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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...DEPRESSION NEAR TROPICAL STORM STRENGTH...RAINBANDS MOVING OVER
THE SOUTHERN CAPE VERDE ISLANDS...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...13.3N 23.0W
ABOUT 140 MI...225 KM SE OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/HR
PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/HR
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES
Member Since: September 2, 2009 Posts: 130 Comments: 21032
2345. angiest
Quoting Levi32:
An interesting fact is that to my knowledge an annular hurricane hasn't made landfall before losing its annular characteristics. They are among the most powerful of all tropical cyclones, and it's hard to get one ashore with that kind of structure. But if one were to make landfall, the devastation would probably be massive.


Aren't you a bundle of joy tonight!
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting Levi32:
An interesting fact is that to my knowledge an annular hurricane hasn't made landfall before losing its annular characteristics. They are among the most powerful of all tropical cyclones, and it's hard to get one ashore with that kind of structure. But if one were to make landfall, the devastation would probably be massive.

That would be a very horrific scene.
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I have often wondered if this hurricane really had 185 mph winds or if they just didn't know how to estimate surface winds at that time. (I am assuming that they did, in fact, have a plane in it to get that estimate.) If Igor is able to avoid EWRC as it passes over the increasingly warmer seas, there is an outside chance we could find out if such a thing is actually possible.
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Is Igor becoming Annular?
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2340. dmaddox
Quoting Levi32:
An interesting fact is that to my knowledge an annular hurricane hasn't made landfall before losing its annular characteristics. They are among the most powerful of all tropical cyclones, and it's hard to get one ashore with that kind of structure. But if one were to make landfall, the devastation would probably be massive.
WOW ..what if Katrina would have been!? :(
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2338. angiest
Quoting all4hurricanes:
yes


LOL, um, which question did you answer?
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting StormW:


What's that have to do with GW?


As Jeff Masters has quoted all this season, all around Global Warming records have been established this year. And that can be noticed in the ammount of Water Vapor in the ITCZ this year.....
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2336. 7544
Quoting hydrus:
This is interesting...CMC...Link

ait
igor BENDS west at the end of run run for cover lol but it could happen wait watch and
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Quoting dmaddox:
can a Cat. 3 or 4 (or even lower) be considered annular or is it just reserved for Cat. 5?
yes Daniel E-pac 06 was a 4 check the wiki page
Member Since: March 29, 2008 Posts: 0 Comments: 2338
2334. Levi32
An interesting fact is that to my knowledge an annular hurricane hasn't made landfall before losing its annular characteristics. They are among the most powerful of all tropical cyclones, and it's hard to get one ashore with that kind of structure. But if one were to make landfall, the devastation would probably be massive.
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Quoting hydrus:
This is interesting...CMC...Link


Wow. I just looked on the 850 vort of that run. CMC brings 92L much farther north. Corpus Christi looks like? Thugh not strongly developed. Link
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2330. dmaddox
can a Cat. 3 or 4 (or even lower) be considered annular or is it just reserved for Cat. 5?
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Quoting angiest:


GFS correctly forecast cyclogenesis of Danielle, Earl, Fiona, Igor, and TD12. Those were all shown rather consistently over several runs up to two weeks ago. While I am not sold of GFS' track forecasting abilities, if it is consistently developing a storm, then I would say we should take notice of it.


+10
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Relax, relax.... It seems that the trough that is affecting 92L northern clouds (about 22N) is going to affect Igor and start moving him WNW.... Relax PR
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Wouldnt it be funny if the Canadian model panned out and CMC would tell the ECWMF, GFS, and the other global models " Haha I told you so"!
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Quoting TerraNova:


Although Earl began to weaken thereafter due to increasingly hostile conditions. Igor will be in a favorable atmosphere for at least another 24 hours.
I'm saying that his current pressure doesn't automatically qualify him as a five, but I have little doubt he will be today or tomorrow.
Member Since: March 29, 2008 Posts: 0 Comments: 2338
Quoting weathermancer:


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




Yep. At Cat 5 they are all analar on the ground.
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Quoting StormW:


I'm not even gonna explain

lol
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Quoting MiamiHurricanes09:
"Miss Piggy" just found a pressure of 1007.4mb in 92L.

