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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3596. leo305
Igor's been moving south of due west since yesterday..
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3595. pcola57
RE post 3570
Well spoken..IMO


African Continent Very Robust
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Quoting hunkerdown:
I believe you are misreading those models...if you put them in motion I believe you will see in all three cases Igor head for and hit the weakness depicted.


Indeed. All 3 models show IGOR moving North at some point...but to a point. The GFS is showing a weakness between the two ridges, but then the ridges filling in...albeit not as strong as the NOGAPS. The NOGAPS on the 00z run shows IGOR turning back to the West after it gets to around 27N. My point was why? Why did it shift? The ridge looks like the answer. Have a look:

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Good Night everyone! Be Safe and we'll see what tomorrow brings!
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Quoting StormJunkie:
Thanks PSL, I may check that one. Really like the idea of having the 200mm zoom (and well...quite honestly...a white lens) but hate that it will be the only top grade lens in my bag and therefore will sacrifice the lower end for a while. Will have to look at the 24-105 though. That would be a better general range. I shoot anything that seems interesting to me. Weather,scenery, & people for the most part.

Almost forgot. The 2.8 is also a huge plus for me on that lens. With that aperture setting, I wouldn't have to go with the much more costly IS version.

And to make sure we stay on topic...Here's Igor

My pleasure. If I can be of assistance in any way, please feel free to WU mail me. I'll be happy to "talk shop" about photography any time you wish. But, unless you plan to shoot off a tripod most of the time, you will be much more satisfied with an IS lens. Technology helps tremendously.
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Well, I think many of us are not PHDs in meteorology. Neither have a degree, but we enjoy this unique science of weather behavior. For novices, that are welcomed here, there is a learning curve period, where erratic comments can be posted. For me the important thing is to keep our comments like most of we do, with respect and giving space to those who want to learn.....
Quoting TXEER:


Thanks...and great points...I just wish I had a "Who's Who in the Zoo" so I could know who to pay attention to..as opposed to who is blownwg smoke and wish casting!
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the next weekend storm some were mentioning? I know, I know its a long ways off. :)

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Quoting KoritheMan:


In general, it should remain in this area for at least the next week. Some fronts will try and push it eastward a tad, but all in all, not too much.


Thanks a bunch! I sure hope we don't get any hurricanes this year in SWLA ...:/
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3587. JLPR2
Julia & convection related to 45L

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3586. xcool
Ryuujin .noo weaker yet
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3585. xcool
sunlinepr dry
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Quoting Joanie38:


Hi KoritheMan:) Thanks for your answer...do you know for how long that ridge is suppose to be there?


In general, it should remain in this area for at least the next week. Some fronts will try and push it eastward a tad, but all in all, not too much.
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3583. TXEER
Quoting dracko19:


Keep in mind, there are people who post in this blog who have a deep background in weather. Not all of them, but you'd be surprised how many. Their expertise in weather may not always be associated with hurricanes directly, but they may understand much more than you realize how the enviornment effects hurricane stearing, intensity and evolution. I have seen former and present meteorolgists, former NHC employees and even former Hurricane Hunters post in these blogs. I agree not every poster has that kind of background, but there might be more credible posters here than you realize.


Thanks...and great points...I just wish I had a "Who's Who in the Zoo" so I could know who to pay attention to..as opposed to who is blownwg smoke and wish casting!
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Quoting texascoastres:
would think if Ike had hit at Freeport, Galveston may have taken it a lot harder. That east side (you would think) would have made it a lot worst. Like Shore Acres, LaPorte and Seabrook
... yep the european model was close.... and it was like 8 days out when it was still in the atlantic... it was the only model to see this ... then the move west happen and the other models followed...
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His SW Spiral Bands expanding and the core and eye Look like shrinking.....Dry air injection??? It's reacting with the trough????


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Quoting F4PHANTOM:
I like to check all NWS stations along the gulf coast to get a better feel of the overall picture.


Yeah I usually do. Went right past that one to Brownsville today. Running late still. I might catch up by their next discussions. :)
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Quoting AtHomeInTX:


Evening Joanie. :) That ridge will protect us if it does weaken or move at the wrong time.


