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 tropicfreak:


Don't forget Ike!


When you are in an above-average year (ever since the warm AMO kicked in during 1995), its the F,G,H,and I names that have the biggest risk it seems of being a major storm because you've gone through more storms by the time you are at the peak (Sept. 10) of the season.

In years that are below-average (cold AMO years), it seems anywhere from A to E is usually the big storm.
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Quoting Levi32:


It would be centered more off to the east, which would open the door for 92L to make a move closer to Texas instead of Mexico.


Thank you.
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Quoting Levi32:


Well it's the Canadian....don't ever take it too seriously, but it's worth taking a look at if it has support from elsewhere, which it does.


Correct me if I am wrong, but I though the CMC performed best last year at 5 days.

Have no idea about this year. Link to that would be appreciated if anyone has it.

I think CyberTeddy posted it before?
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743. MZT
Quoting Stormchaser2007:
CI# /Pressure/ Vmax

6.1 / 947.4mb/117.4kt

Man, 947MB is like going up 2500 feet in altitude. We're getting into some serious pressure gradients here.
Engineering Toolbox: Air Pressure
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Quoting cycloone:


I'm pretty convinced by now that igor is becoming anular


Hey Cycloone! Long time no see!
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Dang, Igor is a beautiful monster.
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Looks like things are starting to get interesting this season! I hope y'all will forgive this tangent: a lot of my loved ones live in hurricane-prone states, and I appreciate with all my heart the up-to-the-minute analysis you provide on this blog every year. My girlfriend's mother is disabled and lives in the Keys, so I also have a soft spot in my heart for Portlight's mission of serving the underserved and make a donation to them whenever I can. I wish you and yours the best, and hope this season provides a ton of weather education and a minimum of loss.

Back to lurking. God bless!
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wow
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The eyewall is really firing some intense cloud tops right now. I would say that Igor is a low-end category 4...currently.

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Quoting MiamiHurricanes09:
Igor might be Isabel's little brother. I gotta say, all these "I" names always have to be bad...

First Isabel, then Ivan, now Igor.


Don't forget Ike
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Quoting Smyrick145:
Drakoen,

Wouldn't the massive high pressure per the CMC push any storm into Florida and then into the GOM? Granted if that scenario would have to materialize.


No because you have an incoming trough
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Quoting MiamiHurricanes09:
TPW?

Toilet Paper War?
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Quoting MiamiHurricanes09:
I hope you're saving loads of images to your Photobucket account, Stormchaser. Beautiful tropical cyclone.


Oh don't worry.

I think I have successfully given myself carpal tunnel.

Here's the link to my account if anyone is interested.



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Quoting Stormchaser2007:



WOW I love mimic
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Quoting sailingallover:



Why when the models/forcast are solid and have Igor re-curving do people insist on west casting him?


Because this seasons sucks, lacks excitement and has been painful to watch...especially watching CV storms traverse the entire Atlantic to recurve at the last minute. I have had to limit myself from coming here because these storms, and the frustration, tension and nervousness which they spawned in my psyche, were consuming me.

YMMV.
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Quoting MiamiHurricanes09:
Igor might be Isabel's little brother. I gotta say, all these "I" names always have to be bad...

First Isabel, then Ivan, now Igor.


Don't forget Ike!
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Quoting aislinnpaps:


Levi,
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?


It would be centered more off to the east, which would open the door for 92L to make a move closer to Texas instead of Mexico.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting MiamiHurricanes09:
I hope you're saving loads of images to your Photobucket account, Stormchaser. Beautiful tropical cyclone.



