Wednesday, September 8, 2010

Hurricane Igor (2010)

Storm Active: September 8-21
On September 6, a strong tropical wave emerged off of Africa. A low became associated with the system on September 7, and the system continued to organize, despite significant shear. On September 8, the system was organized enough to skip the tropical depression stage and intensify directly into Tropical Storm Igor.

The convection and circulation of Igor were at a very high level of organization, even with two low pressure systems in the vicinity. These three lows shared a low pressure trough extending from just off Africa to a few hundred miles north and west, but Igor began to strengthen later on September 8, and asserted its dominance. Igor meandered slowly to the west, before taking a turn north and then northwest on September 9. As it moved into greater shear, it weakened, becoming a tropical depression later that day, as the center became exposed from the east side. Despite this, the circulation deepened, the convection became more organized, and the system regained tropical storm status the next day. The shear had abated once again and Igor began to strengthen. During the morning of September 11, Igor developed an interesting eye feature on the north side of the system, and the storm approached hurricane strength. However, convection decreased during the afternoon before a burst of convection during the evening caused Igor to become a hurricane.

An eye became evident within this convection early on September 12, and Igor underwent explosive strengthening, ballooning from a minimal hurricane to a amazing Category 4 by that afternoon as a result of a drop of 50 mb in 12 hours. Igor's forward motion slowed and the system moved due west throughout that same day. Igor continued to strengthen, reaching an intensity of 150 mph late on September 12, and this remarkable intensity was maintained throughout the day of September 13, as a beautiful symmetric eye dominated the system. By that evening, surf began to increase in the Northern Leeward Islands as Igor approached from the west. Igor made a slight westnorthwest turn that night, and an eye replacement cycle destabilized the system, weakening it. However, it remained a Category 4 through the day of September 14, before organizing further and strengthening once again during the evening. Igor reached a peak intensity of 155 mph and a pressure of 925 mb later that night before the eye clouded over and a weakening trend commenced.

However, Igor organized once again, and the fluctuations in intensity continued as Igor became a powerful Category 4 once more with 145 mph winds. The convection became slightly asymmetrical, with the bulk of the cloud cover on the north side on September 16, but the moisture evened out during the evening as a a pronounced rain band formed south of the center. Also, during the day of September 16, Igor's tropical storm wind field broadened to 506 miles in diameter, making it the third-largest Atlantic hurricane on record. Igor began weakening, however, and finally lost it's Category 4 status during the late afternoon of September 16, after maintaining it for four days. The system continued to weaken over the next day. By the afternoon of September 18, Igor was a Category 2, but the windfield was still broadening, and squally weather was already sweeping over Bermuda. By later that night, Igor's tropical storm force windfield engulfed Bermuda, and the winds increased throughout the day, despite the fact that Igor weakened to a Category 1.

The center of Igor passed just to the west of Bermuda late on September 19, and the island saw sustained winds near hurricane-force as a result. Igor accelerated northeastward, and maintained a minimal hurricane status while the extratropical transition began on September 20. However, this transition wasn't completed by the time Igor passed Newfoundland, and the center passed just to the east of the island, causing sustained winds near hurricane force and dumping over 9 inches of rain in some areas, causing flooding. Igor finally became extratropical on September 21. Igor caused 3 fatalities and about $100 million in damage. The cyclone was also notable for being the largest Atlantic hurricane ever recorded, with a tropical storm force wind diameter of 920 miles, until it was surpassed by Hurricane Sandy of 2012.

Igor near peak intensity.

Track of Igor.

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