Hi there :) Let's hope not!
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3578. Ryuujin
Quoting xcool:




Btw, where is the weakness there? I don't really see one, or am I missing it?
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Quoting OracleDeAtlantis:


I suspect he's feeling the wake of Earl, but it's just a guess.


Then again, it could be a form of strengthening by becoming a more compact storm...
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Quoting KoritheMan:


For now, it should protect us.


Hi KoritheMan:) Thanks for your answer...do you know for how long that ridge is suppose to be there?
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Quoting OracleDeAtlantis:


I suspect he's feeling the wake of Earl, but it's just a guess.


Nope:





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Black out start at 345 or 415?
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3572. Ryuujin
Quoting hurristat:


Is it just me, or did Igor just shed a bunch of his convection?


We think he might be starting an EWRC
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Quoting Joanie38:
Evening all...

I have a question....is that a BIG ridge that is protecting SETEX and Louisiana? Doesn't it block anything that comes up this way??? TIA :)


Evening Joanie. :) That ridge will protect us if it does weaken or move at the wrong time.
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Quoting TXEER:
I've been lurking here most of the season and I have to say that the models and the NHC are certainly more accurate than the hurricane experts who post here.

Things like..."Igor is heading further West" and "Don't see where the NHC can say such and such".

Hey folks the NHC can say it because they are the freaking experts!

I must say it is amusing to watch all the experts who post here act authoritative.


Keep in mind, there are people who post in this blog who have a deep background in weather. Not all of them, but you'd be surprised how many. Their expertise in weather may not always be associated with hurricanes directly, but they may understand much more than you realize how the enviornment effects hurricane stearing, intensity and evolution. I have seen former and present meteorolgists, former NHC employees and even former Hurricane Hunters post in these blogs. I agree not every poster has that kind of background, but there might be more credible posters here than you realize.
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Quoting hurristat:


Is it just me, or did Igor just shed a bunch of his convection?


I suspect he's feeling the wake of Earl, but it's just a guess.
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Quoting Joanie38:
Evening all...

I have a question....is that a BIG ridge that is protecting SETEX and Louisiana? Doesn't it block anything that comes up this way??? TIA :)


For now, it should protect us.
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Quoting sunlinepr:
At least something is going on with Igor, starting to react to the trough (dark upper left incoming area). What will be the response, we'll see...



Is it just me, or did Igor just shed a bunch of his convection?
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Quoting F4PHANTOM:
I don't believe the high is forecast to move that far to the east by thur-sat. We should still be under it's influence. From CC Tex:
THE LONG TERM FORECAST RIDES
HEAVILY ON THE EVENTUAL EVOLUTION OF THE DISTURBANCE. THE MODELS ARE
HINTING NOW THAT THE RIDGE MAY WEAKEN ACROSS THE WESTERN GULF OF
MEXICO BRIEFLY AND ALLOW THE DISTURBANCE TO GAIN A LITTLE BIT OF
LATITUDE. THE GFS KEEPS THE DISTURBANCE AS AN OPEN WAVE WHILE THE
ECMWF DEVELOPS IT INTO A TROPICAL CYCLONE. THEY BOTH MOVE THE
DISTURBANCE TOWARDS CENTRAL/NORTHERN MEXICO. THEREFORE...BUMPED UP
POPS TO CHANCE FOR THE WEEKEND ACROSS THE COASTAL PLAINS AND
SOUTHERN CWA AND HAVE SLIGHT CHANCE POPS ELSEWHERE. TEMPS WILL
REMAIN AT OR ABOVE AVERAGE FOR THE EXTENDED.



Ok. Thanks. Hadn't read that one yet. Hope it does hold firm. :)
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would think if Ike had hit at Freeport, Galveston may have taken it a lot harder. That east side (you would think) would have made it a lot worst. Like Shore Acres, LaPorte and Seabrook
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Evening all...

I have a question....is that a BIG ridge that is protecting SETEX and Louisiana? Doesn't it block anything that comes up this way??? TIA :)
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Quoting 1celia70:
...could igor be making it's own enviroment...by pressing west ...


If he becomes large enough, and with very large outflow, they can influence the environment around them. We saw this with hurricane Gilbert back in 1988, and perhaps Tip in 1979 in the Pacific. They still tend to follow the hills and valleys, in terms of direction, however. How those hills and valleys are changed by the outflow of a very large system, can be trickier than forecasters like to admit sometimes.
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3561. bassis
The suspense is killing me!

