NEXRAD RADAR RAINFALL ESTIMATE
Sept 29th-Oct 1st 2010
The Synoptic Setup (Surface)
|In the Caribbean, a broad area of disturbed weather and disorganized low pressure lingered behind the recently dissipated Tropical Storm Nicole. At the same time, a cold front had made it's way across the Appalachian Mountains, and by Sunday night had become a stationary boundary stalled over the eastern Carolinas as a series of waves of low pressure developed along it.|
A deep plume of moisture along the East Coast of the United States developed on Thursday, the 30th of September. The moisture was associated with the remnants of Tropical Storm Nicole. This moisture was being drawn northward by a deep upper-level low pressure area over the eastern United States. The combined system produced a widespread heavy rainfall all along the East Coast.
The 850 hPa winds show an atypically strong low-level jet (LLJ). Wind anomalies with the surge of high PW air exceed 6 standard deviations above normal. This indicates the potential for a significant “event”. Notice that the more favorable time of strongest anomalies were during the timing of two periods of heavy rainfall (image E and G).
Significant moisture plume from south to north from the Caribbean to the Mid Atlantic Region.
Within this plume of rich tropical moisture, vigorous convective cells were developing over the warm waters of the Gulf Stream and then feeding northward. Enhanced Satellite IR channel data revealed features with cloud top IR brightness temperatures in the -80º to -88º C range (light to dark purple color enhancement).
Notice the fairly narrow heavier bands of rain (red color) bands that over time move over sections of eastern Virginia. These would continue to fall over the same locations (training effect), leading to flooded areas.
Notice how the heavier bands continued to move over eastern Virginia…allowing for significant rainfall to fall over the region w/in a 24 hour period.
Windsor, NC Flooding Photos
Franklin, Va River Gauge