92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012: 8:30 AM
Comparison Between GOES-12 Overshooting Top Detections, WSR-88D Radar Reflectivity and Severe Storm Reports
Room 256 (New Orleans Convention Center )
Richard Dworak, CIMSS/Univ. of Wisconsin, Madison, WI; and K. Bedka, J. Brunner, and W. Feltz

Studies have found that convective storms with overshooting top (OT) signatures in weather satellite imagery often produce hazardous weather such as heavy rainfall, tornadoes, damaging winds, and large hail. An objective satellite-based OT detection product has been developed using 11 μm infrared window (IRW) channel brightness temperatures (BTs). In this study, this method is applied to GOES-12 IRW data that is compared with ground-based weather radar data and severe storm reports over the eastern U.S. The goal of this effort is to improve forecaster understanding of satellite OT signatures relative to commonly available ground-based radar products, assess OT detection product accuracy, and demonstrate the utility of an OT detection product for diagnosing hazardous convective storms. The co-evolution of radar-derived products and satellite OT signatures indicates that an OT often corresponds with the highest radar echo top and relative maxima of precipitation aloft. Validation of OT detections relative to composite reflectivity indicates the lowest FAR values correspond to OTs with the coldest IRW BTs and with OT detected pixels over non-OT pixels for a similar IR BT. OTs were detected near 55% (32%) of reported severe weather events during the U.S. warm (cold) season, with 56% of OTs detected before the time of a severe weather report. The severe weather frequency increases with increasing overshooting magnitude and decreasing IRW BT. The relatively strong OT, severe weather, and heavy rainfall relationships suggest that an objective OT detection product can be used to increase forecaster confidence that a given storm is hazardous.

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