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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2296. angiest
Quoting Levi32:


I can't tell you if there will be a hurricane in the gulf in 10-15 days, but it is likely the SW Atlantic Basin will start heating up as we approach the end of this month, and it's September after all, so just be aware of tropical storms. It's a yearly thing to be watchful if you're posted in the Gulf of Mexico in the summer/fall. Always be ready. Once we get closer to next week we'll have a better picture of whether there will be any storms threatening.


GFS is developing a Caribbean/Gulf storm with some frequency in about 2 weeks, though it doesn't look like it did on the 18Z run.
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Quoting RMM34667:


Here is West Pasco Florida you can get fresh Crispy Cremes at Walgreens.. go figure..
There not hot Donuts!Now that Fresh!!!!!!
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Quoting weatherwart:
Haha! TWC met just call Igor a probable "fish storm."


Maybe just a little ahead of the game, last time I looked the people in Bermuda didn't have fins.
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Quoting MZT:
Igor may be on par with Felix in structure and intensity, but considering where he is, I think Igor is more impressive. After all, Felix was follwing the footsteps of king Gilbert.


Very popular local song that came out about Hurricane Gilbert. Very funny too!

http://www.youtube.com/watch?v=e0d6c99HSKo
Member Since: August 17, 2008 Posts: 0 Comments: 672
Quoting dmaddox:
931mb pressure!? gotta be Cat. 5..
Earl was 928mb he didn't reach 150mph (although I expect some post analysis upgrade) cat 5s generally have pressure below 925
Member Since: March 29, 2008 Posts: 0 Comments: 2342
2291. dmaddox
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2290. Levi32
Quoting MiamiHurricanes09:
Wow. Not good...not good at all. If you're right, Igor has a pretty good chance of becoming a category 5.


Oh I think he will at some point. A good chance of it.
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Quoting tornadolarkin:

That may be one of the horrific things I've heard on this blog yet. Oh, man......


Levi is a great forecaster, but man, he can be scary!
Member Since: August 18, 2008 Posts: 0 Comments: 884
Quoting dmaddox:
931mb pressure!? gotta be Cat. 5..


Not gotta. Cat 5's typically have a pressure of around or below 920mb. That is a very general and loose number and there are exceptions such as Felix with 929mb (one of its advisories even had it at 175mph winds with a pressure of 935mb), but 931mb isn't a "it has to be a cat5 now" pressure.
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Levi, got a question for you. On your tropical tidbit your analysis suggested that any more northward component to 92l would mean a more westward track for Igor. Could you please explain why that is for me again? I would appreciate it!
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2286. angiest
Quoting Hurricanes101:
I really dont think in this case people are just throwing the word annular around without knowing what they are talking about

I think someone had mentioned annular during Earl, well Earl was nowhere close to annular

Igor however again has a pretty large eye, great inner core structure and not much banding. He may not be annular, but he is close


At one point each with Danielle and Earl I questioned if they were transitioning to annular, though I thought neither one of them made it. This is why I came up with the term quasi-annular for storms that have some of the appearance but don't actually qualify. (The first time Earl hit cat 4 I never thought he looked annular, the second time is when I thought he may be on his way there.)
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2285. Levi32
Quoting troy1993:
Levi32..do you think the tropical wave over Africa will develop and will it likely follow the same path as the previous storms?


It might be slower to develop, but it's at a lower latitude so it will probably come farther west than Julia. Beyond that I can't really say right now.
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2284. MZT
"Annular" is a man made classification. As is "Hybrid storm" or "Tropical Storm". A system can be nearly annular and have annualr traits.

Or perhaps not. I think part of the fascination we all have with these storms is the degree of unknowing... It's like a bit of "outer planetary space" to research, but on Earth's oceans.
Member Since: September 24, 2005 Posts: 0 Comments: 793
2283. BDADUDE
Why is Igor going to expand? what would make his physical size increase?
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Quoting Levi32:


Igor has a structure that is very resistant to EWRCs. If he encounters no negative factors, he won't have an EWRC. He will simply remain this way, either becoming annular or close to annular. Isabel lived this way for days without an EWRC and maintained a fairly constant intensity, and Igor will likely do the same.

That may be one of the horrific things I've heard on this blog yet. Oh, man......
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There is definitely the potential for Igor to be a category 5 on the next advisory.
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2280. dmaddox
Quoting hurricane23:
18z Igor model Plots
thx
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Quoting dracko19:
ANNULAR HURRICANE

For those of you who are questioning people asking about IGOR and its Annular status, I think you need to look at the ANNULAR HURRICANE page of wikipedia. There are several examples of ANNULAR hurricanes and I think some of you are confused as to the exact defintion. Take a quick look:

Hurricane Daniel: NOTE: This hurricane WAS classified as ANNULAR by the NHC:



There is some banding going on with daniel. This notion you can't have any banding is silly. Its the symetry and "truck tire" appearance that makes it Annular.

