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AIM

10/12/17

7−1−1

Meteorology

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