Subtropical Storm Andrea (2007)

Infobox Hurricane
Name=Subtropical Storm Andrea
Type=Subtropical storm
Year=2007
Basin=Atl
Image location=Subtropical Storm Andrea (2007).jpg


Formed=May 9, 2007
Dissipated=May 11, 2007
1-min winds=50
Pressure=1001
Da

Inflated=
Fatalities=6 indirect
Areas=Virginia, North Carolina, South Carolina, Georgia, Florida, Bahamas
Hurricane season=2007 Atlantic hurricane season

Subtropical Storm Andrea was the first named storm and first subtropical cyclone of the 2007 Atlantic hurricane season. It developed out of a previously non-tropical low on May 9 about 150 miles (240 km) northeast of Daytona Beach, Florida, three weeks before the start of the season. After encountering dry air and increased vertical wind shear, Andrea weakened to a subtropical depression on May 10 while remaining nearly stationary, and early on May 11 the National Hurricane Center discontinued advisories. Andrea was the first pre-season storm to develop since Tropical Storm Ana in April 2003. Additionally, the storm was the first Atlantic named storm in May since Tropical Storm Arlene in 1981.cite web|author=Hurricane Research Division|year=2007|title=Hurdat Data for Tropical Cyclones 1851-2006|publisher=National Oceanic and Atmospheric Administration|accessdate=2006-10-11|url=http://www.nhc.noaa.gov/tracks1851to2006_atl.txt]

The storm produced rough surf along the coastline from Florida to North Carolina, causing beach erosion and some damage. In some areas, the waves eroded up to 20 feet (6 m) of beach, leaving 70 homes in imminent danger of collapse. Offshore of North Carolina, high waves of 34 feet (10 m) and tropical storm force winds damaged three boats; their combined nine passengers were rescued by the Coast Guard, although all nine sustained injuries. Light rainfall was also reported in some coastal locations. Damage was minimal, although six people drowned as a result of the storm.

Meteorological history

In early May, an upper level trough dropped southward through the western Atlantic Ocean, forcing a back door cold front—a cold front that moves southwestward ahead of a building surface ridge to its north or northeast—southward. For several days, forecast models had anticipated for the trough to evolve into a closed low pressure area,cite web|author=Cangialosi|year=2007|title=May 4 Tropical Weather Discussion|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Atl-Dis/2007050417.AXNT20] and on May 6, a frontal low with a large and well-defined circulation developed about 90 miles (140 km) east of Cape Hatteras. The low maintained scattered convection around its circulation, and in conjunction with the strong high pressure to its north a very tight pressure gradient produced gale force winds near the coastline.cite web|author=Cangialosi|year=2007|title=May 6 Tropical Weather Discussion|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Atl-Dis/2007050623.AXNT20] The extratropical storm tracked southeastward and later turned to the southwest, and steadily deepened; on May 7 it attained hurricane force winds.cite web|author=Jamie R. Rhome, Jack Beven, and Mark Willis|year=2007|title=Subtropical Storm Andrea Tropical Cyclone Report|publisher=National Hurricane Center|accessdate=2007-07-02|url=http://www.nhc.noaa.gov/pdf/TCR-AL012007_Andrea.pdf] With a lack of tropical moisture, its corresponding convection was minimal and scattered.cite web|author=Cangialosi|year=2007|title=May 7 Tropical Weather Discussion|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Atl-Dis/2007050723.AXNT20]

