Meteorological history of Hurricane Dean

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Hurricane Dean
Category 5 hurricane (SSHS)
Track of Hurricane Dean

Track of Hurricane Dean
Formed August 13, 2007
Dissipated August 23, 2007
Highest
winds
175 mph (280 km/h) (1-minute sustained)
Lowest pressure 905 mbar (hPa; 26.74 inHg)
Fatalities {{{Fatalities}}}
Damage Unknown
Areas
affected		 Windward Islands (especially St. Lucia, Martinique and Dominica), Leeward Islands, Puerto Rico, Dominican Republic, Haiti, Jamaica, Cayman Islands, Mexico, Belize, Honduras, Nicaragua
Part of the
2007 Atlantic hurricane season

The meteorological history of Hurricane Dean began in the second week of August 2007 when a vigorous tropical wave moved off the west coast of Africa into the North Atlantic basin. Although the wave initially experienced strong easterly wind shear it quickly moved into an environment better suited for tropical development and began to gain organization. On the morning of August 13 the National Hurricane Center recognized the system's organization and designated it Tropical Depression Four while it was still more than 1500 miles (2400 km) east of the Lesser Antilles.

A deep layered ridge to its north steered the system west as it moved rapidly towards the Caribbean and into warmer waters. On August 14 the depression gained strength and was upgraded to Tropical Storm Dean and by August 16 the storm had intensified further and reached hurricane status. Hurricane Dean continued to intensify as it tracked westward through the Lesser Antilles and into the Caribbean. It brushed the southern coast of Jamaica on August 19 as a Category 4 Hurricane and continued towards the Yucatán Peninsula through even warmer waters. The favorable conditions of the western Caribbean Sea allowed the storm to intensify and it reached Category 5 status the next day. It was the seventh most intense Atlantic hurricane ever recorded (tied with Camille and Mitch).

Contents

[edit] Formation

MODIS image of the Low that eventually became Hurricane Dean. Taken at 1245 UTC on August 12, 2007
MODIS image of the Low that eventually became Hurricane Dean. Taken at 1245 UTC on August 12, 2007
Hurricane Dean as seen from MODIS on Terra at 1400 UTC August 16, 2007, approaching the Lesser Antilles
Hurricane Dean as seen from MODIS on Terra at 1400 UTC August 16, 2007, approaching the Lesser Antilles

On August 11, 2007, a vigorous tropical wave moved off the west coast of Africa,[1] producing disorganized showers and thunderstorms.[2] It encountered conditions favorable for gradual development,[3] and on August 12 it gained organization and became a low.[4] Strong upper-level easterly winds stalled development by preventing much more organization.[5][6] On August 13 the tropical wave organized and, based on visible and infrared satellite imagery, the National Hurricane Center concluded that it had formed into Tropical Depression Four at 1500 UTC about 520 miles (835 km) west-southwest of Cape Verde.[7]

The depression was already exhibiting persistent deep convection, albeit confined to the western portion of its circulation due to easterly wind shear.[8] The depression was expected to strengthen significantly over the coming days[8] due to abating wind shear and warming sea surface temperatures which created conditions favorable for tropical intensification.[9] It moved briskly westward, south of a deep layered ridge,[10] quickly escaping the easterly shear and moving over warmer waters.[11]

Based on microwave satellite images and QuikSCAT data, the depression was upgraded to Tropical Storm Dean at 1500 UTC on August 14.[12] That afternoon its convection waned slightly as part of a diurnal fluctuation, but an AMSU pass suggested growing intensity.[13] Intensity continued to build as convection flared in the center on the night of August 14. This was most likely due to continuing decreases in the easterly wind shear.[14] Dry air and cooler air inflow from the north were slowing structural development, but nevertheless ragged bands began to form on August 15.[15] By mid-morning hints of a banding eye had been spotted on satellite imagery[16] and the storm continued to strengthen.[17] Visible satellite images showed a tightly curved band wrapping around the center later that day and microwave images suggested the formation of a partial eyewall.[18]

