Subtropical Storm One (1992)

Infobox Hurricane
Name=Subtropical Storm One
Type=Subtropical storm
Year=1992
Basin=Atl
Image location=Subtropical Storm One 22 apr 1992 1834Z.jpg


Formed=April 21, 1992
Dissipated=April 24, 1992
1-min winds=45
Pressure=1002
Da

Inflated=
Fatalities=None
Areas=No land areas
Hurricane season=1992 Atlantic hurricane season

Subtropical Storm One in 1992 was the first recorded Atlantic subtropical cyclone during the month of April. It formed on April 21 about 600 miles (1,100 km) southeast of Bermuda, and tracking northwestward reached subtropical storm status on April 22. The cyclone attained peak winds of 50 mph (85 km/h) before increased wind shear weakened the storm. It turned to the east, and on April 24 dissipated without affecting land.

Meteorological history

On April 21, a low- to mid-level low pressure area separated from the prevailing westerlies about 600 miles (1,100 km) southeast of Bermuda. At the time, the system maintained a large comma-shaped cloud pattern, and reports from nearby ships indicated the system was at the surface. Based on its organization and the presence of a low-level circulation, it is estimated the system developed into a subtropical depression at 1200 UTC on April 21;cite web|author=National Hurricane Center|accessdate=2007-08-21|year=1992|title=Subtropical Storm One Preliminary Report|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/prenhc/prelim01.gif] operationally it was not classified until 27 hours later.Cite web|author=Lawrence|year=1992|title=Subtropical Storm One Discussion One|publisher=National Hurricane Center|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/tropdisc/nal0192.001] Removed from well-defined steering currents, the depression tracked northwestward at 12 mph (19 km/h), and intensified into a subtropical storm early on April 22.

The subtropical storm gradually became better organized with a large convective band in its eastern semicircle, and upon being classified it reached peak winds of 50 mph (85 km/h); a ship reported strong winds near the center of the cyclone, and the National Hurricane Center remarked the potential for the system transitioning into a tropical cyclone. With a building ridge to its southeast, the storm tracked northwestward, and under the influence of an approaching trough it decelerated as deep convection diminished.Cite web|author=Jarrell|year=1992|title=Subtropical Storm One Discussion Three|publisher=National Hurricane Center|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/tropdisc/nal0192.003] On April 23 the cyclone became nearly stationary and weakened to depression status after strong upper-level wind shear affected the area. A Hurricane Hunters flight into the system confirmed the decrease in winds; the flight also reported a 1.8° F (1° C) temperature rise in the center, suggesting a warm core and some tropical characteristics.cite web|author=National Hurricane Center|accessdate=2007-08-21|year=1992|title=Subtropical Storm One Preliminary Report (Page 2)|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/prenhc/prelim02.gif]

By early on April 24, the subtropical depression turned eastward, maintaining limited amounts of deep convection on its eastern semicircle. At the time, forecasters anticipated the depression would continue east-northeastward and become an extratropical cyclone, though the possibility of dissipation was mentioned.cite web|author=Rappaport|year=1992|title=Subtropical Depression One Discussion Seven|publisher=National Hurricane Center|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/tropdisc/nal0192.007] By late on April 24, however, the system was too weak to classify using the Dvorak technique; the National Hurricane Center ceased issuing advisories,cite web|author=Lawrence|year=1992|title=Subtropical Depression One Discussion Nine|publisher=National Hurricane Center|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/tropdisc/nal0192.009] and it failed to meet the criteria of a subtropical cyclone. Within 24 hours, the circulation dissipated as the system continued eastward through the westerlies.

Impact, records, and naming

Initially, the subtropical storm appeared to be a threat to Bermuda. The National Hurricane Center issued an 18 percent chance the center of the storm would pass within 65 miles (105 km) of the island;cite web|author=Lawrence|year=1992|title=Subtropical Storm One Strike Probabilities|publisher=National Hurricane Center|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/strike/lal0192.001] however it remained well southeast of the territory. The highest winds reported by a ship was 50 mph (85 km/h), from a vessel with the call signal "C6KD7". The ship recorded a pressure of 1004.1 mbar with swells of 64.4 feet (19.7 m);Cite web|author=National Hurricane Center|year=1992|title=April 22 Ship Data|accessdate=2007-08-21|url=http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/sfcdata/shp2206z.gif] the decision to issue advisories on the cyclone was based primarily on the ship report.

The storm was the first Atlantic subtropical cyclone on record to develop in the month of April. Previously, a tropical or subtropical cyclone had developed in every month but April. In its preliminary report on the cyclone, the National Hurricane Center notes, "subtropical cyclones have only been tracked since 1968 (tropical cyclone records go back to 1871) and it is possible some systems that were designated extratropical prior to 1968 could have been subtropical." Additionally, the subtropical storm was the first not to transition into a tropical cyclone since 1984. Subtropical cyclones were not named at the time, and were not named until 2001; had it been named, it would have been Subtropical Storm Andrew.cite web| author=NHC Hurricane Research Division|title=Atlantic hurricane best track|publisher=NOAA|year=2007|accessdate=2007-08-21|url=http://www.aoml.noaa.gov/hrd/hurdat/easyhurdat_5106.html]

See also

* Subtropical cyclone

External links

* [http://www.nhc.noaa.gov/archive/storm_wallets/atlantic/atl1992/st1/prenhc/prelim01.gifNational Hurricane Center Preliminary Report for Subtropical Storm]
* [http://ams.allenpress.com/archive/1520-0493/122/3/pdf/i1520-0493-122-3-517.pdf 1992 Atlantic Hurricane Season Summary]

References