92L still a threat to develop; Igor a hurricane; TD 12 forming near Africa

By: Dr. Jeff Masters , 2:18 PM GMT on September 12, 2010

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Tropical disturbance (92L) over the Central Caribbean, a few hundred miles south of the Dominican Republic, remains a threat to develop into a tropical depression. Satellite loops this morning show 92L may be starting to form a surface circulation, and an Air Force Hurricane Hunter aircraft will investigate 92L this afternoon to see if a tropical depression is forming.

The storm has only a modest area of heavy thunderstorm with limited low-level spiral banding and upper-level outflow, thanks to an infusion of dry air last night that disrupted the storm. Long range radar out of Puerto Rico shows that heavy rains are affecting that island, but there is no rotation to the radar echoes evident. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are hot, 29.5°C, and these warm waters extend to great depth. Water vapor satellite loops show a large area of dry air lies to the north and west of 92L, and this dry air could interfere with development at times over the next few days.


Figure 1. Morning satellite image of 92L.

Track forecast for 92L
The disturbance is moving west to west-northwest at 15 mph, and steering currents favor a continuation of this motion for the next three days. Model support for development is scattered. The GFS and NOGAPS models do not develop 92L. The GFDL and ECMWF models predict development, with a track taking 92L into Belize or Mexico's Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches today through Monday morning; southern Haiti can expect similar rains tonight through Monday night, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba can expect rains in the 2 - 4 inch range. Once 92L crosses the Yucatan, the ridge of high pressure steering it is expected to remain in place, forcing 92L to a second landfall in Mexico south of the Texas border.

Intensity forecast for 92L
NHC is putting the odds of 92L developing into a tropical depression by Tuesday at 50%; I'd put them higher, at 70%. However, time is running out for 92L to become a hurricane before hitting the Yucatan Peninsula on Wednesday. Given the current disorganized state of 92L, it would be difficult for it to intensify quickly enough to become a hurricane by then. The storm may also suffer another of its mysterious evening collapses, where it loses most of its heavy thunderstorm activity. However, the SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and water temperatures are certainly warm enough to support development. The main detriment to intensification is likely to be dry air, and 92L could wrap in some of the dry air to its northwest at times, slowing down development. There are a number of research flights being made into 92L this afternoon that should help long-term efforts to make better predictions in the future on whether or not disturbances like this will develop or not.


Figure 2. Morning satellite image of Igor.

Igor
Hurricane Igor appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is low, 5 - 10 knots, and is expected to drop below 5 knots for the next five days. Waters are warm, 28°C, and will warm to 29°C by Wednesday. Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor is undergoing a period of rapid intensification today, and will probably be a Category 3 or 4 hurricane by Monday.

The track forecast for Igor remains unchanged. Igor will move west under the influence of a strong ridge of high pressure for the next 2 - 3 days, then turn more to the west-northwest then northwest in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic on Tuesday and Wednesday. This should allow Igor to pass several hundred miles to the northeast of the Lesser Antilles. In the longer range, Igor may be a threat to Bermuda, and does have a small chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 15% of all tropical cyclones that have existed at Igor's current position have gone on to hit the U.S. East Coast; these odds are about 10% for Bermuda and 10% for Canada. The forecast steering pattern for the period 5 - 12 days from now from the ECMWF and GFS models shows a continuation of the pattern we've seen all hurricane season, with regular strong troughs of low pressure moving off the U.S. East Coast. This pattern favors Igor eventually recurving out to sea without affecting any land areas. Recent runs of the ECMWF model indicate that these troughs may not be as intense as previously thought, so it is possible Igor has a higher chance than usual to hit land than climatology suggests. One wild card may be the possible development of TD 12 behind Igor. If TD 12 develops into a hurricane, and moves close to Igor, as some of the models are suggesting, the two hurricanes could rotate around a common center, forcing Igor more towards the coast of the U.S. The long term fate of Igor is difficult to predict at this point.

Tropical Depression Twelve forms
Tropical Depression Twelve formed between the Cape Verdes Islands and coast of Africa this morning, and is already affecting the Cape Verdes with winds near tropical storm strength; sustained winds of 35 mph were recorded in the northwest Cape Verdes this morning. You can follow the progress of TD 12 through the Cape Verdes today using our wundermap.

Next post
I'll have a new post Monday morning, and perhaps late this afternoon if events warrant.

Jeff Masters

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Quoting WeatherMum:
Just pulled pumpkin chocolate chip cookies out of the oven. Other than that, I'm as sweet as you're going to get....it's my day OFF ! LOL.

Are you in the CONUS?
I'll be right over.
Sounds delicious!
Member Since: August 3, 2005 Posts: 10 Comments: 5689
1345. Levi32
I'm gonna put this up to prove a point. See the model consensus, including the GFS ensemble members? Impressive right? Infallable....right? Igor must recurve near 60-65W near Bermuda then, right?

No. Watch Igor run farther west before recurving like Earl did, and we'll probably end up proving for the millionth time that our human brains are better at forecasting than the computers we created. This kind of a consensus looks like a completely confident forecast, but watch it go wrong by several hundred miles.