The National Hurricane Center first mentioned the possibility of tropical cyclogenesis on May 8 while about 230 miles (370 km) east-southeast of the South Carolina coastline. Its associated convection had steadily increased as it tracked slowly westward at 5 – 10 mph (8 – 16 km/h).cite web|author=Knabb|year=2007|title=May 8 Special Tropical Disturbance Statement|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007050813.WONT41] The system changed little throughout the day,cite web|author=Brown|year=2007|title=May 9 Special Tropical Disturbance Statement|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007050903.WONT41] though by the following morning hurricane specialists indicated the low was acquiring subtropical characteristicscite web|author=Franklin/Knabb|year=2007|title=May 9 Special Tropical Disturbance Statement (2)|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007050913.WONT41] as it tracked over progressively warmer waters. Early on May 9, a Hurricane Hunters flight into the system revealed winds of 45 mph (70 km/h) and a flat thermal core, which indicated the system was neither warm-core nor cold-core. In addition, satellite imagery indicated a consolidation of the convection near the center, as well as hints of upper-level outflow and a contraction of the radius of maximum winds from more than 115 miles (185 km) to about 70 miles (120 km). Based on the observations and the hybrid structure of the system, the National Hurricane Center classified the low as Subtropical Storm "Andrea" at 1500 UTC on May 9 about 150 miles (240 km) northeast of Daytona Beach, Florida.cite web|author=Knabb|year=2007|title=Subtropical Storm Andrea Discussion One|publisher=National Hurricane Center|accessdate=2007-05-09|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.001.shtml] During a subsequent analysis of the storm, researchers estimated the storm transitioned into a subtropical cyclone nine hours earlier. Andrea became the first pre-season storm to develop since Tropical Storm Ana in April 2003. Additionally, the storm was the first Atlantic named storm in May since Tropical Storm Arlene in 1981.cite web|author=Hurricane Research Division|year=2007|title=Hurdat Data for Tropical Cyclones 1851-2006|publisher=National Oceanic and Atmospheric Administration|accessdate=2006-10-11|url=http://www.nhc.noaa.gov/tracks1851to2006_atl.txt] Upon first becoming a subtropical cyclone, Andrea was embedded within a large, nearly stationary deep-layer trough, resulting in a westward movement. Drifting over sea surface temperatures of no more than 77º F (25º C), the organization of the system deteriorated with a significant decrease in convection;cite web|author=Knabb|year=2007|title=Subtropical Storm Andrea Discussion Two|publisher=National Hurricane Center|accessdate=2007-05-09|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.002.shtml] by early on May 10 much of the associated weather was located to the east of the cyclone within a band of moderate convection due to a brief spell of westerly vertical wind shear. Additionally, the center of circulation had become disorganized, with several small cloud swirls within the larger circulation.cite web|author=Avila|year=2007|title=Subtropical Storm Andrea Discussion Three|publisher=National Hurricane Center|accessdate=2007-05-09|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.003.shtml] This disorganization of the center, combined with increasing wind shear and dry air suppressing convective activity, caused it to begin weakening later that morning.cite web|author=Mainelli|year=2007|title=Subtropical Storm Andrea Discussion Four|publisher=National Hurricane Center|accessdate=2007-05-10|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.004.shtml] By 1500 UTC on May 10, only a few thunderstorms remained near the center, and thus the NHC downgraded Andrea to subtropical depression status.cite web|author=Knabb|year=2007|title=Subtropical Depression Andrea Discussion Five|publisher=National Hurricane Center|accessdate=2007-05-10|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.005.shtml?] Though a few intermittent thunderstorms persisted over the eastern semicircle, it was disorganized and weak; having been without significant deep convection for 18 hours, the National Hurricane Center discontinued advisories early on May 11 while located about 80 miles (125 km) northeast of Cape Canaveral, Florida.cite web|author=Rhome|year=2007|title=Subtropical Depression Andrea Discussion Seven|accessdate=2007-05-10|url=http://www.nhc.noaa.gov/archive/2007/al01/al012007.discus.007.shtml?]

Later on May 11, convection again re-fired over the center as it drifted south-southeastward, though it lacked sufficient organization to qualify it as a tropical cyclone.cite web|author=Knabb|year=2007|title=May 11 Special Tropical Disturbance Statement|accessdate=2007-05-11|publisher=National Hurricane Center|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007051118.WONT41] By May 12, shower activity had organized greatly to the east of the center, and the National Hurricane Center remarked that a small increase in convection would result in the formation of a tropical depression.cite web|author=Franklin|year=2007|title=May 12 Special Tropical Disturbance Statement|publisher=National Hurricane Center|accessdate=2007-05-13|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007051118.WONT41] It accelerated east-northeastward away from the continental United States without redeveloping, and after passing over cooler waterscite web|author=Beven|year=2007|title=May 13 Special Tropical Disturbance Statement|publisher=National Hurricane Center|accessdate=2007-05-13|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Disturbance/2007051314.WONT41] the remnants of Andrea merged with an approaching cold front on May 14.cite web|author=National Hurricane Center|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Outlook-A/2007060109.ABNT20|title=June 1 Tropical Weather Outlook|accessdate=2007-06-01]

