Hurricane Danny (1997) - Meteorological History

Meteorological History

A broad mid-tropospheric trough over the southeastern United States spawned an area of convection over the lower Mississippi River Valley on July 13, and drifted southward towards the warm waters of the Gulf of Mexico. As it moved into the Gulf of Mexico, a weak and isolated surface low pressure area formed off the coast of Louisiana. The circulation in the system steadily expanded, and initially the surface winds and convection were intermittent. On July 16, deep convection increased and organized near the center, and oil rigs and surface buoys reported surface winds of 30 mph (50 km/h). Based on the observations, it is estimated the system developed into Tropical Depression Four on July 16 while about 150 miles (240 km) south of the southwestern Louisiana coastline.

The depression slowly organized for the next day, as it drifted to the northeast. On July 17, the rate of organization and development of deep convection increased considerably, and the depression strengthened into Tropical Storm Danny later that day. From the night of July 17 through July 18, Danny quickly developed deep convection and banding features in the favorable environment of the Gulf of Mexico, and reached hurricane status later on July 18. Located between two high pressure systems, Danny continued its unusual July track to the northeast, and crossed over southeastern Louisiana near the Mississippi River Delta. A small storm, Danny continued to strengthen after reaching the coastal waters off Mississippi on the night of July 18, and attained a peak of 80 mph (130 km/h) early on July 19. The hurricane force winds, however, were confined to the eyewall. After stalling near the mouth of Mobile Bay on July 19, Hurricane Danny turned to the east, and made its final landfall near Mullet Point, Alabama later that day.

The storm rapidly weakened as it continued northward, and degenerated into a tropical depression by July 20. The weak depression moved through Alabama, Georgia, South Carolina, and North Carolina, maintaining a well-defined cloud signature. Due to a front behind the system, Danny unusually strengthened to a tropical storm over North Carolina on July 24. This rare phenomenon occurred due to interaction with a developing trough and its associated baroclinic zone. Danny entered the Atlantic Ocean, north of the North Carolina-Virginia border, near Virginia Beach. It quickly reached a secondary peak of 60 miles per hour (100 km/h), and continued rapidly northeastward towards the waters of the Atlantic. A strong mid to upper-level cyclone turned Danny northward, threatening Massachusetts. It stalled while just 30 miles (50 km) southeast of Nantucket on July 26, turned to the east out to sea, and became extratropical later that day. On July 27, the former hurricane merged with a frontal zone.