1987 Gulf Coast Tropical Storm - Meteorological History

Meteorological History

On July 29, 1987, a tropical wave emerged off the west coast of Africa into the Atlantic Ocean. Tracking westward along the southern edge of the Saharan Air Layer, a feature associated with large masses of dry air, little convective development took place over the following several days. Once near the Lesser Antilles in early August, atmospheric conditions became more favorable for development. Traveling across the Caribbean Sea, the system became increasingly organized and a mid-level circulation formed shortly before the wave moved inland over Central America on August 7. The following day, the northern portion of the wave interacted with a cold-core low over the Gulf of Mexico, resulting in the formation of a low-level circulation, exhibiting tropical characteristics, on August 9. Over the following two days, the system tracked in a general north-northwest direction towards the Texas coastline. Aided by an anticyclone aloft, outflow became pronounced and convection increased in coverage and intensity. Around 1200 UTC (7:00 a.m. CDT), the National Hurricane Center (NHC) estimated that the system developed into a tropical depression roughly 145 miles (235 km) south-southeast of Galveston, Texas.

Hours after being classified a tropical depression, the convective structure of the system deteriorated, a sign of a weakening storm; however, nearby oil rigs indicated a gradual increase in winds. Later on August 9, several rigs reported tropical storm-force winds – winds greater than 39 mph (63 km/h) – and the NHC estimated that the depression strengthened into a tropical storm. Operationally, however, these winds were considered to be related to local convective activity rather than the storm itself and it was not considered to be a tropical storm until post-storm analysis. As such, it was not named and is officially classified as "Unnamed Tropical Storm." Additionally, the strongest winds were located well away from the center of circulation, a signature of subtropical cyclones.

Remaining relatively weak, the unnamed system attained peak winds of 45 mph (75 km/h) before making landfall along the Texas coastline between Galveston and Beaumont. Once over land, the storm weakened to a tropical depression as it neared the Texas-Louisiana border and began a gradual turn towards the east-southeast. On August 12, while over central Mississippi, the cyclone attained its lowest barometric pressure of 1007 mbar (hPa; 29.74 inHg). On August 15, the low emerged back over the Gulf of Mexico after crossing the Florida Panhandle. No redevelopment took place during its brief time back over water before making its final landfall near St. Marks, Florida the following day. The depression gradually diminished before losing its identity over eastern Georgia on August 17.