Flash Flood — St. John, Virgin Islands

2011-08-22 · near St John, St. John, Virgin Islands

Event narrative

Flooding, downed trees and power lines were reported in Saint John.

Wider weather episode

Irene was a quite large and impressive tropical wave during most of its journey across the Atlantic Ocean during the week of August 14-20, 2011. For most of this time the wave was nearly surrounded by dry air and with enough vertical wind shear to ensure that any intensification would be slow. Its forward speed of 20 mph somewhat aided the shear in keeping it weak.

By the time the wave was approaching the Lesser Antilles an Air Force Reserve Hurricane Hunter aircraft had found a low level circulation and 53 knots of sustained wind 1,400 feet above the ocean surface. The system was located at 14.9N, 58.5W at 700 pm AST (2300 UTC) on August 20 and the National Hurricane Center issued its initial warnings, including a tropical storm warning for the U.S. Virgin Islands.

The best forecast estimate for the center of Irene was still to pass south of St. Croix, and across the Puerto Rico coastal waters in the Caribbean Sea.

On August 21 at about 600 pm AST the center of Irene passed over St. Croix but the strongest winds were farther north. At 556 pm AST (2156 UTC) Cyril E. King Airport at Charlotte Amalie, St. Thomas recorded a wind gust to 60 knots (69 mph), also when the WSR-88D radar in Puerto Rico showed the strongest winds over and just south of St. Thomas. By 1236 am AST August 22 sustained winds were reported over Vieques of 52 mph with a gust to 71 mph, while a buoy near Esperanza, PR (Vieques) reported a gust to 66 knots (76 mph) at 106 am AST.

Damage from flooding was extensive across the region from Irene, however, though wind caused widespread damage it was relatively minor compared to a more significant hurricane. Numerous trees were blown down on Sunday night (August 21-22) in St. Thomas and St. John. Flooding was reported at Estate La Grange and La Grande Princesse on Saint Croix. The La Grande gut overflowed its banks flooding the legislature parking lot.

View location on OpenStreetMap → (18.3298, -64.7945)

Source: NOAA Storm Events Database, event_id 340012. Narrative written by the NWS forecast office that issued the report.