Intensification continued through the night[19] and the storm was upgraded to Hurricane Dean at 5 am EDT (9 am UTC) August 16.[20] A strong deep-layered ridge continued to steer the system west, towards the Caribbean Sea.[21] That same afternoon convective banding and increasing upper-level outflow strengthened the storm to a Category 2 hurricane on the Saffir-Simpson Hurricane Scale.[22] The eye disappeared briefly overnight, possibly as part of a diurnal fluctuation,[23] and a ragged eye had returned by the early morning of August 17. Dry air intrusion and slight westerly shear appeared to slow but not reverse the storm's development.[24]

[edit] Caribbean Sea

Infrared satellite image of Hurricane Dean on August 18, 2007 as it churned through the eastern Caribbean Sea
Infrared satellite image of Hurricane Dean on August 18, 2007 as it churned through the eastern Caribbean Sea
Hurricane Dean as seen from MODIS on Terra at 1525 UTC August 18, 2007, south of the island of Hispaniola
Hurricane Dean as seen from MODIS on Terra at 1525 UTC August 18, 2007, south of the island of Hispaniola

A reconnaissance aircraft later on morning of August 17 discovered a closed eyewall, and increased banding created a more organized cloud pattern on satellite imagery.[25] Data from the aircraft also indicated that Hurricane Dean had strengthened to a Category 3 hurricane.[26] Satellite imagery on the evening of August 17 showed a well defined eye feature as numerous cyclonically curved convective bands remained over the Lesser Antilles. Low shear and increasing ocean temperatures along the storm's westward track lead forecasters to predict a continued intensifying trend.[27] That evening another reconnaissance aircraft reached the hurricane and discovered that it had strengthened into a Category 4 hurricane.[28] Additional reconnaissance aircraft equipped with a stepped-frequency microwave radiometer confirmed the Dvorak estimates which showed that Hurricane Dean was steadily intensifying through the night. By early on August 18, Dean reached Category 5 intensity for the first time with 165 mph (270 km/h) winds.[29] The aircraft data also showed that the wind radii had increased in all quadrants as the storm grew not only in intensity but also in size.[30][31] Tt 4 a.m. AST (0800 UTC) August 18, NOAA sea buoy 42059 took a direct hit from Hurricane Dean[30] and reported a significant wave height of 33 feet (10 m).[32] Another reconnaissance aircraft on August 18 reported the presence of a double eyewall,[33] indicating an eyewall replacement cycle and causing short term fluctuations in intensity as Dean weakened back to Category 4 intensity.[29][34][35] That afternoon the hurricane was seen to have numerous spiral bands and continued to improve its outflow, giving it a well defined satellite presentation.[33] Hurricane Dean weakened slightly on morning of August 19 and experienced some trochiodal wobbles as it finished the eyewall replacement cycle.[36][37]

[edit] Peak intensity and landfall

Most intense Atlantic hurricanes
Intensity is measured solely by central pressure
Rank Hurricane Season Min. pressure
1 Wilma 2005 882 mbar (hPa)
2 Gilbert 1988 888 mbar (hPa)
3 "Labor Day" 1935 892 mbar (hPa)
4 Rita 2005 895 mbar (hPa)
5 Allen 1980 899 mbar (hPa)
6 Katrina 2005 902 mbar (hPa)
7 Camille 1969 905 mbar (hPa)
Mitch 1998 905 mbar (hPa)
Dean 2007 905 mbar (hPa)
10 Ivan 2004 910 mbar (hPa)
Source: U.S. Department of Commerce
Hurricane Dean as a Category 4 storm on August 20 at approximately 1841 UTC, 14 hours before landfall.
Hurricane Dean as a Category 4 storm on August 20 at approximately 1841 UTC, 14 hours before landfall.

