NSSL scientists to explore “bow echoes” in BAMEX: The Bow Echo and MCV EXperiment

Each year in the United States, damaging winds from thunderstorms pose a significant hazard to life and property. According to "Storm Data," from January 1995 to July 2000 over $1.4 billion in property damage, 72 deaths and 1,008 injuries were reported to the National Weather Service (NWS) as having been caused by such wind events. Particularly hazardous is a type of organized convective system popularly referred to as a "bow echo" (so named due to its characteristic bow shape on weather radar displays). First described in detail by Ted Fujita, bow echoes now represent one of the best-known modes of convective organization associated with severe weather events, especially for high surface winds.

Bow echoes can be quite extensive in length (over 300 km), last for several hours, and generate mid-level cyclonic vortices of diameters ~10-50 km (see also the companion article). Such mesovortices often consolidate and grow in scale to become a mesoscale convective vortex (MCV) with diameters ~100-200 km that persist long after the parent convective system has dissipated. Some MCV's re-initiate convective storms for several days thereafter as they travel distances of 1000 km or more. BAMEX, the Bow Echo and MCV EXperiment, seeks to understand both of these related mesoscale phenomena.

NSSL scientists Dave Jorgensen, Jeff Trapp (CIMMS), Brad Smull and Conrad Ziegler are joining with NCAR, NWS and University scientists as Principal Investigators (PI's) of BAMEX. One of the main goals of BAMEX, according to one of the PI's, Morris Weisman of NCAR, is to "understand the processes and improve prediction of systems that produce severe winds, through special data sets that can be used to initiate and validate numerical simulations." This and other goals can best be achieved through a highly mobile field experiment, given the fact that such systems are long-lived, affect extensive geographical areas, and can occur anywhere within a broad latitudinal band during the early warm season. Consequently, BAMEX observations will be collected via an airborne and a ground-based armada that will be deployed into several convective systems during May-July of 2003, the period bow echoes and MCV's occur most frequently. The proposed base of operations is St. Louis, Missouri. For more information contact Dave Jorgensen or Jeff Trapp at: davej@ucar.edu or jeff.trapp@nssl.noaa.gov.