27 October 2011

Rina downgraded to Tropical Storm

In a battle against increasing vertical shear, Rina was downgraded to a 60kt tropical storm at 15Z today.  The center is located just south of Cozumel and heading NNW at 5kts. You can also track it on Cancun's radar: http://smn.cna.gob.mx/radares/cancun/cancun.php

Now that it has weakened and the convective area associated with it has shrunk drastically, it is steered by different layers of the atmosphere.  Deeper systems are steered by a deeper layer, and weaker/shallower systems are steered by a lower and shallower layer.  That said, the forecast track now calls for Rina to stall in place, just meandering around in a loop waiting for some stronger steering flow to pick it up.  The track plot in the map below shows forecasts from 3 dynamical models, and the NHC forecast is basically an average of these.  The thin light lines are prior 00Z forecasts and can be ignored.  The official intensity forecast also follows the model guidance closely: gradual weakening over the next several days.

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