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Tropical Storm Debby (2006)

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This article is about the 2006 storm. For past storms, see Hurricane Debby.
Tropical Storm Debby
tropical storm
FormedAugust 21, 2006
DissipatedAugust 27, 2006

Tropical Storm Debby was the fourth named storm of the 2006 Atlantic hurricane season. Debby formed just off the coast of Africa on August 21 from a tropical wave. After passing near the Cape Verde islands, Debby moved generally northwestward for much of its life, reaching a peak intensity of 50 mph (85 km/h). Strong wind shear weakened the storm, and Debby dissipated on August 27 over the northern Atlantic Ocean.

Early in its life, Debby was forecasted to pass through the southern Cape Verde islands as a tropical storm, potentially causing life-threatening flooding. Most computer models consistently predicted Debby to track to the northwest throughout its lifetime, though intensity was more problematic for forecasters. The National Hurricane Center continually predicted Debby to intensify to hurricane status, though strong vertical shear ultimately prevented the storm from becoming a hurricane.

Storm history

Map plotting the storm's track and intensity, according to the Saffir–Simpson scale
Map key
Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
triangle Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

A vigorous tropical wave moved off the coast of Africa late on August 20, and immediately showed signs of organization.[1] A broad area of low pressure formed within the wave the next day while located 260 miles southeast of the Cape Verde islands. Though convection decreased early on August 21, the area of low pressure remained well-organized[2] with well-defined banding features, and the system developed into Tropical Depression Four late on August 21. Water temperatures remained warm enough for development, while upper level shear was minimal as the depression moved west-northwestward due to a ridge of high pressure to its north.[3] Initial predictions by the National Hurricane Center also forecasted a motion to the northwest based on consistent model predictions, though, as quoted by forecaster James Franklin, "The models have also been excellently wrong thus far".[4]

Despite a decrease in convection shortly after forming, the large depression remained well organized, with a 575 mile wide wind field.[4] On August 22, as it passed 140 miles (225 km) miles to south of the Cape Verde islands, deep convection developed over the center of circulation,[5] and later that night the depression intensified into Tropical Storm Debby about 300 miles southwest of Cape Verde.[6] Banding features continued to organize as the system slowly strengthened,[7] and on August 23 Debby attained a peak intensity of 50 mph over the open waters of the Atlantic Ocean. Forecasters predicted Debby to continue to intensify to attain hurricane status, while its projected path placed the storm in an area of warm water temperatures and moderate upper level shear.[8]

Shortly after reaching its peak intensity, Debby encountered an area of dry air, and subsequently weakened. The low level circulation detached itself from the diminishing convection while the system as a whole continued west-northwestward.[9] Convection redeveloped over a portion of the center, while banding features redeveloped as well.[10] Organization continued, and Debby again reached its peak intensity of 50 mph on August 24.[11] Southerly wind shear displaced the convection to the north of the center, and Debby weakened to a minimal tropical storm on August 25.[12] The center of the storm became asymmetric and elongated,[13] and on August 26 Debby weakened to a tropical depression.[14] Convection remained minimal, and on August 27 the National Hurricane Center issued the last advisory on the dissipating system.[15]

Preparation and Impact

Tropical Depression Four to the southeast of the Cape Verde islands

The government of the Cape Verde islands issued a tropical storm warning coinciding with the issuance of the first advisory on Tropical Depression Four, meaning tropical storm conditions were expected in the area within 24 hours. The National Hurricane Center stated that heavy rainfall, potentially as high as 10 inches in mountainous areas, would be possible in the territory, possibly causing life-threatening flash floods and mudslides.[16] However, due to a reformation further to the south,[4] tropical storm advisories were discontinued as the depression passed away from the area.[17] Outer bands from the storm produced rainfall across the Cape Verde islands, though no damage was reported.[18]

Long range forecasts brought the storm near Bermuda.[18] However Debby remained over 900 miles from the island at its closest approach.[19]

Though the storm was forecasted to remain far away from the Gulf of Mexico, investors tracking the storm caused the price of crude oil to rise 60 cents a barrel due to the potential impact to oil installations.[20]

See also

Template:Tcportal

References

  1. ^ Brown/Stewart (2006). "August 20 Tropical Weather Outlook". NHC. Retrieved 2006-09-05.
  2. ^ Blake/Franklin (2006). "August 21 Tropical Weather Outlook". NHC. Retrieved 2006-09-05.
  3. ^ Franklin (2006). "Tropical Depression One Discussion". NHC. Retrieved 2006-09-05.
  4. ^ a b c Franklin (2006). "Tropical Depression Four Discussion Two". NHC. Retrieved 2006-09-05.
  5. ^ Brown (2006). "Tropical Depression Four Discussion Three". NHC. Retrieved 2006-09-05.
  6. ^ Stewart (2006). "Tropical Storm Debby Discussion Six". NHC. Retrieved 2006-09-05.
  7. ^ Brown (2006). "Tropical Storm Debby Discussion Seven". NHC. Retrieved 2006-09-05.
  8. ^ Franklin (2006). "Tropical Storm Debby Discussion Eight". NHC. Retrieved 2006-09-05.
  9. ^ Franklin (2006). "Tropical Storm Debby Discussion Nine". NHC. Retrieved 2006-09-05.
  10. ^ Stewart (2006). "Tropical Storm Debby Discussion Ten". NHC. Retrieved 2006-09-05.
  11. ^ Franklin (2006). "Tropical Storm Debby Discussion Twelve". NHC. Retrieved 2006-09-05.
  12. ^ Roberts/Beven (2006). "Tropical Storm Debby Discussion Sixteen". NHC. Retrieved 2006-09-05.
  13. ^ Berg/Knabb (2006). "Tropical Storm Debby Discussion Eighteen". NHC. Retrieved 2006-09-05.
  14. ^ Blake/Avila (2006). "Tropical Depression Debby Discussion Nineteen". NHC. Retrieved 2006-09-05.
  15. ^ Roberts/Pasch (2006). "Tropical Depression Debby Discussion Twenty-Five". NHC. Retrieved 2006-09-05.
  16. ^ Franklin (2006). "Tropical Depression Public Advisory One". NHC. Retrieved 2006-09-05.
  17. ^ Franklin (2006). "Tropical Depression Four Public Advisory Four". NHC. Retrieved 2006-09-05.
  18. ^ a b Associated Press (2006). "Tropical Depression Reaches Cape Verde Islands". Retrieved 2006-09-05.
  19. ^ Blake/Stewart (2006). "Tropical Depression Debby Discussion 23". NHC. Retrieved 2006-09-05.
  20. ^ Agence France-Presse (2006). "Oil prices up on new BP cut". Retrieved 2006-09-05.
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