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NOAA's AVIATION WEATHER SERVICES

October 16, 2002 —The latest weather forecast is crucial for both pilots and air traffic controllers in making the right decisions about whether to fly or not. The NOAA National Weather Service uses a combination of high-technology and skilled meteorologists to develop aviation weather forecasts for each flight in the United States, and for two-thirds of air traffic around the globe.

Behind the Scenes in Aviation Weather Forecasting
NOAA issues a total average of nearly 4,000 aviation weather forecasts each day (Click here for Aviation Weather Data and Products Flow Chart).

NOAA Weather Forecast Offices: The 121 NWS weather forecast offices issue close to 2,500 aviation weather forecasts to 537 airports around the nation every day. The local offices also issue nearly 1,300 en route flight forecasts a day.
Aviation Weather Centers: Meteorologists at the AWC in Kansas City, Mo., and the Alaska Aviation Weather Unit in Anchorage issue a combined 275 weather products — forecasts, warnings and advisories — daily (The Weather Forecast Offices in Honolulu, Hawaii, and Guam are international Meteorological Watch Offices and issue aviation forecasts and advisories).
Center Weather Service Unit: Additionally, CWSU meteorologists — four positioned at each of the 21 FAA Air Route Traffic Control Centers across the country — provide in-person guidance to air traffic controllers about threatening weather conditions as they happen.

Creating Aviation Weather Forecasts
To generate aviation weather forecasts, meteorologists at the AWC, AAWU and other weather forecast offices in the Pacific (i.e., Guam and Hawaii) use images from satellites circling the globe, improved model data from the NOAA National Centers for Environmental Prediction, real-time weather data from Doppler radar, and Automated Surface Observation System units at America's airports, ASOS provides minute-by-minute updates on vital weather information, including cloud heights, wind speed and precipitation. That information is available to forecasters around the clock.

Background
On Dec. 17, 2003, the world will celebrate the 100^th anniversary of the first powered flight by the Wright Brothers. Before their historic flight, the Wright Brothers used weather information provided by the Weather Bureau to select Kitty Hawk, N.C., as their flight test site. On December 1, 1918, the first government route forecast was issued for aviation. The forecast was issued for the Aerial Mail Service route between New York City and Chicago. Since 1918, the Weather Bureau and the National Weather Service have provided aviation observations and forecasts in support of general aviation, commercial airlines and space exploration.

The Aviation Weather Center
The AWC is one of nine national service centers under the management of the NCEP and focuses exclusively on aviation. The other eight national centers are the Climate Prediction Center, Environmental Modeling Center, Hydrometeorological Prediction Center, Marine Prediction Center, NCEP Central Operations, Space Environment Center, Storm Prediction Center and the Tropical Prediction Center. AWC operates 24 hours a day, seven days a week and is the primary source for domestic and international en-route weather information. Specifically, it enhances aviation safety by issuing accurate warnings, forecasts and analysis of (existing or imminent) hazardous weather for aircraft in flight and creates warnings for transmission to the aviation community. Warnings of flight hazards for all altitudes above the Earth's surface (such as turbulence, icing, thunderstorms, sand, dust and volcanic ash) and advisories for low clouds and reduced visibilities remain most critical for the protection of life and property over the United States and from the east coast of Asia eastward to the west coast of Europe and Africa. The Center also originates operational forecasts of weather conditions that will affect domestic and international interests out to two days for two thirds of the world's airspace. Through international agreement, the Center has responsibility to backup the London World Area Forecast Center with aviation products distributed through the WAFS. The Center also provides weather graphics and information to all foreign aircraft operating to and from the United States through it's International Flight Folder Documentation Program. Furthermore, operational support within the AWC includes 24-hour problem identification and resolution services and electronic and workstation support. This internal support is in part an extension of the NCEP Central Operations.

