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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 9th most intense Atlantic hurricane ever recorded.
Formation
MODIS image of the Low that eventually became Hurricane Dean. Taken at 1245
UTC on
August 12,
2007On
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
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]
Caribbean Sea
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. 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.
[29][30] Tt 4 a.m.
AST (0800
UTC)
August 18,
NOAA sea buoy 42059 took a direct hit from Hurricane Dean
[29] 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.
[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 very slightly on morning of
August 19 and experienced some
trochiodal wobbles as it finished the eyewall replacement cycle.
[37][38]
Peak intensity and 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.
[39] The storm began to intensify again that night
[40] and a contracting single-walled eye confirmed that the storm had completed its eyewall replacement cycle.
[41] 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).
[42] 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.
[43] The eyewall became even better defined throughout the day and the cloud tops cooled, signifying a strengthening trend.
[44] That afternoon a reconnaissance aircraft reported a falling minimum central pressure
[45] and winds of 160 mph, making Hurricane Dean a
Category 5 hurricane
[dropsondes. Based on data from a dropsonde in the northern eyewall the NHC estimated surface level winds of 145 knots, 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, measured a central pressure of 906 mb, making Dean the 9th most intense Atlantic hurricane ever recorded.[47][48] 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.[49] As expected the landfall caused significant weakening of the storm: the eye filled and the cold cloud-tops warmed.[50] By the time Dean had crossed the Yucatán Peninsula it had weakened to a Category 1 storm.[51]]
Gulf of Mexico
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,[52] 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.[53] 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.[54] 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.[55] 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.[Pacific as a broad area of low pressure.[57]]
See also
★ 2007 Atlantic hurricane season
★ Hurricane Dean (2007)
References
1. August 11 Tropical Weather Outlook (1130) Knabb
2. August 11 Tropical Weather Outlook (1730) Rhome
3. August 12 Tropical Weather Outlook (0530) Rhome
4. August 12 Tropical Weather Outlook (1130) Rhome
5. August 12 Tropical Weather Outlook (1730) Brown/Franklin
6. August 12 Tropical Weather Outlook (2230) Brown
7. August 13 Tropical Weather Outlook (1130) Knabb/Blake
8. Tropical Depression Four Discussion One Knabb
9. Tropical Depression Four Discussion Two Knabb
10. Tropical Depression Four Discussion Three Brown/Franklin
11. Tropical Depression Four Discussion Four Rhome
12. Tropical Storm Dean Discussion Five Avila
13. Tropical Storm Dean Discussion Six Landsea/Knabb
14. Tropical Storm Dean Discussion Seven Brown
15. Tropical Storm Dean Discussion Eight Beven
16. Tropical Storm Dean Discussion Nine Blake
17. Tropical Storm Dean Public Advisory Nine Blake
18. Tropical Storm Dean Discussion Ten Blake
19. Tropical Storm Dean Discussion Eleven Brown
20. Hurricane Dean Discussion Twelve Beven
21. Hurricane Dean Discussion Thirteen Blake
22. Hurricane Dean Discussion Fourteen Avila/Blake
23. Hurricane Dean Discussion Fifteen Franklin
24. Hurricane Dean Discussion Sixteen Beven
25. Hurricane Dean Discussion Seventeen Avila
26. Hurricane Dean Discussion Eighteen Avila/Mainelli
27. Hurricane Dean Special Discussion Nineteen Avila
28.
Hurricane Dean Intermediate Advisory Nineteen 'A' Knabb
29. Hurricane Dean Discussion Twenty Knabb
30. Hurricane Dean Discussion Twenty One Beven
31. Hurricane Dean Discussion Twenty Knabb
32. Significant Wave Height at 42059 NOAA
33. Hurricane Dean Discussion Twenty Three Avila
34. Hurricane Dean Discussion Twenty Two Avila
35. Hurricane Dean Discussion Twenty Four Knabb
36. Hurricane Dean Discussion Twenty Three Avila
37. Hurricane Dean Discussion Twenty Five Pasch/Brown
38. Hurricane Dean Discussion Twenty Six Franklin
39. Hurricane Dean Discussion Twenty Seven Franklin/Rhome
40. Hurricane Dean Public Advisory Twenty Eight Blake
41. Hurricane Dean Discussion Twenty Eight Knabb
42. Significant Wave Height at 42056 NOAA
43. Hurricane Dean Discussion Twenty Nine Pasch/Brown
44. Hurricane Dean Discussion Thirty Franklin
45. Hurricane Dean Discussion Thirty One Franklin
46. Hurricane Dean Intermediate Advisory Thirty One A Knabb/Roberts
47.
Hurricane Dean Intermediate Advisory Thirty Two A Pasch/Brown
48. Hurricane Dean Discussion Thirty Three Pasch/Brown
49. Hurricane Dean Public Advisory Thirty Three Blake
50. Hurricane Dean Discussion Thirty Four Franklin
51. Hurricane Dean Intermediate Advisory Thirty Four A Franklin/Rhome
52. Hurricane Dean Discussion Thirty Five Franklin
53. Hurricane Dean Discussion Thirty Six Avila
54. Hurricane Dean Discussion Thirty Seven Beven
55. Hurricane Dean Discussion Thirty Eight Franklin/Mainelli
56. Hurricane Dean Discussion Thirty Nine Mainelli/Franklin
57. Hurricane Dean Discussion Fourty Avila
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