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Tropical Cyclone Narelle (08S) Intensity at 80 Knots – January 13th, 2013

21.2S 111.7E

January 13th, 2013 Category: Image of the day, Tropical Storms

Tropical Storm 08S – January 12th, 2013

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Track of Tropical Storm 08S - January 12th, 2013 © Univ. of Wisconsin

Track of TS 08S

Tropical Cyclone Narelle (08S), located approximately 195 nm west-northwest of Learmonth, Australia, has tracked southwestward at 10 knots over the past six hours. Maximum significant wave height is 32 feet.

Animated multispectral satellite imagery (MSI) indicates that TC 08S remains tightly wrapped around a well defined low level circulation center (LLCC) but convection has continued to weaken. A TRMM microwave image reveals the bulk of deep convection remains limited to the western semi-circle. The initial position is based on the well defined LLCC readily apparent in the MSI loop.

The initial intensity is assessed at 80 knots based on Dvorak current intensity estimates of the 77 knots from PGTW and KNES and is line with the latest CIMSS satcon intensity estimate of 81 knots. Upper level analysis reveals Narelle is located equatorward of the subtropical ridge (STR) axis with strong poleward outflow into the westerlies and moderate (10-20 knots) easterly vertical wind shear.

TC 08S is currently tracking southwestward along the western periphery of the STR located over Western Australia. The system is forecast to continue tracking southward along the western edge of this STR through TAU 24. After TAU 24, the system will recurve southeastward in response to a deep midlatitude shortwave trough. Narelle is expected to weaken rapidly as it tracks over cool sea surface temperatures (SST), beginning extra-tropical transition (ETT) by TAU 36 and is expected to complete ETT by TAU 48. Due to forecast strong vertical wind shear and cold SSTs, a possibility still remains for dissipation of the system before completing ETT.

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