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1985 Puerto Rico floods

Flood event that took place in Puerto Rico

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  • 4 chapters

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Meteorological history

The tropical wave that caused the flooding moved off the west coast of Africa on September 29. Moving westward, the system entered the eastern Caribbean Sea on October 5, although rainfall began spreading across Puerto Rico the day prior. The wave's associated convection, or thunderstorms, were amplified by an upper-level trough to its west. It was developing into a tropical cyclone while it moved across Puerto Rico. When the system's rainbands reached the mountains of southern Puerto Rico, it produced torrential rainfall, and additional precipitation occurred owing to the system's slow movement.

The most intense rainfall occurred on October 6, and on that day two stations recorded 24-hour precipitation totals exceeding 23 in (580 mm). These totals broke the 24-hour rainfall records set during the 1899 San Ciriaco hurricane, and amounted to nearly half of the annual precipitation totals. The town of Peñuelas reported very high rainfall totals in a short amount of time, including 2.75 in (70 mm) in one hour and 5.5 in (140 mm) in two hours. The highest rainfall total in Puerto Rico was 31.67 in (804 mm) in Toro Negro State Forest. Rainfall spread across the island, and the southern half of Puerto Rico experienced totals of over 10 in (250 mm). Rainfall totals over 7 in (180 mm) spread across the United States Virgin Islands. The tropical wave later spawned a low-pressure area north of Hispaniola that became Tropical Storm Isabel on October 7, a day before the rains subsided in Puerto Rico. The storm ultimately struck Florida before dissipating on October 15.

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