Hurricane Alicia - Meteorological History

Meteorological History

The origins of Hurricane Alicia were from a cold front that extended from New England through the central Gulf of Mexico. On August 14, mesoscale low-pressure area developed off the Alabama and Mississippi coastlines. Around 0100 UTC on August 15, the low had maintained convection, or area of thunderstorms, for 12 hours, as well as a circulation for six hours; as a result, the National Hurricane Center (NHC) began issuing Dvorak classifications on the system. By a few hours later, the deep convection became organized in the circulation's southern semicircle, which prompted a Hurricane Hunters flight into the system. At 1200 UTC that day, the system developed into Tropical Depression Three about 350 miles (560 km) south-southwest of the Mississippi River Delta. A few hours later, the Hurricane Hunters confirmed its development. Such development along the tail end of a cold front is more typical earlier or later in the hurricane season.

After becoming a tropical cyclone, the depression was moving slowly westward, due to a ridge to its north. A Hurricane Hunters flight late on August 15 reported that the depression reached winds of 50 mph (80 km/h); as a result, the NHC upgraded the cyclone to Tropical Storm Alicia. At the time of its upgrade, the storm was located in an area of higher than normal atmospheric pressure, although conditions favored further development. Due to high pressures surrounding the storm, Alicia was a smaller than normal tropical cyclone; as a result, it produced stronger than normal winds, in comparison to its minimum central pressure. The storm continued slowly to the west-northwest, and by August 17 attained hurricane status, about 160 miles (255 km) southeast of Galveston, Texas. Shortly thereafter, an eye became visible on radar, as the hurricane executed several small loops. Its slow movement over warm waters, in addition to an anticyclone becoming established over the hurricane, caused Alicia to undergo rapid deepening.

At 0600 UTC on August 18, the winds reached 115 mph (185 km/h), just before Alicia made landfall about 25 mi (40 km) southwest of Galveston, Texas. Upon moving ashore, the gale-force winds extended 125 mi (201 km) from the center, and hurricane force winds spread across an area from Freeport to 60 mi (97 km) northeast. Its atmospheric pressure was 962 mbar (hPa; 28.41 inHg) around the time of landfall, and radar imagery indicated the presence of a rare double-eye structure. Alicia quickly weakened, passing over central Houston with sustained winds of 80 mph (130 km/h). It accelerated toward the northwest, weakening to tropical storm status late on August 18 and to tropical depression status twelve hours later. Tropical Depression Alicia moved into Oklahoma and interacted with an approaching frontal trough. By 0600 UTC on August 20, Alicia had transitioned into an extratropical cyclone over northwestern Oklahoma, and by the next day it was no longer identifiable after merging with the trough over eastern Nebraska.