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Tropical Cyclone 20P (Joni) Expected to Weaken

March 13th, 2009 Category: Tropical Cyclones

Tropical Cyclone 20P (Joni) - March 13th, 2009 © Univ. of Wisconsin

Tropical Cyclone 20P (Joni) - March 13th, 2009

TC 20P - March 13th, 2009 © Univ. of Wisconsin

TC 20P - March 13th, 2009

Tropical Cyclone 20P (Joni), located approximately 390 nautical miles south of Rarotonga, Cook islands, has tracked southward at 16 knots over the past 6 hours.

Joni has maintained an initial intensity of 55 knots despite gradually degrading upper level conditions and decreased sea surface temperatures. Dvorak satellite intensity estimates are at 3.5 or 55 knots from PGTW and KNES.

The initial position is based on a series of microwave images, which suggest that the LLCC is tucked in under the western edge of the remaining deep convection.

Equatorward outflow has weakened over the past 12 hours as the upper level low to the east moved closer to the system. This low is expected to cut off equatorward outflow all together within the next 12 hours as it moves even closer.

From the West, a longwave trough will bring heightened vertical wind shear and drier air, and the mid-level reflection will accelerate the cyclone poleward. Sea surface temperatures will continue to drop below sustainable levels.

All of these factors will rapidly weaken Joni over the next day. Maximum significant wave height at 130600z is 12 feet.

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