Hurricane Dean (1989) - Meteorological History

Meteorological History

A tropical wave moved off the coast of Africa on July 27 as detected by Meteosat imagery. By July 31 the tropical wave began being classified, using the Dvorak Technique, by satellite analysts at the National Hurricane Center, in part due to persistent deep convection. Shortly thereafter the system organized enough that the National Hurricane Center began classifying it as Tropical Depression Five, roughly halfway between Cape Verde and the Lesser Antilles. The depression moved westward at 17 mph (28 km/h), intensifying as it did so, and eventually intensified enough to be upgraded to a tropical storm, which was named Dean by the National Hurricane Center.

Continuing generally westward, Dean continued to gradually intensify and became a hurricane on August 2 after an Air Force reconnaissance flight had recorded hurricane force winds. The following day a decreasing ridge of high pressure to the north and a trough of low pressure forming off the East Coast of the United States caused Dean to slow in its forward motion and turn northwest. The trough of low pressure forming off the East Coast of the United States was deepening, causing Dean to curve northward while remaining nearly stationary. After remaining nearly stationary, Dean began to accelerate to a forward speed of 17 mph (28 km/h) as it headed toward Bermuda. Thereafter, Dean intensified into a Category 2 hurricane, whilst the eastern half of the eyewall brushed Bermuda. Dean continued to intensify slightly after passing the island of Bermuda and became a Category 2 hurricane on August 7. While Dean was a Category 2 hurricane, it attained its peak intensity with winds of 105 mph (165 km/h) and a minimum pressure of 968 mbar (hPa; 28.59 inHg).

After peak intensity, the forward speed of Dean continued to increase as it approached Atlantic Canada while weakening back to a Category 1 hurricane. While approaching southern Newfoundland, Dean had weakened enough to be downgraded to a tropical storm on August 8. Shortly thereafter, Dean then made landfall on the south coast of Newfoundland with winds of 65 mph (105 km/h). Later that day, Dean emerged into the far north Atlantic and rapidly transitioned into an extratropical cyclone on the following day.