Tuesday, September 14, 2010

Hurricane Igor, Hurricane Julia, and Tropical Storm Karl: September 14, Update A

Three named systems at the same time! My my, aren't we going up in the world? ;-)
Hurricane Igor:
Igor took a little rest earlier today and dropped down to a weak cat 4, with light breezy winds of only 135mph (!). It was a well-earned break because he's been working quite a lot lately, poor fellow. But clearly he wasn't going to sit around doing so little for long because his vorticity is WAY too strong throughout the entire troposphere (the lowest section of our atmosphere which, in the vicinity of Igor, goes up to a height of about 10-12km above the earth's surface). Officially he's now got estimated winds of 145mph so he's a mid-sized cat 4 (range: 131-155mph) but I think he's going to get stronger. Central pressure is estimated to be 933mb. I will not be surprised if he becomes the first official cat 5 of the season - as you know, I thought he was a cat 5 briefly yesterday and he might get there again.
He's currently located at 18.9N, 53.2W, and is officially moving WNW at a slow 8mph.  At least he crossed that 18N line, so he's moving in that general direction and away from the northern Leeward Islands. But it means he's moving towards Bermuda instead. One or two of you may have noticed that the center of the cone goes directly over the little itsy bitsy island of Bermuda. He's forecast to get there on Sunday afternoon as a major hurricane (probably a cat 4). Now, whether it's a direct hit on Bermuda or not, he's strong enough and big enough to cause some problems there. For you Bermudians, make sure you've got your supplies ready: plenty of rum, water, wine, rum (I figured that would be cheapest thing out there), ice cream, batteries, rum, a book or two to read etc. You know... the usual stuff. Oh, and a raincoat too. Just in case. ;-) Seriously, I know you have gone through this sort of thing before so you know the drill. The chances are he won't pay a direct visit anyway, but will be swing by on one side. There is also a possibility that he will decrease in intensity before he gets to you because you are days away yet. Wouldn't that be nice?  
Convection continues to remain really strong of course, with associated tornadoes and thunderstorms. He still has dry air ahead of him that is trying, somewhat unsuccessfully, to get into the system. Sea surface temperatures are around 29 deg C, with 26.5 deg C in the upper 75-100m. There is actually a bit of wind shear to his west. It's not big compared to the storm, but it's enough to make a small dent and may keep him as a cat 4 for a while longer - at least overnight and into tomorrow. It's difficult for me to assess how long this shear will last.   
Hurricane Julia:
She's now officially a mid-size cat 1 storm with estimated winds of 85 mph (range: 74-95mph) and a central pressure of 982 mb. Her center is at about 16.7N, 30.2W and she's moving WNW at 9mph. Although she has circulation throughout the troposphere and some strong convective activity, she is experiencing wind shear which is keeping her from intensifying too quickly and is keeping the bulk of the convection to the east and south of the center of circulation. You can see the impact of wind shear in satellite images as well because there's a long stream of convection spreading away from her to the northeast. Water temperatures are around 27-28 deg C.  I think she's a little stronger than the official intensity, maybe a strong cat 1. At the moment I agree with the NHC on her track forecast. She will move in a more WNW/NWestward direction for the next day at least, and will most likely remain in the Atlantic instead of crossing it, like Igor.  
Tropical Storm Karl:
He's formerly my Caribbean Blob, and before that he was a Blobette. It's all so confusing sometimes! ;-) 
Karl went straight from an area of invest to a weak Tropical Storm with winds of 40mph (TS range: 39-73mph) and a central pressure of 1001mb. A plane was sent to investigate this so these are actual values not estimates. His center is at 18.3N,  84.2W.
The good thing about this baby is that he decided to develop in the northwestern Caribbean and is heading WNW at 15mph, towards the Yucatan Peninsula. This is good because he's already close to land, so hopefully he won't become all bulked up before landfall. The bad thing about this baby is that he decided to develop in the northwestern Caribbean, which has the deepest warm water anywhere in the Atlantic/Caribbean/Gulf of Mexico region. The surface water temperatures are 29-30 deg C, but waters warmer than 26.5 deg C can be found as deep as 150-175m! So, no matter how much churning of the water he does, he'll still have warm water to feed from. I think that the land will be the greater of the two influences, so he shouldn't get too strong before landfall.
Circulation (Vorticity) is good in the lowest half of the troposphere - it's slightly stronger than it was yesterday. Nothing going on in the upper levels of the troposphere. This means he's not anywhere near hurricane strength. We can see this also in the satellite imagery because the convection is not very well organized.
That's it for today.
I think I'll take a nap now, but will be back tomorrow. Lots to see and do. It's all shiney. ;-)
Blog archives at http://jyotikastorms.blogspot.com/

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 was there and was going to "run away, run away" (Monty Python), I'll let you know.

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