Friday, October 26, 2012

Sandy becoming extra tropical

Sandy is quickly transforming into a baroclinic system as the storm expands. The forecast gets interesting now and there is a lot of conjecture and hype with the storm and what is going to occur. The way to avoid the impending panic from the media is to turn the channel. Turn on your computer and go to then click on your location on the map. 
The talk from the forecast offices is calm and they know the problems locally better than most others because these offices have been around a long time and seen many of these transitional storms move up the US coastline. With this in mind I will give you some observations that may be useful.
The latest reconnaissance mission through the storm has found only 40 knots near the center but there are flight level winds surrounding the broad circulation nearing 50 to 55 knots. 

URNT12 KWBC 270029
A. 26/23:52:49Z
B. 27 deg 25 min N
  077 deg 14 min W
D. 40 kt
E. 132 deg 79 nm
F. 234 deg 57 kt
G. 132 deg 69 nm
H. 971 mb
I. 12 C / 3659 m
J. 13 C / 3660 m
K. 9 C / NA
N. 12345 / NA
O. 1 / 6 nm
P. NOAA2 1218A SANDY OB 21
The strong banding features are associated with the large circulation expanding and transitioning to a baroclinic low. When a tropical system transitions into an extra tropical low it implies the poleward motion of the cyclone displaced from the low level circulation and the primary energy source is the baroclinic, or a change in temperature and pressure rather than the pressure and release of latent heat release of condensation due to rising warm moist air off the surface. (fig 1)

If you live along the eastern seaboard of the United States the main issue is for the coastal communities for seas, some coastal flooding especially those very low lying areas, and for rainfall from the storm which may be significant. I can only say that "IF" the model guidance is correct this could be a very large player in the forecast for the weekend. That it is the weekend that the timing could be much worse and involve commuters to work. The storm is coinciding with the astronomical high tide due to the fall tide maximum and a full moon which will add to the coastal flooding.  
My advise is to be prepared, don't panic because your been here before either in hurricanes or nor'easters. Be sure to keep your weather radio handy and get supplies early. Power outages may occur, there could be some flash flooding in those areas prone to it. The best plan is to have a plan and be ready to implement it!
Let me know if and what impacts you receive from the storm. Be Safe

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. :-)

Tuesday, October 16, 2012

Rafael fighting to the last

Rafael is working against the shear as much as it can. We can see the sheared storm environment with the bulk of the cloud off to the north and east of the center. 
Courtesy of CIMSS 
The storm is holding on by the skin of its teeth and from ship observations we see the extent of the wind field is limited to the near storm environment. 

A look at wind vectors and then vorticity we can see the trough moving across the western Atlantic which  is the catalyst for pushing Rafael east of Bermuda. The image below shows the high shear surrounding the storm.
The highlighted areas in the final image indicate 200 mb vorticity which is the trough over the western Atlantic and ultimately what will pick up Rafael and begin the rapid exit of the storm to the northeast of Bermuda. 
Obviously there will be some higher winds across Bermuda but the more important issue will be wind waves and swell from the time Rafael has spent over the open waters. 

Friday, October 12, 2012


Rafael has been initiated. I will hold off on the obvious and let those of you that know me interpret the facts.
50 knots of shear with a immense ridge building off the Eastern Seaboard which will only add to the shearing environment.
 The track if Rafael holds on keeps the storm heading more north and if you notice the distance between the forecast points, it really speeds up as it get caught up in the trough. This should keep the impacts to Bermuda minimal in both intensity and duration. Winds should be gradually increasing with the trough closing in and may get a little squally Monday night. Not nearly as bad as a strong front dropping out of a Nor'easter.

Patty and Invest 98L

Good morning everyone,

Just a few notes of the tropics with the last gasp from Patty, and a open wave that may be named Rafael. Patty is being absorbed by a trough sitting across the Bahamas and will likely be out of the picture this evening. The structure of Patty is already non tropical with very little indication of a closed circulation at the surface. 
Thanks to CIMSS for image
With this said lets focus on Invest 98L. 98L is indicated on the above image by the I over the Windward Islands. A recent OSACT pass has a very good representation of the environment around the area. 
 This circulation has a couple of problems least of which is the interaction with the northern coast of Venezuela that is inhibiting the circulation on the southern semicircle of the system. The only storms in recent history that I can remember surviving this interaction were Dennis and Emily in 2005.  The shear across the area north and west of 98L is extremely hostile for development but there is ample deep convection over the Windwards near Barbados that warrent at least keeping an eye on the area. Forecast models are consistently developing a hurricane but the track is almost due north. The other problem is that the ridge over the southeast will offer plenty shear to the west which is the likely reason for the track north. The only issue for this system which may be named Rafael, is Bermuda. 
The following images show the shear then the shear tendency over the area. 
The season isn't over yet.