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Tropical Cyclone 22S (Ilsa) Weakens Over Past 12 Hours

March 23rd, 2009 Category: Tropical Cyclones

Tropical Cyclone 22S (Ilsa) - March 23rd, 2009

Tropical Cyclone 22S (Ilsa) - March 23rd, 2009

TC 22S - enhanced image

TC 22S - enhanced image

Tropical Cyclone 22S (Ilsa), located approximately 365 nautical miles south-southwest of Cocos Island, has tracked west-southwestward at 12 knots over the past six hours. Maximum significant wave height is 20 feet.

Over the past 12 hours TC 22S has continued to weaken with significant decreases in convection. Elongation of the low level circulation center (LLCC) is apparent in animated multi-spectral imagery.

An AMSU-B pass shows mid-level dry air being entrained into the LLCC with little deep convection present. Upper level analysis indicates that Ilsa is located near an upper level subtropical ridge axis in a region of good difluent flow and low vertical wind shear.

Track of TC 22S © Univ. of Wisconsin

Track of TC 22S

Ilsa is currently tracking west-southwestward around the subtropical ridge located to the south of the system. Intensity will continue to weaken due to a combination of unfavorable surface conditions and dry air entrainment.

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