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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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.
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Quoting MiamiHurricanes09:
No.

Miami may you answer 2205 please.Thank you.
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2244. dmaddox
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.
thank you!
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Even if it goes NW, Igor is growing......

Member Since: August 2, 2010 Posts: 21 Comments: 9882
Quoting Patrap:
Now Im going out to get a Dozen Krispy Kreme fo sho..
I couldn't take it anymore.
I went out for some 30 minutes ago.
Worth the trip.
The "hot now" sign was flashing!!
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Member Since: June 9, 2007 Posts: 4 Comments: 15950
2239. Levi32
Quoting dmaddox:
any hints of eyewall replacement cycle with Igor yet!??


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.
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Quoting pilotguy1:

Typical snotty response. Says respectfully then snarky. Still don't see anything coherent.
Two fouls on the play! Using Snarky and Snotty in the same post....Saying respectfully and them being disrespectful....penalties offset...repost!
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img src="http://4.bp.blogspot.com/_rs51u5UHxdA/TAVEB6T9qBI/AAAAAAAABck/gwm81qUmtYc/s1600/MartyFeldmanIgo r.jpg" alt="" /

Handsome feller.
Member Since: August 27, 2006 Posts: 0 Comments: 249
Member Since: June 9, 2007 Posts: 4 Comments: 15950
2234. dmaddox
Quoting Melagoo:


IGOR



FELIX - 165 mph
so they have the same pressure but the wind speed is 20mph different!?
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Quoting Stormchaser2007:
22:15

Excellent inner core structure. And, no EWRC in the near future.
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2232. Max1023
Quoting Stormchaser2007:
22:15



That is close to a perfect inner core structure.
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2231. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
2230. Melagoo


IGOR



FELIX - 165 mph
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22:15

Member Since: June 9, 2007 Posts: 4 Comments: 15950
Quoting 2133. Jedkins01:



gosh what is it with people in here and annular hurricanes? They are very rare, just because Igor is very intense and well organized does not make in annular. Dang.
I think people in general like the unusual, rare or perhaps anomalies. Shucks, no-one really cares about the normal, run-of-the-mill humdrum Category 5 Hurricane...Nah.
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2225. dmaddox
Quoting hydrus:
Igor is growing.
that image is WAY old
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Quoting sunlinepr:
Any names left for Me???

Look s like the african wave train will not stop anytime soon.
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Quoting hunkerdown:
fresh Krispy Kremes, or "Hot Donuts Now" can only be gotten at an actual Krispy Kreme locations.


Sorry .. I just notice them at the checkout. I haven't eaten a donut in about four years since me niece informed us that she learned in health class it takes five days to digest one..

and back on topic. I think the word annular (probably spelled that wrong too) is being thrown around so much due the "almost" prefect shape of Igor. You don't see that too often.
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934.2/ +2.0 /129.6 6.6 6.8 6.9

Member Since: June 9, 2007 Posts: 4 Comments: 15950
2221. angiest
Quoting Hurricanes101:
thank you StormW

instead of just bashing people like Jedkins did you actually explained it

and yes Igor is very close to annular


I'll give him the quasi-annular label now. But I really coulda sworn that the transition to annular followed an EWRC, which Igor clearly has not.
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2220. bassis
Quoting MiamiHurricanes09:
The Advanced Dvorak Technique


thanks my freind
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2219. hydrus
Igor is growing.
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Quoting dmaddox:
any hints of eyewall replacement cycle with Igor yet!??
No.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Based on what I've learned from the xperts here, Igor's gonna have to loose that little "tail" before he is a classic annular. imho - just a learner.
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Quoting TropicalAnalystwx13:


That will likely be Karl.


I think 92L would likely be Karl
Member Since: March 10, 2010 Posts: 1 Comments: 7874
Quoting flhurricane:
does it matter if igor is annular or not as far as path?
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
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2213. dmaddox
any hints of eyewall replacement cycle with Igor yet!??
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Quoting bassis:


where can I find some explanations on the T#
The Advanced Dvorak Technique
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting sunlinepr:
Any names left for Me???



That will likely be Karl.
Member Since: July 6, 2010 Posts: 113 Comments: 32853
2209. dmaddox
Quoting sunlinepr:
Any names left for Me???

WOW!
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2208. bassis
Quoting MiamiHurricanes09:
It's higher than that. I don't know why, but CIMSS always puts it a little lower than SSD.

On the SSD site, the Raw T# is up to 6.9.


where can I find some explanations on the T#
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Quoting RecordSeason:
Yeah, Igor is tapped into some serious joo joo right now.

The SE quadrant is improving even more on Shortwave. There is no dry air issue at all for this storm any time soon, IMO.



It almost looks like there are several sub-votices ... possibly tornados around the "donut".
Member Since: August 29, 2009 Posts: 12 Comments: 483
Mmm okay so if I'm reading this correctly then the trof's look flatter,and weaker meaning they won't have an impact on him?.Someone help me out please.Hubby is getting on my nerves yelling,and shouting over the game.
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Quoting MiamiHurricanes09:

Category 5?
Member Since: July 7, 2010 Posts: 0 Comments: 5725
Any names left for Me???

Member Since: August 2, 2010 Posts: 21 Comments: 9882
2202. Max1023
Igor is literally AT his MPI, if he is actually a category 5 he is above it. This proves that the MPI maps are low.
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2201. Walshy
Quoting flhurricane:
does it matter if igor is annular or not as far as path?


Yes. They are sneaky.
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Quoting MiamiHurricanes09:
It's higher than that. I don't know why, but CIMSS always puts it a little lower than SSD.

On the SSD site, the Raw T# is up to 6.9.


Great scott!
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Quoting CybrTeddy:
Great scott..
CI# /Pressure/ Vmax
6.6 / 934.2mb/129.6kt


Final T# Adj T# Raw T#
6.6 6.7 6.7

It's higher than that. I don't know why, but CIMSS always puts it a little lower than SSD.

On the SSD site, the Raw T# is up to 6.9.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Hurricanes101:
thank you StormW

instead of just bashing people like Jedkins did you actually explained it

and yes Igor is very close to annular


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.
Member Since: August 11, 2010 Posts: 0 Comments: 895

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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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