I don't care if it's not a US landfall. It doesn't have to hit land for the model consensus to be wrong. We'll see how it goes.

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1344. Gearsts
The cmc 2010091212 Forecast slp Java Animation is crazy!
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I'm getting deja vu, here. This is Earl all over again.

"It's going west of the models."

"if it gets to 75W, it'll hit the Carolinas."

"The trough is moving too slowly. It ain't gonna reach."

"Any chance of it hitting Florida?"

"No, it's going to New York."

Models have been excellent this year, with regard to tracks. I've given up disagreeing with them. Intensity forecasts are still a joke, though

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Petrol due to my name, you are inclined to understand that I am saying I am watching this one extremely well.
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Quoting Levi32:


No I have no clue what that is but it's not actually the CMC ensemble. I used to think it was, but it's far different from the official ensemble maps at the Canadian Meteorological Center. It must be something else, but I can't figure out what. It's not the CMC operational or ensemble. Perhaps it's one individual ensemble member, but that would be a wacko thing to put on there.


Probably...
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1339. Melagoo




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Quoting sailingallover:

If we average the ECMWF and GFS Bermuda gets a close to direct hit in seven days...


On my blog post last evening, I was hinting at a pass just southwest of Bermuda, with a turn to the north between Bermuda and the US East Coast.
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1337. Max1023
The intensity models are bad - not one of them predicted Igor to reach the strength is has now let alone what it will likely achieve.
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Quoting Levi32:
12z Euro starts out farther south, but tends up slightly farther east than the 0z run.



Not nice for Bermuda.
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1334. dmaddox
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Quoting MZT:
OK, enough on the "sub 800mb" subject...



They're still at that?!?!?!

Guys, I know what sub-800 means. I used it in the correct context! I meant less than 800!

I have learned a valuable lesson today - refrain from using the "sub-" prefix on the blogs. Now if we could just get that written into the Community Standards. ;-)
Member Since: August 19, 2008 Posts: 104 Comments: 503
Look at the way Igor just sucked in all the ITCZ energy.. this will be one monster storm soon.
http://www.ssd.noaa.gov/goes/east/tatl/loop-avn.html
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Quoting NCHurricane2009:


Even if you look at that west case scenario provided by UKMET and CMC, those models seem to suggest a hurricane that will curve norhtwestward and stay offshore of the US east coast, passing between Bermuda and NC. Tell me when the models show a west-northwest track parallel and just north of the Bahamas.


When? 144 hours.
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Super Typoon Tip in 1979 ( Pacific Ocean) had a record pressure of 870mb's, an overall diameter of OVER 1300 MILES WIDE , ( Katrina was 480 miles wide) and sustained winds of 190mph. FYI
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1328. Levi32
12z Euro starts out farther south, but tends up slightly farther east than the 0z run.

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Levi32, StormW, Drakeon, or any other knowedlegable blogger I have seen that you guys have stated that the UKMET has a fairly good track on Igor. I also saw you mention yesterday that the UKMET forecasted a pattern that could potentially allow Igor to threaten and that the Japanese model is forecasting Igor to countinue west towards the Bahamas. Also according to the tone of the National Hurricane Center they arent to keen on a recurve out to sea. Carl Parker on the Weather Channel said we can not rule out a U.S landfall so what is your take on this and is it true that Igor's future impact's isnt as straightfoward as it was for Danielle and Earl because the models keep flip flopping and there is a huge disagreement between the models.
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1326. dmaddox
this guy is moving due West! wow! speed it up a little! Link
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1325. Hhunter
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1324. angiest
Sincve becoming a tropical storm again on the 10th, Igor has been pretty well on that forecast track with only minor deviations.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting NCHurricane2009:


Even if you look at that west case scenario provided by UKMET and CMC, those models seem to suggest a hurricane that will curve norhtwestward and stay offshore of the US east coast, passing between Bermuda and NC. Tell me when the models show a west-northwest track parallel and just north of the Bahamas.

If we average the ECMWF and GFS Bermuda gets a close to direct hit in seven days...
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Quoting jurakantaino:
Agree, UKMET seems to even reflect the tad southward that extremely dangerous hurricane IGOR is taken at the moment.


Igor is moving due west, and pretty much all of the models are saying due west till 50/55W, so at this point, its seems Igor is following closely all the models and not just the UKMET IMO.
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Just pulled pumpkin chocolate chip cookies out of the oven. Other than that, I'm as sweet as you're going to get....it's my day OFF ! LOL.
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Quoting StormW:


I have to agree.


what is the ukmet model doing now has it shifted south or north in other words right or left?
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1319. dmaddox
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1318. Levi32
I still believe recurvature east of the US is more likely than a landfall, but I am going to point out all of the possibilities that could lead to a landfall so that people are aware of them in case they actually do happen. The JMA isn't completely wacko in that it makes meteorological sense, but so do the other models (not the GFS though lol).
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1317. help4u
UKMET,out to sea.
Member Since: September 18, 2006 Posts: 0 Comments: 1301
1316. Max1023
Quoting leo305:


800MB would probably be way above 190mph


800mb would be a CDO about 2000 miles wide with a 100nm eye. Only in the movies or back when earth was 10 degrees warmer. (Millions of years ago)
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Quoting StormW:


I have to agree.


