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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Latest CMC:

Link

92L into Corpus Christi next weekend...
(caution: 7 day track errors can be infinite)
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Quoting HurricaneFCast:


That would be Ike in 2008.. He dropped 44 mb in 12 hours between 2PM (EST) on 9/3 and 2AM (EST) on 9/4


Thats it!
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Quoting pottery:

You are being much too harsh here.
You are obviously not reading the thing in the context it was intended.


Some people are just to annular around here lol! JOKE
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Igor appears to be on the way to a cat. 5

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Quoting pottery:

You are being much too harsh here.
You are obviously not reading the thing in the context it was intended.


Thank you!
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Quoting StormW:


Not quite.


He needs to look at the track of Earl, if Earl didn't jog back to the right after passing 75W, the Carolinas would have had a landfalling storm, as well as Cape Cod. It was that one jog to the east just before hitting the Carolinas that saved everyone.
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Quoting atmoaggie:
UTC time is 4 hours ahead of EDT (5 ahead of EST).

Thus, 15 UTC = 11 EDT.


Thanks Atmo, Yeah, I knew, I just wanted him to recheck his reference, it's a good way to learn and with everything in the weatherworld being based on UTC, it's good to know where you are in the stream of time. Even on computers, EDT is corrected automatically.

I think Dr Masters lives in PST zone. I live in Central, but most Tropical events from the Atlantic happen to MOST of us in the EDT to CST zone. So, apparently, there isn't an official "blog time".

But the original poster said that he believed Igor would be Cat 4 by 2PM. So when is that to him? Or us? Or Igor?
So, he could be right or wrong based on when 2 o'clock is to him.

It's enough to drive a man to drink! Which reminds me, it's 5 o'clock somewhere.......
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Quoting TropicalAnalystwx13:


Wilma '05 I believe.

Did Ike '08 go through ED?
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538. MZT
Quoting Bordonaro:

Under perfect conditions the SST's & atmosphere would support an 880MB storm. Lets hope that does NOT happen!!!
876MB is standard air pressure at 4500 feet. That would be one heck of an "ear popping" experience (assuming you were in a cave, since no structure would withstand the winds of sych a storm.) =:-O

http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html
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LOL...

A sub-800mb hurricane...

Would require a geothermal event like a VEI8 erruption, a super plume, or a meteor to happen in the first place to get the TCHP you'd need, but if it did somehow happen...

Maybe 400mph sustained winds?
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Quoting caneswatch:
Reading this blog, i'm really shocked that everyone's calling fish on Igor already. While I respect your opinions, there's a lot that factors into where Igor goes. The second trough is getting flatter and there's a high coming from near Texas that may move in to block Igor from any northward movement, if it gets here fast enough. So, it would be unwise to call this a fish storm now.


Yo Conner. I think things could go either way as for this being a fish. We just need to wait for this to pan out.
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Quoting WeatherNerdPR:

When was the last time Explosive Deepening happened in the Atlantic?


That would be Ike in 2008.. He dropped 44 mb in 12 hours between 2PM (EST) on 9/3 and 2AM (EST) on 9/4
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Quoting Stormchaser2007:



They say 127KTS, I'd say about 115KTS or about 130MPH a high end CAT 3 as we speak, in my humble opinion!!
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Quoting hunkerdown:
that is NOT what you said, your quote:

We could see sub-900. I'm not completely confident in the sub-800 calculation. If I was so sure of it, I'd get myself some professional help; trust me. ;-)

forget being confident or not, the fact that you even mention a sub-800, which would be pressures in the 700s, has to say something, either you truly don't understand or maybe you really do need help.

You are being much too harsh here.
You are obviously not reading the thing in the context it was intended.
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Quoting StormW:
Good afternoon!

Hi Storm!
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Reading this blog, i'm really shocked that everyone's calling fish on Igor already. While I respect your opinions, there's a lot that factors into where Igor goes. The second trough is getting flatter and there's a high coming from near Texas that may move in to block Igor from any northward movement, if it gets here fast enough. So, it would be unwise to call this a fish storm now.
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Quoting StormW:
Good afternoon!


Hi Senior Chief.
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Quoting reedzone:
Trends are still going westward with Igor and you all are straight out calling for it to recurve, wow... Give it a few days until it actually turns north. Apparently you all haven't learned anything from Earl.


I learned a lot from Earl...it's called media hype..
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Quoting Bordonaro:
My gues is that Igor is a CAT 3 with 120MPH winds at present with a central pressure near 955MBS!!!

Looking like the beginnings of an annular Hurricane to me


LOL! Igor giving himself a perfect 10
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Quoting StormW:
Good afternoon!


Hey Storm!

We have an unofficial Category 3/4 on our hands.

We also have an unofficial Julia on our hands.
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Quoting hunkerdown:
that is NOT what you said, your quote:

We could see sub-900. I'm not completely confident in the sub-800 calculation. If I was so sure of it, I'd get myself some professional help; trust me. ;-)

forget being confident or not, the fact that you even mention a sub-800, which would be pressures in the 700s, has to say something, either you truly don't understand or maybe you really do need help.


Admin, please troll wipe this stubborn, intolerant person.

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Quoting WeatherNerdPR:

When was the last time Explosive Deepening happened in the Atlantic?