Is it a square?
Is it a rectangle?
or an equilateral...

oops, wrong shape
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3560. xcool


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Quoting dracko19:
The NOGAPS and ECMWF build a very large ridge over the East Coast, blocking IGOR from going N. The GFS is now developing that same ridge. Not as strong as the NOGAPS/ECMWF one, but all the models are starting to agree that the fronts coming off the US are going to leave behind a ridge that could block IGOR. This will either leave IGOR in a weakly steered enviornment with a weak ridge (GFS) or will push it West (NOGAPS/ECWMF). Either way, it is not good if you own beachfront property.

GFS



NOGAPS



ECMWF

I believe you are misreading those models...if you put them in motion I believe you will see in all three cases Igor head for and hit the weakness depicted.
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Thanks PSL, I may check that one. Really like the idea of having the 200mm zoom (and well...quite honestly...a white lens) but hate that it will be the only top grade lens in my bag and therefore will sacrifice the lower end for a while. Will have to look at the 24-105 though. That would be a better general range. I shoot anything that seems interesting to me. Weather,scenery, & people for the most part.

Almost forgot. The 2.8 is also a huge plus for me on that lens. With that aperture setting, I wouldn't have to go with the much more costly IS version.

And to make sure we stay on topic...Here's Igor

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Quoting TXEER:
I've been lurking here most of the season and I have to say that the models and the NHC are certainly more accurate than the hurricane experts who post here.

Things like..."Igor is heading further West" and "Don't see where the NHC can say such and such".

Hey folks the NHC can say it because they are the freaking experts!

I must say it is amusing to watch all the experts who post here act authoritative.
... your right ..glad we have a hurricane center... but it's weather... and it does change.. i remember when one said hurricane ike was going to move northwest and head to east coast... only the european model had it early ...moving into gulf and hitting near freeport,tx... that was 8 to 9 days out .. we know what happen.... but i am glad the hurricane center and set us straight....
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Quoting 1celia70:
..earlier at 10 ...channel 13 had also said to watch for something towards next weekend ... still not sure if it will be anything ... we saw how quick hermine formed.. gulf is hot ..but the high pressure could help.. but if it moves to far east ..could it effect ..igor...???


I'm not sure. Levi spoke about this on his blog/video better than I could explain it. And yes the gulf is hot. It's scary having anything that could develop in the gulf or Caribbean because like you said it wouldn't take long.
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Quoting StormJunkie:
So...Any photographers in here tonight? Thinking about taking the plunge on an L-series lens. The 70-200, but I think I read it isn't weather sealed...That would be a real downside for me.
An amateur, but an avid one. I have an L-series. Mine is the 24-105 IS. Great walking around lens with excellent short to medium focus. Sounds like you're looking for a telephoto at medium to long range. Depends on what you're looking to shoot.
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At least something is going on with Igor, starting to react to the trough (dark upper left incoming area). What will be the response, we'll see...

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AOI

AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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Quoting AtHomeInTX:


Ok. Thanks. Our (Beaumont) channel said about the same earlier. Seeing things like the high moving east by Thursday and the upper ridge weakening was getting knida worrisome. Hopefully 92L won't get too bad.
..earlier at 10 ...channel 13 had also said to watch for something towards next weekend ... still not sure if it will be anything ... we saw how quick hermine formed.. gulf is hot ..but the high pressure could help.. but if it moves to far east ..could it effect ..igor...???
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3550. TXEER
I've been lurking here most of the season and I have to say that the models and the NHC are certainly more accurate than the hurricane experts who post here.

Things like..."Igor is heading further West" and "Don't see where the NHC can say such and such".

Hey folks the NHC can say it because they are the freaking experts!

I must say it is amusing to watch all the experts who post here act authoritative.
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3549. flsky
MSNBC says Julia has formed.
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Quoting PrivateIdaho:
...do a round of golf in about 45 minutes I suspect. :^)
Alas, I'm not allowed to take it on the course as of yet. Also, I have to make too many swings at the ball to go that fast. Working on it though.
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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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