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AIM

10/12/17

7−1−5

Meteorology

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 observa-

tions; for example, contract towers and airport
operators may be approved by the Feder

al

Government to provide weather observations.

2. Enhanced Weather Information System

(EWINS). An EWINS is an FAA authorized,

proprietary system for tracking, evaluating, report-

ing, and forecasting the presence or lack of adverse

weather phenomena. The FAA authorizes a certifi-

cate holder to use an EWINS 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 Flight Standards Information Management

System 8900.1.

3. Commercial Weather Information

Providers. In general, commercial providers pro-

duce 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 propri-

etary weather products that substantially alter the

information contained in government−produced

products. However, those proprietary weather

products that substantially alter government−pro-

duced 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.

7−1−4. Graphical Forecasts for Aviation

(GFA)

a. The GFA website is intended to provide the

necessary aviation weather information to give users

a complete picture of the weather that may affect

flight in the continental United States (CONUS). The

website includes observational data, forecasts, and

warnings that can be viewed from 14 hours in the past

to 15 hours in the future, including thunderstorms,

clouds, flight category, precipitation, icing, turbu-

lence, and wind. Hourly model data and forecasts,

including information on clouds, flight category,

precipitation, icing, turbulence, wind, and graphical

output from the National Weather Service’s (NWS)

National Digital Forecast Data (NDFD) are available.

Wind, icing, and turbulence forecasts are available in

3,000 ft increments from the surface up to 30,000 ft

MSL, and in 6,000 ft increments from 30,000 ft MSL

to 48,000 ft MSL. Turbulence forecasts are also

broken into low (below 18,000 ft MSL) and high (at

or above 18,000 ft MSL) graphics. A maximum icing

graphic and maximum wind velocity graphic

(regardless of altitude) are also available. Built with

modern geospatial information tools, users can pan

and zoom to focus on areas of greatest interest. Target

users are commercial and general aviation pilots,

operators, briefers, and dispatchers.

b. Weather Products.

1. The Aviation Forecasts include gridded

displays of various weather parameters as well as

NWS textual weather observations, forecasts, and

warnings. Icing, turbulence, and wind gridded

products are three−dimensional. Other gridded

products are two−dimensional and may represent a

“composite” of a three−dimensional weather phe-

nomenon or a surface weather variable, such as

horizontal visibility. The following are examples of

aviation forecasts depicted on the GFA: 

(a) Terminal Aerodrome Forecast (TAF)
(b) Ceiling & Visibility (CIG/VIS)
(c) Clouds
(d) Precipitation / Weather (PCPN/WX)
(e) Thunderstorm (TS)
(f) Winds
(g) Turbulence
(h) Ice