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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"..CONVENTIONAL AND MICROWAVE IMAGERY SHOWS THAT IGOR IS GOING THROUGHA PERIOD OF RAPID INTENSIFICATION. VISIBLE IMAGERY DEPICTS A
CLEARING EYE AND INFRARED IMAGERY AND AN SSMIS OVERPASS REVEAL AN
INTENSE FULLY-DEVELOPED INNER RING OF DEEP CONVECTION. THE OUTFLOW
HAS BECOME QUITE IMPRESSIVE...PARTICULARLY OVER THE EASTERN PORTION
OF THE CYCLONE WHERE THE COLDEST CLOUD TOPS RESIDE..."

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Igor has stayed on a Westerly path. I see not realy southerly compnent.
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Quoting atmoaggie:
They do turn on every 1 minute visible sometimes. Did for Earl a couple of times.

They can do RSO, which is every 7.5 minutes.
And SRSO, every 1 minute.


I did not know that... Hmh.. you learn something everyday.. Thanks
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Is that Igor eating Julia?



taste like chicken...
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Awaiting for all the updates on TD12 to come in so i can update my Website. Everything else will be current unless Invest 92L becomes a TD today. Then i will have to change that. Alot of work.....LOL
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Quoting WeatherNerdPR:
Ok, so Igor's a Cat2 in the Central Atlantic still moving westward. For how much longer will he keep moving in that direction?


Hopefully it will start moving WNW before the islands. I believe it will miss the islands to the north but not convinced of the total recurvature as of yet that puts it on Bermuda
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Quoting earthlydragonfly:
I tell you guys one thing that now space and bandwidth is not as precious on the web and computers.... I think the satellites should start taking pictures every 10 minutes. Now that may be a limitation of the satellites themselves.. This would give a more fluid presentation of the storms. JMO
They do turn on every 1 minute visible sometimes. Did for Earl a couple of times.

They can do RSO, which is every 7.5 minutes.
And SRSO, every 1 minute.
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Quoting Stormchaser2007:
Again, the 00z ECMWF does not take it to the SE coast.





Is that Igor eating Julia?



That didn't sound right...
Member Since: August 22, 2006 Posts: 0 Comments: 1451
2010 Storms
All Active Year


Atlantic
92L.INVEST
12L.TWELVE
11L.IGOR

East Pacific

Central Pacific

West Pacific
93W.INVEST

Indian Ocean

Southern Hemisphere
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Let Igor keep it up for a day and it may stay far enough south to miss the trough hook-up.
That'd be real bad for a bunch of folks!
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135. Relix
Quoting WeatherNerdPR:
Ok, so Igor's a Cat2 in the Central Atlantic still moving westward. For how much longer will he keep moving in that direction?


24-36 hours
Member Since: August 3, 2006 Posts: 0 Comments: 2648
The computers and NHC actually did a very nice job with Earl's track so I would not put too much emphasis on a short term wobble with Igor....It's not the wobbles in the middle of the Atlantic that worry me so much as opposed to the wobbles as the storm curves towards the US and Bermuda later on in the period where it could make the difference between a glancing blow or direct impact if Igor ends up with a Earl type track close to the US.
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Wobble it is, I knew that, just wanted to get a reaction. Persistent motion for 3-6 hours will determine if it is a distinct motion or not, but wobble for now.
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Do you guys think the United States is safe from any landfalling hurricanes this year because it seems like ever since 2005 with the exception of Gustav and Ike the U.S has been realatively lucky as far as strong landfalling systems

Question: Are we trending toward a period where the United States is less likely to see landfalling hurricanes?
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Ok, so Igor's a Cat2 in the Central Atlantic still moving westward. For how much longer will he keep moving in that direction?
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Quoting sailingallover:
Anyone else who can't get to any *weather*.gov sites? I'm trying to get a recent surface analysis to track the strength of the AZ High.
No prob.

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I tell you guys one thing that now space and bandwidth is not as precious on the web and computers.... I think the satellites should start taking pictures every 10 minutes. Now that may be a limitation of the satellites themselves.. This would give a more fluid presentation of the storms. JMO
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NOGAPS has a funny urge to develop anything that ventures into the southwest Caribbean Sea, roughly north of Panama. Never really comes to fruition and tends to be the western outlier with these Cape Verde Hurricanes, exception with Igor is that the CMC is the western Outlier, coupled with the EURO.
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Quoting stormpetrol:
I could swear Igor is moving WSW in the last few frames.


