Monday, July 18, 2011

Tropical Storm Bret (2011)

Storm Active: July 17-22

Following the departure of a cold front from the U.S. east coast, a west-to-east situated stationary front stalled over the Florida coast and adjacent Atlantic waters. On July 16, a weak low pressure center formed in association with this front, and produced an area of showers and thunderstorms off of the eastern Florida coast. The pressure of the system remained high as it drifted slowly southward over the next day, but a clearly defined closed circulation formed during the afternoon of July 17, and the low was upgraded to Tropical Depression Two. Further deepening quickly followed, and the cyclone achieved tropical storm status a mere three hours later.

The newly formed Tropical Storm Bret experienced almost no motion overnight, drifting southward and then eastward, all the while meandering over the Northern Bahamas. Despite some wind shear out of the west that was bringing dry air into the system, convection persisted, and even developed during the morning of July 18, and the strengthening trend continued. Bret even developed a ragged eye amidst its tight circulation that evening, reaching a strong tropical storm intensity of 70 mph winds and a minimum pressure of 995 mb.

However, dry air penetrated the system late that night, causing weakening as the cyclone continued to move slowly north-northeast. As Bret paralleled the southern portion of the U.S. east coast early on July 19, nearly all convection was lost, and the system packed winds of only 50 mph. Some convection returned that morning, and Bret managed to maintain its intensity despite increasing shear from the northwest. With the exception of the southeastern quadrant, which contained some cloud cover, but even it was struggling, Bret had no associated convection whatsoever, and was essentially a bare circulation. Bret moved northeast through the day, and even into July 20 maintained the same intensity, despite very adverse conditions.

The storm finally began to weaken again that evening as it moved over slightly cooler waters, becoming a minimal tropical storm by July 21. Late that night, the storm was downgraded to a tropical depression while located between the Outer Banks of North Carolina and Bermuda. It also underwent significant acceleration to the northeast, reaching speeds over 20 mph. Yet despite the lack of convection, the system persisted as a tropical cyclone through most of July 22, and finally degenerated into a remnant low that afternoon. Bret's only effects were scattered storms and gusty winds in the northern Bahamas.

Bret at peak intensity just northeast of the Bahamas.

Track of Bret.

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