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Tropical Cyclone 09S Remaining Stationary

13.2S 75.4E

January 13th, 2013 Category: Tropical Storms

Tropical Storm 09S – January 12th, 2013

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Track of Tropical Storm 09S - January 12th, 2013 © Univ. of Wisconsin

Track of TS 09S

Tropical Cyclone 09S, located approximately 545 nm east-southeast of Diego Garcia has tracked westward at 1 knot, exhibiting quasistationary movement. Maximum significant wave height is 12 feet.

Animated infrared satellite imagery depicts a consolidating system with improved deep convective banding wrapping into a well-defined low-level circulation center (LLCC). An SSMIS microwave image wind product shows 30 to 35 knot winds located in the formative banding to the south. Based on this, and overall improved storm structure, the intensity is assessed at 35 knots.

Upper level analysis reveals TC 09S is located slightly equatorward of the subtropical ridge axis and vertical wind shear has decreased to moderate (10-20 knot) levels allowing for the recent improvement. The system is currently located in a weak steering environment between the steering influences of the low to mid-level near equatorial ridge and subtropical ridge (STR).

TC 09S is forecast to remain nearly quasistationary for the next 24 hours as it slowly intensifies. After TAU 24, the system will slowly track more southwest as the mid to deep level subtropical ridge to the southeast becomes the more dominant steering influence and cause a more westward track through TAU 120. It will struggle to intensify through the forecast as VWS will remain at moderate levels and increase to strong levels in the later TAUs. Dynamic model guidance is widely spread but generally agrees on slow track to the south to southwest and slow intensification. Due to this poor agreement among the models, forecast confidence is low.

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