232600 1702N 07412W 7101 03029 0074 +115 +073 075020 020 /// /// 03

That's interesting considering it doesn't look too great.
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if 92l shifts more north what part of texas has the greatest strike probability.
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2319. Melagoo
Quoting sunlinepr:
Some scientists say: Hey, there is no global warming, that's an illusion......



Wow look at that ... African wave pool
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2318. dmaddox
Quoting RecordSeason:


Definitely continuing to intensify.

Apparantly this thing is just going to keep on intensifying...
that light grey is now showing up on the northern AND southern sides now... not good....
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2317. Levi32
Quoting muddertracker:
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!


It's not a direct relationship, but it would support a more westward track for Igor.

From my blog:

"The Euro has dropped us a major clue in that it now takes what will probably be Karl (92L) northwest in the western gulf, more towards south Texas, and this is very different than the west or even SW movement that it had been showing in the Bay of Campeche. A storm fading northwest implies more of a trough digging into the west-central US and forcing the Texan ridge to build further east and connect to the Atlantic ridge, which would ultimately lead to a further west track for Igor."

3:40 to 4:50 of my video illustrates it:

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2316. angiest
Quoting pilotguy1:


Is this another case of forecasting eight of the last two storms?


GFS correctly forecast cyclogenesis of Danielle, Earl, Fiona, Igor, and TD12. Those were all shown rather consistently over several runs up to two weeks ago. While I am not sold of GFS' track forecasting abilities, if it is consistently developing a storm, then I would say we should take notice of it.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
2315. Vero1
Quoting MiamiHurricanes09:
"Miss Piggy" just found a pressure of 1007.4mb in 92L.

232600 1702N 07412W 7101 03029 0074 +115 +073 075020 020 /// /// 03


GRIP's GLOBAL HAWK and DC-8 are also in that area.
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2313. bird72
Quoting Levi32:


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.

Hi, the models for 92l are showing a track directed to a more nw direction in the gulf, that's the clue you were talking about regarding Igor final move?
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Quoting pilotguy1:

Typical snotty response. Says respectfully then snarky. Still don't see anything coherent.


btwntx08 is right about the spin though....it is there. It was easier to see a few hours ago but it is still there.
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Quoting hydrus:
This is interesting...CMC...Link


Is that showing the BH building in strong and turning Igor more westward? I'm no good at reading those runs.
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Quoting TerraNova:


Although Earl began to weaken thereafter due to increasingly hostile conditions. Igor will be in a favorable atmosphere for at least another 24 hours.


For the next several days...
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2308. dmaddox
wish we had a Hunter in there right now.. :/
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Some scientists say: Hey, there is no global warming, that's an illusion......

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Quoting all4hurricanes:
Earl was 928mb he didn't reach 150mph (although I expect some post analysis upgrade) cat 5s generally have pressure below 925


Although Earl began to weaken thereafter due to increasingly hostile conditions. Igor will be in a favorable atmosphere for at least another 24 hours.
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"Miss Piggy" just found a pressure of 1007.4mb in 92L.

232600 1702N 07412W 7101 03029 0074 +115 +073 075020 020 /// /// 03
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting TexasHurricane:
Looks like it may be shifting more north...?



Hey Tex. Just getting caught up today. Haven't taken a good look at 92L yet. Still trying to get past the WOW factor of Igor. Hope he stays out to sea.
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Quoting kimoskee:


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

http://www.youtube.com/watch?v=e0d6c99HSKo
See me new stereo. A Gilbert give me. LOL. I remember it well.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
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Quoting extreme236:
There is definitely the potential for Igor to be a category 5 on the next advisory.


I agree. I don't suppose anybody's mentioned the word "annular" yet? ;)
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2297. hydrus
This is interesting...CMC...Link
Member Since: September 27, 2007 Posts: 1 Comments: 19494
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.
Member Since: August 26, 2006 Posts: 16 Comments: 4766

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.