Blended TPW (produced by CIRA) assists with MIA flood forecast

The blended TPW product and associated anomaly increase the forecaster’s awareness for potential flooding rains.  One such event occurred from April 6-8, 2008, affecting the Miami, FL WFO.    Pablo Santos and staff forecasters had been tracking an area of moisture developing in the GOMEX and Caribbean.  The TPW anomaly product for early on April 6 shows abnormally high values mostly in mid-latitudes with tropical areas closer to normal for this time of year.  However, a small area to the west of FL indicated TPW anomalies of 200% with values over 2 inches for TPW itself.  A frontal boundary associated with a mid-latitude cyclone was pushing south into the GOMEX and FL, and the upper level analysis showed weak divergence aloft over FL.  This image of abnormally high moisture in the blended TPW provided additional lead time to forecasters that the rain event about to occur in the next 48 hours had a good potential of resulting in flooding. Over the course of the next 2 days the forcing from the boundary and the large TPW resulted in 5-10 inches of total precipitation over a large area due to training of cells.

Blended TPW for April 6, 2008 at 0500Z. Note the red area of 2 inches of TPW. This area was propagating toward Southern Florida.

The Blended TPW Anomaly shows that much of the mid-lattitude front pushing southward has TPW of 200% of normal although TPW values themselves are not extremely large. However, the area over the Gulf of Mexicon with 2 inches of TPW is abnormally high, even for the more tropical location, and is of largest concern.

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