As Hurricane Dean passed south of Jamaica on the evening of August 19 the eye began to clear and the outer eyewall became dominant over the inner one.[38] The storm began to intensify again that night[39] and a contracting single-walled eye confirmed that the storm had completed its eyewall replacement cycle.[40] At 0100 UTC August 20 the storm passed 120 miles (190 km) to the south of sea buoy 42056 which recorded a significant wave height of 36 feet (11 m).[41] A concentric eyewall was briefly observed again on the morning of August 20, but did not last long. In conditions of low wind shear, the hurricane moved over waters with extremely high heat content and Hurricane Dean exhibited a classic upper-tropospheric outflow pattern. The deep-layer high pressure system over the southeastern United States continued to steer the storm west, towards the Yucatán Peninsula.[42] The eyewall became even better defined throughout the day and the cloud tops cooled, signifying a strengthening trend.[43] That afternoon a reconnaissance aircraft reported a falling minimum central pressure[44] and winds of 160 mph, making Hurricane Dean a Category 5 hurricane[45] less than 210 miles (335 km) from its first landfall.[46] Although many of the convective bands were already located over the Yucatán Peninsula Hurricane Dean continued to intensify right up to landfall.

Another aircraft reached the storm just hours before landfall and deployed several dropsondes. Based on data from a dropsonde in the northern eyewall the NHC estimated surface level winds of 175 mph (280 km/h)[29], making Dean the first storm to make landfall as a Category 5 hurricane in the Atlantic basin since Hurricane Andrew in 1992. Another dropsonde, this one in the eye, estimated a central pressure of 905 mbar, tying Dean with Camille and Mitch for the seventh most intense Atlantic hurricane ever recorded, and was the third most intense landfalling Atlantic storm in history (after the Labor Day Hurricane of 1935 and Hurricane Gilbert of 1988).[29] The landfall itself occurred in a sparsely populated area of the Costa Maya region of the Mexican state of Quintana Roo near 18.7 N 87.8 W at 4 a.m. CDT (0900 UTC) August 21 and brought with it a storm surge of 12 to 18 feet.[47] As expected the landfall caused significant weakening of the storm: the eye filled and the cold cloud-tops warmed.[48] By the time Dean had crossed the Yucatán Peninsula it had weakened to a Category 1 storm.[49]

[edit] Gulf of Mexico and Demise

Hurricane Dean emerged into the Bay of Campeche shortly after 5 p.m. CDT (1000 UTC) as a Category 1 hurricane. Its inner core was thought to have remained largely intact throughout the land interaction and deep convection persisted over the center,[50] so when a ragged eye to quickly reform over the warm waters of the bay forecasters were predicting that Dean could reintensity into a Category 3 hurricane before making its second landfall.[51] However Hurricane Hunters discovered on August 22 that the core had collapsed as it passed over the Yucatán Peninsula on the previous day and forecasters reduced their estimates.[52] Later that morning the inner core wind field contracted and winds increased as the hurricane re-strengthened to Category 2 storm, but it was too close to its second landfall to strengthen much further.[53] Hurricane Dean made its final landfall at 11:30 a.m. CDT (1600 UTC) August 22 near Tecolutla, Veracruz, just east of Gutiérrez Zamora and about 40 miles (65 km) south-southeast of Tuxpan.[54] The storm generated deep convection even as its overall cloud pattern deteriorated on its westward course towards the mountains.[55] Dean weakened rapidly, losing its low level circulation within hours and its mid-level circulation by the next day. The remnants passed over the mountains and into the eastern Pacific as a broad area of low pressure.[56]

