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 PRweathercenter:

Sometimes if a storm is stronger, it can make it's track, it will be interesting if Igor is obedient or not, Bermuda and even the East Coast should keep an eye on this.



Yeah, rapidly intensifying hurricanes, or just extremely intense ones in general are known for defying forecasts unexpectedly, Charley was a great example.


Keep in mind, its not like it always happens, but it does happen enough times that we must keep a very close eye on Igor. That and the fact that is could end many lives if it makes landfall.


By the way, Igor's model consensus is not nearly as tight as Earl's was, and even Earl continued to push much farther west than the models had been saying all along, thank God it finally did turn north, but originally models consistently had it passing well east of Bermuda, it ended up less than 100 miles from NC, lol.
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Quoting leo305:


look at the outer bands to the north of the system, notice how they are getting blown apart by northerly shear.. and how IGOR's ouflow isn't as strong on the north side as the southern side
Where's the northerly shear?

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Max1023:


Its a hurricane symbol inside a hurricane symbol. Igor is now a double Monster lol.


lol
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1943. flsky
Quoting TropicalAnalystwx13:

I don't like the looks of that heart.
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1942. leo305
Quoting stillwaiting:
91l appears to have closed off surface low now,centered about 100 miles south of haiti's southern fork,should be classified a td anytime,tonight should be a good show w/further organization as it moves nw....


yep I agree
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92L firing deeper convection when usually this time of day its waning, another sign it might be finally starting to take off, jmo.
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Quoting superpete:
Stormwatcher, I think we may get some solid rain from 92L here this week.? Will be interesting to see if it develops more tonight thru Monday evening.Been a slow developer up to now, but that can change, as you well know?
Yes, and got a funny feeling it is starting to pull itself together pretty good now and we know how fast they can develop in the Caribbean.
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1939. leo305
Quoting Max1023:


I respectfully disagree. You can clearly see a cirrus streamer on the NW edge of the CDO which is almost a degree wide. That would not exist if shear was more than 10 knots. Also, most of Igor's outflow is going SW so it wouldn't make a difference. Unless shear can completely stop outflow on one side the storm will not feel it as it ventilates in a different direction.


look at the thin outer bands to the north of the system, notice how they are getting blown apart by northerly shear.. and how IGOR's ouflow isn't as strong on the north side as the southern side
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92l appears to have closed off surface low now,centered about 100 miles south of haiti's southern fork,should be classified a td anytime,tonight should be a good show w/further organization as it moves nw....
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1937. Max1023
Quoting TropicalAnalystwx13:


Its a hurricane symbol inside a hurricane symbol. Igor is now a double Monster lol.
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1936. angiest
Once more, GFS is showing Igor taking a long tim to clear Bermuda.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting bassis:


Great link, thanks!!





Thanks for the link
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Quoting stormwatcherCI:
East End had gusts to 96 mph and some roof damage and trees down up here but the most rain I ever saw was with Paloma.
Stormwatcher, I think we may get some solid rain from 92L here this week.? Will be interesting to see if it develops more tonight thru Monday evening.Been a slow developer up to now, but that can change, as you well know?
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Quoting leo305:
the north western and northern outflow is being chocked by northerly shear..

it's unlikely to make CAT 5 strength with those conditions
Outflow is relatively good...notice the cirrus clouds fanning out. And with an anticyclone centered over the system providing for sub-5kt vertical wind shear, I see no reason why it couldn't attain category 5 status.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
1931. hydrus
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1929. mbjjm
Quoting all4hurricanes:
Igor being a cat 4 I think is enough to warrant

It's Sunday, There is no immediate threat to land.
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1928. Max1023
Quoting leo305:
the north western and northern outflow is being chocked by northerly shear..

it's unlikely to make CAT 5 strength with those conditions


I respectfully disagree. You can clearly see a cirrus streamer on the NW edge of the CDO which is almost a degree wide. That would not exist if shear was more than 10 knots. Also, most of Igor's outflow is going SW so it wouldn't make a difference. Unless shear can completely stop outflow on one side the storm will not feel it as it ventilates in a different direction.
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Quoting PRweathercenter:
lol, yes, my Spanish is not good.


Well, I can't speak hardly a word of it, but grew up hearing it, and also old enough to remember Cesar Romero. lol
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1925. bassis
Quoting AWeatherLover:


Link


Great link, thanks!!
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1924. angiest
Is that high trying to bridge north of Igor?

