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A weakened Igor bears down on Bermuda; 94L likely to develop

By: Dr. Jeff Masters, 2:17 PM GMT on September 19, 2010

Hurricane Igor is closing in on Bermuda, but the hurricane's eyewall has collapsed, weakening Igor into a large but still dangerous Category 1 hurricane with 85 mph winds. Winds in Bermuda are rising, and exceeded tropical storm-force for the first time at 9:55 am AST this morning. Bermuda radar shows the island is now embedded in one of the main heavy rains bands of Igor, and is experiencing heavy rain and high winds. As of 11 am AST local time, winds at the Bermuda Airport were sustained at 46 mph, gusting to 63 mph. Winds will continue to rise today as the storm's core approaches. Hurricane force winds should arrive at the island between 4 - 8pm AST today, and last for 4 - 8 hours. The Bermuda Weather Service is calling for Category 1 hurricane conditions with waves of 25 - 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; thus damage on the island may be just a few million dollars. With its eyewall gone, it is highly unlikely that Igor will be able to intensify before making landfall.

Figure 1. Hurricane Igor as seen from a "radar in space" microwave instrument on the polar-orbiting F-16 satellite at 7:36 am AST Sunday September 19, 2010. The eyewall has mostly collapsed, leaving just one fragment behind on the northwest side of Igor's center. Image credit: Navy Research Lab, Monterey.

A tropical wave (Invest 94L) off the coast of Africa, a few hundred miles west of the Cape Verdes Islands, has developed a broad surface circulation and is threat to develop into a tropical depression. The wave is under a low 5 - 10 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 modest amount of heavy thunderstorm activity associated with it. Shear is expected to be low for the next four days, and all of the major models develop 94L into a tropical depression 1 - 3 days from now. NHC is giving the wave a 70% of developing into a tropical depression by Tuesday. With the exception of the NOGAPS model, the models predict that 94L will move northwestward out to sea.

Figure 2. Morning satellite image of Invest 94L.

Tropical Storm Julia is being ripped apart by wind shear from Igor, and will likely dissipate on Monday or Tuesday.

Typhoon Fanapi
Typhoon Fanapi made landfall in northern Taiwan early Sunday morning local time as a Category 3 storm with 120 mph winds. Fanapi killed three people on the island, and brought rains of up to 690 mm (27.2 inches) to mountainous regions in the interior. Fanapi is the strongest typhoon so far this year, in what has been an exceptionally quiet Western Pacific typhoon season. 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. As seen on Taiwan radar, Fanapi has crossed over Taiwan and is now in the Taiwan Strait between the island and mainland China. Fanapi is expected to hit China about 150 miles east-northeast of Hong Kong on Monday, as a Category 1 typhoon.

Figure 3. Typhoon Fanapi at landfall in Taiwan at 7:10 local time on September 19, 2010. Image credit: Taiwan Central Weather Bureau.

Elsewhere in the tropics
In many recent runs, the NOGAPS and GFS models have been predicting development of a strong tropical disturbance or tropical depression in the Central Caribbean 6 - 9 days from now. However, the timing, location, and track of the potential development have been inconsistent from run to run. We should merely take note of the fact that these models predict that the Caribbean will be ripe for tropical storm development late this week and early next week, and not put much faith in the specifics of these highly unreliable long-range forecasts.

I'll have a new post on Monday.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.