Was there a waterspout/tornado in western Puerto Rico?

July 17th, 2010 |
GOES-13 0.63 µm visible images

GOES-13 0.63 µm visible images

There were numerous media reports of a waterspout/tornado that moved inland near Mayaguez (station identifier TJMZ) in far western Puerto Rico around 16:45 UTC (12:45 pm local time) on 17 July 2010, causing tree and structural damage along with multiple injuries. However, due to a lack of visual confirmation, the NWS is not classifying this as a waterspout or a tornado event. McIDAS images of 1-km resolution GOES-13 0.63 µm visible channel data (above) did show a fast-moving outflow boundary / gust front moving from east to west across the island, causing wind gusts in excess of 50 mph at a number of locations. A strong thunderstorm then developed along this fast-moving boundary as it reached the far western end of the Puerto Rico.

Surface analyses from the NWS Ocean Prediction Center (below) depicted a westward-moving tropical wave  along the InterTropical Convergence Zone (ITCZ) that may have played a role in providing forcing for the convection that produced the initial  outflow boundary / gust front that raced westward across Puerto Rico.

NWS Ocean Prediction Center surface analysis

NWS Ocean Prediction Center surface analysis

The corresponding 4-km resolution GOES-13 10.7 µm IR images (below) revealed that cloud top IR brightness temperatures were as cold as -68º C (black color enhancement) at 17:45 UTC as the thunderstorm continued to grow and intensify.

GOES-13 10.7 µm IR images

GOES-13 10.7 µm IR images

A closer look using 1-km resolution Aqua MODIS 11.0 µm IR imagery at 17:44 UTC (below) showed what appeared to be a subtle “enhanced-v” storm top signature associated with this thunderstorm. The color enhancement is slightly different than that shown with the GOES-13 IR imagery, but the coldest/warmest IR brightnes temperatures within the enhanced-v signature were -75º C / -67º C respectively, making for a delta-T of 8º C. Enhanced-v storm top signatures over the continental US can exhibit delta-T values as large as 20-30º C, but to see an enhanced-v signature (even a subtle one) over Puerto Rico is rather unusual.

MODIS 11.0 µm IR image

MODIS 11.0 µm IR image

Related information:

Radar animation

YouTube damage video

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