Omar (2008)

A tropical wave that moved off west Africa on September 30 developed into Tropical Depression Fifteen about 0600 UTC October 13, 2008 in the central Caribbean Sea roughly 165 nautical miles south of the Dominican Republic. The system became Tropical Storm Omar on October 14 and moved generally northeastward from the southern Caribbean through the northern Leeward Islands region. Omar underwent two brief, rapid intensification periods between October 13–16, reached peak intensity on October 16, then weakened quickly as wind shear and dry air disrupted its core. The system became a remnant low by 1200 UTC October 18 and dissipated about 0600 UTC October 21, roughly 700 nautical miles west of the Azores.

Omar did not make a direct landfall with its strongest core over any major inhabited island. Its closest approaches occurred on October 16 when the hurricane center passed about 30 nautical miles southeast of Virgin Gorda (British Virgin Islands) and roughly 50 nautical miles west of Anguilla and St. Martin/St. Maarten. Because the eye moved through the Anegada Passage, the core of major hurricane-force winds did not pass over populated islands; Sombrero Island (uninhabited) likely experienced the eye.

Maximum sustained winds at peak were estimated at 115 kt (132.3 mph) with a minimum central pressure of 958 mb at about 0600 UTC on October 16, making Omar a high-end Category 3 hurricane on the Saffir–Simpson scale by pressure and a Category 4 by wind if using the 115 kt value (115 kt equals 132.3 mph, Category 4 threshold is 130 mph). Aircraft and instrument data (SFMR and flight-level winds) support the 115 kt peak estimate; satellite-based techniques gave slightly lower values. After peak, Omar weakened rapidly, then briefly re-intensified on October 17 before final decay.

Storm surge and rainfall were concentrated in the Virgin Islands and northern Leeward Islands. Antigua experienced an estimated surge of 2.0–3.5 ft with waves of 4.5–7 ft and recorded the largest island rainfall total of 9.13 inches. St. Croix (U.S. Virgin Islands) recorded 5.30 inches of rain at the airport and a measured storm tide/surge of about 2.2 ft at Christiansted Harbor; an unofficial site at the Buccaneer Resort reported a 9.11-inch rainfall. Other storm total rainfall amounts included 5.49 inches at St. Maarten and 4.53 inches at Grand Case, St. Martin. Buoy 42059 measured a peak significant wave height of 17.7 ft.

There were no known fatalities associated with Omar. Damage was focused on coastal facilities, buildings, and infrastructure in the northern Leeward Islands, the Netherlands Antilles (Aruba, Bonaire, Curaçao), and the U.S. Virgin Islands. In St. Croix, downed trees and poles caused power outages, 47 vessels were sunk (33 in Christiansted Harbor), substantial road damage and landslides occurred, about 80 people sought shelter, and reported total damage was approximately $5 million. Aruba, Bonaire, and Curaçao experienced beach erosion, coastal facility damage, roof damage to houses, and localized flooding.

Noteworthy aspects include Omar’s unusually fast swings in intensity—two rapid intensification periods followed by very rapid weakening—and the timing and location such that the strongest winds missed most populated islands. The storm’s genesis was anticipated in forecasts, but the rapid strengthening was underpredicted initially and later the rapid weakening and subsequent brief re-strengthening presented forecasting challenges; official track forecasts also had a significant slow bias, producing larger-than-average track errors.