Aviation Weather Services

any associated with lesser rates of precipitation. Turbulence • Graphical cloud tops (CLD TOPS) should be expected to occur near convective activity, even • Graphical lightning strikes (LTNG) in clear air. Thunderstorms are a form of convective activity • Graphical storm cell movement (CELL MOV) that imply severe or greater turbulence. Operation within 20 miles of thunderstorms should be approached with great • NEXRAD radar coverage (information displayed with caution, as the severity of turbulence can be much greater than the NEXRAD data) the precipitation intensity might indicate. • SIGMETs/AIRMETs (SIG/AIR) • Surface analysis to include city forecasts (SFC) Weather Avoidance Assistance To the extent possible, controllers will issue pertinent • County warnings (COUNTY) information on weather and assist pilots in avoiding such • Freezing levels (FRZ LVL) areas when requested. Pilots should respond to a weather advisory by either acknowledging the advisory or by • Hurricane track (CYCLONE) acknowledging the advisory and requesting an alternative • Temporary flight restrictions (TFR) course of action as follows: • Request to deviate off course by stating the number Pilots must be familiar with any EFD or MFD used and the of miles and the direction of the requested deviation. data link weather products available on the display. • Request a new route to avoid the affected area. Weather Products Age and Expiration • Request a change of altitude. The information displayed using a data link weather link is • Request radar vectors around the affected areas. near real time but should not be thought of as instantaneous, up-to-date information. Each type of weather display is stamped with the age information on the MFD. The time is The controller’s primary function is to provide safe separation referenced from Zulu when the information was assembled at between aircraft. Any additional service, such as weather the ground station. The age should not be assumed to be the avoidance assistance, can only be provided to the extent time when the FIS received the information from the data link. that it does not detract from the primary function. It’s also worth noting that the separation workload is generally greater Two types of weather are displayed on the screen: “current” than normal when weather disrupts the usual flow of traffic. weather and forecast data. Current information is displayed ATC radar limitations and frequency congestion may also by an age while the forecast data has a data stamp in the form be a factor in limiting the controller’s capability to provide of “__ / __ __ : __.” [Figure 13-16] additional service. The Next Generation Weather Radar System Electronic Flight Displays (EFD) /Multi- (NEXRAD) Function Display (MFD) Weather The NEXRAD system is comprised of a series of 159 Weather Many aircraft manufacturers now include data link weather Surveillance Radar–1988 Doppler (WSR-88D) sites situated services with new electronic flight display (EFD) systems. throughout the United States, as well as selected overseas EFDs give a pilot access to many of the data link weather sites. The NEXRAD system is a joint venture between the services available. United States Department of Commerce (DOC), the United States DOD, as well as the United States Department of Products available to a pilot on the display pictured in Transportation (DOT). The individual agencies that have Figure 13-15 are listed as follows. The letters in parentheses control over the system are the NWS, Air Force Weather indicate the soft key to press in order to access the data. Agency (AFWA) and the FAA. [Figure 13-17] • Graphical NEXRAD data (NEXRAD) NEXRAD data for up to a 2,000 mile range can be displayed. • Graphical METAR data (METAR) It is important to realize that the radar image is not real time • Textual METAR data and can be up to 5 minutes old. The NTSB has reported on 2 fatal accidents where in-cockpit NEXRAD mosaic imagery • Textual terminal aerodrome forecasts (TAF) was available to pilots operating near quickly-developing and • City forecast data fast-moving convective weather. In one of these accidents, • Graphical wind data (WIND) the images were from 6 to 8 minutes old. In some cases, NEXRAD data can age significantly by the time the mosaic • Graphical echo tops (ECHO T,,,OPS) image is created. In some extreme latency cases, the actual 13-18