[edit] See also

Tropical cyclones Portal

[edit] References

  1. ^ Knabb (2007). August 11 Tropical Weather Outlook (1130). National Hurricane Center. Retrieved on 2007-08-14.
  2. ^ Rhome (2007). August 11 Tropical Weather Outlook (1730). National Hurricane Center. Retrieved on 2007-08-14.
  3. ^ Rhome (2007). August 12 Tropical Weather Outlook (0530). National Hurricane Center. Retrieved on 2007-08-14.
  4. ^ Rhome (2007). August 12 Tropical Weather Outlook (1130). National Hurricane Center. Retrieved on 2007-08-14.
  5. ^ Brown/Franklin (2007). August 12 Tropical Weather Outlook (1730). National Hurricane Center. Retrieved on 2007-08-14.
  6. ^ Brown (2007). August 12 Tropical Weather Outlook (2230). National Hurricane Center. Retrieved on 2007-08-14.
  7. ^ Knabb/Blake (2007). August 13 Tropical Weather Outlook (1130). National Hurricane Center. Retrieved on 2007-08-14.
  8. ^ a b Knabb (2007). Tropical Depression Four Discussion One. National Hurricane Center. Retrieved on 2007-08-14.
  9. ^ Knabb (2007). Tropical Depression Four Discussion Two. National Hurricane Center. Retrieved on 2007-08-14.
  10. ^ Brown/Franklin (2007). Tropical Depression Four Discussion Three. National Hurricane Center. Retrieved on 2007-08-14.
  11. ^ Rhome (2007). Tropical Depression Four Discussion Four. National Hurricane Center. Retrieved on 2007-08-14.
  12. ^ Avila (2007). Tropical Storm Dean Discussion Five. National Hurricane Center. Retrieved on 2007-08-14.
  13. ^ Landsea/Knabb (2007). Tropical Storm Dean Discussion Six. National Hurricane Center. Retrieved on 2007-08-15.
  14. ^ Brown (2007). Tropical Storm Dean Discussion Seven. National Hurricane Center. Retrieved on 2007-08-15.
  15. ^ Beven (2007). Tropical Storm Dean Discussion Eight. National Hurricane Center. Retrieved on 2007-08-15.
  16. ^ Blake (2007). Tropical Storm Dean Discussion Nine. National Hurricane Center. Retrieved on 2007-08-15.
  17. ^ Blake (2007). Tropical Storm Dean Public Advisory Nine. National Hurricane Center. Retrieved on 2007-08-15.
  18. ^ Blake (2007). Tropical Storm Dean Discussion Ten. National Hurricane Center. Retrieved on 2007-08-15.
  19. ^ Brown (2007). Tropical Storm Dean Discussion Eleven. National Hurricane Center. Retrieved on 2007-08-16.
  20. ^ Beven (2007). Hurricane Dean Discussion Twelve. National Hurricane Center. Retrieved on 2007-08-16.
  21. ^ Blake (2007). Hurricane Dean Discussion Thirteen. National Hurricane Center. Retrieved on 2007-08-16.
  22. ^ Avila/Blake (2007). Hurricane Dean Discussion Fourteen. National Hurricane Center. Retrieved on 2007-08-16.
  23. ^ Franklin (2007). Hurricane Dean Discussion Fifteen. National Hurricane Center. Retrieved on 2007-08-17.
  24. ^ Beven (2007). Hurricane Dean Discussion Sixteen. National Hurricane Center. Retrieved on 2007-08-16.
  25. ^ Avila (2007). Hurricane Dean Discussion Seventeen. National Hurricane Center. Retrieved on 2007-08-17.
  26. ^ Avila/Mainelli (2007). Hurricane Dean Discussion Eighteen. National Hurricane Center. Retrieved on 2007-08-17.
  27. ^ Avila (2007). Hurricane Dean Special Discussion Nineteen. National Hurricane Center. Retrieved on 2007-08-17.
  28. ^ Knabb (2007). Hurricane Dean Intermediate Advisory Nineteen 'A'. National Hurricane Center. Retrieved on 2007-08-17.
