Thursday, September 16, 2010

Hurricanes Igor, Julia and Karl: September 16, Update A

Boy oh boy, this is going to be a loooong month! So, we have three hurricanes out there and I actually agree that they are all hurricanes! I'm not so keen on the official categories, but the status at least. This is just the 9th time (I think) that we've had three active hurricanes at the same time since records began (1851), the last time being in 1998. The caveat to this (hence the 'I think') is that we didn't really know what was going on in the eastern Atlantic until around the 1940s, when planes flew across the remote parts of the ocean basin. In 1998 we actually had four simultaneously active hurricanes: Georges, Ivan, Jeanne, and Karl. And if you are reading this on my blog page (link is below if you want to check it out), the satellite image slice at the top is from 2004 and from left to right you see the fully formed Hurricane Ivan, the northern edge of the almost-developed Hurricane Jeanne, and the African Easterly Wave that became Hurricane Karl! Obviously Karl is a sociable fellow and likes to hang out with his 'peeps'. ;-)
Hurricane Igor:
Igor is still a big storm and holding onto that cat 4 mantle. There are some fluctuations, which are to be expected, but currently his estimated winds are about 140mph so he's a mid-sized cat 4 (range: 131-155mph), with an estimated central pressure of 934mb. His center is currently at 21.5N, 57.6W and he is moving NW at 7mph.
I agree with the NW track for now. The intensity might be a fraction too high, but he still has a pretty good eye so a strong cat 3 or weak cat 4 is where I'd place him. He's experiencing a little bit of wind shear from the northwest, which you can see in the satellite images because the eye is just a bit closer to the northwestern edge. Although the shear is not strong its enough to allow some dry air into the system, which continues to inhibit his growth. Once that shear goes he's got enough oomph to get stronger again. A plane will be sent into the system today to get a better reading of what's going on.
In the back of my head is a little voice that's wondering if he's going to slow down a bit or move a bit more westward. It looked like there was an area of higher pressure in front of him, but I don't have high enough resolution pressure field data to be sure. I guess we'll find out tomorrow. In either case, it'll be a close pass by Bermuda on Sunday (or possibly Monday if he slows down).
Hurricane Julia:
I agree she's a hurricane, but only just. I still completely disagree with the category! She's not had an eye all day, and the wind shear was so strong that most of the convection was to her northeast. Not only that, but the convection consists of a bit of rain with hardly any thunderstorms. Daily summer showers in the tropics have more to them! The only reason I'd put her as a weak cat 1 (if I ruled this gig) would be because she is a bit on the breezy side and has very strong vorticity in the lowest half of the troposphere. The mid-to-upper troposphere does not have the structure of a tropical storm but rather that of a low pressure front.
Anyway, the NHC have steadily decreased her intensity (I am *so* not surprised). She's now officially a weak cat 2 (range: 96-110mph) with estimated winds of 100mph and an estimated central pressure of 971mb. I expect a further decrease in the next advisory or two, down to a cat 1, and then gradually downward. She's centered at 22.4N, 38.6W and is moving WNW at a whopping 25mph (hmm... usually the sort of speeds one sees when a storm is embedded in a front...hmm... funny that).
About her future track. This might get interesting. We'll see how close she gets to Igor because that will affect how strong she remains and whether or not she survives as a stand-alone storm. There's a small chance we'll see the Fujiwhara effect yet (see That would be SO COOL! (although it might be a bit of a mess in terms of forecasting and storms and whatnot). We'll know in the next couple of days.
Hurricane Karl:
As I said yesterday, I think this little guy's intensity was underestimated before landfall and they continued to underestimate him until they sent in a plane to investigate earlier today (over the Gulf). I think he was a cat 1 at landfall, because he downgraded as he crossed the Yucatan Peninsula to a Tropical Storm, which was his status in as he emerged into the Gulf. If he was a TS, he'd have been a Tropical Depression by the time he reached the Gulf. Anyway, he got into the southern Gulf today (overnight = local time), and after the plane sent back better information, the NHC quickly bumped him up to a very strong Tropical Storm and then Hurricane shortly thereafter.
Also as I suspected yesterday, he's taken a more southern track than the center of cone forecast had for him initially. He's now at 19.8N, 93.5W and moving W at 12mph (possibly WNW I think). I still think he'll continue to move slightly south of the center of the cone. His central pressure is 983mb with winds of 75mph, making him a weak cat 1 storm (cat 1 range: 74-95mph). Again, I think he's a bit stronger than that, but I don't think he'll get beyond a cat 1. His convection has been very good, but in the last few hours it's started to decrease as he's interacting with land to the south, west and to the east, and he's also experiencing some wind shear from the north. His vorticity (circulation) is good in the lower half of the troposphere, but there's only a small signal in the upper troposphere - the sort we see with a cat 1 storm but not a cat 2.    
And there we have the reckoning from today. Wasn't I far more agreeable today? ;-) That wine and ice cream must have worked. ;-)
Until tomorrow!
Toodle pip!
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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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