We all see it. Whether its significant or not only time will tell. My guess is, It's just wobbling.
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i think we may have another fran or another isabel on our hands here next week in the mid atlantic
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125. Relix
Well darn it did wobble WSW haha
Member Since: August 3, 2006 Posts: 0 Comments: 2648
I could swear Igor is moving WSW in the last few frames.
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Quoting TheDawnAwakening:
Link

Igor is moving, or taking a wobble to the southwest.


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The difference in 92L on last two EURO runs.



A whole day later and farther north.



Don't know if y'all saw some of the discussions about the high I posted on dc's earlier blog. Just hope it holds. Can stay here all year fine with me. :)
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Quoting TampaSpin:
Hemed in with no where to go but, WEST toward NORTH CAROLINA.....JUST SAYIN!





I believe this is what StormW has been alluding to for a couple of days now.
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Prolly a wobble. I wouldn't read much into it unless it persists for several more hours.
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Link

Igor is moving, or taking a wobble to the southwest.
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Quoting sailingallover:

NOGAP has been pretty unreliable this year.


Especially with its southern Caribbean storm fetish so far this season.
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Quoting sailingallover:

NOGAP has been pretty unreliable this year.


Very unreliable.

Tons of ghost systems and poor tracks.

Kind of like the CMC back in 2007.
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Anyone else who can't get to any *weather*.gov sites? I'm trying to get a recent surface analysis to track the strength of the AZ High.
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Igor a Category 2, predicted to peak at 145 mph.

Suspect it might peak at 150-160.
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Quoting Hhunter:


wannabee


Hey.....Just keeping an eye on things from the house today; I'll be back at it from work tommorow....... :)
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That looks eerie.

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105 for Igor
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Quoting breald:


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

NOGAP has been pretty unreliable this year.
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Quoting Relix:


Every. Single. Day.

Hahaha. It's moving due west =P


LOL
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ESTIMATED MINIMUM CENTRAL PRESSURE 970 MB
MAX SUSTAINED WINDS 90 KT WITH GUSTS TO 110 KT.
64 KT....... 30NE 15SE 15SW 20NW.
50 KT....... 50NE 40SE 30SW 40NW.
34 KT.......120NE 80SE 80SW 120NW.
12 FT SEAS..270NE 90SE 60SW 90NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
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Quoting weathermanwannabe:
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).


wannabee
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Quoting Patrap:
12z Early Cycle NHC model tracks
Igor
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)




Dynamic Models (More sophisticated models)






that defined bend west at the end in a large number of the Dynamic models is worrysome
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100. Relix
Quoting RecordSeason:
Visible imagery strongly suggests igor is moving south of west, at maybe 255 to 260 degrees over the past few hours...


Every. Single. Day.

Hahaha. It's moving due west =P
Member Since: August 3, 2006 Posts: 0 Comments: 2648
Quoting Patrap:


I will pay good cash money if u can shove it 30 Miles mo South atmo..
That's a tall order. The Lake warms the nighttime air so very well, and no mixing at night.
Quoting doorman79:


Where u at Atmo? Ponchatoula here
Covington. Howdy, western neighbor.
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...TROPICAL DEPRESSION FORMS IN THE FAR EASTERN ATLANTIC...TROPICAL
STORM WARNING ISSUED FOR THE SOUTHERN CAPE VERDE ISLANDS...




000
WTNT22 KNHC 121452
TCMAT2
TROPICAL DEPRESSION TWELVE FORECAST/ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010
1500 UTC SUN SEP 12 2010

CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

THE GOVERNMENT OF THE CAPE VERDE ISLANDS HAS ISSUED A TROPICAL STORM
WARNING FOR THE SOUTHERN CAPE VERDE ISLANDS...INCLUDING MAIO..SAO
TIAGO...FOGO...AND BRAVA.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE SOUTHERN CAPE VERDE ISLANDS...INCLUDING MAIO..SAO TIAGO...
FOGO...AND BRAVA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED IN THE WARNING AREA...IN THIS CASE IN THE NEXT 12 TO 24
HOURS.

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Quoting Stormchaser2007:
The 00z ECMWF took Igor up to 134 knots

thx!
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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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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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