Hurricane Danny (1997)

Hurricane Danny

Category 1 hurricane ( SSHS)
Hurricane Danny at peak intensity
Formed	July 16, 1997
Dissipated	July 27, 1997
Highest winds	1-minute sustained: 80 mph (130 km/h)
Lowest pressure	984 mbar ( hPa); 29.06 inHg
Fatalities	4 direct, 5 indirect
Damage	$100 million (1997 USD)
Areas affected	Louisiana, Mississippi, Alabama, Florida, Georgia, the Carolinas, Virginia, Massachusetts
Part of the 1997 Atlantic hurricane season

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 5th tropical or subtropical storm of the Atlantic season when it reached 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 had an extended northeast track through the Gulf of Mexico, caused by two high pressure systems, a rare occurrence in the middle of July. The storm moved across the southeastern United States, after making landfall in the Gulf Coast, and impacted parts of Massachusetts with rain and wind.

Danny is noted for the extreme rainfall, tornadoes, and damage it produced on its path, causing four direct fatalities and $100 million (1997 USD, $128 million 2007 USD) in damage. The storm dropped a record amount of rainfall for Alabama, at least 36.71 inches (932 mm) on Dauphin Island. Flooding, power outages, and erosion occurred in many areas of the Gulf Coast, and rescues from flooded roads had to be performed. Various tornadoes on the East Coast caused a great amount of damage. Danny caused one death off the coast of Alabama, four deaths in Georgia, two deaths in South Carolina, and two deaths in North Carolina.

Storm 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 centre, 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 the 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 strengthened baroclinically over North Carolina to a tropical storm on July 24. This is quite rare for a tropical cyclone, but it occurred due to interaction with a developing trough and its associated barolinic zone. Danny entered the Atlantic Ocean, north of the North Carolina- Virginia border, near Virginia Beach. It quickly reached a secondary peak of 60 mph (96 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 (48 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.

Preparations

The National Hurricane Centre 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, 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 being unable to leave the island. With a 5 foot (1.5 m) storm surge possibility, it 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.

Prior to the arrival of the hurricane, the governors of Mississippi and Alabama declared disaster emergencies, expecting a 9-foot (2.7 m) storm surge and up to 20 inches (510 mm) of rain at that time. Six shelters were opened in Mobile County, though few attended. Officials also considered opening shelters near local casinos and beaches in Biloxi, Mississippi.

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

Being a small storm, Danny caused a damage toll of only $100 million (1997 USD, $128 million 2007 USD). It caused a total of 4 direct and 5 indirect deaths.

Gulf Coast

Heavy rain and winds impacted many parishes located east of the city of New Orleans. A small radius near the centre 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 worst hit in Louisiana. Grand Isle reported a wind gust of 100 mph (160  km/h) and a storm surge of 5.2 feet (1.6 m). A gage reported a water level of 4.85 feet (1.5 m) in Venice. Storm tides were 2 to 3 feet (0.6 to 0.9 meters) above normal on average.

At least 10,000 people lost electricity in Louisiana. Also, 130 boats were damaged or sunk at a large marina in Buras, Louisiana, due to the storm surge of over 4 feet (1.2 m), in a matter of minuets. Both Grand Isle and Grand Terre Island received erosion on their shores. Around 160 households and 80 businesses reported damage on Grand Isle. Jefferson Parish, on Grand Isle, had $1.5 million (1997 USD, $1.93 million 2007 USD) total in damage. Plaquemines Parish, on Grand Isle, had $3.5 million (1997 USD, $4.5 million 2007 USD) in damage. Empire and Venice had the greatest damage in Plaquemines Parish. Within the hurricane protection levees in the parish, trees, power lines, house roofs, and mobile homes had damage inflicted, as well as the localized flooding that occurred in Plaquemines, after about 10 inches of rain. Some highways were flooded, due to storm tides, in lower Terrebonne Parish, and a few roads 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 most impact throughout Mississippi. Pascagoula reported a wind gust of 35 mph (55 km/h) on July 19. Pascagoula airport reported 7.87 inches (200 mm) 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.

