Hurricane Ernesto (2006) - Meteorological History

Meteorological History

On August 18, a tropical wave moved off the coast of Africa. It tracked westward, and its convection began organizing and concentrating on August 22. The next day, convection increased along the wave axis, and Dvorak classifications from the Tropical Analysis and Forecast Branch of the National Hurricane Center began at 1200 UTC on August 23. As it approached the Lesser Antilles, a surface low developed, and with the confirmation of a closed low-level circulation from the Hurricane Hunters, it is estimated the system developed into Tropical Depression Five on August 24 about 50 mi (80 km) north-northwest of Grenada.

Located to the south of a ridge across the southwestern Atlantic Ocean, the depression tracked west-northwestward through an area of dry air and westerly wind shear. Despite the shear, convection intensified near the center as banding features improved, and on August 24, the depression intensified into Tropical Storm Ernesto. Convection deepened and expanded, though wind shear displaced the low-level center to the west of the convection. By August 26, the structure had become much better-defined, and within five days Ernesto was forecast to be located about 275 mi (445 km) south of the Gulf Coast of the United States as a powerful hurricane. The center reformed under the deepest convection after wind shear decreased, and at the same time outflow increased in all quadrants. Turning northwestward, a small eye formed, and early on August 27 Ernesto attained hurricane status about 95 mi (200 km) south-southwest of the border between Haiti and the Dominican Republic.

Upon becoming a hurricane, Ernesto was believed to be undergoing rapid intensification. However, the small inner core deteriorated as the circulation interacted with the mountainous terrain of southwest Haiti, and it quickly weakened back to tropical storm status. The center became broad and ill-defined, though it was forecast to re-intensify to hurricane status before striking Cuba. It continued to weaken due to land interaction, and early on August 28 Ernesto passed just offshore of the southwestern tip of Haiti with winds of 45 mph (70 km/h). Hindered by increased wind shear from an upper-level low over the Bahamas, the storm weakened further before striking just west of Guantánamo Bay in Cuba as a minimal tropical storm. With very warm water temperatures and a favorable upper-level environment, one forecast remarked the possibility of Ernesto strengthening greatly over the Straits of Florida and eastern Gulf of Mexico to hit western Florida as a major hurricane. Ernesto remained over land as a minimal tropical storm for about 18 hours before reaching the Straits of Florida. Convection gradually increased over the warm waters, though Ernesto failed to strengthen significantly due to its disrupted inner core. An eastward-moving high pressure system over the southeastern United States allowed a continued northwest movement, and at 0300 UTC on August 30 the storm struck Plantation Key in the upper Florida Keys with winds of 45 mph (70 km/h). Two hours later, Ernesto made landfall on the Florida mainland in southwestern Miami-Dade County.

Moving through a weakness in the subtropical ridge, the storm turned to the north through the state. Operationally, the National Hurricane Center downgraded Ernesto to tropical depression status while over the state, though post-analysis indicated the system maintained tropical storm status. Ernesto retained a well-organized cloud pattern over land, and after emerging over the Atlantic Ocean near Cape Canaveral, convection again increased and began wrapping into the circulation. Upon reaching the Atlantic Ocean, Ernesto accelerated north-northeastward ahead of an approaching deep layer trough. The convection increased as the storm strengthened over warm waters, and late on August 31 Ernesto attained an intensity of 70 mph (110 km/h) while located about 170 mi (270 km) south-southwest of Wilmington, North Carolina. Shortly prior to moving ashore, an eye began to develop, and early on September 1 the storm made landfall on Oak Island, North Carolina very near the threshold between tropical storm and hurricane status. The National Hurricane Center remarked the possibility that Ernesto could have been a hurricane at landfall, due to the possibility that the strongest maximum wind was not sampled.

After landfall the storm rapidly weakened, and about eight hours after moving ashore, Ernesto deteriorated to tropical depression status. Interacting with a pre-existing frontal zone that extended eastward through Virginia, Ernesto quickly lost its tropical characteristics, and late on September 1 it transitioned into an extratropical cyclone. It re-intensified to a gale over the Mid-Atlantic states, only to weaken to an extratropical depression near Pennsylvania. With a large high pressure area to its east, the remnants turned to the north-northwest, reaching southern Ontario on September 3. After turning northeastward, the extratropical remnants of Ernesto were absorbed into a larger storm over Quebec on September 4.