Tuesday, October 23, 2012

TS Sandy

Tropical Storm Sandy is in the Caribbean just south of Jamaica at 11 pm EDT on 10.23.12.
This would put the center about 715 miles south southeast of Key West and it is moving north northeast near 8 mph. The maximum sustained winds are 50 knots but Hurricane Hunter Aircraft have measured 60 knots by dropsonde during a recent pass through the storm.
The structure of Sandy is troubling with respect to the forecast track and intensity. 
Shear(yellow), Shear vectors(white), and vis/wv satellite via CIMSS
The shear vectors are obviously tilting the storm to the east and northeast with the magnitude of the shear at 60 knots over the Bahamas...and near 20 knots across the center fix of the storm. All the shear is out of the southwest. The satellite image shows the slant of the system and a closer look with IR satellite shows the western semicircle of the storm is quite dry and pushing a dry slot into the circulation itself. see below
The latest advisory has the fix further to the east and is the reason for the bend in the track to the east initially. My thinking is this is a trend that will continue for several reasons. First the shear is tilting the storm, this is causing the wind field to expand which is indicating a system that is in transition from tropical to post or extra tropical. Then the culprit for the transition is the upper level low over the eastern Gulf of Mexico which is also helping to steer Sandy, while pulling dry air aloft into the circulation. Finally the last consensus model runs all have a easterly trend to the tracks. see next image

 We find the tracks are east of the official beginning as the storm crosses eastern Cuba. In almost all cases it has been shown that if the consensus moves in a certain direction the tracks will follow. 

As for intensity we will have to wait but would expect that category two will be the maximum that the storm is advertised from NHC but with the expanding wind field, most of the winds should remain aloft and not mix down to the surface. Jamaica will give us a good idea of the energy at the surface as will Cuba. Then the next stop on the Sandy train after the Bahamas will Bermuda but the forward speed should less the duration of impacts no matter what the intensity. 
If you're heading to Key West its going to be windy but this will not stop the debauchery on Duval Street. :-)

1 comment:

  1. it's actually a knowledge full post. thanks to shear . this post has removed my a number of wrong thing . i thing if you to-do your acctivetice you will achive much popularety.. at last..thanks.
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