Chapter 7. Safety of Flight
Section 1. Meteorology

7-1-1. National Weather Service Aviation
Weather Service Program

a. Weather service to aviation is a joint effort of the
National Oceanic and Atmospheric Administration
(NOAA), the National Weather Service (NWS), the
Federal Aviation Administration (FAA), Department
of Defense, and various private sector aviation
weather service providers. Requirements for all
aviation weather products originate from the FAA,
which is the Meteorological Authority for the U.S.
b. NWS meteorologists are assigned to all air
route traffic control centers (ARTCC) as part of the
Center Weather Service Units (CWSU) as well as the
Air Traffic Control System Command Center
(ATCSCC). These meteorologists provide special-
ized briefings as well as tailored forecasts to support
the needs of the FAA and other users of the NAS.

c. Aviation Products

1. The NWS maintains an extensive surface,
upper air, and radar weather observing program; and
a nationwide aviation weather forecasting service.

2. Airport observations (METAR and SPECI)
supported by the NWS are provided by automated
observing systems.

3. Terminal Aerodrome Forecasts (TAF) are

prepared by 123 NWS Weather Forecast Offices

(WFOs) for over 700 airports. These forecasts are

valid for 24 or 30 hours and amended as required.

4. Inflight aviation advisories (for example,
Significant Meteorological Information (SIGMETs)
and Airmen's Meteorological Information (AIR-
METs)) are issued by three NWS Meteorological
Watch Offices; the Aviation Weather Center (AWC)
in Kansas City, MO, the Alaska Aviation Weather
Unit (AAWU) in Anchorage, AK, and the WFO in
Honolulu, HI. Both the AWC and the AAWU issue
area forecasts (FA) for selected areas. In addition,
NWS meteorologists assigned to most ARTCCs as
part of the Center Weather Service Unit (CWSU)
provide Center Weather Advisories (CWAs) and

gather weather information to support the needs of
the FAA and other users of the system.

5. Several NWS National Centers for Environ-
mental Production (NCEP) provide aviation specific
weather forecasts, or select public forecasts which are
of interest to pilots and operators.
(a) The Aviation Weather Center (AWC)
displays a variety of domestic and international
aviation forecast products over the Internet at
aviationweather.gov.
(b) The NCEP Central Operations (NCO) is
responsible for the operation of many numerical
weather prediction models, including those which
produce the many wind and temperature aloft
forecasts.
(c) The Storm Prediction Center (SPC) issues
tornado and severe weather watches along with other
guidance forecasts.

(d) The National Hurricane Center (NHC)
issues forecasts on tropical weather systems (for
example, hurricanes).

(e) The Space Weather Prediction Center
(SWPC) provides alerts, watches, warnings and
forecasts for space weather events (for example, solar
storms) affecting or expected to affect Earth's
environment.

(f) The Weather Prediction Center (WPC)

provides analysis and forecast products on a national

scale including surface pressure and frontal analyses.

6. NOAA operates two Volcanic Ash Advisory
Centers (VAAC) which issue forecasts of ash clouds
following a volcanic eruption in their area of
responsibility.

7. Details on the products provided by the above
listed offices and centers is available in FAA
Advisory Circular 00-45, Aviation Weather Services.
d. 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