Heavy Rain — Toa Alta, Puerto Rico

2009-08-16 · near Toa Alta, Toa Alta, Puerto Rico

Event narrative

Street flooding was reported by 911 in Rio El Mandril sector of Toa Alta.

Wider weather episode

A well organized tropical wave with an area of low pressure and significant thunderstorm activity moved offshore the African coastline on August 9th. The system moved northwest until reaching the southern Cape Verde Islands, then turned westward out into the open Atlantic. The system was upgraded to a tropical depression on August 11th, but easterly vertical wind shear kept the system from strengthening, and led to a reduction of thunderstorm activity which devolved the system into a remnant low pressure area on the 13th. By the 14th, the system redeveloped thunderstorm activity and redeveloped into a tropical depression, which strengthened into a tropical storm early on the 15th well to the east of the Lesser Antilles. Late on the 15th, a tropical storm watch was issued for the U.S. Virgin Islands, when the system was located about 910 miles east southeast of Saint Croix. At 5 am on the 16th, the tropical storm watch was extended to Puerto Rico, when the system was located about 850 miles southeast of San Juan. Soon afterwards, vertical wind shear from the west began to displace thunderstorms east and northeast of the center, beginning Ana's weakening trend. Also, the high pressure system steering Ana caused the system to accelerate westward. The weakening tropical storm Ana crossed the Lesser Antilles, and was downgraded to a tropical depression on the 16th at 5 pm, when it was located about 440 miles east southeast of Saint Croix. In spite of this, the tropical storm watch was kept in effect in case of any unexpected changes. Ana's local effects were mainly periods of heavy rain, gusty winds and cloud to ground lightning. Urban flooding, fallen trees, downed power poles and lines, rock slides, and power and water utility interruptions in several places. During the day on the 17th, aircraft reconnaissance determined that the system had dissipated southwest of Puerto Rico, as it no longer had a low-level circulation. At 5 pm, on the 17th, the tropical storm watch was discontinued for the U.S. Virgin Islands and Puerto Rico.

View location on OpenStreetMap → (18.3876, -66.2500)

Source: NOAA Storm Events Database, event_id 195253. Narrative written by the NWS forecast office that issued the report.