Extreme amounts of rainfall were produced over Alabama. Dauphin Island had the highest amount of rainfall, 37.75 inches (959 mm) reported by the HPC. Dauphin Island Sea Lab recorded 36.71 inches (932 mm) 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 43 inches (1,090 mm) of rain fell off the coast of Dauphin Island. A storm surge of over 6.5 feet (1.98  m) occurred off Highway 182, midway between Gulf Shores, and Fort Morgan, Alabama, 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, with the exception of river channels, it would be possible to walk across the bay. In addition, three tornadoes occurred in Alabama, one being in Orange Beach, another in Opelika, while the other one occurred in Port Alabama. A couple of other tornadoes also caused minimal damage.

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. $60.5 million (1997 USD, $77 million 2007 USD) in total property damage occurred in Alabama, in addition to pecan and pine tree damage costing $2.5 million (1997 USD, $3.21 million 2007 USD).

East Coast

In the state of Florida, Some damage to the cotton crop occurred in Escambia County. Otherwise in northwestern Florida, very little damage resulted from the storm. The Panama City area had some minor fresh water flooding. By the time Danny reached Georgia and the Carolinas, its impact potential had weakened, though it still managed to cause 8-12 inches (203.2-304.8 mm) of rain as it drifted through the western portions of the states. A severe thunderstorm cell in South Carolina produced five tornadoes that touched down, one of which killed a woman in her destroyed duplex while passing through Lexington County. A F2 tornado began 4 miles (6.4 km) northeast of Gaston, South Carolina, which ended 7 miles (11 km) northeast of Gaston, with a width of 200 yards (183 m) and a length of 4 miles (6.5 kilometers), caused $942,000 (1997 USD, $1.21 million 2007 USD) in damage. It killed one person, injured 6 others, destroyed 2 houses, 2 apartments, and 7 mobile houses, damaging many others. Several tornadoes and waterspouts were spawned over Virginia; most of them occurred in Norfolk, Portsmouth, and Hampton. A F1 tornado occurred 1-mile (1.6 km) south of Norfolk, with a width of 50 yards (46 m) and a length of 1-mile (1.6 km), caused $400,000 (1997 USD, $513,890 2007 USD) in damage. It destroyed one car wash, six other businesses had major roof damage, and one other house had damage. Rainfall in Fayetteville measured 2.85 inches (72.4 mm) of rain, while the remainder of the Mid-Atlantic states received approximately 3 inches (75 mm) of rain.

The heavy rains caused two people to drown in Charlotte. A girl drowned after being swept into a creek by the floodwaters. Another woman drowned from the floodwaters while in her car. Four indirect deaths occurred from traffic accidents during the storm's onslaught in Georgia. The tornado in Portsmouth wiped out a car wash, caused six other businesses to suffer lesser damage, including a lumber company that had its roof torn off, and one large truck big-rig wheeler overturned. A severe drought had been in place in the Mid-Atlantic States during the month of July. Copious rainfall amounts helped bring a minor relief to the drought. Only minor damage occurred, despite strong winds experienced in southeastern Massachusetts. The minor damage included minimal flooding, power outages, and downed tree limbs.

Aftermath and records

Debris remained in the inland waters of Alabama, at least up until August 12, 1997. Endangered or threatened sea turtles, which all within U.S waters are identified as, lived in these waters. Specialized turtle exclusion devices, known as TED's, or specialized nets that allowed the turtles to escape them, were required before Danny for shrimp trawlers. The Director of the Marine Resources Division of the Alabama Department of Conservation and Natural Resources said that the "inordinate amount of debris is causing extraordinary difficulty with the performance of (TED's) in these areas." Therefore, the United States Environmental Protection Agency allowed an alternative to the TED's, of shorter tow times of a maximum of 55 minutes from April 1 through October 31, and a maximum of 75 minutes from November 1 through March 31. The EPA intended to minimize any sea turtle casualties as a result of allowing trawlers to remove the TED's.

The storm dropped 36.71 inches (932 mm) of rain on Dauphin Island, setting the new record for the most tropical or subtropical cyclone related rainfall in the state of Alabama, and is among the largest in the United States. The storm also became the earliest 5th tropical or subtropical storm of a season when it reached tropical storm strength on July 17. This record was broken in the 2005 Atlantic hurricane season when Hurricane Emily first attained tropical storm status on July 12, just five days earlier.

The name Danny was not retired by the World Meteorological Organization in the spring of 1998 and it was re-used in the 2003 Atlantic hurricane season. It is currently on the list of names to be used again in the 2009 Atlantic hurricane season.