Now, look at IGOR:



Its not quite perfect symetry, but it is very very close and the ANNULAR comparisons are extremely relevant. Please be respectful and stop dismissing such discussion. You are looking rather foolish when you do so.


Excellent post.
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Hi Everyone...interesting tonight..Rita
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Quoting bwat:
I hate to use this word, because it so un often that it happens, but does anyone else agree with me in saying that Igor looks to be becoming annular? From the definition on wiki, he seems to be fitting all of the requirments. Can someone inform me more?


Quoting Walshy:



annular??? yes or no...
I say not yet... still too much banding, plus ring of worst storms not "solid". I still think it's got a chance at that descriptor, though.

And Jed, pple are talking about annular status for Igor mainly because it's the first storm in a while [basically since Isabel 2003 in our basin] to seriously exhibit genuine annular qualities. This is more than just "it's a strong storm".
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2276. Vero1
Quoting weatherwart:
Haha! TWC met just call Igor a probable "fish storm."


They have a direct link to this blog and they are starting to listen to the trolls.
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Quoting all4hurricanes:
Annular hurricanes have an uncanny ability to persist in cooler water, dry air or high shear, they are rare so all aspects and differences are not known or completely understood


ok cool thanks.
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2274. Levi32
Quoting OffshoreRep:


Levi--I'm still new here. This is for you or Storm W. I work offshore about 40 miles off of Venice, LA. I'm scheduled to go back the middle of next week. Will I be allright?


I can't tell you if there will be a hurricane in the gulf in 10-15 days, but it is likely the SW Atlantic Basin will start heating up as we approach the end of this month, and it's September after all, so just be aware of tropical storms. It's a yearly thing to be watchful if you're posted in the Gulf of Mexico in the summer/fall. Always be ready. Once we get closer to next week we'll have a better picture of whether there will be any storms threatening.
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TD12 better organized...very likely a tropical storm.
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2272. dmaddox
Quoting MiamiHurricanes09:
CI# up to 6.7. Raw # still at 6.9.

2010SEP12 231500 6.7 931.4/ +2.0 /132.2 6.7 6.9 6.9 NO LIMIT OFF OFF 16.04 -71.33 EYE 25 IR 17.66 47.00 COMBO
931mb pressure!? gotta be Cat. 5..
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18z Igor model Plots
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Quoting MZT:
Igor may be on par with Felix in structure and intensity, but considering where he is, I think Igor is more impressive. After all, Felix was follwing the footsteps of king Gilbert.

Felix was smaller too which makes it's winds faster.
Member Since: March 29, 2008 Posts: 0 Comments: 2342
Quoting dracko19:
ANNULAR HURRICANE

For those of you who are questioning people asking about IGOR and its Annular status, I think you need to look at the ANNULAR HURRICANE page of wikipedia. There are several examples of ANNULAR hurricanes and I think some of you are confused as to the exact defintion. Take a quick look:

Hurricane Daniel: NOTE: This hurricane WAS classified as ANNULAR by the NHC:



There is some banding going on with daniel. This notion you can't have any banding is silly. Its the symetry and "truck tire" appearance that makes it Annular.

Now, look at IGOR:



Its not quite perfect symetry, but it is very very close and the ANNULAR comparisons are extremely relevant. Please be respectful and stop dismissing such discussion. You are looking rather foolish when you do so.
... nahh dont see any difrence between them... :/ yeah i am stupid
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How is it going weather peeps, New here to the site and love it already. Just so much info going back and forth all day long.

Jeremy
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Haha! TWC met just called Igor a probable "fish storm."
Member Since: August 18, 2008 Posts: 0 Comments: 884
2265. Engine2
CMC says west
http://moe.met.fsu.edu/cgi-bin/cmctc2.cgi?time=2010091212&field=Sea+Level+Pressure&hour=Animation
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Quoting doorman79:


Storm is a favorite on here for a reason. He takes time to teach those of us who want to learn. Plus, gotta preety good sense of humor.


Agreed. I don't ask questions, but pay attention to Storm. Heckuva nice guy from what I've followed.
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Quoting dracko19:
ANNULAR HURRICANE

For those of you who are questioning people asking about IGOR and its Annular status, I think you need to look at the ANNULAR HURRICANE page of wikipedia. There are several examples of ANNULAR hurricanes and I think some of you are confused as to the exact defintion. Take a quick look:

Hurricane Daniel: NOTE: This hurricane WAS classified as ANNULAR by the NHC:



There is some banding going on with daniel. This notion you can't have any banding is silly. Its the symetry and "truck tire" appearance that makes it Annular.

