Friday, September 17, 2010

Hurricanes Igor, Julia and Karl: September 17, Update A

Another interesting day out there. Not quite as interesting as I was hoping regarding Igor and Julia, but more interesting than I was expecting regarding Karl!
Hurricane Igor:
After the plane returned data from Igor yesterday the NHC downgraded him to a strong cat 3, which is what I thought they would find. He's been slowly decreasing in strength and, based on the latest Hurricane Hunter plane observations, he is currently a strong cat 2 storm with winds of 105mph (cat 2 range: 96 - 110mph) and a central pressure of 947mb. He's moving NW at 10mph and officially his center is at 23.7N, 61.1W. It looks to me as though he's about 0.5 degree east of this - at 23.7N, 60.7W, but the satellite image I have is a couple of hours old, so maybe he took a sharp westward turn in the past couple of hours. Still, he's generally doing the NW path thing, but is forecast to turn NNW tomorrow afternoon and then North - the sooner he makes that turn, the better for Bermuda. 
Spatially, Igor is HUGE! From north to south his outer bands cover something like 1200 miles! So although his center is 665 miles SSE of Bermuda, everyone from Bermuda to the Leeward Islands in the Caribbean are feeling some effects from Igor. Fortunately there aren't too many people in that area, mostly fish and possibly some aliens, depending on what you believe about the Bermuda Triangle ;-). Hurricane force winds (greater than 73mph) can be felt up to 105 miles from the center, and tropical storm force winds extend out 345 miles. Vorticity is still very strong throughout the troposphere for Igor, which means there's a small chance he could get a little stronger before weakening (this is in agreement with the NHC). Convection is also quite good too - plenty of thunder and lightning and stuff closer to the center. There is some wind shear affecting his northern edge and you can see that in the satellite images as clouds stream off to the northeast. As he moves farther north, this shear will be a greater impact so he shouldn't get too strong by the time he gets that far north (past Bermuda).
A hurricane warning was issued for Bermuda earlier today (about 3-4 hours ago), meaning they will get Tropical Force winds (greater than 39mph) within the next 36 hours. The current center of cone track does take the eye close to Bermuda. 
Dear Igor, I would like you to shift to the east a smidge and turn NNW tomorrow morning. Or overnight. Thank you.
Hurricane Julia:
Again as I expected yesterday, they downgraded her intensity quite rapidly to a cat 1 (range: 74-95mph), and then gradually decreased it after that. I won't bother telling you my opinion, cos you can read it in the last two entries if you missed it. I've recovered now. ;-) 
She's still being held as a cat 1 storm, but barely, with winds of 75mph and an estimated central pressure of 987mb. I think this is perfectly acceptable. Her vorticity (circulation) is still strong in the lowest half of the troposphere, but her convection has decreased a lot.  
I was so hoping she'd do a little dance with Igor today and we'd see the Fujiwhara interaction in all it's glory because that would have been so cool, but it looks like she was just too little compared to Igor and instead she reminded me of a tree trunk meeting a wood chipper... any time she got close to the swirling saw of Igor's winds her clouds kept getting lopped off so she got smaller and smaller. Maybe there will be a little of the Fujiwhara effect still though, and maybe she will tug Igor to the east a bit. We'll see. (I'm remain optimistic!). However, in her limited interactions with Igor I think she still did us all a favour because I think that's what helped to bring Igor's intensity down. He didn't (and still doesn't) have much room to expand on his east side (outflow was inhibited). 
She's currently at 25.2N, 48.2W, moving WNW at 18mph.
Hurricane Karl:
As well behaved as Igor and Julia have been today, bad boy Karl more than made up for that! He turned into a cat 3 storm!! I was wrong in thinking he'd remain a cat 1. The vorticity still wasn't strong enough to support a cat 3 storm, but he definitely had a lot of convection and a good looking eye. I'm thinking that there is a piece of this intensification that is connected solely to the convection which he really picked up before he crossed the Yucatan, but interestingly, he also got from the entire western Gulf despite being so far south. He was actually also a large storm spatially, and although he was in the Bay of Campeche (I think is the southernmost cat 3 storm detected so far) he was affecting the atmosphere as far as the northern Gulf (clouds and some rain). We were just really really lucky that he was partly over land, otherwise he would have been a monster storm!
He made landfall just north-northwest of Veracruz, Mexico this morning (around 9.30 or 10.30 am local time). He generally remained south of the forecast center of cone track. He's over land now and they still have him as a strong cat 1 hurricane with winds of 90mph (cat 1 range: 74-95mph) with a central pressure of 985mb. I'd agree with a strong cat 1 at this stage. He is at 19.1N, 96.6W and is moving WSW at 9mph.   

He's forecast to decrease in intensity as one would expect over land, and then dissipate by Sunday as he gets to the mountains in Mexico. I think this is a likely scenario, but his vorticity is still quite strong in the lowest half of the troposphere, and there is still a signal in the upper troposphere, even though he is over land. Something to keep an eye on (but not a hurricane eye! ;-)).
More fun and games from the Atlantic tomorrow... where we might have another Blobette in the making (you didn't really think we were done yet, did you?).
Adios amigos!
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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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