Karl dies over Mexico's mountains; Igor bears down on Bermuda

Hurricane Karl dissipated early this morning over the high mountains east of Mexico City. Karl made landfall yesterday on the Mexican coast about ten miles northwest of Veracruz at 1pm EDT, as a Category 3 hurricane with 115 mph winds. Karl was the first landfalling major hurricane in the Atlantic basin since Hurricane Ike over Cuba in 2008, and the first major hurricane to make landfall on the Gulf of Mexico coast since Hurricane Wilma in Southwest Florida in 2005. Veracruz was on the weak (left) side of Karl's eyewall, and did not receive hurricane force winds, except perhaps at the extreme northern edge of the city. Winds at the Veracruz Airport, located on the west side of the city, peaked at sustained speeds of 46 mph, gusting to 58 mph, at 11:54am local time. Karl has dumped very heavy rains in Mexico's Veracruz state, with 218 mm (8.6") measured at Hacienda Yland Ylang, and 171 mm (6.7") at Japala.


Figure 1. Hurricane Karl as seen in this visible moonlight image from the F-16 polar orbiting satellite at 9:08pm EDT Thursday, September 16, 2010. The bright city lights of Mexico City are visible due west of Karl, and gas flares from the PEMEX drilling platforms in the Gulf of Mexico to the east of Karl also make a bright splash of light. Image credit: Navy Research Lab, Monterey.

Igor
The Hurricane Hunters just arrived in Hurricane Igor, and found that the inner 23-mile wide eyewall had collapsed. Igor now has a huge 92-mile wide eye, thanks to this eyewall replacement cycle. As is usually the case in eyewall replacement cycles, the peak winds of the hurricane have decreased, but hurricane force winds are now spread out over a larger area. Top winds at the surface as seen by the SFMR instrument were Category 1 strength, 82 mph, though the aircraft did see 130 mph winds at 10,000 feet, which suggests the surface winds should be of Category 3 strength, 115 mph. These stronger winds are apparently not mixing down to the surface in the usual fashion. A sonde dropped in the eye at 11:20am AST recorded a central pressure of 945 mb, about 6 mb higher than what NHC was estimating in their 11am AST advisory. Though conditions for intensification will remain favorable through Sunday afternoon, with moderate wind shear of 10 - 20 knots and warm water temperatures of 28.5°C, we can expect only slow intensification of Igor. With such a huge eye, it will take Igor considerable time for it to bring the winds in this new eyewall back to Category 3 strength, and it will be difficult for the hurricane to be stronger than a high-end Category 2 storm with 110 mph winds when it makes its closest pass by Bermuda Sunday night.


Figure 2. Hurricane Igor as seen from a "radar in space" microwave instrument on the polar-orbiting F-16 satellite at 7:50 am AST Saturday September 18, 2010. A 22-mile wide inner eyewall was collapsing, and being replaced by a huge 92-mile diameter outer eyewall. Image credit: Navy Research Lab, Monterey.

Igor's impact on Bermuda
Hurricane warnings are flying for Bermuda, and winds are starting to rise on the island. Winds were blowing out of the northeast and had risen to 22 mph as of noon local time today. Igor's outer rain bands are now visible on Bermuda radar, and will reach the island late this afternoon. Igor is a huge storm, and tropical storm force winds extend out 340 miles to the north of its center. Igor will be moving at about 12 - 13 mph during its approach to Bermuda, so the island can expect a period of 39+ mph tropical storm force winds to begin near 7 - 9pm AST tonight. Hurricane force winds will arrive at the island near 8 - 10pm AST Sunday night, and last for 8 - 10 hours. Igor will speed up to about 15 mph as it passes the island near midnight Sunday night, and Bermuda's battering by tropical storm force winds will not be as long as Igor moves away, perhaps 12 - 14 hours. The Bermuda Weather Service is calling for Category 2 hurricane conditions to arrive at the island on Sunday night, with waves of 20 - 45 feet affecting the island's offshore waters during the peak of the storm. Buildings in Bermuda are some of the best-constructed in the world, and are generally located at higher elevations out of storm surge zones. If Igor remains below Category 3 strength, as currently appears likely, damage on the island may be just a few million dollars. According to AIR Worldwide, "Homes in Bermuda are typically one or two stories and constructed of 'Bermuda Stone,' a locally quarried limestone, or of concrete blocks. Roofs are commonly made of limestone slate tiles cemented together. Commercial buildings, typically of reinforced concrete construction, rarely exceed six stories. In both residential and commercial buildings, window openings are generally small and window shutters are common. These features make Bermuda's building stock quite resistant to winds, and homes are designed to withstand sustained winds of 110 mph and gusts of up to 150 mph."

Bermuda's hurricane history
Igor is similar in strength and projected track to Hurricane Fabian of 2003. Fabian hit Bermuda as a Category 3 hurricane with 120 mph winds. It was the most damaging hurricane ever to hit the island, with $355 million in damage. Fabian's storm surge killed four people crossing a causeway on the island. These were the first hurricane deaths on Bermuda since 1926. The most powerful hurricane on record to strike Bermuda was the Category 4 Havana-Bermuda Hurricane, which hit on October 22, 1926, with 135 mph winds. The hurricane sank two British warships, claiming 88 lives, but no one was killed on the island. The deadliest hurricane to affect the island occurred on September 12, 1839, when a Category 3 hurricane with 125 mph winds and an 11-foot storm surge hit, tearing off the roofs of hundreds of buildings and wrecking several ships. An estimated 100 people were killed (source: Encyclopedia of Hurricanes, Typhoons, and Cyclones, by David Longshore.)

94L
A tropical wave (Invest 94L) off the coast of Africa, a few hundred miles southwest of the Cape Verdes Islands, has developed a broad surface circulation and is threat to develop into a tropical depression early next week. The wave is under a moderate 10 - 20 knots of wind shear, and is over warm 28°C waters. Dry air from the Sahara is interfering with development, and 94L only has a small amount of heavy thunderstorm activity associated with it. Shear is expected to be low to moderate for the next four days, and 94L should be able to develop into a tropical depression if it can fight off the dry air to its north. The ECMWF model develops 94L into a tropical depression 4 - 5 days from now. NHC is giving the wave a 30% of developing into a tropical depression by Monday. Steering currents favor 94L moving northwest out to sea.

Typhoon Fanapi
The strongest typhoon of the very quiet Western Pacific typhoon season is now Typhoon Fanapi, a Category 3 storm with 120 mph winds. Fanapi is on track to hit Taiwan on Sunday morning as a Category 3 typhoon, then hit mainland China on Monday morning as a tropical storm. The previous strongest typhoon this season was Typhoon Kompasu, a low-end Category 3 storm with 115 mph winds that hit South Korea in early September.


Figure 3. Typhoon Fanapi at 04:45 UTC on September 17, 2010, as it approached Taiwan from the Philippine Sea. Image credit: NASA.

Elsewhere in the tropics
An area of disturbed weather off the coast of South Texas is due to an region of upper level winds that are spreading out, encouraging thunderstorm updrafts to pull more air aloft. I don't expect this region to develop due to its close proximity to the coast. The NOGAPS model is predicting development of a strong tropical disturbance in the Western Caribbean 6 - 7 days from now. The GFS model has backed off developing anything in the Caribbean next week.

I'll have a new post on Sunday.

Jeff Masters

Hurricane

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