Hurricane Danny was the only hurricane to make landfall in the United States during the 1997 Atlantic hurricane season, and the second hurricane and fourth tropical storm of the season. The system became the earliest-formed fifth tropical or subtropical storm of the Atlantic season in history when it attained tropical storm strength on July 17, and held that record until the 2005 Atlantic hurricane season when Tropical Storm Emily broke that record by several days. Like the previous four tropical or subtropical cyclones of the season, Danny had a non-tropical origin, after a trough spawned convection that entered the warm waters of the Gulf of Mexico. Danny was guided northeast through the Gulf of Mexico by two high pressure areas, a rare occurrence in the middle of July. After making landfall on the Gulf Coast, Danny tracked across the southeastern United States and ultimately affected parts of New England with rain and wind.
Danny is notable for its extreme rainfall, the tornadoes generated by it, and the destruction it produced on its path, causing a total of nine fatalities and $ (1997 USD, $ USD) in damage. The storm dropped a record amount of rainfall for Alabama, as at least fell on Dauphin Island. Flooding, power outages, and erosion occurred in many areas of the Gulf Coast, and rescues had to be executed from flooded roadways. Tornadoes generated by Danny on the East Coast caused a great amount of damage. Of the nine fatalities caused by Danny, one happened off the coast of Alabama, four occurred in Georgia, two occurred in South Carolina, and two occurred in North Carolina.
Meteorological history
On July 13, a broad mid-tropospheric trough of low pressure over the southeastern United States helped to initiate an area of atmospheric convection over the lower Mississippi River Valley. The area of convection moved southwards and appeared to contribute to the formation of a weak and isolated surface low pressure area in the Gulf of Mexico near the coast of Louisiana during the next day. Over the next couple of days, the systems circulation gradually expanded, however, surface winds remained weak and convection over the system did not persist or become well organized.
On July 16, deep convection increased and organized near the center, and oil rigs and surface buoys reported surface winds of . Based on the observations, it is estimated the system developed into Tropical Depression Four on July 16 while located about 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 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 , 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 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.
Preparations
The National Hurricane Center issued a hurricane watch on July 17, as Danny strengthened to a tropical storm, for the coasts of Louisiana, Mississippi, and Alabama. When Danny strengthened to a hurricane on July 18, a few hours before its landfall in far southeastern Louisiana and over a day before landfall in Alabama, the hurricane watch was upgraded to a hurricane warning. Grand Isle mayor Arthur Ballenger ordered the evacuation of the town's 1,500 residents, a decision made due to the large number of tourists on the island and to prevent anyone from being unable to leave the island. With a storm surge possibility, Danny had the potential to flood the only highway out of the island. Officials distributed sandbags to residents in St. Bernard Parish to seal off easily flooded roads, with officials recommending that residents leave the area. Accessed via the Wayback Machine.
Prior to the arrival of the hurricane, the governors of Mississippi and Alabama declared disaster emergencies, expecting a storm surge and up to of rain at that time. Six shelters were opened in Mobile County, Alabama, though few utilized them. Officials also considered opening shelters near local casinos and beaches in Biloxi, Mississippi. Accessed via the Wayback Machine. Alabama Governor Fob James also activated the state's National Guard ahead of the storm and directed 30,000 sandbags to the Alabama coast for protection.
Southeastern Massachusetts also had a tropical storm warning issued, a few hours before sustained tropical storm force winds affected the area and less than 12 hours before its closest approach to the coastline.
Impact
As a small storm, Hurricane Danny only caused a damage toll of $ (1997 USD, $ USD). A total of 4 direct and 5 indirect deaths resulted from the effects of Danny.
Gulf Coast Heavy rain and winds buffeted many parishes located east of the city of New Orleans. A small radius near the center of the storm had much of the extreme rainfall, and limited the flooding, which could have been disastrous if it were widespread. Grand Isle and portions of the lower Plaquemines Parish were the worst hit in Louisiana. Additionally, Grand Isle reported a wind gust of and a storm surge of . At New Orleans International Airport, sustained winds of and gusts of were reported on July 19. A gauge reported a water level of in Venice. Storm tides were above normal on average.
