Otto (2010)

A tropical wave that left Africa on September 26 organized into a surface circulation by 0600 UTC October 6 about 230 nautical miles north-northwest of San Juan, Puerto Rico. It began as a subtropical depression that same day, quickly became subtropical storm Otto, transitioned to a tropical storm on October 7, and strengthened into a hurricane on October 8. Otto moved generally north-northwest then northeast, accelerated under southwesterly flow, weakened on October 9, became a tropical storm again by 0000 UTC October 10, and lost tropical characteristics about 0600 UTC October 10 roughly 900 n mi east-northeast of Bermuda. The remnant extratropical low persisted and finally dissipated near the northwest coast of Africa on October 18.

Otto did not make any landfall as a tropical cyclone recorded in the best track; its primary impacts in the Caribbean came from heavy rain associated with Otto and its precursor disturbance while it passed near the northeastern Caribbean islands from October 4–8. The report does not list specific hurricane or tropical-storm intensity landfalls on islands, only widespread heavy rainfall and flooding across Puerto Rico, the U.S. Virgin Islands, and the British Virgin Islands during that period.

Maximum sustained winds reached 75 kt (about 85 mph) at 0000 and 0600 UTC October 9, with the lowest estimated central pressure 976 mb, making Otto a Category 1 hurricane at peak intensity. The best-track chronology shows peak winds of 75 kt and a peak pressure of 976 mb centered on October 9 as the storm accelerated northeastward.

Storm surge observations in the report are limited; no large coastal surge values are highlighted for major damage, but storm-tide and surge columns in the data summary are mostly blank or small. Rainfall was the primary hazard: many locations in the northeastern Caribbean reported very heavy totals. Specific measured totals include 15.63 inches at Río Portugués (Puerto Rico), 15.55 inches at Lago Patillas (Ponce, Puerto Rico), 14.85 inches at Río Inabón (Ponce), 12.94 inches at Charlotte Amalie (St. Thomas), about 12.15 inches at Golden Rock Airport (St. Kitts), and multiple other sites in Puerto Rico, the U.S. Virgin Islands, and neighboring islands with totals exceeding 10–15 inches in several basins.

There were no reported fatalities from Otto in the NHC report. Damage was driven by heavy rains: mudslides, flooded homes, toppled power lines, overturned cars, and washed-out roads were reported, with the British Virgin Islands especially hard hit—media described the flooding there as the worst in its history. The NHC noted that official track and intensity forecasts for Otto were unusually accurate compared with recent averages; the European model (ECMWF) also performed well on the track. No ships reported tropical-storm-force winds while Otto was tropical or subtropical.