The Center trains forecasters in the latest meteorological theories, develops and improves forecast techniques and evaluates data source and technology. AWC continues to collaborate with universities and federal research laboratories to investigate aviation weather hazards and develop new forecast techniques. The Center has developed strong partnerships with the Research Applications Program at the National Center for Atmospheric Research and with NOAA’s Forecast Systems Laboratory. Collaboration between these laboratories and agencies is coordinated through Product Development Teams supported by the FAA/Aviation Weather Research Program. AWC will help define new products, which are accessible to the pilot in the cockpit, as well as at the console of flight controllers and dispatchers. All this should help to increase weather awareness and economic efficiency in the national air space system, making the skies safer for the flying public.

AWC Products
The AWC issues a suite of products to support the safe and efficient utilization of both domestic and international airspace. These products include:

Convective SIGMETs — advisories for the contiguous 48 United States for thunderstorm hazards. These include thunderstorms in fast moving lines, thunderstorms embedded in other clouds (not visible to the naked eye) or severe thunderstorms, which produce tornadoes, hail, and/or strong wind gusts. Convective SIGMETs are valid for two hours and updated every hour.
SIGMET Warnings — warnings issued to notify pilots, dispatchers and air traffic controllers of weather hazards not associated with thunderstorms over the contiguous 48 United States and coastal waters. These warnings are of concern to all aircraft operating at all altitudes and are valid for up to four hours. They are issued for severe turbulence, severe icing, intense sand and/or dust storms, and volcanic ash cloud conditions.
International SIGMETs — warnings issued for thunderstorms, tropical cyclones and the same phenomena as domestic SIGMETs. These warning are of concern to all aircraft operating at all altitudes and are valid up to four hours (except for tropical cyclones and volcanic ash, which are valid for six hours).
AIRMET Advisories — advisories issued every six hours for low clouds and reduced visibility, strong surface winds, and less severe (but still hazardous) conditions for icing and turbulence and are applicable to all aircraft at risk operating below flight level 45,000 feet.
High Level Significant Weather Charts — a 24-hour forecast of weather charts displaying conditions above flight level (24,000 feet) pertaining to the location and speed of jet streams; areas, vertical extent and intensity of turbulence; areas and coverage of thunderstorms and their tops; tropopause heights and surface fronts. The charts also depict the location of tropical cyclones, volcanic eruptions and radiological discharges. The area covered by these forecasts extend from pole to pole and over two thirds of the globe's airspace.
Low Level Significant Weather Forecast Charts — weather charts covering the 48 contiguous United States and adjacent coastal waters, extending from the surface to 24,000 feet. These charts depict areas of low cloud ceilings and surface visibilities, turbulence, and freezing levels. The charts also show areas of Instrument Flight Rule (i.e., cloud ceilings less than 1,000 feet and/or surface visibility less than three miles) and Marginal Visual Flight Rule conditions (i.e., cloud ceilings from 1,000 feet to 3,000 feet and/or surface visibility from 3 to 5 miles) conditions.
Area Forecasts for the contiguous 48 United States — aviation forecasts, issued for six geographical areas three times a day. These forecasts contain a brief description of the location and movement of weather fronts and surface pressure systems, as well as descriptions of clouds and other weather conditions.
Area Forecasts for the Caribbean — a general aviation area forecast, including icing and turbulence information for the Gulf of Mexico, Caribbean Sea and southern portions of the North Atlantic Ocean. It is issued every six hours and includes AIRMET criteria for turbulence and icing.
Aviation and Marine Forecast for Northern Portions of the Gulf of Mexico — a general aviation area forecast issued for the northern portions of the Gulf of Mexico. It is issued twice a day (with updates issued as necessary) and contains AIRMET criteria for icing, turbulence and forecasts of very low clouds and extremely reduced visibility. Marine forecast information provided by the Tropical Prediction Center is also included in this forecast.
Collaborative Convective Forecast Product — a two to six hour outlook of thunderstorm activity over the contiguous 48 United States. This is a collaborative forecast product between the NWS, Federal Aviation Administration, and commercial airlines, which aims to reduce weather-related flight delays and cancellations. Specifically, this interactive forecast technique allows all three parties to agree on a weather forecast in an Internet chat room.
National Convective Weather Forecast Product — provides current convective hazards and one hour extrapolation forecasts of thunderstorm hazard locations. The hazard field and forecasts are updated every five minutes.
International Flight Folder Documentation Program — services provided as part of United States treaty obligations to the International Civil Aviation Organization, including provision of weather information to all arriving and departing international aircraft in the United States airspace from the Caribbean westward across the contiguous 48 states, Alaska, Hawaii, and U.S. territories in the Pacific Ocean. The program is operated 24 hours a day and seven days a week and includes both fax back and Internet services.
Current Icing Potential — a computer graphic which is an automatically generated index of current icing potential. The CIP can be used to supplement the NWS AIRMETs and SIGMETs, but does not substitute for the intensity and forecast information contained in them. CIP is a gridded icing diagnostic that updates hourly.