Preparations

Due to rough surf from the precursor low, local National Weather Service offices issued a High Surf Advisory for much of the coastline from Florida through North Carolina. Upon first becoming a subtropical cyclone, the National Hurricane Center issued a tropical storm watch from the mouth of the Altamaha River in Georgia southward to Flagler Beach, Florida.cite web|author=Knabb|year=2007|title=Subtropical Storm Andrea Public Advisory One|publisher=National Hurricane Center|accessdate=2007-05-09|url=http://www.nhc.noaa.gov/text/refresh/MIATCPAT1+shtml/091443.shtml] The watch was discontinued after Andrea weakened to a subtropical depression. Additionally, a gale warning was issued for much of the South Carolina coastline.cite web|author=Jennifer Wilson|year=2007|title=Forecasters: Subtropical Storm Andrea has formed|publisher=WIStv Columbia, South Carolina|accessdate=2007-05-09|url=http://www.wistv.com/Global/story.asp?S=6488453&nav=menu36_2]

At Isle of Palms in South Carolina, workers and dozens of firefighters prepared sandbags in preparation for high tide after waves from the storm previously caused moderate beach erosion. As a precaution, officials there intentionally cut power and gas to multiple uninhabited buildings. Officials closed schools in Dare County, North Carolina due to the threat for high winds from the storm. The North Carolina Department of Transportation also canceled ferry transportation to and from Ocracoke and Knotts Island, North Carolina.

Impact

Prior to becoming a subtropical cyclone, the low produced gale force winds and dangerous surf near the coast from North Carolina through Georgia, and later along the coast of Florida. Significant swells were also reported in the Bahamas.cite web|author=Willis|year=2007|title=May 8 Tropical Weather Discussion|publisher=National Hurricane Center|accessdate=2007-05-09|url=ftp://ftp.met.fsu.edu/pub/weather/tropical/Atl-Dis/2007050810.AXNT20] The waves caused beach erosion and washed up against coastal house along the southeast coast of the United States.cite web|author=Jessica Gresko|year=2007|title=Year's first named storm becomes Andrea, forms 3 weeks before hurricane season begins|publisher=Associated Press|accessdate=2007-05-09|url=http://www.sun-sentinel.com/news/weather/hurricane/sfl-59andrea,0,6774716.story?coll=sfla-news-hurricane]

Off the coast of North Carolina, the storm produced 34-foot (10-m) waves and storm force winds which damaged three boats; their combined nine passengers were rescued by the Coast Guard. All nine were injured to some degree; three endured hypothermia, one received a broken rib, and one Coast Guardsman experienced back injuries from the surf.cite news|author=Virginia Pilot|date=2007-05-08|title=High drama on high seas|accessdate=2007-05-09] Another boat and its four occupants were reported missing,cite web|author=Lauren King and Kristin Davis|year=2007|title=Season's first named storm unleashes band of rain|publisher=Virginia Pilot|accessdate=2007-05-09|url=http://content.hamptonroads.com/story.cfm?story=124356&ran=45076] cite web|author=Sunbeam Television|year=2007|title=Coast Guard continues search for missing sailors|accessdate=2007-05-10|url=http://www3.whdh.com/news/articles/local/BO51728] and after twelve days they remain missing. [cite web|author=Amanda Milkovits|year=2007|title=Sailors’ circle holds hope|publisher=The Providence Journal|accessdate=2007-05-18|url=http://www.projo.com/news/content/a_sailors_life_05-18-07_UB5M866.355c273.html] Rough waves from the precursor low left two kayakers missing near Seabrook Island, South Carolina. One was found the next day,cite web|author=Associated Press|year=2007|title=First named '07 Atlantic storm forms near coast|accessdate=2007-05-09|url=http://www.msnbc.msn.com/id/18573390/] and the other was found dead a week later.cite web|author=Associated Press|year=2007|title=DNA identifies missing Atlanta kayaker's body in S.C.|accessdate=2007-05-26|url=http://www.macon.com/220/story/49774.html]

