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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Quoting TampaSpin:


A Trough Split i believe will occur as High pressure from the PLAINS comes in full aboard.


We'll see what happens.

If the guidance shifts west, we may have something to worry about again.
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The 00z ECMWF took Igor up to 134 knots

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NHC running late.. nothing updated :/
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Quoting Stormchaser2007:
Again, the 00z ECMWF does not take it to the SE coast.





A Trough Split i believe will occur as High pressure from the PLAINS comes in full aboard.
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Quoting atmoaggie:
:-)
you saying you want me to send some below 70F lows across the lake?


Where u at Atmo? Ponchatoula here
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Bogalusa is fine folks,,but the place is a Stinky un..I have to agree.

Member Since: July 3, 2005 Posts: 426 Comments: 128866
Thanks Dr. M. Once again we have a higher track issue with Igor, with a potential threat to the US East Coast, which is consitent with a La Nina season..........So good so far for Florida and the Gulf which are the most vulnerable US locations during H-Seasons (assuming that 92L continues to move west towards the Yucatan).
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00z ECMWF shows it will be a strong cat 4 up there. So if Igor goes a bit to the west Newfoundland may have its first cat 4!
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Quoting Stormchaser2007:


Im well aware of that...

I was merely stating that it didn't have any type of landfall.


No worries. Just pointing it out for those that may not realize.
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Final T# Adj T# Raw T#
5.9 5.9 6.0

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Quoting Ryuujin:


And basically what is happening according to the Euro and NOGAPS models is that huge flat trof off the west coast is going to shove the High currently over Texas to the east, causing it to bridge with the High over the Atlantic, right?


If the high that is protecting the TX/LA coast right now bridges with the other, will that move the high off the TX/LA coast?
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Quoting Ryuujin:


And basically what is happening according to the Euro and NOGAPS models is that huge flat trof off the west coast is going to shove the High currently over Texas to the east, causing it to bridge with the High over the Atlantic, right?


Yes and the Trough Splits in the bridging process i believe will occur.
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Quoting Stormchaser2007:


Full run takes it out to sea.





The problem with that is the models are notorious for breaking ridges that are climatologically impossible to break. The have hurricanes pressing through the middle of 1025 mb Highs for example, which in my limited amount of knowledge would equate to a ant flattening a semi.
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yea, that thing stinks lol! I hate when I have to go up there to work. What's funny is the people that live in bougalusa don't even notice it.
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Quoting Seastep:


You're talking 10 days out.

I personally, pay no attention to that. Errors are large.


Im well aware of that...

I was merely stating that it didn't have any type of landfall.
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Quoting atmoaggie:
:-)
you saying you want me to send some below 70F lows across the lake?


I will pay good cash money if u can shove it 30 Miles mo South atmo..
Member Since: July 3, 2005 Posts: 426 Comments: 128866
Quoting Stormchaser2007:


Full run takes it out to sea.



930mb that far north!?? good gracious! LOL
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Spaghetti Patrap posted look to bend it back to the west after moving NW. Is that the high building back in?
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51. peak season?
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Quoting Stormchaser2007:
Again, the 00z ECMWF does not take it to the SE coast.





You're talking 10 days out.

I personally, pay no attention to that. Errors are large.
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Dang NHC might not have enough Floaters! They only have 4.....LOL
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Quoting Patrap:
Sharing is what the Wunderground is all about really..
:-)
you saying you want me to send some below 70F lows across the lake?
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Quoting TampaSpin:
If you all wanna look at the Models i just posted and other....go to my WU blog. I have them up and running there that stay updated.

Thanks Tampa.
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Again, the 00z ECMWF does not take it to the SE coast.



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Quoting TampaSpin:


Yes it has! It is a very Conservative Model as well as other models show development that does not happen NOGAPS rarely shows development that does not occur. Lets hope its wrong this time tho.


And basically what is happening according to the Euro and NOGAPS models is that huge flat trof off the west coast is going to shove the High currently over Texas to the east, causing it to bridge with the High over the Atlantic, right?
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Quoting TampaSpin:
Gang i just posted 2 very reliable models that trap Igor and force it toward the North Carolina area. I know things can change but, the trend for the past 3 days now have continued to be further and further West with every model. The Western Trend either stops very soon "today" with the models are this will become more like a reality thing.


Agree 100% and this ain't no Carolina Casting.
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ATCF files have Igor at 85 knots, so that will be the intensity at 11 I'm betting.
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Quoting TampaSpin:
Hemed in with no where to go but, WEST toward NORTH CAROLINA.....JUST SAYIN!





Full run takes it out to sea.



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If you all wanna look at the Models i just posted and other....go to my WU blog. I have them up and running there that stay updated.
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Quoting atmoaggie:
I can say that it smells a little like fall here, 40 miles N of NOLA.
(Really, though, north winds enough make the smell from the paper mill 30 miles NE of me to be detectable, a normal occurrence with a cold front.)

about 2 weeks ago, a system came through and left us with a light north wind...boy it was nice. If only for a couple of days
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Im takinh a guess at the next advisories pressure reading. Currently at 988? My guess is its now at 975. A 13mb decrease since the 5am advisory. Winds of 105mph.
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Quoting Ryuujin:


That is a scary looking scenario. NOGAPShas been fairly accurate this year, hasn't it?


I think NOGAPS was one of the models the NHC relied on to track Earl.
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Quoting Ryuujin:


That is a scary looking scenario. NOGAPShas been fairly accurate this year, hasn't it?


Yes it has! It is a very Conservative Model as well as other models show development that does not happen NOGAPS rarely shows development that does not occur. Lets hope its wrong this time tho.
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NHC will probably only raise it to 95 mph at 11am.

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Quoting ajcamsmom2:
Thanks Dr. Masters, sure am glad that the high is in place protecting the TX/LA Gulf Coast...

Me too....and I'll be happy to start a fundraiser to keep it there!
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Sharing is what the Wunderground is all about really..
Member Since: July 3, 2005 Posts: 426 Comments: 128866
Quoting hurricanehanna:

Sigh....that's what I thought. You have a good Sunday too!
I can say that it smells a little like fall here, 40 miles N of NOLA.
(Really, though, north winds enough make the smell from the paper mill 30 miles NE of me to be detectable, a normal occurrence with a cold front.)
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Quoting TampaSpin:
Gang i just posted 2 very reliable models that trap Igor and force it toward the North Carolina area. I know things can change but, the trend for the past 3 days now have continued to be further and further West with every model. The Western Trend either stops very soon "today" with the models are this will become more like a reality thing.


Wholly crap, the Euro model is on it too? Eeeh...
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Quoting Stormchaser2007:


Its not official keep in mind.

Just an estimate based on the ADT.

Know that but i got a little excited!
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ATCF images (Hurricane Track Models)

Current Storms:
Invest92
Igor
Invest93
Member Since: July 3, 2005 Posts: 426 Comments: 128866
Quoting TampaSpin:
Hemed in with no where to go but, WEST toward NORTH CAROLINA.....JUST SAYIN!





That is a scary looking scenario. NOGAPShas been fairly accurate this year, hasn't it?
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Quoting hurricanehunter27:

Now that is the fastest intensifaction iv ever seen!


Its not official keep in mind.

Just an estimate based on the ADT.
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Gang i just posted 2 very reliable models that trap Igor and force it toward the North Carolina area. I know things can change but, the trend for the past 3 days now have continued to be further and further West with every model. The Western Trend either stops very soon "today" with the models are this will become more like a reality thing.
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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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