Hurricane Dean - Meteorological History

Meteorological History

On August 11, 2007, a tropical wave moved off the west coast of Africa, and, encountering favorable conditions, quickly developed into Tropical Depression Four about 520 miles (835 km) west-southwest of Cape Verde on August 13. The depression moved briskly westward, and was upgraded to Tropical Storm Dean at 1500 UTC on August 14. The storm's intensity continued to build although dry air and cooler air inflow from the north were slowing structural development. Ragged bands formed on August 15 and the formation of a partial eyewall was observed later that day.

Intensification continued and the storm was upgraded to Hurricane Dean at 5 am EDT (0900 UTC) August 16. The deep-layered ridge to the north continued to steer the system west, towards the Caribbean Sea. The storm quickly strengthened to a Category 2 hurricane on the Saffir–Simpson Hurricane Scale. The storm's development slowed slightly but a reconnaissance aircraft discovered a closed eyewall on August 17 as the storm passed through the Lesser Antilles. Data from the aircraft indicated that Hurricane Dean had strengthened to a Category 3 hurricane and its trailing bands were still over the Lesser Antilles. During the evening of August 17, Dean strengthened into a Category 4 hurricane and continued to steadily grow in both size and intensity through the night. On August 18 the presence of a double eyewall was noted, indicating an eyewall replacement cycle and causing short term fluctuations in intensity. These fluctuations did not affect the storm's well defined satellite presentation. Operationally, Dean was thought to have only been a Category 4 on the 18th, but post-storm analysis shows that Dean had become a 165 miles per hour (265 km/h) Category 5 that day. Dean weakened very slightly on the morning of August 19 as it finished the eyewall replacement cycle and began to interact with the island of Jamaica

Hurricane Dean passed south of Jamaica on the evening of August 19 and began to intensify again that night. Its eyewall replacement cycle was thought to be completed. A concentric eyewall was briefly observed again on the morning of August 20, but did not last long. The hurricane, still tracking west-northwest under the influence of a strengthening deep-layered high pressure system to the north, moved over waters with extremely high heat content and began to strengthen once again. The eyewall became even better defined during the day, and, at 8:35 pm AST on August 20 (0035 August 21, UTC), Dean restrengthened to a Category 5 hurricane, the highest rating on the Saffir–Simpson Hurricane Scale. It made landfall as a Category 5 storm in Quintana Roo's Costa Maya region, 40 mi (65 km) northeast of the border between Mexico and Belize, and weakened on its way over land, reemerging on the western side of Yucatán as a Category 1 storm. Dean regained strength as it crossed the Gulf of Mexico, and made its second landfall as a Category 2 storm on August 22, at around 11:30 CDT, near Tecolutla, Veracruz, to the south of Tuxpan, where after it moved westward, losing strength and disintegrating over central Mexico. A small remnant circulation reached the Pacific Ocean, eventually moving northwestward around an anticyclone, roughly parallel to the Mexican coast and finally back inland over the southwestern United States, where it completely dissipated on August 27.