I second (or third) that.
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Quoting WeatherMum:
I have a dust bunny in the Met Office, will that do?
Thank you but I don't think so.
We need an elf.
On top of their powers they make good chocolate chip cookies, and after all that cheesecake talk(thanks for nothing Pottery:))....and now donuts....this blog needs something sweet.
Member Since: August 3, 2005 Posts: 10 Comments: 5689
pimples = hot towers in outer bands??
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Quoting Stormchaser2007:


Agree, UKMET seems to even reflect the tad southward that extremely dangerous hurricane IGOR is taken at the moment.
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Quoting StormW:


Thanks!

I wanted to point out to him though, that Igor just bust the first trof.

Storm what are you calling the first trof?
right now it almost appears there are three due to the small low the first trough is absorbing.
http://www.goes.noaa.gov/GIFS/ATIR.JPG
The trough does not need to fully recurve Igor only needs to leave a weakness in the ridge to allow it to go north so it gets picked up by the second or a low which develops along the stalled front left by the trough.
He is simply saying statistically there are more troughs than normal to move hurricane poleward where they get picked up and fully recurved sooner or later
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Quoting TerraNova:
UKMET along with the CMC is at the southern end of the current guidance.



Even if you look at that west case scenario provided by UKMET and CMC, those models seem to suggest a hurricane that will curve norhtwestward and stay offshore of the US east coast, passing between Bermuda and NC. Tell me when the models show a west-northwest track parallel and just north of the Bahamas.
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1308. leo305
Quoting Gearsts:
cat 6 would be 190mph winds 800mb...lol


800MB would probably be way above 190mph
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If I was in the Bahamas , I'd watch Igor very closely, jmo.
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1305. dmaddox
Quoting BenBIogger:


This was yesterdays 12z CMC Ensemble RUN. It had it knocking on your door.

264hrs (Long-Range)

whats that over tampa!??
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Good afternoon, all.

92L continues westwards disorganized, unable to get an LLC going. The weakness north of Hispaniola has had no effect in pulling the ugly mass northwards and in continues to move towards the Yucatan in the substantial low-level steering flow. It's breeched the 75w barrier from the dead zone and where there is higher TCHP where further development may occur. However, there is still substantial high pressure (though dissipating) to the north of the system in the GoM and even with development, I expect this system to only get a bump northwards from natural coriolis movement with better organization. If it develops at all, its mostly like a Mexico landfall, tracking through Belize or the sYucatan, possible following xG across the sBoC and into Mexico. IMO, it's not headed to TX or the nGoM from what I can see and "not" see happening at this time.



Igor continues to strengthen and should comes more westwards initially, missing any turn from the first weak approaching trough, but with him eventually turning seaward with the weakness diving seastwards across the eastern CONUS.



The norther islands, possibly the eastern Bahamas may get some tough winds before the turn. IMO, should follow a pattern and track similar to Earl. And, I guess this can all change, depending on the strength of the second trough and how deep it comes - so, needs watching, still could be a threat to the eastern seaboard.

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1303. Max1023
Quoting RecordSeason:


Hi!

I'm Igor!



Somehow, I'm positive it has continued to intensify since last advisory. Probably 140 to 145mph sustained right now, if not stronger...


It has almost filled out a complete ring of white, earlier today it was 2 shades lighter around the eye. Once we see a ring of white with a bit of the first gray after white then we probably have a 5 on our hands.

Moderate 4 profile: +15 degree eye -70 eyewall
Strong 4 (130-135 knots) +20 degree eye -75 eyewall

5 +22-24 degree eye -80 eyewall
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1301. Vero1
Member Since: July 21, 2008 Posts: 4 Comments: 2233
Quoting CosmicEvents:
We need an elf.
Any members out there have an elf in the family?
I have a dust bunny in the Met Office, will that do?
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Quoting StormW:


Good question...never seen that before...gonna have to take a closer look...now see...now ya got me doin more research. LOL!
\

I was thinking rapid intensification??
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1298. Levi32
Quoting BenBIogger:


This was yesterdays 12z CMC Ensemble RUN. It had it knocking on your door.

264hrs (Long-Range)



No I have no clue what that is but it's not actually the CMC ensemble. I used to think it was, but it's far different from the official ensemble maps at the Canadian Meteorological Center. It must be something else, but I can't figure out what. It's not the CMC operational or ensemble. Perhaps it's one individual ensemble member, but that would be a wacko thing to put on there.
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Looks like Igor has a good chance of becoming Annular with its very large eyewall ( above 14wiles wide) and extremely warm SST's in front of it. Your right Storm W the first trough has missed Igor, and its up to the 2nd one to pick it up. I also see a bend back towards the WNW at the end of the model runs. This one like the others will be interesting come Wednesday
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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