Friday, August 24, 2012

Tropical Storm Isaac and Tropical Depression Joyce: August 24, Update A

Even less time for sloth and idleness today!! Only time for cheesy puffs and coffee for lunch… (it’s one way of losing weight ;-))

Tropical Storm Isaac
Since my last update the Jamaican govt. issued a Tropical Storm watch for Jamaica, the NHC shifted the center southward again, and they adjusted the track to the south and west, no longer going over as much of Hispaniola as expected, and going closer to Jamaica.

I finally agree with their latest center and intensity! I am very happy for them. The storm is now stronger with winds of 60mph, central pressure 1000mb. The center is around 16.3N, 70.8W and he is moving WNW at 14mph. Now that they know it is stronger than they thought, they can reduce the intensity and still keep it a tropical storm. J The intensity should decrease because it is interacting with the islands of Hispaniola and Cuba to the north, but because it is so large, it is also interacting with South America to the south as you can see in this satellite image of the Atlantic:

Now… the track. This is very important for everyone in the northern Gulf, Florida, the Bahamas, and the eastern seaboard so please try and stay awake for the next bit! Although the storm is passing more south of Hispaniola than the official forecast was suggesting yesterday, there is another change in the pressure fields which will allow it to turn NW tomorrow, which will take it to Cuba. However, it currently looks like there is room for it to move NNW, taking it back to my original path of the east coast of Florida/Bahamas. The complication with this forecast is that the high pressure ridge that was keeping Isaac to the south and ensuring the westward track as he crossed into the Caribbean is breaking… You can see this in the satellite image – that front that was over Florida for the past couple of days has now moved across and out to the Atlantic, but is Isaac too far south for it to have an impact is the question. So… some possible scenarios:

1. The storm stays on the current track, crosses Cuba and the Straits of Florida, and then heads up the eastern Gulf of Mexico for landfall in the northern Gulf (probably panhandle). In this case Isaac’s intensity will decrease as he crosses the length of Cuba. He may not even survive as a Tropical Storm by the time he emerges. He will then cross the warm waters of the Straits, but then move over the shallow west Florida Shelf and he will be interacting with Florida. This will limit his intensity. I don’t think he’ll be a hurricane as he moves north, but if he is, he will be weak.

2. The storm enters southern Florida and moves north overland and back to the Atlantic. Again he will have to cross Cuba, which will knock some steam out of him and he may not be a Tropical Storm as he emerges. As he moves over Florida, he will decrease in intensity (once he gets past the Everglades) so he shouldn’t be too strong. Unknown is the future track if he does take this option.

3. He takes a more northward path, he will still interact with Cuba, but not as much as the previous cases, and then he heads over to the eastern side of Florida, possibly clipping the Bahamas. In this case, there is room for him to intensify because he may be over the Straits and then over the Gulf Stream. Again, the intensity depends on the track.

4. And the final scenario is that he is too far south to take advantage of the break in the high and it builds up. In which case he will move NW in the short term, over Cuba, and then maybe back to a more WNW track. Not so sure about this at all. The models haven’t said a peep about the high rebuilding and I don’t see it yet in the pressure fields.

The forecast track may be shifting back to the east to reflect this – we’ll know more by tomorrow morning, when he is supposed to be approaching Cuba. The NHC have repeatedly said that there is significant uncertainty in the forecast at 3-5 days out. But everyone should be keeping an eye on him and where he is when he crosses the vicinity of Cuba.

Tropical Depression Joyce
The sun shed some light on her center of circulation this morning and the birds were tweeting. But it matters not because she’s fallen apart and is now just a low pressure system. The circulation continued to deteriorate and this is my last update on her.

More later!

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

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