AIM
4/3/14
7−1−1
Meteorology
Chapter 7. Safety of Flight
Section 1. Meteorology
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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). Pilot weather briefings are pro-
vided by personnel at Flight Service Stations
operated by FAA (in Alaska) or by federal contract
facilities (elsewhere in the U.S.). 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), Automated
Surface Observing System (ASOS), and Automated
Weather Sensor System (AWSS).
REFERENCE
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AIM, Para 7
−1−12, Weather Observing Programs.
b.
Aerodrome forecasts are prepared by 122
Weather Forecast Offices (WFOs). These offices
prepare and distribute 625 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 or 30 hours and amended as
required. 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 (AIRMET−text bulletins [WA] and
graphics [G−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
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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.
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2. FAA Weather Services
a.
The FAA maintains a nationwide network of
Flight Service Stations (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 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.
REFERENCE
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AIM, Para 7
−1−4, Preflight Briefing, explains the types of preflight
briefings available and the information contained in each.