Onshore, winds reached 52 mph (84 km/h) in Norfolk, Virginia, with an unofficial report of 57 mph (92 km/h) near Virginia Beach. Similar observations occurred along the Outer Banks,cite news|author="Virginia Pilot"|date=2007-05-07|title=Wind and chill chase away spring today's weather|accessdate=2007-05-09] with the winds knocking some tree limbs onto power lines;cite web|author=Francine Sawyer|publisher=New Bern Sun Journal|accessdate=2007-05-09|year=2007|title=Storm moving away from coast|url=http://www.newbernsj.com/news/weather_34221___article.html/service_winds.html] some isolated power outages were reported. Wind damage included some roofs losing shingles from the winds. In Elizabeth City, North Carolina, an outer rainband dropped 0.5 inches (10 mm) of precipitation in about two hours as well as several lightning strikes; one bolt of lightning injured two firefighters. The winds covered portions of North Carolina Highway 12 with sand,cite news|author=Virginia Pilot|date=2007-05-07|title=Wind and chill chase away spring today's weather|accessdate=2007-05-09] and for a day the route was closed after waves from the storm washed out about 200 feet (60 m) of roadway. In some locations, the waves eroded up to 20 feet (6 m) of beach, leaving 70 homes in imminent danger.cite web|author=Bryan Mims|publisher=WRAL.com|year=2007|accessdate=2007-05-09|title=Offshore Storm System Raked N.C. Beaches|url=http://www.wral.com/weather/story/1399195/] On St. Simons Island in Georgia, the storm produced a storm tide of 8.09 feet (2.43 m). Trace amounts of rainfall occurred in the southeastern portion of the state.

In Florida, waves of over 10 feet (3 m) in height capsized a boat near Lantana; the two occupants were rescued without injury. Additionally, the waves displaced a sailboat that had previously been washed ashore in Juno Beach. Large waves flooded a parking lot and destroyed several fences and tree branches at Jupiter Beach, which resulted in its temporary closure; nearby a maintenance shed was destroyed. Eight Leatherback Sea Turtle nests in Boca Raton were destroyed after the surf reached the dunes.cite news|author=Erika Pesantes, Sally Apgar and Chrystian Tejedor|date=2007-05-09|title=Sweeping erosion hits Palm Beach County coast: Low-pressure system sucks swaths of sand; Jupiter feels brunt of it|publisher="South Florida Sun-Sentinel"|accessdate=2007-05-09] Due to high surf, the beach pier at Flagler Beach was closed for about a day. Minor to moderate beach erosion caused the Florida Department of Transportation to fill in areas near the seawall with sand. One death occurred when a surfer drowned in the rough waves off the coast at New Smyrna Beach in Volusia County.cite web|author=Tanya Caldwell|year=2007|title=Holly Hill surfer drowns after taking on 'gigantic wave' in New Smyrna Beach | publisher= Orlando Sentinel | accessdate=2007-05-10 | url=http://www.orlandosentinel.com/news/local/volusia/orl-bk-surfer050907,0,934936.story?coll=orl-home-headlines] Outer rainbands produced light rainfall, with the highest report in the Jacksonville National Weather Service area of responsibility totaling 0.77 inches (20 mm); the bands also cause tropical storm force wind gusts in the northeastern portion of the state.cite web|author=Keegan, Shashy, McAllister, & Enyedi|year=2007|title=Post-Tropical Cyclone Report|publisher=Jacksonville, Florida National Weather Service|accessdate=2007-05-19|url=http://www.webcitation.org/5Oy3NRnN6] The winds spread smoke from local brush fires through the Tampa Bay area to Miami.cite web|author=Staff Writer|year=2007|title=Subtropical storm Andrea is swirling off the north Florida coastline|publisher=Bradenton Herald|accessdate=2007-05-09|url=http://www.bradenton.com/180/story/43841.html] cite web|author=CNN Staff Writer|year=2007|title=Atlantic's first named storm whips up wildfires
publisher=CNN|accessdate=2007-05-10|url=http://www.cnn.com/2007/WEATHER/05/09/storm.andrea/index.html] High winds from Andrea were reported as fueling severe wildfires in northern Florida and southern Georgia.cite news | title = 'Fire of a lifetime' hits North Florida | url = http://www.orlandosentinel.com/news/local/state/orl-fire1207may12,0,3010146.story?coll=orl-news-headlines-state | accessdate = 2007-05-13 | date = 2007-05-12 | author = Kevin Spear and Jim Stratton | publisher = Orlando Sentinel]

Because the damage from Subtropical Storm Andrea was minimal, the name Andrea was not retired, and is on the list of names for the 2013 Atlantic hurricane season.

See also

*

References

External links

* [http://www.nhc.noaa.gov/pdf/TCR-AL012007_Andrea.pdf Tropical Cyclone Report]
* [http://www.nhc.noaa.gov/archive/2007/ANDREA.shtml? Advisory archive on Subtropical Storm Andrea]