Hurricane Dennis - Meteorological History

Meteorological History

Hurricane Dennis began as Tropical Depression Four in the southeastern Caribbean Sea on the evening of July 4, the first storm of the season to form away from Mexico and Central America. Almost immediately, it made landfall on Grenada as a tropical depression with 30 mph (48 km/h) winds. On the morning of July 5, it strengthened into Tropical Storm Dennis in the eastern Caribbean; at the time, this was the earliest formation of an Atlantic season's fourth storm (by comparison, during the 2004 season, Hurricane Alex formed in early August and Hurricane Charley made landfall in Cuba on August 12), although this record was later surpassed when Tropical Storm Debby formed on 23 June 2012. The newly named Dennis began moving rapidly to the west-northwest.

It was clear from early weather forecasting models that Dennis had the potential to be a major storm, and it was already predicted to reach hurricane status while it was still a tropical depression. It reached hurricane strength on the afternoon of July 6 while approaching the southern coast of Hispaniola, and it quickly became a strong and well-organized Category 1 storm on the Saffir-Simpson Hurricane Scale. The next day it strengthened rapidly to become a Category 4 major hurricane, the earliest in an Atlantic hurricane season that a storm had reached that strength since Hurricane Audrey in the 1957 season. After rapid strengthening, Dennis's track became slightly more northerly, bringing it between Jamaica and Haiti by July 7; both countries experienced high winds and heavy rain. As it approached Cuba and strengthened to just under Category 5 intensity, Dennis's track began to wobble. Meteorologists from the National Hurricane Center (NHC) stated, "this type of erratic motion is not unusual for intensifying major hurricanes." On July 7, Hurricane warnings were issued for Cuba at 11 am EDT (1500 UTC). Dennis made landfall near Punta dal Inglés with 140 mph (220 km/h) winds late that day, and dropped down to a Category 3 storm while crossing the peninsula. As it moved back into the Gulf of Guacanayabo, its wind speed increased to a peak of 150 mph (240 km/h). Dennis then slammed into south-central Cuba just west of Punta Mangles Altos on July 8, again with 140 mph (220 km/h) winds.

Crossing Cuba's mountainous terrain disrupted the storm's circulation, weakening Dennis to Category 1 intensity. However, NHC forecasts continued to indicate the possibility of a rebound to Category 4 status after convection was re-established, and because conditions remained favorable. This prediction was borne out when Dennis rapidly reintensified on the afternoon of July 9 over the Gulf Loop Current, a reintensification described by NHC as having occurred "at a rate that bordered on insane." The storm reached Category 4 intensity again on the morning of July 10. At 1200 UTC, the storm reached its peak intensity of 930 mbar (27.47 inHg), surpassing Hurricane Audrey and setting a new record for the strongest storm to form prior to August; the new record stood for only six days before Hurricane Emily surpassed it by reaching a pressure of 929 mbar (27.43 inHg).

The storm continued moving north-northwest towards the central Gulf Coast, which had seen the landfalls of Tropical Storm Arlene in June and Hurricane Cindy the previous week. By the morning of July 10, hurricane warnings were in effect in the U.S. for the Florida Panhandle, Alabama, and Mississippi, with tropical storm warnings extending further east and west along the coast. The NHC predicted a landing at near full strength in the late afternoon. However, much like Hurricane Ivan which struck in the same area the previous year, the storm weakened just before landfall; its maximum sustained winds dropped from 145 mph (235 km/h, Category 4 strength) to 125 mph (195 km/h, Category 3 strength).

Continental landfall occurred at Santa Rosa Island, between Pensacola, Florida, and Navarre Beach, Florida, at 2:25 pm CDT (1925 UTC) on July 10. Dennis was a Category 3 hurricane with winds of 120 to 125 mph (185 to 195 km/h). The highest official wind speed reported was a 121 mph (195 km/h) wind gust at Navarre Beach. The storm lost strength over the day and was a tropical depression by early on July 11. The depression persisted, however, and gained a little strength while stalled over Illinois the next day. It finally dissipated in Ontario on July 13, with advisories ceasing a full three days after landfall.