Tropical Storm Warning Issued for Northern Gulf Coast

The National Hurricane Center issued a Tropical Storm Warning for a portion of the northern coast of the Gulf of Mexico on Thursday afternoon. A Tropical Storm Warning was issued for the portion of the coast from Intracoastal City, Louisiana to the Alabama border including New Orleans, Lake Pontchartrain and Lake Maurepas.

At 5:00 p.m. EDT on Thursday the center of Potential Tropical Cyclone Three (03L) was located at latitude 22.9°N and longitude 92.4.W which put it about 475 miles (765 km) south of Morgan City, Louisiana. Potential Tropical Cyclone Three was moving toward the north at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1008 mb.

The weather system designated as Potential Tropical Cyclone Three consisted of a complex circulation containing of parts of several different weather features. A broad surface low pressure system was over the southwestern Gulf of Mexico. A low pressure system in the middle and upper troposphere was over the western gulf of Mexico. An upper level ridge was over the northwestern Caribbean Sea and the eastern Gulf of Mexico. Thunderstorms were occurring in bands on the eastern periphery of the broad surface low. Drier air in the middle and upper levels of the upper level low was over the southwestern Gulf of Mexico and the drier air was inhibiting the formation of thunderstorms in that region. Several small circulation centers that originally formed within clusters of thunderstorms on the eastern side of the broader low were revolving counterclockwise around the broad center of the surface low.

The environment around Potential Tropical Cyclone Three will become a little more favorable for the formation of a tropical depression during the next 24 hours. Potential Tropical Cyclone Three will move over an area where the Sea Surface Temperatures are near 29°C. The upper level low and the upper ridge will interact to produce southerly winds which will blow toward the top of Potential Tropical Cyclone Three. Those winds will cause moderate vertical wind shear, but they will also produce upper level divergence to the east of Potential Tropical Cyclone Three. The upper level divergence will cause the surface pressure to decrease slowly. The drier air over the western Gulf of Mexico will continue to inhibit the formation of thunderstorms on the western side of the broad low pressure system. The inner end of a rainband will wrap closer to the center, but most of the thunderstorms are likely to remain in the eastern half of Potential Tropical Cyclone Three. The National Hurricane Center could designate the system as a tropical depression if more thunderstorms develop closer to the center of circulation. The maximum sustained wind speed is forecast to increase to tropical storm force by Friday afternoon.

The upper level low and the upper ridge will steer Potential Tropical Cyclone Three slowly toward the north during the next 36 hours. On its anticipated track the system could approach the coast of Louisiana by Friday evening. It is possible that a new center of circulation could form along the northern end of a rainband, which could bring it to the coast sooner. Potential Tropical Cyclone Three could be a tropical depression or a tropical storm when it approaches the coast. It will bring gusty winds to southeast Louisiana and the coasts of Mississippi and Alabama. The system could cause a storm surge of 3 to 5 feet (1.0 to 1.5 meters) along parts of the coast. It will likely drop locally heavy rain when it moves inland. Heavy rain could cause flash floods over parts of the southeastern U.S. There may also be enough low level wind shear to produce tornadoes when the rainbands in the eastern side of the circulation move inland.