Remarks. If remarks are included in the observation, the
word "REMARKS" is announced following the altimeter setting.
(a)
Automated "Remarks."
(1)
Density Altitude.
(2)
Variable Visibility.
(3)
Variable Wind Direction.
(b)
Manual Input Remarks. Manual input remarks are prefaced
with the phrase "OBSERVER WEATHER." As a general rule the
manual remarks are limited to:
(1)
Type and intensity of precipitation.
(2)
Thunderstorms and direction; and
(3)
Obstructions to vision when the visibility is 3 miles or
less.
EXAMPLE-
"Remarks ... density altitude, two thousand five hundred ...
visibility variable between one and two ... wind direction
variable between two four zero and three one zero
...observed weather ... thunderstorm moderate rain showers
and fog ... thunderstorm overhead."
(c)
If an automated parameter is "missing" and no manual
input for that parameter is available, the parameter is
announced as "MISSING." For example, a report with the dew
point "missing" and no manual input available, would be
announced as follows:
EXAMPLE-
"Ceiling one thousand overcast ... visibility three ...
precipitation ... temperature three zero, dew point missing
... wind calm ... altimeter three zero zero one."
(d)
"REMARKS" are announced in the following order of
priority:
(1)
Automated "REMARKS."
[a]
Density Altitude.
[b]
Variable Visibility.
[c]
Variable Wind Direction.
(2)
Manual Input "REMARKS."
[a]
Sky Condition.
[b]
Visibility.
[c]
Weather and Obstructions to Vision.
[d]
Temperature.
[e]
Dew Point.
[f]
Wind; and
[g]
Altimeter Setting.
EXAMPLE-
"Remarks ... density altitude, two thousand five hundred ...
visibility variable between one and two ... wind direction
variable between two four zero and three one zero ...
observer ceiling estimated two thousand broken ... observer
temperature two, dew point minus five."
d.
Automated Surface Observing System (ASOS)/Automated Weather
Sensor System (AWSS). The ASOS/AWSS is the primary
surface weather observing system of the U.S. (See Key to
Decode an ASOS/AWSS (METAR) Observation, FIG
7-1-8 and FIG
7-1-9.) The program to install
and operate these systems throughout the U.S. is a joint
effort of the NWS, the FAA and the Department of Defense.
AWSS is a follow-on program that provides identical data as
ASOS. ASOS/AWSS is designed to support aviation operations
and weather forecast activities. The ASOS/AWSS will provide
continuous minute-by-minute observations and perform the
basic observing functions necessary to generate an aviation
routine weather report (METAR) and other aviation weather
information. The information may be transmitted over a
discrete VHF radio frequency or the voice portion of a local
NAVAID. ASOS/AWSS transmissions on a discrete VHF radio
frequency are engineered to be receivable to a maximum of 25
NM from the ASOS/AWSS site and a maximum altitude of 10,000
feet AGL. At many locations, ASOS/AWSS signals may be
received on the surface of the airport, but local conditions
may limit the maximum reception distance and/or altitude.
While the automated system and the human may differ in their
methods of data collection and interpretation, both produce
an observation quite similar in form and content. For the
"objective" elements such as pressure, ambient temperature,
dew point temperature, wind, and precipitation accumulation,
both the automated system and the observer use a fixed
location and time-averaging technique. The quantitative
differences between the observer and the automated
observation of these elements are negligible. For the
"subjective" elements, however, observers use a fixed time,
spatial averaging technique to describe the visual elements
(sky condition, visibility and present weather), while the
automated systems use a fixed location, time averaging
technique. Although this is a fundamental change, the manual
and automated techniques yield remarkably similar results
within the limits of their respective capabilities.
1.
System Description.
(a)
The ASOS/AWSS at each airport location consists of four
main components:
(1)
Individual weather sensors.
(2)
Data collection and processing units.
(3)
Peripherals and displays.
(b)
The ASOS/AWSS sensors perform the basic function of data
acquisition. They continuously sample and measure the
ambient environment, derive raw sensor data and make them
available to the collection and processing units.
2.
Every ASOS/AWSS will contain the following basic set of
sensors:
(a)
Cloud height indicator (one or possibly three).
(b)
Visibility sensor (one or possibly three).
(c)
Precipitation identification sensor.
(d)
Freezing rain sensor (at select sites).
(e)
Pressure sensors (two sensors at small airports; three
sensors at large airports).
(f)
Ambient temperature/Dew point temperature sensor.
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