Tropical Storm Abby was an exceptionally small tropical cyclone that had minor effects across Southeast Texas in early August 1964. Forming as a tropical depression out of a trough south of Louisiana on August 5, the system moved generally westward. It was not until August 7 that the system began to organize. That day, an eye rapidly formed within the system and it became a tropical storm just southeast of Galveston, Texas. Soon thereafter, a weather reconnaissance plane reported a barometric pressure of 1000 mbar (hPa; ) at the storm's center. Around 18:00 UTC (1:00 p.m. CDT), the newly named Abby attained peak winds of . It subsequently made landfall near Matagorda, Texas four hours later. Once onshore gradual weakening ensued, though a brief period of re-organization delayed its dissipation. Abby degenerated into an area of showers on August 8 southwest of San Antonio, Texas.
Prior to Abby's landfall in Texas, gale warnings were issued for the coast and residents on Matagorda Island were evacuated. Overall, the storm's impacts were limited due to its small size. Only two structures sustained damage in Matagorda, one being destroyed by a possible tornado, and the remaining effects resulted from flooding in Jackson and Victoria Counties. Total damage from the storm was estimated at $750,000 with the majority stemming from crops.
Meteorological history
On August 5, 1964, a weak trough emerged from Florida over the northeastern Gulf of Mexico. According to the Atlantic hurricane database (referred to as HURDAT), the system developed into a tropical depression by 18:00 UTC (1:00 p.m. CDT) that day, with its center located roughly south-southeast of the Mississippi River Delta. Moving generally west, the system exhibited no signs of further development as it neared the Texas coastline. However, on August 7, radar images from Brownsville, Galveston, Lake Charles, and Victoria showed an abrupt increase in organization. During the afternoon hours, banding features consolidated around a developing eye and weather reconnaissance planes were dispatched to the system. Forecasters initially mistook the eye as a hook echo-type feature at the end of a squall line. It is estimated that the depression became a tropical storm by 12:00 UTC (7:00 a.m. CDT), roughly southeast of Galveston, Texas. Operationally, the system was not even monitored as a depression this time, with the classification and naming of Tropical Storm Abby occurring at 16:00 UTC (11:00 a.m. CDT) on August 7.
Abby was an unusually small storm, with its entire circulation being far less than in diameter. Around 16:00 UTC (11:00 a.m. CDT) on August 7, reconnaissance measured a central barometric pressure of 1000 mbar (hPa; ) within Abby, the lowest in relation to the system. They also reported peak winds of in squalls, which would rank as a Category 1 hurricane on the modern-day Saffir–Simpson hurricane wind scale. These winds were seen to be an overestimate by forecasters and discarded, however. The system attained its maximum winds of by 18:00 UTC (1:00 p.m. CDT) and subsequently made landfall just northeast of Matagorda, Texas at 22:00 UTC (5:00 p.m. CDT). Irvin Velbrecht, a forecaster at the Weather Bureau (now known as the National Weather Service) in Galveston, described the storm as a "perfectly miniature hurricane." Despite moving onshore, Abby's core continued to organize and it developed a closed eyewall roughly three hours later. Thereafter the storm began to gradually weaken, passing over Edna around 02:00 UTC on August 8 (9:00 p.m. CDT on August 7). Weakening to a depression hours later, Abby ultimately degenerated into an area of showers and dissipated southwest of San Antonio by 12:00 UTC (7:00 a.m. CDT).