Now, look at IGOR:



Its not quite perfect symetry, but it is very very close and the ANNULAR comparisons are extremely relevant. Please be respectful and stop dismissing such discussion. You are looking rather foolish when you do so.


+10 Good post...good info.
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CI# up to 6.7 (indicating a pressure of 931b and winds of 132kt). Raw T# still at 6.9.

2010SEP12 231500 6.7 931.4/ 2.0 /132.2 6.7 6.9 6.9 NO LIMIT OFF OFF 16.04 -71.33 EYE 25 IR 17.66 47.00 COMBO
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting DestinJeff:
Don't Feed the Annulars.


Dooooohhhhnuts... accchchchchhchchchwhwhhcr...

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2260. Melagoo
Quoting dmaddox:
so they have the same pressure but the wind speed is 20mph different!?


I'd say Igor in nearing Cat 5 by now
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Quoting dracko19:
ANNULAR HURRICANE

For those of you who are questioning people asking about IGOR and its Annular status, I think you need to look at the ANNULAR HURRICANE page of wikipedia. There are several examples of ANNULAR hurricanes and I think some of you are confused as to the exact defintion. Take a quick look:

Hurricane Daniel: NOTE: This hurricane WAS classified as ANNULAR by the NHC:



There is some banding going on with daniel. This notion you can't have any banding is silly. Its the symetry and "truck tire" appearance that makes it Annular.

Now, look at IGOR:



Its not quite perfect symetry, but it is very very close and the ANNULAR comparisons are extremely relevant. Please be respectful and stop dismissing such discussion. You are looking rather foolish when you do so.


+1000
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Quoting Levi32:


Igor has a structure that is very resistant to EWRCs. If he encounters no negative factors, he won't have an EWRC. He will simply remain this way, either becoming annular or close to annular. Isabel lived this way for days without an EWRC and a fairly constant intensity, and Igor will likely do the same.


Levi--I'm still new here. This is for you or Storm W. I work offshore about 40 miles off of Venice, LA. I'm scheduled to go back the middle of next week. Will I be allright?
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Looking at 200mb streamlines it appears trough is flattening out Igor may go a little further west than forecast. Can I here a pump the ridge Igor,bust the trough baby. Lastly StormW got a pair when it comes to forecasting.
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I really dont think in this case people are just throwing the word annular around without knowing what they are talking about

I think someone had mentioned annular during Earl, well Earl was nowhere close to annular

Igor however again has a pretty large eye, great inner core structure and not much banding. He may not be annular, but he is close
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Quoting LightningCharmer:
I think people in general like the unusual, rare or perhap anomalies. Shucks, no-one really cares about the normal, run-of-the-mill humdrum Category 5 Hurricane...Nah.


Its only "annular" to satellites anyways...
down below in the wrath of it... well... different matter.


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Levi32..do you think the tropical wave over Africa will develop and will it likely follow the same path as the previous storms?
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ANNULAR HURRICANE

For those of you who are questioning people asking about IGOR and its Annular status, I think you need to look at the ANNULAR HURRICANE page of wikipedia. There are several examples of ANNULAR hurricanes and I think some of you are confused as to the exact defintion. Take a quick look:

Hurricane Daniel: NOTE: This hurricane WAS classified as ANNULAR by the NHC:



There is some banding going on with daniel. This notion you can't have any banding is silly. Its the symetry and "truck tire" appearance that makes it Annular.

Now, look at IGOR:



Its not quite perfect symetry, but it is very very close and the ANNULAR comparisons are extremely relevant. Please be respectful and stop dismissing such discussion. You are looking rather foolish when you do so.
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2250. dmaddox
Quoting sunlinepr:
Even if it goes NW, Igor is growing......

the wind field should start to greatly expand after it passes N of 20 degrees....
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Quoting Levi32:


Igor has a structure that is very resistant to EWRCs. If he encounters no negative factors, he won't have an EWRC. He will simply remain this way, either becoming annular or close to annular. Isabel lived this way for days without an EWRC and maintained a fairly constant intensity, and Igor will likely do the same.
Wow. Not good...not good at all. If you're right, Igor has a pretty good chance of becoming a category 5.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
2248. hydrus
Member Since: September 27, 2007 Posts: 1 Comments: 20328
Igor has an awsome sat appearance this evening thankfully were in an active trough pattern across the lower 48, and if you ask me it does not appear that we will see the kind of ridging this season that you need to send these storms anywhere other than between the uprights of Bermuda and the east coast--or even farther right. This year's pattern is quite a far cry from the stubborn and intractable ridging we saw across the basin in 2004 when two 'canes were shoved into Florida within just a couple of weeks.
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2246. MZT
Igor may be on par with Felix in structure and intensity, but considering where he is, I think Igor is more impressive. After all, Felix was follwing the footsteps of king Gilbert.
Member Since: September 24, 2005 Posts: 0 Comments: 793

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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.