Wilma '05 I believe.
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Quoting nyhurricaneboy:


That's what I said...

No need to put your unnecessary repetition in a negative connotation.

that is NOT what you said, your quote:

We could see sub-900. I'm not completely confident in the sub-800 calculation. If I was so sure of it, I'd get myself some professional help; trust me. ;-)

forget being confident or not, the fact that you even mention a sub-800, which would be pressures in the 700s, has to say something, either you truly don't understand or maybe you really do need help.
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Quoting WeatherNerdPR:

When was the last time Explosive Deepening happened in the Atlantic?


I think it was Earl.

Probably wrong.
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Quoting Stormchaser2007:


I dont think it was Apocalyptocanecasters. Rather just a kid not understanding how something works.


I DO KNOW HOW IT WORKS. I CORRECTED MY UNCLEAR POSTING. I GUESS SO MANY PEOPLE POOFED ME THAT THAT DIDN'T SEE IT.

I DO NOT THINK THAT IT'S GOING TO DEEPEN THAT MUCH. I WAS JUST ANALYZING A TREND. PLEASE END THIS NOW.
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Trends are still going westward with Igor and you all are straight out calling for it to recurve, wow... Give it a few days until it actually turns north. Apparently you all haven't learned anything from Earl.
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Quoting weatherlover94:


i wouldnt be suprised if it isnt already a strong cat 3 minimal cat 4 at 5 pm

At the rate Igor is ramping up, he may be a CAT 4 within 2-3 hrs!!

Swat does CIMSS say his Dvorak or T # is an estimated central pressure??
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not a Cat. 2... sorry NHC!!!
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Quoting BenBIogger:


Interesting feature just east of the Antilles.

LOL, you noticed that too, did you?
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Quoting MiamiHurricanes09:
I think this is what Igor is currently doing:

Explosive Deepening:
A decrease in the minimum sea-level pressure of a tropical cyclone of 2.5 mb/hr for at least 12 hours or 5 mb/hr for at least six hours.

When was the last time Explosive Deepening happened in the Atlantic?
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Quoting Bordonaro:
My gues is that Igor is a CAT 3 with 120MPH winds at present with a central pressure near 955MBS!!!

Looking like the beginnings of an annular Hurricane to me


i wouldnt be suprised if it isnt already a strong cat 3 minimal cat 4 at 5 pm
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Quoting Cotillion:
By the way, for the Apocalyptocanecasters (say that 10 times after a few pints), the deepest storm in the Central Atlantic is Isabel with 915mb (of what has been recorded - if Dog was 185mph in reality, his pressure would have been sub-905mb, potentially sub-900mb. But, we'll never know).


I dont think it was Apocalyptocanecasters. Rather just a kid not understanding how something works.
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507. Vero1
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Quoting KanKunKid:


Is there an official blog time zone?

I can't really understand what you said. 1500 UTC = 9 AM EDT? I also don't get 2PM /5PM, that's a 3 hour window. I'm not trying to be difficult, I just need some clarification please.
2pm / 5pm = two different forecast times. Both were likely EDT.

No official blog time... we've got regular bloggers from 4 different time zones here [z-4 to z-7], not to mention Cotillion, Orca, and our Oz-resident family members...
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The 18z SHIPS text will let us know whether Igor is annular or not. Personally, I don't believe he is, but ya' never know...I guess.
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My gues is that Igor is a CAT 3 with 120MPH winds at present with a central pressure near 955MBS!!!

Looking like the beginnings of an annular Hurricane to me
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Quoting KanKunKid:


I used to do that, at night. thankfully, I grew out of it.
What are you thankful for?
Diurnal max was fine by me.
This diurnal min is a downer.
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I think this is what Igor is currently doing:

Explosive Deepening:
A decrease in the minimum sea-level pressure of a tropical cyclone of 2.5 mb/hr for at least 12 hours or 5 mb/hr for at least six hours.
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Quoting hunkerdown:
one last remark to your senseless thinking (unless you don;t know what the prefix "sub" means)...a sub-800 would be pressures in the 700s which is purely ridiculous. sub-900, possible, yes. the lowest Atlantic cane ever was Wilma at 882 mb and the lowest recorded anywhere was Tip at 870mb.


That's what I said...

No need to put your unnecessary repetition in a negative connotation.

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Quoting Stormchaser2007:


Igor definitely IR
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By the way, for the Apocalyptocanecasters (say that 10 times after a few pints), the deepest storm in the Central Atlantic is Isabel with 915mb (of what has been recorded - if Dog was 185mph in reality, his pressure would have been sub-905mb, potentially sub-900mb. But, we'll never know).
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Quoting KanKunKid:


Is there an official blog time zone?

I can't really understand what you said. 1500 UTC = 9 AM EDT? I also don't get 2PM /5PM, that's a 3 hour window. I'm not trying to be difficult, I just need some clarification please.
UTC time is 4 hours ahead of EDT (5 ahead of EST).

Thus, 15 UTC = 11 EDT.
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Quoting KanKunKid:


I used to do that, at night. thankfully, I grew out of it.

LOL
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no dry is being affected it created moisture around it
Member Since: July 13, 2008 Posts: 6 Comments: 10796

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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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