Member Since: August 26, 2006 Posts: 16 Comments: 4766
1923. mbjjm


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Quoting MZT:
If 92L gets named, we may see another Jeff Masters post. He did say he could step in if events warrant it.
Igor being a cat 4 I think is enough to warrant
Member Since: March 29, 2008 Posts: 0 Comments: 2351
1920. leo305
the north western and northern sides of the hurricane are being chocked by northerly shear..

so it doesn't have much outflow on those sides

it's unlikely to make CAT 5 strength with those conditions
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1919. Walshy
92L getting a circular ball of convection going. Looks less disorganized, but would like to see this persist into this time tomorrow for development.






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1918. angiest
144 hours and I think 92L is still hanging around the BOC.

Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting PcolaDan:
It would be Romero y Julia in the Spanish version, no? ;)
lol, yes, my Spanish is not good.
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1915. MZT
If 92L gets named, we may see another Jeff Masters post. He did say he could step in if events warrant it.
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Quoting superpete:
Gustav flooded our garden, put 12 inches sea water in it!!
East End had gusts to 96 mph and some roof damage and trees down up here but the most rain I ever saw was with Paloma.
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Quoting Jedkins01:
Igor sure looks like a category 5 now to me, if not it must be no less than 5 mph shy of that, Igor already looks to already have grown significant more powerful since the latest NHC update!


BTW, I'm not gonna buy another northern turn till I see one... Tho models may be right, but just considering how powerful Igor is, meteorologists definitely do not want to write off Igor, in case it does continue west, and the current track were to be wrong.

Sometimes if a storm is stronger, it can make it's track, it will be interesting if Igor is obedient or not, Bermuda and even the East Coast should keep an eye on this.
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1912. IKE
GFS takes 92L(or a designated system), into northern Mexico on Friday....

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Quoting PRweathercenter:

Where's Romeo? lol
It would be Romero y Julia in the Spanish version, no? ;)
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1910. hydrus
Quoting CybrTeddy:
To be honest, I think this is making a run at Category 5 status. Lets see what happens.
Hello Cyber (King Geek) Teddy. I also believe that Igor will in fact become this seasons first Cat-5 hurricane in the Atlantic.
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does anyone have a forecast map of Isabel from September 10 or 11 2003? or maybe some definitive proof that I won't get hit again
Member Since: March 29, 2008 Posts: 0 Comments: 2351
1908. Max1023
Igor has closed off a pink ring on WU IR as of 1 min ago. That plus a black eye says to me that this thing is now a 140 knot Category 5. At least a 130 knot Cat 4.
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Quoting PRweathercenter:

Where's Romeo? lol

With David and Victoria Beckham :p
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Quoting stormwatcherCI:
Yep.
Gustav flooded our garden, put 12 inches sea water in it!!
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Quoting superpete:
Sounds like Gustav?


Because it is Gustav lol
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1903. IKE
Quoting angiest:


Assuming that is 92L, that is about the most GFS has done with it in a long time.


Agree.
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Igor sure looks like a category 5 now to me, if not it must be no less than 5 mph shy of that, Igor already looks to already have grown significant more powerful since the latest NHC update!


BTW, I'm not gonna buy another northern turn till I see one... Tho models may be right, but just considering how powerful Igor is, meteorologists definitely do not want to write off Igor, in case it does continue west, and the current track were to be wrong.
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Quoting CybrTeddy:
I'm going out on a limb and saying this is Juliet now.


Hey Teddy, what do you think of NHC track?
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1900. angiest
Quoting IKE:
GFS now showing vorticity in the BOC with 92L....@ 96 hours...



Assuming that is 92L, that is about the most GFS has done with it in a long time.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting WeatherNerdPR:

I thought it was JULIA.

Where's Romeo? lol
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1898. angiest
Quoting remembercelia:
If the NHC had taken storm surge forecasts out of the Saffir-Simpson Scale, as they should have done after 2005, more people might have evacuated before Ike. Katrina was a strong cat-3 at landfall with a "cat-5" surge, and Ike was a strong cat-2 with a "cat-4" surge. Size of storm and shape of coastline together can be as important as windspeed in many situations. I hope the NHC and other organizations will emphasize this and completely uncouple surge forecasts from the SSS.


I remember reading plenty of forecast products for Ike discussing how he would produce cat 4-like storm surge. Public awareness is not there, and public officials were horrible.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
1897. IKE
GFS now showing vorticity in the BOC with 92L....@ 96 hours...

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Quoting goldenpixie1:


That's an awesome resource! Thanks!


You're welcome. It's been a very resourceful site for me. I've used it in many of my papers. It is great for those who work with GIS also because you can export the tracks to GIS shapefiles.
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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.