This brochure is designed to help you use the NATIONAL AVIATION WEATHER
SYSTEM to the fullest extent possible. The information and services described
here are available from the National Weather Service (NWS), the Federal
Aviation Administration (FAA), and information service companies.
For more detailed weather information consult AVIATION WEATHER (FAA Advisory
circular 00-6A); AVIATION WEATHER SERVICES (FAA Advisory Circular 00-45);
and the AIRMAN'S INFORMATION MANUAL, (Chapter 7, Safety of Flight). These
publications are available at local government bookstores and from the Superintendent
of Documents, U.S. Government Printing Office, Washington, D.C. 20402.
The following is a list of abbreviations and acronyms used in this brochure:
Preparation for your weather briefing:
A.M. WEATHER is a 15-minute television weather program designed for pilots
and can be seen on more than 300 PBS stations Monday through Friday mornings.
Check your local TV listings for exact time and station.
Meteorological and aeronautical information is provided by continuous
recorded Transcribed Weather Broadcasts (TWEB), the
Pilot's Automatic Telephone Answering Service (PATWAS), and the
Telephone Information Briefing Service (TIBS). Complete
weather information is available by telephone call or visit to the nearest
FAA Flight Service Station (FSS) or designated NOAA
Weather Service Office. Information is also available from private
commercial vendors. During periods of marginal weather, briefers are busy
and telephone delays may occur. While waiting for the briefer, you may get
basic information from TWEBs, PATWAS, or TIBS - - but do continue to wait
for the briefer. The latest hourly aviation weather observations from distant
stations are normally available by 5 minutes past the hour.
Pilots may obtain Federal pre-flight weather briefings tailored to your
individual needs. Any one of three types of briefings may be requested:
standard, abbreviated or outlook.
A standard briefing should normally be requested even
when you have received prerecorded or mass media weather information (e.g.,
TWEB, A.M. WEATHER, etc.). After giving the briefer the necessary background
information, you will automatically receive the following:
* Not provided by NWS briefers
An abbreviated briefing should be requested if you have
used prerecorded or mass media weather information to make a go/no-go decision
and only selected additional information is required. You should provide
the pertinent background information, tell the briefer what previous information
source you have used, and ask for an abbreviated briefing with specified
observation or forecast products.
An outlook briefing should be requested for long-range
flight planning. This briefing contains forecasts for a flight beginning
more than 6 hours in the future. An abbreviated or standard briefing should
then be obtained when closer to the time of departure.
For your pre-flight weather briefing, give the briefer the following
Type of flight VFR, IFR or DVFR
After receiving weather information, either for short or long-range flights,
consider carefully if conditions are suitable for your intended flight.
During marginal VFR or IFR conditions, keep a particularly close check
on en route, terminal and alternate airport weather. Routine weather information
is available by radio from any FAA FSS. Selected FSSs broadcast In-flight
Advisories (SIGMETs, Convective SIGMETs, Center Weather Advisories [CWAs],
Alert Weather Watches [AWW] and AIRMETs) and severe weather information.
TWEBs also can be received while airborne. Pilots should monitor Hazardous
In-flight Weather Advisory Service (HIWAS) weather broadcasts routinely.
See the Airport/Facility Directory (A/FD) and aeronautical charts
for frequencies. Do not hesitate to request specific information from the
En Route Flight Advisory Service (EFAS) - "Flight Watch" - on
122.0 MHZ below 18,000 feet MSL. See the A/FD for high altitude frequencies.
In-flight briefing procedures are explained in detail in the Airman's
Prior to descent, request current weather for the terminal area and conditions
at your destination airport. At many airports, this information is continuously
broadcast on ATIS, ASOS, AWOS, or selected navigation aids. These broadcasts
reduce pilot and controller communications workloads.
CEILING AND VISIBILITY CATEGORIES
EXAMPLE OF TERMINAL FORECAST:
DCA 221010 10 SCT C18 BKN 5SW- 3415G25 OCNL C8 X ½ SW.
12Z C50 BKN 3312G22.
04Z MVFR CIG..
Decoded Example: Washington National Airport for the 22nd of the
month valid from 10Z to 10Z. Scattered clouds at 1000 feet, ceiling 1800
feet broken, visibility 5 miles in light snow showers, surface wind 340
degrees at 15 knots, gusts to 25 knots. Occasional ceiling 800 feet, sky
obscured, visibility one-half mile in moderate snow showers. By 12Z becoming
ceiling 5000 feet broken, surface wind 330 degrees at 12 knots, gusts to
22 knots. The categorical outlook for the last 6 hours beginning at 04Z
calls for marginal VFR conditions due to ceiling.
