Potentially dangerous 92L steadily developing; Igor nears hurricane strength

By: Dr. Jeff Masters , 3:04 PM GMT on September 11, 2010

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A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°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-northwest at 11 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 Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)

Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. 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. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.


Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.

Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-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 has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% 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 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model 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. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.

Next post
This may be my only post today; I'll have a new post Sunday morning.

Jeff Masters

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Quoting WeatherNerdPR:

Yeah, unless they turn into trolls, which isn't gonna happen. For now. lol


Nah, those guys will never be trolls. They're far above that.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
East winds in central-eastern Caribbean?

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Quoting StormW:
92L
The 64 dollar question is: A continuing trend toward consolidation?
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1420. Levi32
Invest 93L looks remarkably good for how close it is to Africa.
Member Since: November 24, 2005 Posts: 635 Comments: 26569
Quoting KoritheMan:


Correct. That's why I love these guys.

Yeah, unless they turn into trolls, which isn't gonna happen. For now. lol
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Quoting zicoille:
Someone promised me Igor...I hope we will have it. Earl was joke !


You're gonna get a lot of flak for that. You understand that, right? Rightly so, perhaps.

But I also think that people shouldn't be so quick to judge such comments. I understand how you feel, and won't condemn you for it.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
Quoting tropiccian:
Taz, good evening sir. How did you find out about the 78% chance of landfall in S. TX?



thats my ch are
Member Since: May 21, 2006 Posts: 5091 Comments: 114792
Quoting Stormchaser2007:
CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt


I suspected he'd be around 70 kt at 11:00 PM.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
Quoting stormwatcherCI:
I know I can learn from all of you but I am sure you can all learn from each other also.


Correct. That's why I love these guys.
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Quoting StormW:
92L


Looks like 15 N. The small blob is just N of the center
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+1

Agreed...great discussion on the blog tonight...thanks.

Quoting stormwatcherCI:
The blog is great tonight. Some fantastic heads on here debating and this is how we learn. Thanks Storm, Kman, Kori, Drak, Levi and the rest of the knowledgable folks on here.
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Taz, good evening sir. How did you find out about the 78% chance of landfall in S. TX?
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Quoting Stormchaser2007:
CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt

wow
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Quoting KoritheMan:


Yes. This is why I love when all those guys are on. There's nothing quite like good, spirited debate. We're always going to have differing opinions, because we're human and thus see things differently. But as you said, it's how we learn.
I know I can learn from all of you but I am sure you can all learn from each other also.
Member Since: October 9, 2008 Posts: 0 Comments: 8288
Quoting StormW:


Time for the show to begin.

To the layman, a bunch of squiggly lines. To us, thats freakin downright scary!
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1405. pcola57
Hey Storm don't bail on me...
Re: post 1376..
Your Thought's??
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CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt
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Quoting pottery:

Well, dont take the 'trivial' too seriously.
Generally, the info is good.
I don't. Not a general indictment of the blog. Just a rant at those who try to disrupt. My bp is good.















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Quoting stormwatcherCI:
The blog is great tonight. Some fantastic heads on here debating and this is how we learn. Thanks Storm, Kman, Kori, Drak, Levi and the rest of the knowledgable folks on here.


Yes. This is why I love when all those guys are on. There's nothing quite like good, spirited debate. We're always going to have differing opinions, because we're human and thus see things differently. But as you said, it's how we learn.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
1400. Levi32
Quoting kmanislander:


Take a look at the Ramsdis loop. I am not suggesting a motion to the SW. My last post said a "due West motion "


I added this to my post:

"The track likely won't turn that hard left but it's still going to take some effort to pull 92L away from the weakness."
Member Since: November 24, 2005 Posts: 635 Comments: 26569
Quoting earthlydragonfly:
Got a new shot tonight .... Let me know what you guy think of it....

Lightning

Impressive.
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Quoting Tazmanian:



oh nic we get the K storm then


I've had a bad feeling about Karl prior to the season. I still have that today.
Member Since: March 7, 2007 Posts: 561 Comments: 20069


Is this why we don't hear about the UKMET often anymore?
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1395. Drakoen
Very healthy looking deep-layered trough:

Member Since: October 28, 2006 Posts: 57 Comments: 29942
The blog is great tonight. Some fantastic heads on here debating and this is how we learn. Thanks Storm, Kman, Kori, Drak, Levi and the rest of the knowledgable folks on here.
Member Since: October 9, 2008 Posts: 0 Comments: 8288
Definitely moistened at Curacao in the last 12 hours.