The Alaska Aviation Weather Unit and Anchorage Volcanic Ash Advisory Center:
The Alaska Aviation Weather Unit is a relatively new unit in the NWS, which became operational on Jan. 2, 1996. It is co-located with the Anchorage Weather Forecast Office and the Alaska River Forecast Center in Anchorage. AAWU is an international Meteorological Watch Office and produces domestic and international aviation warnings and forecasts. AAWU’s area of responsibility includes all of Alaska and portions of the North Pacific Ocean, Bering Sea, and Arctic Ocean, extending to the North Pole and a large area of northeast Russia. AAWU operates 24 hours a day, 7 days a week, with two forecasters on duty at all times.

The AAWU has also been designated one of nine Volcanic Ash Advisory Centers in the world. The VAACs are responsible for warning and advising aviation interests on hazards from volcanic eruptions and airborne volcanic ash.

AAWU Products

SIGMET Advisories — advisories issued to notify pilots, dispatchers and air traffic controllers of severe weather conditions of concern to all aircraft operating at or below 45,000 feet. SIGMETS are valid for up to four hours and are issued for significant thunderstorm activity, severe turbulence, severe icing, and volcanic eruptions. SIGMETs (valid for up to six hours with an additional 12 hour outlook) are also issued for volcanic ash cloud conditions and for tropical cyclones.
AIRMET Advisories — issued every six hours for less severe, but still hazardous conditions of concern to single engine, light twin-engine and jet aircraft that fly at lower altitudes. These conditions include moderate turbulence, moderate icing, Instrument Flight Rules (IFR) conditions, mountain obscuration, low level wind shear and strong surface winds.
Area Forecasts — issued for 25 separate zones over Alaska and coastal waters every six hours. The Area Forecast contains a brief description of the position of weather fronts and surface pressure systems.
Volcanic Ash Advisory — issued every six hours during a volcanic event (eruption and/or ash cloud) affecting the AAWU area of responsibility or northeastern Russia (north of 60° north latitude and east of 150° east longitude). The VAA provides information on the volcano, the eruption, the area and vertical extent of the ash cloud, a six hour forecast of volcanic ash area — plus an additional 12 hour outlook of the volcanic ash area.

The AAWU produces a suite of aviation weather graphics for Alaska. These graphics are disseminated into the FAA communications system and to the Internet:

The Graphic Area Forecast — is produced four times a day. This graphic package consists of four charts: surface, icing and freezing level, turbulence charts, and a chart showing areas of IFR, MVFR conditions, strong surface winds, and thunderstorms.
The Low Level Significant Weather Graphic — is a package of three charts produced twice a day. These charts depict 24, 36 and 48-hour forecasts of significant weather, including areas of IFR/MVFR, moderate or greater turbulence below 25,000 feet and forecast freezing levels.

