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Tropical Cyclone Imelda (21S) May Re-intensify – April 12th, 2013

11.8S 54.8E

April 12th, 2013 Category: Image of the day, Tropical Cyclones

Tropical Storm Twenty One (21S) – April 11th, 2013

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Track of Tropical Storm Twenty One (21S) - April 11th, 2013 © Univ. of Wisconsin

Track of TC 21S

Tropical Cyclone Imelda (TC 21S) is forecast to continue tracking generally southward through TAU 48 as the steering ridge becomes re- established.

Beyond TAU 48 the system will shift to a southeastward track as it rounds the southern periphery of the steering ridge. Model guidance is in fair agreement with the forecast track, with NVGM being the western-most outlier and EGRR the eastern-most. There is also fair agreement with this scenario in the available ensemble model products.

Despite the slight weakening trend over the past 12 hours, favorable (28 to 29 degrees Celsius) sea surface temperatures, low to moderate vertical wind shear (VWS), and enhanced outflow from the deep-layer trough (DLT) should allow for a period of slight re-intensification through TAU 48. After that time, increasing interaction with mid-latitude westerlies will result in higher VWS, beginning a gradual dissipation of TC 21S.

Although there is some variability in the track speeds among dynamical models, they suggest that TC 21S will begin to interact with the baroclinic mid-latitude flow around TAU 120. Based on the fair agreement in model guidance there is high confidence in the forecast track. Maximum significant wave height is 30 feet.

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