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 MiamiHurricanes09:
Yeah, I agree.


I agree as well, the EURO and UKMET have a good handle on Igor. The NHC track is a blend of both these model runs from 00Z, should stay the same for the next update.
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Quoting NCHurricane2009:


What's the UKMET showing?
12z UKMET
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1293. angiest
Quoting Stormchaser2007:
Purple haze


Igor is really kissing the sky.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting StormW:


Levi, is that further west than previous?


This was yesterdays 12z CMC Ensemble RUN. It had it knocking on your door.

264hrs (Long-Range)

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UKMET along with the CMC is at the southern end of the current guidance.

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Quoting MiamiHurricanes09:
Yeah, I agree.


What's the UKMET showing?
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Quoting StormW:


Good thing!

Can ya put in some overtime on Igor?
Quoting DestinJeff:


Reed.


Sorry. it was me!
Should have not been playing with the voodoo spells and chicken bones last night ;)
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1287. Levi32
Quoting Stormchaser2007:
Purple haze


I honestly have never seen that before.
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1286. dmaddox
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Quoting KanKunKid:


Sure silly! In Fairy tale forecasts, there's always a magical trough! You know that!
We need an elf.
Any members out there have an elf in the family?
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Quoting Drakoen:
I think the UKMET has a good track on Igor


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Quoting NCHurricane2009:


Planned? Is someone controlling the weather and made a mistake? LOL! More like further west than originally forecast.


Same difference.
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1282. Levi32
Quoting Drakoen:
I think the UKMET has a good track on Igor


I think so too. Link
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So this is what a wave will do in the Caribbean right now?
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Purple haze
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Quoting Max1023:


I was thinking more along the lines of what you said beer-battered and deep fried in hydrogenated vegetable oil.
Bleh. That's a new level. More than just tummy would be angry...
Quoting StormW:


Definitely one you don't to have your morning coffee with!

Hey atmo!
Hey storm. What say you about the pimples exhibited on the NW side? Odd formation...
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Storm you expecting a TCFA to come out on TD 12 yet?
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1274. dmaddox
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Quoting Drakoen:
I think the UKMET has a good track on Igor
Yeah, I agree.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting weatherlover94:


i think its more like a 60% chance the us is threatened and a 40% chance it goes out to sea



Looking at the track forecast its a high possibility. I also don't understand why a few are saying Igor will curve. I haven't read anything like that in the NHC report. Whats going to recurve Igor? I would think the NHC would have mentioned it by now. But in any case Igor bares watching.
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drak you got a photo of that track. in between watching the dolphin game and blogging.
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Quoting StormW:


I'm not sure at this point how close he "may" come to the U.S., but he will come further west than what was originally planned.


Planned? Is someone controlling the weather and made a mistake? LOL! More like further west than originally forecast.
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according the weather underground wunder map i think the beyond 3 day forecast is shifting to the right again((farther away from the us)) but then again the hwrf model has shifter farther left any thoughts guys?
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1265. dmaddox
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1262. Drakoen
I think the UKMET has a good track on Igor
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1261. IKE
92L....

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1260. Levi32
Quoting Stormchaser2007:


Levi,

The JMA is available on Accuweather Pro as well.


This I know, but it doesn't come out there until later.
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atmo you have the worst timing when it comes to making these storms into something that drives my mind nuts and stomach crzy
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1258. Max1023
Quoting atmoaggie:
...a really mean donut...worse than a glazed, chocolate, Bavarian cream - stuffed one, covered in colored sugar and sprinkles. (Though my tummy would call that pretty mean, indeed.)


I was thinking more along the lines of what you said beer-battered and deep fried in hydrogenated vegetable oil.
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1257. Levi32
Quoting StormW:


Levi, is that further west than previous?


The 0z CMC ensemble mean last night had Igor at about 68W, 32N at the same time frame. This morning's 12z ensemble mean has him near 68W, 28N, much farther south.
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Quoting Stormchaser2007:
I think we could see a 120 knot storm at 5pm

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 181500 UTC
Lat : 17:39:45 N Lon : 46:06:10 W


CI# /Pressure/ Vmax
6.4 / 939.6mb/124.6kt


Final T# Adj T# Raw T#
6.4 6.6 6.6


Sounds right.
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1254. Melagoo
It appears that almost all MODELS have IGOR as a FISH
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1253. xcool
AL, 92, 2010091218, , BEST, 0, 158N, 721W, 25, 1007, DB
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Quoting Max1023:


Annular hurricane is a hurricane with a large 30-40nm eye surrounded by a uniform ring of eyewall convection extending at least 50 miles out from the eye. They have very few spiral rainbands and are usually resistant to shear - 20 knots would be shrugged off by most annular hurricanes.

Basically instead of a buzzsaw you get a donut.
...a really mean donut...worse than a glazed, chocolate, Bavarian cream - stuffed one, covered in colored sugar and sprinkles. (Though my tummy would call that pretty mean, indeed.)
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Quoting Levi32:
12z Japanese from today still is far southwest of the other models and puts Igor just north of the Bahamas. The future track after this (it only goes out to 144 hours on this site) is uncertain, but it is within striking distance of the SE US.



Levi,

The JMA is available on Accuweather Pro as well.
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1249. IKE
GFS ensemble members on Igor...

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1246. scott39
Hello Everyone, What lattitude does Igor have to be at to feel the weakness and the second trough?
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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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