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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Igor has done well its doing what i ask it to do

Link
Member Since: May 21, 2006 Posts: 5089 Comments: 114075
Quoting stormwatcherCI:
Do you still feel like it stands a good chance on being a threat to us ?


I'm thinking CAT 1 at worst. I don't see this becoming a TD before late tomorrow assuming it can refire and hold on to the convection.

BUT, here we go again.

Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting kmanislander:
Good evening folks

92L now starting to organize. This blow up is right over the center.

It looks the best it ever has, the storms are firing up right over the center, now it can fully develop
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Quoting StormW:


Yeah...kinda like a crossover ceremony.


i don't think this is going to be that slow of an development once it gets going either.
tomorrow mornings going to surprise a lot of folks
"IMO"
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Well, Igor looks........ decent.
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Quoting JLPR2:


Yeah, here is one with pretty colors LOL!
Maybe TS watches or warnings for the southward Cape Verde islands.
i wouldn't be surprised
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Quoting sunlinepr:
Although 93L is quite low, models are moving it North


The models will shift further south.

Blog Update
Link
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Quoting kmanislander:


First time we are seeing anything of note right near the center.
Do you still feel like it stands a good chance on being a threat to us ?
Member Since: October 9, 2008 Posts: 0 Comments: 8242
Quoting StormW:


Yeah...kinda like a crossover ceremony.


Or a right of passage.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Quoting bassis:


Noticed that. he's got a singularity


First time we are seeing anything of note right near the center.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
1176. want2lrn 1:05 AM GMT on September 12, 2010
Out of lurk mode to make an observation. If it is incorrect please say so, as i am trying to learn. It appears to me that just south of what appears to be thunderstorms? (red dot) i think that i see the circulation starting to look better. Am i correct and would this be a low level or mid level feature? talking about 92L TIA
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Quoting StormW:


Evening kman!


Hello Storm

92L now closing in on 70 West. No surprise that we are seeing the seeds of something new. 75 West is where I expect to see consolidation begin.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
1259. pottery
Quoting stormwatcherCI:


If dry air has been the problem for 92L doesn't look like it should be for much longer. Almost gone to the west of it now.

That's all it needs, is some moist air soon...
Member Since: October 24, 2005 Posts: 0 Comments: 23115
Quoting StormW:


It's possible...if you look at that wave, notice how close it is to the trof, and it's still heading west, granted, Igor is much deeper now...but if you look very close, especially at DVORAK LOOP zoomed in, you can see the ridge nosing west, just north of him.

DVORAK


Rainbow
yes i checked it out, wow, also looked at the wave that has a 10percent chance, well anyway it looks to be nearly stationary, if the trough was strong you would think the wave would've kicked northeast fairly quickly, thanks for your insight
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1257. bassis
Quoting kmanislander:
92L now starting to organize. This blow up is right over the center.



Noticed that. he's got a singularity
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Quoting stormwatcherCI:


If dry air has been the problem for 92L doesn't look like it should be for much longer. Almost gone to the west of it now.


Agreed. That was the only thing restraining it over the last several days. Now all parameters are a-go, especially since satellite imagery reveals a tightening of the low-level circulation.
Member Since: March 7, 2007 Posts: 521 Comments: 19146
Quoting StormW:


The circulation is starting to wind up:

LINK


My...My...My! Not only is it starting to wind up, but it's doing it rather well. The Little Invest That Could! ;)

Evenin' Storm! Hope you and yours are well.
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1252. JRRP
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Good evening folks

92L now starting to organize. This blow up is right over the center.

Member Since: August 19, 2006 Posts: 0 Comments: 15671


If dry air has been the problem for 92L doesn't look like it should be for much longer. Almost gone to the west of it now.
Member Since: October 9, 2008 Posts: 0 Comments: 8242
1248. JLPR2
Quoting Stormchaser2007:
This should be a depression very soon. Maybe by 5am.



Yeah, here is one with pretty colors LOL!
Maybe TS watches or warnings for the southward Cape Verde islands.
Member Since: September 4, 2007 Posts: 7 Comments: 8459
Quoting PSLFLCaneVet:
Sorry, but your nasty attitude tells me you need a timeout. Poof.


You broke my heart
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Puerto Rico Tropical Forecast * Hurricane IGOR and Tropical Storm Julia? Affects in Eastern Puerto Rico

Link

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This should be a depression very soon. Maybe by 5am.

Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting sunlinepr:
Although 93L is quite low, models are moving it North

BAMD's acting up LOL.
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1241. Bonz
Quoting StormW:


???


clwstmchasr thinks that 93L was the circled area in Africa to which you were referring and was pointing out that it won't be coming across the pond.

But in reality, you have a different area circled that is south of 93L and moreover, is still over land.
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Quoting Eugeniopr:


Your are spoiling the blogers needs of a real catastrophe. But I think and hope you are right.
Sorry, but your nasty attitude tells me you need a timeout. Poof.
Member Since: July 23, 2010 Posts: 1 Comments: 12414
Have never used the "-" as much as tonight. Looks like someone has created multiple accounts so "storm" the blog on one night. But with those types of comments sure it won't last long.

93L Looks pretty mean, glad all the model at taking that one out sea at the get go!
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Quoting StormW:


The circulation is starting to wind up:

LINK


Storm,
Do you think 92L will impact Jamaica and if so when?
One Love
Tracy
Member Since: July 16, 2008 Posts: 0 Comments: 48


Dry air (not much) surrounding 93L...
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1236. beell
I don't really see much ridge building behind this first trough. And there really is not much sign of a second or third trough. I do see the polar jet dipping south around that polar vortex and flattening out. Maybe as far S as 40N. Strong westerlies will push any attempt at ridge building to the east. The weakness remains waiting for Igor to slide up into the westerlies along the periphery of the remaining mid-Atlantic ridge-which is under attack from the polar jet.
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Quoting GeoffreyWPB:
Going out on a huge limb here...I think it is possible that 92L will make a run towards the Mona Passage.


Storm, Drak, Levi or anyone...Too outlandish or possible?
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stormw good evening,
Do you think that the tropical wave to the westnwest of Igor will enhance some ridging and keep igor on a westward course???
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1232. Drakoen
Igor
Member Since: October 28, 2006 Posts: 57 Comments: 29714
93L mode runs are way too far N
Member Since: May 21, 2006 Posts: 5089 Comments: 114075
The Eastern Atlantic is pretty moist and 93L shouldn't have any problems with dry air until it reaches the central ATL.
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Although 93L is quite low, models are moving it North

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Quoting StormW:


Something that far south with the upcoming pattern change, should be able to make it across the pond.


No trofs dipping down that far south, 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.