Tuesday, August 18, 2015

Hurricane Danny (2015)

Storm Active: August 18-24

At the beginning of the third week of August, a the most vigorous tropical wave of the season thus far moved off of the African coastline. The system developed a surface low pressure center almost immediately. The low moved westward, tracking well south of the Cape Verde Islands early on August 16. Within two days, the low had acquired a closed circulation, and was classified Tropical Depression Four. Low shear conditions dominated the central Atlantic at the depression's low latitude (near 10°N) and the system strengthened to Tropical Storm Danny within hours.

The system experienced modest strengthening through the morning of August 19, but the center became exposed during the day as Saharan dry air infiltrated the northern half of the circulation. Meanwhile, a weakness in the ridge north of Danny allowed it to slow its forward motion and turn toward the west-northwest. Overnight, the cyclone's convective structure recovered, and a small area of concentrated thunderstorm activity appeared near Danny's center by the morning of August 20. Later that morning, an eye formed at the center of the system and Danny rapidly intensified into a category 1 hurricane, the first of the season. After its reformation, the structure of the system was very compact: tropical storm force winds extended only about 50 miles from the center, and hurricane force winds only 10 miles.

Surrounded by a low-shear environment and recovered from its encounter with dry air, Danny continued to strengthen over the next day. A period of rapid deepening brought the hurricane to its peak intensity as a category 3 major hurricane during the afternoon of August 21, with sustained winds of 115 mph and a central pressure of 974 mb. After attaining this peak intensity, however, wind shear increased and the system's cloud pattern decayed. Danny had become a minimal hurricane by the afternoon of August 22 and weakened to a tropical storm overnight. Meanwhile, the ridge north of the cyclone reformed, turning its motion back toward the west and increasing its forward speed. On August 23, Danny's center became exposed, and it became a minimal tropical storm that night. The system finally reached the Caribbean the morning of August 24, passing near Guadeloupe now as a tropical depression. By late that morning, Danny had lost its closed circulation and degenerated into a trough of low pressure in the far eastern Caribbean. Its remnants continued to spread areas of heavy rain westward over Puerto Rico on August 25 before fading away.

The above image shows Danny on August 21 when it briefly attained major hurricane intensity.

Danny dissipated on August 24, just as it entered the Caribbean Sea.

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