Subtropical Storm Andrea (2007)
Subtropical Storm Andrea was a subtropical cyclone and first named storm of the Atlantic hurricane season of 2007. It developed on May 9 from an originally non-tropical low pressure area, about 240 kilometers northeast of Daytona Beach, Florida, three weeks before the official start of the hurricane season. After the storm was taken to dry air and wind shear vertical become stronger, he weakened on May 10 at a sub-tropical low pressure area and became almost stationary. On the morning of May 11, the National Hurricane Center put its weather warnings about Andrea no longer continue. The storm caused along the coast from Florida to North Carolina fierce waves, as well as coastal erosion and some property damage. Six people have drowned as a result of the storm.
Andrea was the first storm that formed since Tropical Storm Ana in April 2003 before the start of the official hurricane season and also the first benamte Storm in a Mai Since Arlene in 1981.
Storm History
Beginning of May ran a high-pressure trough in height southward in the western Atlantic Ocean, leading to its back, a cold front to the south. For a few days the Wettervorhersagmodelle assumed that the channel developed a closed low pressure area, and on May 6, located about 140 kilometers east of Cape Hatteras developed such a large and well-developed circulation. The low chatted sufficient convection and the interaction with the strong high pressure area in its north called a compact pressure gradient squalls near the coast out. The extratropical storm headed southeast and later turned to the southwest and the air pressure dropped steadily. On May 7, Andrea gusts reached hurricane force. Due to the lack of tropical moisture, the associated convection was minimal and dispersed.
The National Hurricane Center moved for the first time on May 8, the possibility of tropical cyclogenesis into consideration, when Andrea was 370 km east-southeast of the coast of South Carolina. The convection had increased steadily, as the system with 8-16 km / h moving westward. It changed little during the day, although the next morning found the hurricane experts that the low began to take on characteristics of a subtropical storm as it moved over first warm water. In the early 9th Mai fell a reconnaissance flight into the system persistent wind speeds of 70 km / h per hour and a shallow thermal core. This indicated that the system is neither a tropical cyclone was still an extratropical cyclone. In addition, the analysis of satellite imagery revealed a consolidation of convection near the center and sign an outflow in height and contraction of the radius of maximum wind speed of more than 185 km before to only about 120 km. Based on these observations and the hybrid structure of the system classified the National Hurricane Center, the low pressure area on May 9 at 15:00 UTC as Subtropical Storm Andrea. The system had its center at the time about 240 kilometers northeast of Daytona Beach in Florida. Due to an analysis carried out of the storm, the weather researchers suspected that the storm had nine hours earlier converted into a subtropical cyclone. Andrea was the first system since Tropical Storm Ana in April 2003, which developed before the official start of the Atlantic hurricane season. At the same time Andrea benamte the first storm was in May since Tropical Storm Arlene in 1981.
From the moment when Andrea was a subtropical cyclone, the storm was embedded in a large, almost stationary trough of low pressure, which led to a movement to the west. When Andrea came upon an area where the surface temperature of the sea water was not more than 25 ° C, the organizational structure of the system and the scattered convection decreased significantly. In the early morning of May 10, there was the bulk of the associated with Andrea weather east of the cyclone, within a band structure with slight convection due to a short period of western vertical wind shear. Moreover, the structure of the circulation center had suffered because had formed several smaller clouds swirl within the large circulation. This and increasing wind shear associated with dry air, which suppressed the convection caused a little later this morning a weakening of the storm. Around 15:00 UTC on May 10, just a few thunderstorms were left near the center and therefore classified the NHC Andrea to a sub-tropical low pressure area down. Although some little lasting thunderstorm survived in the eastern semicircle, the system was poorly organized and weak. Because since eighteen hours, there was no significant deep convection, the National Hurricane Center has not continued on the morning of May 11 the weather warnings when the system was about 125 km north-east of Cape Canaveral in Florida. Later that day, as the system moved to South - Southeast, the convection began again over the center. However, it lacked a strong enough organization to qualify as a tropical cyclone. Until May 12, the shower activity has shifted largely to the east side of the system and the National Hurricane Center noted that a small increase in convection in the formation of a tropical low pressure area would result. Andrea accelerated in an east - northeasterly direction, from the mainland of the United States away without neuzuentwickeln and after the system came over colder water, the remnants of Andrea merged on 14 May with an approaching cold front.
Preparations
Due to the high surf of the preceding lows the competent office of the National Weather Service had issued a warning for the largest part of the coast between Florida and North Carolina. From the scale-up to the subtropical storm at the National Hurricane Center announced a warning before a tropical storm for the area of the mouth of the Altamaha River in Georgia south to Flagler Beach in Florida. This warning was revoked, as Andrea weakened into a subtropical depression. A warning of gusts had been issued for the coast of South Carolina.
In Isle of Palms in South Carolina Volunteers and firefighters filled sandbags to be prepared for a high tide, after the surf caused by the storm had previously caused little beach erosion. As a precaution, the leaders broke off power and gas supply for several unoccupied buildings. The schools in Dare County in North Carolina were closed due to the threat of strong winds. The North Carolina Department of Transportation hired the ferry to and from Ocracoke and Knotts Iceland Iceland.
Effects
Before Andrea was a subtropical cyclone, the depression has caused high winds and dangerous waves along the coasts of North Carolina and Georgia, which later became the Florida coast concerned. Significant waves were also observed in the Bahamas. The waves caused beach erosion and washed against coastal settlements along the American east coast.
Off the coast of North Carolina, the storm caused waves of 10 m and strong wind storm that damaged three boats, so the crew had to be rescued by the Coast Guard. Another boat and its crew four people were reported missing and canceled the search, the Coast Guard after twelve days without result. Two kayakers drowned near Seabrook Iceland. One of them was found the next day and the body of the other a week later.
On the shore the wind reached a speed of 84 km / h in Norfolk, with unconfirmed 92 km / h near Virginia Beach. Similar observations were made along the Outer Banks, where the wind umknickte some trees and thereby interrupting power lines; some limited power outages were associated with it. In Elizabeth City, North Carolina the edge of a rain band brought within two hours of 10 mm of precipitation and lightning strikes; by which two firefighters were injured. The winds damaged houses and roofs covered parts of North Carolina Highway 12 with sand. The road had to be closed for a day because the storm had washed away about 60 m of the road. In some places, the storm eroded up to six meters of the shore, making 70 houses fell into immediate danger. On St. Simons Iceland in Georgia, the storm caused a storm surge of 2:43 m above normal. The recorded rainfall affected the southeastern corner of the state.
In Florida, about three meters high surf brought near Lantana a boat capsized; the two people on board were rescued unharmed. In addition, the waves washed away a sailboat, which had been thrown in Juno Beach shore. High waves flooded a parking lot and destroyed fences and hedges in Jupiter; near a maintenance shed was destroyed. Eight nests of the leatherback turtle in Boca Raton were destroyed when the surf reached the dunes. Because of the high waves of the Huntington Beach Pier had to be closed for a day in Flagler Beach. Low to medium coastal erosion prompted the Florida Department of Transportation to fill areas along the sea wall with sand. A surfer drowned in high surf off the coast of New Smyrna Beach in Volusia County. The outer band structure caused light rainfall, the maximum of about 20 mm occurred in Jacksonville responsibility of the National Weather Services. The gusts reached in the northeast of the state, the strength of a tropical storm. The winds spread the smoke from local forest fires over the area from Tampa Bay to Miami and fanned the heavy bush fires in northern Florida and southern Georgia on.