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Good Evening. What's been going on?
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Quoting Levi32:


It won't buck it but it hasn't gotten to that point yet in my opinion. There's still a little way to go yet before 92L will be forced to turn west, and it may very well take its sweet time if the weakness is strong enough, because it's darn hard to turn a tropical system southwest.


Take a look at the Ramsdis loop. I am not suggesting a motion to the SW. My last post said a "due West motion "
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1388. Drakoen
Quoting Levi32:


It won't buck it but it hasn't gotten to that point yet in my opinion. There's still a little way to go yet before 92L will be forced to turn west, and it may very well take its sweet time if the weakness is strong enough, because it's darn hard to turn a tropical system southwest.


Exactly
Member Since: October 28, 2006 Posts: 57 Comments: 29942
Got a new shot tonight .... Let me know what you guy think of it....

Lightning
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Quoting btwntx08:
good evening will not make it in the gom ehhh i trend to disagree


Considering 85% (my estimation, not official) of all Caribbean storms eventually make it into the GoM, odds are quite good, I'd say.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
Quoting KoritheMan:


92L won't be Julia. 93L will beat it.



oh nic we get the K storm then
Member Since: May 21, 2006 Posts: 5091 Comments: 114792
Quoting btwntx08:
good evening will not make it in the gom ehhh i trend to disagree


I think the discussion meant " will not make it into the Northern GOM ". The odds for the BOC have always been high.
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1383. Levi32
Quoting kmanislander:


That high pressure center is producing a SW flow from the center of the weakness and off to the West. I don't see 92L bucking that flow.


It won't buck it but it hasn't gotten to that point yet in my opinion. There's still a little way to go yet before 92L will be forced to turn west, and it may very well take its sweet time if the weakness is strong enough, because it's darn hard to turn a tropical system southwest. The track likely won't turn that hard left but it's still going to take some effort to pull 92L away from the weakness.
Member Since: November 24, 2005 Posts: 635 Comments: 26569
Quoting HouGalv08:
I have to agree with you Chicklit. Possible "Julia" had to clean house first, open all the windows to get the dry air out, and moisturize before the party could begin.


92L won't be Julia. 93L will beat it.
Member Since: March 7, 2007 Posts: 561 Comments: 20069
well i new we where going too see some in sooner or later well what see what 92L dos
Member Since: May 21, 2006 Posts: 5091 Comments: 114792
Quoting Drakoen:


I would have to disagree on its closeness to the high pressure center off the the northwest looking at the Dvorak and Water vapor imagery. 92L seems to be right within the weakness.


That high pressure center is producing a SW flow from the center of the weakness and off to the West. I don't see 92L bucking that flow.
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Quoting Chicklit:
Kinda looks like 92L has feathered its nest.
I have to agree with you Chicklit. Possible "Julia" had to clean house first, open all the windows to get the dry air out, and moisturize before the party could begin.
Member Since: July 21, 2008 Posts: 0 Comments: 357
Quoting StormW:


Time for the show to begin.




right 60% ch of 92L be comeing cat 5 70% ch of Igor be comeing a cat 5 has well
Member Since: May 21, 2006 Posts: 5091 Comments: 114792
1376. pcola57
Thanks Storm for your synopsis..i also recognize the subtle changes in steering you mention previously..I did dead reconing on both Igor and 92L 48 hrs out..I'm not sold on the Ensemble/Dynamic presentations at this point on either..I agree with you on 92L..allowing for limited data
the TVCH seems more plausible and probable..I mentioned on the blog last night that some adjustment in data input to the models and extrap thereof, seems to be on the table and being applied..bad time of year and I believe wrong year...the storms I've seen so far have some anomylous traits...I think bouy data is going to be a key component this part of the season...JMO of course...any comment on my take would be appreciated..
Thanks again Storm..you've gotten me to open up the tool box and use/understand the info to a higher degree this year...I really appreciate that...
Again..Well Done Chief
v/r
Moe
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Quoting Tazmanian:
what would 2010 hurricane season be with out one cat 5


lol

You and those Cat 5's. ;)
Member Since: March 7, 2007 Posts: 561 Comments: 20069
Taz,
"L" key broken again huh?
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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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