Pacific Region
In the NWS’s Pacific Region, the weather forecast offices in Honolulu, Hawaii and Guam, share a unique responsibility. These two offices are also international Meteorological Watch Offices and produce domestic and international aviation warnings and forecasts. WFO Guam has Western Pacific SIGMET responsibility. WFO Honolulu is responsible for SIGMETs, AIRMETs, upper level wind and temperature forecasts, route forecasts and aviation area forecasts over the Central Pacific.

Weather Forecast Offices
In addition to their responsibilities of issuing public forecasts and weather warnings, each of the 121 NWS WFOs have a aviation forecast responsibility. The WFOs issue Terminal Aerodrome Forecasts for 537 airports. A TAF is a concise forecast of meteorological conditions expected at an airport during a specific time period — usually twenty-four hours. The TAF will contain information on expected surface winds, wind shear, surface visibility, weather phenomena and sky conditions. TAFs are issued four times a day and amended as required. These forecasts are used by a wide variety of aviation customers; including domestic and international commercial airlines, general aviation pilots, FAA air traffic controllers and FAA pilot weather briefers. WFOs also issue a transcribed weather broadcast forecast for more than 200 aircraft routes and local areas across the country. A TWEB route forecast is for a 50 nautical mile corridor along a line connecting the end points of a route. A TWEB local vicinity forecast covers an area within a fifty nautical mile radius of a point.

Center Weather Service Units
In 1977, the National Transportation Safety Board recommended establishing a better means of communicating vital weather information to pilots. Based on this recommendation, the FAA established Center Weather Service Units at each of the twenty-one Air Route Traffic Control Centers. The CWSUs are joint NWS/FAA weather support units, each staffed by four NWS meteorologists and FAA Traffic Management Unit personnel. The CWSU meteorologists provide weather consultation, forecasts and advisories to FAA managers and staff in the ARTCC and other FAA facilities. CWSU meteorologists issue Center Weather Advisories and Meteorological Impact Statements. A CWA is an advisory for aviation hazards within the ARTCC airspace and is valid for two hours. The MIS is an Air Traffic Control planning forecast for weather hazards, which could impact air traffic across the ARTCC airspace and is valid for a two to twelve hour period.

FAA Academy Instructors
Since 1961, the NWS has partnered with the FAA to provide weather training for FAA pilot weather briefers. Today, a staff of seven NWS employees is located at the Mike Monroney Aeronautical Center in Oklahoma City, Okla. Their mission is to provide weather training for FAA air traffic controllers, certify FAA specialists at Flight Service Stations to perform pilot weather briefer tasks, write weather reference materials, and administer NWS certification examinations for FAA pilot weather briefers and airport tower visibility observers.

Spaceflight Meteorology Group
The Weather Bureau and the NWS have provided direct weather support to the National Aeronautics and Space Administration for the Mercury, Gemini, Apollo, Space Shuttle and other programs. When the Manned Space Center opened in Houston in 1962, a contingent of Weather Bureau employees went to Houston to provide spacecraft recovery weather support. In the 1960s and 1970s, the Spaceflight Meteorology Branch of the Weather Bureau consisted of offices at the Johnson Space Center in Houston, Texas, Cape Canaveral, Fla., and at Weather Bureau offices in Miami, Fla., Honolulu, Hawaii, and the District of Columbia. In the late 1970s, NASA allowed each center to select its weather support structures. At that time, the Kennedy Space Center opted to use the U.S. Air Force for weather support, while JSC opted to retain the NWS for weather support services.

The Spaceflight Meteorology Group meteorologists provide unique weather support to the U.S. Human Spaceflight effort by providing weather forecasts and briefings to NASA personnel, providing pre- and post-spaceflight weather analyses and documentation, advising the JSC community of adverse weather impacting the JSC complex, and serving as meteorological consultants to the JSC community for current and future spaceflight endeavors.

Photo of NOAA aircraft superimposed on aviation map.
Since 1918, the Weather Bureau and the NWS have been providing aviation services for the protection of life and property and the enhancement of the national economy. The NWS has and will continue to work to ensure the most current meteorological theories and information are available for the aviation community.