At least 10,000 people lost electricity in Louisiana. Furthermore, 130 boats were damaged or sunk at a large marina in Buras, Louisiana, due to the storm surge of over , in a matter of minutes. Both Grand Isle and Grand Terre Island received erosion on their shores, while many commercial fishing boats in Grand Isle were also heavily damaged. Accessed via the Wayback Machine. Around 160 households and 80 businesses reported damage on Grand Isle. Jefferson Parish and Plaquemines Parish had $ (1997 USD$, USD) and $ (1997 USD$, USD) total in damage respectively. Significant flooding happened throughout Jefferson Parish, with the floods affecting a total of 163 houses and 84 businesses. Meanwhile, in Plaquemines Parish, ten houses and 35 trailers had damage, with 8 businesses at least partially flooded and 40 commercial fishing boats also damaged. Lafourche Parish had no significant damage to report. Empire and Venice were the most damaged areas in Plaquemines Parish. In the areas of Plaquemines Parish within the hurricane protection levees, trees, power lines, house roofs, and mobile homes sustained damage, in addition to localized flooding throughout the parish after about 10 inches of rain. In lower Terrebonne Parish, some highways were flooded, due to storm tides, and a few roads were also flooded in St. Bernard and Orleans parishes, which were outside the hurricane protection levees. Negligible damage occurred elsewhere in the extreme southeastern portion of Louisiana, due to Danny being a small tropical cyclone and a minimal hurricane.
Eastern Jackson County had the greatest impact throughout Mississippi. Pascagoula reported a wind gust of on July 19. Pascagoula airport reported of rain from July 17 through July 19. Some streets and a few homes were flooded in far southeastern Jackson County, in areas of poor drainage systems. The coast of Mississippi had no significant damage according to emergency management officials. An oil rig off the coast of Pascagoula was ripped from its moorings and collided with a tank that spilled 500 gallons (1,892 L) of fuel into the Bayou Casotte stream.
By late on July 19, the American Red Cross was providing shelter to over 2,000 people in Alabama, Mississippi, and Florida.
Extreme amounts of rainfall were produced over Alabama. Dauphin Island had the highest amount of rainfall, reported by the HPC. Dauphin Island Sea Lab recorded of rain, but not all the rain may have recorded in the rain gauge at this location, so it is possible the rainfall may have been underestimated. Doppler weather radar estimates show that around of rain fell off the coast of Dauphin Island. A storm surge of over occurred off Highway 182, midway between Gulf Shores and Fort Morgan, in addition to the rainfall. Unusually, when the storm stalled off the coast of Alabama, prevailing northerly winds forced the water out of Mobile Bay, causing tides to be two feet (0.61 m) below normal. Observers noted that, if river channels had not remained, it would have been possible to walk across the bay unhindered by water. Additionally, a four-story condominium project that was under construction in Gulf Shores crashed due to high winds. In addition, three tornadoes occurred in Alabama, destroying a marina just south of Orange Beach and damaging several of the boats; Opelika, where damage was minimal; and Alabama Port respectively.
Despite its effects in the northern Gulf of Mexico, only one person was directly killed from the storm there; a man drowned off the coast when he fell off his sailboat near Fort Morgan, Alabama. One indirect casualty also occurred in the area, when a man had a heart attack while trying to secure a boat off the Alabama coast during the storm. Numerous roads became flooded and impassable for several days, south and along I-10 in Mobile, south and central Choctaw, and Baldwin counties. Along the Fowl and Fish rivers, in Mobile and Baldwin counties respectively, significant damage to homes occurred due to flooding. Most roads on Dauphin Island were flooded in over a foot of water. A few homes were close to falling into Mobile Bay, and one home had to be moved backwards towards land to prevent its destruction. At the peak of the storm in Alabama, at least 44,000 people were without power in Mobile and Baldwin counties. In rural Choctaw County, north of Mobile, several families were rescued from flooded roads and trapped cars. The majority of houses and businesses on Dauphin Island and buildings from the western shore of Mobile Bay, and from Fort Morgan east to Orange Beach, had roof damage$. (1997 USD$, USD) in total property damage occurred in Alabama, in addition to pecan and pine tree damage costing $ (1997 USD$, USD).
East Coast