AREA FORECASTS (FA) provide an 18-hour synopsis of expected weather
patterns; a 12-hour forecast of VFR cloud cover, weather and visibility;
and a 6-hour categorical outlook. FAs are prepared 3 times a day (4 times
a day in Alaska and Hawaii) and are supplemented and updated by SIGMETs,
AIRMETs, and by FA amendments. Heights in the FA are above mean sea level
(MSL) unless stated as above ground level (AGL). Ceilings (CIG) are always
WIND and TEMPERATURE ALOFT FORECASTS (FD) are 6, 12, and 24-hour
forecasts of wind direction, speed, and temperatures for selected altitudes
to 53,000 feet MSL at specified locations. Direction is relative to true
north rounded to the nearest 10 degrees. Speed is in knots. Temperatures
aloft (in degrees Celsius) are included with wind data for all but the 3000-foot
MSL level and those levels within 2500 feet of the ground. Temperatures
above 24,000 feet MSL are always negative. Winds at other locations and
altitudes can be obtained by interpolation.
Decoded example: For Atlantic City, N.J., at 6000 feet MSL wind
from 280 degrees true at 33 knots, temperature 2 degrees Celsius.
IN-FLIGHT ADVISORIES warn pilots of potentially hazardous weather.
They include SIGMETs, CONVECTIVE SIGMETs, AIRMETs, and Center Weather Advisories
(CWA). SIGMETs warn of hazardous conditions of importance to all
aircraft i.e. severe icing or turbulence, duststorms, sandstorms, and volcanic
ash. AIRMETs warn of less severe conditions which may be hazardous
to some aircraft or pilots. SIGMETs are issued as needed. AIRMET bulletins
are issued routinely and supplement the Area Forecast (FA). CONVECTIVE
SIGMETs are issued hourly for thunderstorms in the continuous U.S. Center
Weather Advisories, issued as needed, are detailed advisories of conditions
which meet or approach SIGMET or AIRMET criteria.
EXAMPLE OF SIGMET:
Decoded Example: SIGMET OSCAR 2 is valid until 2100Z on the 5th
day of the month. For Kansas and Nebraska from Pawnee City VORTAC to Oswego
VORTAC to Liberal VORTAC to Pawnee City VORTAC. Severe turbulence below
6000 feet expected due to strong northwesterly flow behind a coldfront.
Conditions continuing beyond 2100Z.
TRANSCRIBED WEATHER BROADCASTs (TWEB) are continuous broadcasts
of recorded NOTAM and weather information prepared for a 50-nautical mile
wide zone along a route and for selected terminal areas. TWEBs are broadcast
over selected NDB and VOR facilities and generally contain a weather synopsis,
in-flight advisories, route and/or local vicinity forecasts. Winds Aloft
Forecasts, current weather reports, NOTAMs, and special notices. TWEB outlets
are listed below by state:
VOR facilities (108.00 - 117.95 MHZ) have line-of-sight range.
NDB (L/MF) facilities (190 - 535 kHz) have varying ranges.
PILOT'S AUTOMATIC TELEPHONE WEATHER ANSWERING SERVICE (PATWAS),
and the TELEPHONE INFORMATION BRIEFING SERVICE (TIBS), provide continuous
recordings of weather and aeronautical information. The information may
include area and/or route briefings, airspace procedures, and special announcements.
Telephone numbers for PATWAS and TIBS locations are found in the Airport/Facility
TWEBs, PATWAS, and TIBS are for preflight or inflight planning and should
not be considered a substitute for formal preflight briefings.
From 50 miles south of Albuquerque to 30 miles north of Phoenix, 1210Z
to 1250Z, occasional Moderate Rime Ice, 10,000 feet, PA34.
NOTE: Pilots should report location(s), time (UTC or Z), intensity,
whether in or near clouds, altitude, type of aircraft and when applicable,
duration of turbulence. Duration may be based on time between two locations
or over a single location. All locations should be readily identifiable.
Over Omaha, 1232Z, Moderate Turbulence, in cloud, Flight Level 310, B767.
TORNADO (when augmented).