I knew it, Igor was destined to be a strong hurricane from an African tropical wave all along! Its an appropriate name for a beast of a Cape Verde hurricane. Its perfect, LOL
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Quoting WeatherNerdPR:

2009 gave us a break, though.
Oops, I forgot about Ike in 2008.
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The ECMWF starting to show northwest movement of 92L in the Bay of Campeche is a big clue to Igor's track. The Euro was showing south of west movement in the BOC with 92L just a couple days ago. If the storm instead fades northwest, that implies more of a trough digging into the west-central US which would force the Texan ridge to build further east, implying a more westerly track for Igor and a more northerly one for 92L.
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Quoting FloridaTigers:
So could we see Igor become annular?

Yes
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What's the diameter of Igor's eye? Seems huge...
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Quoting Levi32:
CMC also has 92L not really developing but moving northwest into Texas in 6 days.


Levi,
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 BahaHurican:
Anybody want 2 post the MIMIC on Igor? That should be interesting....

TPW? You can even see the eye...wow.

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Cracks me up that every time a hurricane forms, someone asks if it's annular.
"Annular hurricanes are very rare."

Please see wiki article on them below.
annularhurricane
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Quoting MiamiHurricanes09:
Igor might be Isabel's little brother. I gotta say, all these "I" names always have to be bad...

First Isabel, then Ivan, now Igor.

2009 gave us a break, though.
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Quoting BahaHurican:
Anybody want 2 post the MIMIC on Igor? That should be interesting....



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Quoting TropicalAnalystwx13:
Igor is a Category 4 Hurricane right now.

It has to be.

Why isn't the NHC making a Special Advisory (SA)

WHY WHY WHY?!?!?

I'm through...lol


Well, its nowhere near land, so issuing a special advisory doesn't seem needed. But, I am not so sure about Igor being a cat. 4 just yet. Its possible it will be that this evening (right now its probably a cat. 3).

Darn, I didn't foresee this rapid of an intensfication in my forecast last night. Intensity forecasting is hard!
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I hope you're saving loads of images to your Photobucket account, Stormchaser. Beautiful tropical cyclone.

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CMC also has 92L not really developing but moving northwest into Texas in 6 days.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Comrade Igor

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Quoting btwntx08:
692: say that to the #1 ecmwf
he looks bad right now. i know you want it develop and come near you but right now i'm just sayin it looks bad.
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Anybody want 2 post the MIMIC on Igor? That should be interesting....

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Quoting Drakoen:
Set up like this would bring Igor close to the U.S. eastern seaboard. You've got high pressure to the north of the system and a trough out over the Ohio and Tennessee river valleys

Last run of ECMWF I saw this morning did have it brushing the Eastern seaboard ala Earl
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Quoting btwntx08:
couple of hrs old but

lets see what 18z says


Does that mean that the wave still has a "low" in it? (not sure if I'm making sense)
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Drakoen,

Wouldn't the massive high pressure per the CMC push any storm into Florida and then into the GOM? Granted if that scenario would have to materialize.
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Igor is a Category 4 Hurricane right now.

It has to be.

Why isn't the NHC making a Special Advisory (SA)

WHY WHY WHY?!?!?

I'm through...lol
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Quoting Ameister12:
Is Igor an Annular Hurricane?


Cuz it looks a lot like one.
Not quite, with the banding. But looking more that way...
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Quoting KimberlyB:


Afternoon all.

Drak? Are you referring to Igor there?! Apparently I need to take a look at that sucker.


Yes
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Quoting atmoaggie:
good ob, let's see if it persists.
Igor might be Isabel's little brother. I gotta say, all these "I" names always have to be bad...

First Isabel, then Ivan, now Igor.
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Quoting MiamiHurricanes09:
Of course I'm a Dolphins fan :). So far, so good, 3-0.


10-0 baby now
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Quoting dmaddox:
WOW! Not good!


see like bastardi said this option is in play
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Quoting KimberlyB:


Afternoon all.

Drak? Are you referring to Igor there?! Apparently I need to take a look at that sucker.


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Freaking Beautiful.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting cycloone:
Is it me or is there a pinwheel eye forming??





Exactly, I was about to say Igor looks like a mini-Isabel!! Wow, Igor, wow!
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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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