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Ilsa Expected to Weaken Gradually While Tracking West-Southwestward

March 20th, 2009 Category: Tropical Cyclones

Tropical Cyclone 22S (Ilsa) - March 20th, 2009 © Univ. of Wisconsin

Tropical Cyclone 22S (Ilsa) - March 20th, 2009

TC 22S (Ilsa) - March 19th, 2009 © JTWC

TC 22S (Ilsa) - March 19th, 2009

Tropical Cyclone 22S (Ilsa), located approximately 530 nautical miles east-southeast of Cocos Island, has tracked westward at 10 knots over the past six hours.

The system has slightly intensified as convective bands that are wrapped around the low level circulation center have consolidated and deepened over the past 12 hours.

Enhanced poleward outflow is also evident on animated water vapor satellite imagery. Upper level analysis indicates the cyclone is tracking under an area of low vertical wind shear (VWS) along the northwestern periphery of a subtropical ridge extension.

The current position and intensity estimates are based on Dvorak satellite fixes from PGTW and APRF with T-number values at 5.5 and 5.0, respectively.

The cyclone is expected to track west-southwestward through the forecast period under the continued steering influence of the sub-tropical ridge.

TC 22S will gradually weaken as VWS will begin to increase and along-track sea surface temperatures drop to below 26 degrees Celsius. Maximum significant wave height at 200000z was 28 feet.

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