Session 12A.4 Severe storm environments on different continents

Wednesday, 13 October 2010: 2:30 PM
Grand Mesa Ballroom F (Hyatt Regency Tech Center)
Daniel J. Cecil, University of Alabama, Huntsville, AL; and M. O. Felix and C. B. Blankenship

Presentation PDF (2.5 MB)

Extremely low passive microwave satellite brightness temperatures have been empirically matched to reports of large hail in the U.S. This forms the basis for interpreting maps of extremely low brightness temperature events as hailstorm climatologies, and examining the environments accompanying these storms. In this study, we use reanalysis data to compare and contrast severe storm composite environments for active regions of North America, South America, Africa, and Central Asia. We also compare and contrast environments associated with the lowest brightness temperatures (those most likely to have large hail, or to have larger hailstones) to those associated with slightly higher brightness temperatures (analogous to a comparison between "severe" and "significant severe" weather events). Initial work with storms from Northern Argentina and adjacent parts of South America show that the lowest brightness temperature storms tend to be located near the equatorward entrance region of an upper level jet in NCEP-NCAR Reanalysis data. They also tend to be near the nose of a low-level jet, with Lifted Indices near -6. Weaker storms are associated with similar synoptic features, but they are less well-defined in the composites and have slightly less thermodynamic instability. Broad storms producing heavy rainfall are associated with the strongest large-scale dynamic forcing, with weaker thermodynamic instability.
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