quality of exhibits. Karl Pfeiffer, representing the Nominating Committee, announced the results of the elections for the 1995-96 chapter officers. The new officers are Ron Przybylinski of the NWS St. Louis, president; Rich Woodford of United States Air Force Technical Applications Center (USAFETAC), vice president; Norm Modlin of USAFETAC, secretary; and Sean Nolan of St. Louis University, treasurer. The guest speaker for the evening A Global Numerical was Jim Wilson of the National Center for Atmospheric Research (NCAR). He Prediction for Apollo 13 spoke briefly on the evolution of avia- tion weather. According to Wilson, there were not many technological advances The first global numerical in the area of aviation weather until a analysis and prediction to be few years ago. The 1975 airliner crash made under operational con- at the JFK Airport began the advances. ditions were produced by the Ted Fujita, suspecting that a gust front Weather Bureau, ESSA, on 16 April was the culprit, convinced the National 1970. The prediction, made at the Na- Science Foundation and NCAR to field tional Meteorological Center, was for the NIMROD (Northern Illinois Mete- the guidance of the Spaceflight Meteorology Group in support orogical Research on Downbursts) of the unscheduled splashdown at 21.6° south latitude, 165.4° project. During the project, three radars west longitude of Apollo 13 the following day. were set out in the Chicago area and The prediction model was barotropic, formulated using the these identified, in May 1978, a so-called primitive equations. The model was designed by microburst for the first time. Research- Vanderman to aid in the development of numerical systems ers theorized that a microburst, not a for global predictions with primitive equations. It was cast in a gust front, led to the JFK crash. How- grid of 7082 points separated regularly by 3° in latitude and ever, some experts still were not con- longitude. The model produced 36-hr forecasts of the wind vinced about the existence of micro- and height fields at 500 mb over the whole globe. bursts. The initial analysis was produced using a system devel- To study the issue, Wilson stated oped by Maj. Thomas W. Flattery of the U.S. Air Force at that researchers set up another project, Operating Location 10, Air Weather Service, as part of the called JAWS (Joint Airport Weather cooperative Weather Bureau-Air Weather Service effort in Services), this time in the Denver area, numerical modeling. Flattery's system fits Hough functions putting radars closer together. When (solutions of the linear tidal equation) to global data. All funding for the project ran out, JAWS available data at 500 mb for both hemispheres were used. In was in jeopardy. But then, after a Pan Am addition to conventional synoptic data, aircraft winds and flight crashed in New Orleans, the Fed- heights obtained from satellite infrared spectrometer (SIRS) eral Aviation Administration decided to data from Nimbus III were available for the Northern Hemi- contribute funds to keep the study go- sphere. In all, 602 height observations and 679 wind observa- ing. tions were used, including 28 heights and 78 winds in the According to Wilson, researchers Southern Hemisphere. found that microbursts are a low-level phenomeno n driven by rain and downdraft processes. They typically Bull. Amer. Meteor. Soc., 51,594. have velocity differentials of 60-70 knots. Microbursts cause aircraft to experience head winds followed by tre- mendous tail winds that cause aircraft that encounter the microbursts to crash. With the PanAm crash, confusing LLWAS (Low-Level Wind Sheer Alert System) displays contributed to the crash. This led to the use of Doppler radar to alert aircrews to expect microbursts and wind shear events. With intensive education on the microburst phenomenon, today's pilots save many aircraft and lives. The future will bring on-line the TDWR, an extremely fine detection radar, as well as other interesting products and systems to help air traffic control efforts, in conjunction with Lincoln Labs and NCAR, to improve aviation safety.—Lauraleen O'Connor. • Bulletin of the American Meteorological Society
Bulletin of the American Meteorological Society – American Meteorological Society
Published: Jul 1, 1995
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