  29. ^ a b c d Franklin (2008). Tropical Cyclone Report for Hurricane Dean. National Hurricane Center. Retrieved on 2008-01-31.
  30. ^ a b Knabb (2007). Hurricane Dean Discussion Twenty. National Hurricane Center. Retrieved on 2007-08-17.
  31. ^ Beven (2007). Hurricane Dean Discussion Twenty One. National Hurricane Center. Retrieved on 2007-08-18.
  32. ^ NOAA (2007). Significant Wave Height at 42059. National Data Buoy Center. Retrieved on 2007-08-16.
  33. ^ a b Avila (2007). Hurricane Dean Discussion Twenty Three. National Hurricane Center. Retrieved on 2007-08-18.
  34. ^ Avila (2007). Hurricane Dean Discussion Twenty Two. National Hurricane Center. Retrieved on 2007-08-18.
  35. ^ Knabb (2007). Hurricane Dean Discussion Twenty Four. National Hurricane Center. Retrieved on 2007-08-18.
  36. ^ Pasch/Brown (2007). Hurricane Dean Discussion Twenty Five. National Hurricane Center. Retrieved on 2007-08-19.
  37. ^ Franklin (2007). Hurricane Dean Discussion Twenty Six. National Hurricane Center. Retrieved on 2007-08-19.
  38. ^ Franklin/Rhome (2007). Hurricane Dean Discussion Twenty Seven. National Hurricane Center. Retrieved on 2007-08-20.
  39. ^ Blake (2007). Hurricane Dean Public Advisory Twenty Eight. National Hurricane Center. Retrieved on 2007-08-20.
  40. ^ Knabb (2007). Hurricane Dean Discussion Twenty Eight. National Hurricane Center. Retrieved on 2007-08-20.
  41. ^ NOAA (2007-08-20). Significant Wave Height at 42056. National Data Buoy Center. Retrieved on 2007-08-20.
  42. ^ Pasch/Brown (2007). Hurricane Dean Discussion Twenty Nine. National Hurricane Center. Retrieved on 2007-08-20.
  43. ^ Franklin (2007). Hurricane Dean Discussion Thirty. National Hurricane Center. Retrieved on 2007-08-20.
  44. ^ Franklin (2007). Hurricane Dean Discussion Thirty One. National Hurricane Center. Retrieved on 2007-08-20.
  45. ^ Knabb (2007). Hurricane Dean Tropical Cyclone Update. National Hurricane Center. Retrieved on 2007-08-20.
  46. ^ Knabb/Roberts (2007-08-20). Hurricane Dean Intermediate Advisory Thirty One A. National Hurricane Center. Retrieved on 2007-08-20.
  47. ^ Blake (2007-08-21). Hurricane Dean Public Advisory Thirty Three. National Hurricane Center. Retrieved on 2007-08-21.
  48. ^ Franklin (2007-08-21). Hurricane Dean Discussion Thirty Four. National Hurricane Center. Retrieved on 2007-08-21.
  49. ^ Franklin/Rhome (2007-08-21). Hurricane Dean Intermediate Advisory Thirty Four A. National Hurricane Center. Retrieved on 2007-08-21.
  50. ^ Franklin (2007-08-21). Hurricane Dean Discussion Thirty Five. National Hurricane Center. Retrieved on 2007-08-21.
  51. ^ Avila (2007-08-21). Hurricane Dean Discussion Thirty Six. National Hurricane Center. Retrieved on 2007-08-21.
  52. ^ Beven (2007-08-22). Hurricane Dean Discussion Thirty Seven. National Hurricane Center. Retrieved on 2007-08-22.
  53. ^ Franklin/Mainelli (2007-08-22). Hurricane Dean Discussion Thirty Eight. National Hurricane Center. Retrieved on 2007-08-22.
  54. ^ Franklin (2007-08-22). Hurricane Dean Tropical Cyclone Update. National Hurricane Center. Retrieved on 2007-08-22.
  55. ^ Mainelli/Franklin (2007-08-22). Hurricane Dean Discussion Thirty Nine. National Hurricane Center. Retrieved on 2007-08-22.
  56. ^ Avila (2007-08-22). Hurricane Dean Discussion Forty. National Hurricane Center. Retrieved on 2007-08-22.
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