Formation
On August 11, 2007, a vigorous tropical wave moved off the west coast of Africa, producing disorganized showers and thunderstorms. It encountered conditions favorable for gradual development, and on August 12 it gained organization and became a low. Strong upper-level easterly winds slowed development, but on August 13 the tropical wave gained enough organization that the National Hurricane Center designated it Tropical Depression Four. At this time it was centered about 520 mi (835 km) west-southwest of Cape Verde.
The depression was already exhibiting persistent deep convection in the western portion of its circulation. It moved quickly westward, south of a deep layered ridge, escaping the easterly wind shear that had been slowing its development and moving over warmer waters. At 1500 UTC on August 14, the depression was upgraded to Tropical Storm Dean while still 1450 mi (2300 km) east of Barbados. Even as its convection waned slightly that afternoon, its intensity grew, and convection flared in the center that night. Dry air and cooler air inflow from the north slowed structural development; nevertheless, ragged bands began to form on August 15. By mid-morning, a rough banding eye had formed, and by the next morning a full eye developed. The storm was upgraded to Hurricane Dean at 0900 UTC August 16, 550 mi (890 km) east of Barbados.
A strong ridge of high pressure continued to push the system west, towards the Caribbean Sea. That afternoon, convective banding and increasing upper-level outflow strengthened the storm to a Category 2 hurricane on the Saffir-Simpson Hurricane Scale. The eye disappeared briefly overnight, possibly as part of a diurnal fluctuation, but returned by the morning of August 17.
Read more about this topic: Meteorological History Of Hurricane Dean
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