THE CWSU ENVIRONMENT
THE CWSU ENVIRONMENT
There are 21 Center Weather Service Units across the nation. By the way, CWSU is an abbreviation, not an acronym, since pronouncing the letters never really caught on. Each CWSU is located within the confines of an ARTCC or Air Route Traffic Control Center. ARTCCs provide air traffic control services to aircraft operating in between the nation's airports and their associated TRACON (Terminal Radar Approach Control) facilities. ARTCCs mainly serve aircraft on IFR flight plans operating at the higher altitudes, but also can serve smaller aircraft through VFR flight following. What is IFR and VFR? find out this and more here.
The catalyst that placed weather personnel in each ARTCC was the 1978 crash of Southern Airways flight number 242, which flew into a thunderstorm and crashed en-route to Atlanta. Both engines flamed out due to hail ingestion. The ensuing NTSB investigation suggested that Air Traffic Controllers needed a better way to receive timely weather information, hence the CWSU program was born.
Center Weather Service Units are comprised of National Weather Service meteorologists under contract to the FAA. Each CWSU provides meteorological support at least 16 hours per day, seven days per week, 365 days per year. Most CWSUs operate between 5 or 6 am and 9 or 10 pm. This period represents the peak hours of commercial air traffic within the continental United States. A handful of ARTCCs are busy overnight due to air cargo operations, such as Memphis and Indianapolis Centers, but CWSU coverage overnight is currently not available.
The emphasis of the ZME (Memphis) CWSU is service. Our main customer, the FAA Traffic Management Unit or TMU, needs to be kept abreast of the latest changes in current and forecast weather. ZME meteorologists provide two daily "standup" briefings for the benefit of TMU personnel, supervisors from each of the five 'areas' within ZME, facility management staff and Airway Facilities personnel. These briefings begin by highlighting areas of active weather, then proceed to alert participants to potential future weather impacts during their shift. The main impact for air traffic is thunderstorm activity, with icing and turbulence a secondary concern. Low cloud ceilings and poor visibility at the major hub airports is also a prime concern. Predicted wind speed and direction is also important at these hubs, since landing patterns are sensitive to wind speed and direction changes. The "acceptance rate", or number of aircraft a hub facility can handle per hour, can be seriously disrupted by a sudden change in wind speed or direction, often resulting in flight delays, even on days when the sky is crystal clear and blue. Clear air turbulence, commonly referred to as "cat", can also occur on a clear sky day and cause deviations in aircraft routings. No one likes a bumpy flight! Keeping aircraft out of these turbulent areas is challenging for meteorologists, but decision making tools are improving as computer power increases.
CWSU meteorologists also participate in the FAA Collaborative Decision Making process (CDM) by taking part in the CCFP, or Collaborative Convective Forecast Product. Collaborators currently include meteorologists from CWSU and most major commercial passenger and cargo airlines, along with representatives from Canada's Environmental Prediction Unit and from FAA's Air Traffic Control System Command Center (ATCSCC). The chat sessions are moderated by meteorologists from the National Weather Service's Aviation Weather Center (AWC). Each 30 minute chat begins with a proposed 2, 4 and 6 hour thunderstorm forecast chart displayed on an internet white board, which is subsequently discussed among the participants who are free to offer suggestions for changes. These changes may be annotated on the white board or relayed through text. Should an impasse arise, AWC meteorologists are responsible for making the final call, as the forecast was not intended to be a consensus. The final forecast product generated from these CCFP chat sessions becomes a key piece of information used by FAA Traffic Management personnel to formulate their Strategic Plan of Operations, which details how air traffic flows will be managed on any given day.
Meteorologists at the CWSUs also prepare two products, a Meteorological Impact Statement (MIS) and a Center Weather Advisory (CWA). The MIS product details weather expected to impact the safe and efficient flow of air traffic within the Center airspace within a 2 to 12 hour period. The CWA product is a short term nowcast, pinpointing hazardous weather already causing an impact or expected to cause an impact within a 2 hour period. The MIS is for planning purposes only, while the CWA is an in-flight advisory.
CWSU meteorologists use a variety of computer hardware to receive and review data. The main system used is called WARP, or Weather and Radar Processor. This system provides satellite, radar and computer model data, as well as alphanumeric data. Radar data flowing into the WARP system is now also being used to provide weather radar overlays on Air Traffic Controllers radar displays, or DSR. Computer model data received through WARP is being used to feed forecast wind information to the FAA's CCLD/URET system, which supports the FAA Free-Flight Program. CWSU meteorologists also possess a single screen AWIPs workstation, providing the same information available to their neighboring counterparts at the National Weather Service Weather Forecast Offices. This workstation allows a CWSU meteorologist to become familiar and proficient with the equipment used through the rest of the NWS, a definite plus if personnel decide to transfer. The Internet is also used quite extensively due to its proliferation of information regarding weather in general. It also serves as backup should the main systems fail.
The life of a CWSU meteorologist is similar to other weather professionals, feast or famine. When weather impacts any part of the Memphis ARTCC airspace, or the surrounding ARTCCs, the meteorologist is called upon to provide updates and short term forecasts. It can get rather hectic when thunderstorms block major air routes, therefore accurate and timely forecasts are a must. Since safety is a huge issue in the world of aviation, some of the information provided by the CWSU can be a matter of life and death. Examples include providing weather support to controllers dealing with VFR pilots trapped on top of cloud decks to assisting Traffic Management Coordinators during times when major airports are shut down by thunderstorms or other phenomena.
What's in the future? Well, everyone wants better forecasts. With computer processing power increasing, the ability to deliver timely and more accurate forecasts should improve resulting in better service to the FAA decision-makers, and hence safer and more efficient use of the National Airspace System.