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Tropical Cyclone Eighteen (18S) Tracking Erratically

13S 100.5E

February 26th, 2013 Category: Tropical Cyclones

Tropical Cyclone Eighteen (18S) – February 25th, 2013

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Track of Tropical Cyclone Eighteen (18S) - February 26th, 2013 © Univ. of Wisconsin

Track of TC 17S

Tropical Cyclone Eighteen (18S), located approximately 180 nm south- southeast of Cocos Island, Australia, has tracked west-southwestward at 06 knots over the past six hours.

Animated multispectral satellite imagery (MSI) depicts a broad low-level circulation center (LLCC) with deep convection sheared west of the center. An SSMIS image depicts weak, shallow convective banding wrapping loosely into a defined LLCC.

TC 18S has tracked erratically over the past 12 hours. However, recent MSI indicates that the system is now tracking slowly eastward. Due to the broad nature of the LLCC and lack of visible imagery, there has been low confidence in the initial position over the past 12 hours; however, there is increased confidence in the current position based on the MSI, which showed the center was located about 80 nm west of the 25/12z TAU 12 forecasted position.

TC 18S is located within a competing steering environment between a strong high to the south and a near-equatorial ridge (NER) to the north. TC 18 is forecast to track slowly eastward through TAU 48 due to the complex steering environment and is expected to accelerate eastward after TAU 48 as the subtropical high to the south weakens and the NER becomes the dominant steering influence.

Dynamic model guidance has trended toward a much slower overall track with GFS and GFDN indicating excessively fast tracks, therefore, this forecast is positioned slower than the multi-model consensus favoring the ECMWF tracker. There is low confidence in the JTWC forecast track.

TC 18S is forecast to maintain at 35 knots through TAU 48 then will gradually intensify to a peak intensity of 55 knots by TAU 120 as vertical wind shear decreases. There is low confidence in the intensity forecast. Maximum significant wave height is 15 feet.

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