Wednesday, 17 January 2007: 11:15 AM
Cool season heavy rainfall events over west central Florida
214A (Henry B. Gonzalez Convention Center)
On occasion west central Florida is affected by nearly stationary bands of precipitation with a procession of cells moving northeast from the Gulf of Mexico producing heavy coastal rains. Twenty two non-tropical cases of widespread coastal rains with at least 5 inches from September through May from 1948-2006 were chosen. These events typically occur every 2 to 7 years. Comparisons to longer term climate data indicates event frequency linked to ENSO with most occurrences during the neutral or warm phase. A third of the events occurred during the 1997-98 El Nino. NCEP Reanalysis Data were then utilized in composites to show general trends and anomalies. Radiosonde data were cross referenced to show thermodynamic profiles. The typical heavy rainfall day has surface low pressure to the west with an elongated east-west nearly stationary trough over Florida. A southerly flow brings deep moisture from south of Cuba with resulting precipitable water values increasing over 40 mm (1.57 in). Lifted index values are in the moderate (-1 to -3) range to produce convection. Above the surface, winds continue with a southerly component but veer more westward to 200 mb. The details of this study provide forecasters with a guide for predicting heavy rainfall events.