k. Not all sources of aviation weather information are able to provide all three types of weather 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
observations; for example, contract towers and airport operators may be approved by the Federal Government
to provide weather observations.
2. Enhanced Weather Information System (EWINS). An EWINS is an FAA authorized, proprietary
system for tracking, evaluating, reporting, and forecasting the presence or lack of adverse weather phenomena.
The FAA authorizes a certificate 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 produce 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 proprietary weather products that substantially alter the
information contained in government-produced products. However, those proprietary weather products that
substantially alter government-produced 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, turbulence, 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 phenomenon 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)

7-1-6

Meteorology