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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It looks like Igor is taking another jog to the wsw.
Link
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Whew!!!!
The last time I saw Igor he had been downgraded to a TD, and now this!

He's gotten a little stronger since then, no? jajajaj
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Quoting pottery:

Good for you, you made it through. 15-20 isnt nice, one bit.
Been in that as well, on a 38 Hatteras. Thought it was The End, between here and Grenada. Nearly 5 hours of Doom...


LOL....I had three buddies with me then and that was like 7 years ago and when we get together they all still swear I was trying to kill them......lol....and that I acted like I wasn't even scared........I should have received an Emmy award.....I WAS PETRAFIED!!
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Quoting RitaEvac:
Hell with Igor, we got a home bread system coming into the Gulf end of the week
Hell with ur home bread system coming into the Gulf end of the week, we got Igor bearing down on us at the same time.

Member Since: October 25, 2005 Posts: 19 Comments: 22357
Which update are you referring to Oracle? Maybe we can help?

Quoting OracleDeAtlantis:
I wonder why the update is delayed? Rethinking the models, perhaps? A disagreement, maybe?
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2840. mbjjm
Quoting shawn26:
Half of the models have it coming bsck towards the U.S. now


Not true, most are east of Bermuda, a few are west . They all keep Igor away from the US. Computer Models
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2839. pottery
Quoting xcool:


uppdatee

That's something to be concerned about.....
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Quoting RecordSeason:
2825:

gonna be so close, but I think the forecast is busted big time.

Igor should stay well south of the most recent center line, and probably south of the most recent cone...
Busted>? Do they need another tube in the Univac? I think by 11, they will have it sorted out for a tiny tiny shift.
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I wonder why the update is delayed? Rethinking the models, perhaps? A disagreement, maybe?
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2824 and 2826, thanks for verifying.

I am glad I had that documentation to back it up though!
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2833. pottery
Quoting traumaboyy:


NO I CAN NOT.....my boat is 43' and I have been in 15-20 one time and my BP goes up with the memories of that day.....I can not imagine just the seas....and with the wind you would not be able to see at all.

Good for you, you made it through. 15-20 isnt nice, one bit.
Been in that as well, on a 38 Hatteras. Thought it was The End, between here and Grenada. Nearly 5 hours of Doom...
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2831. emcf30
Levi and others
What are your thoughts on the low pressure system over Canada which is moving towards the East and is supposed to be the saving grace for the CONUS. Do you see anything that could keep it from weaking the ridge as the models are seeing it. I noticed the last CMC run it shows high pressure building back in and moving Igor more to the West at the end of the run. I hope the rest of the models do not start pi8cking up on this pattern. I realize it is a longrange forcast tand will likly bounce back and forth on each run. Thanks
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Thanks xcool!

Quoting xcool:


uppdatee
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So far the northern GOM has been very fortunate this year. Do you think we can make it til the end of the season still feeling lucky?
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Sorry, I am really not trying to be argumentative tonight, just seeing things a little differently. Where I do see deep layer steering is giving us a window of wsw movement, it is not reflected in the models yet...(these are a little old though, so hang on for the 0z which are getting ready to run.

SFWMD model plots

Quoting shawn26:
Half of the models have it coming bsck towards the U.S. now
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Quoting muddertracker:
Does anyone have a sattelite image that updates more often than 30 minutes? tia


They haven't ordered a rapid-scan operation unfortunately.

30 minutes is the best we have right now.
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Quoting JupiterFL:


Goldenblack,
You posted the right chart. Its the same chart that Levi and Drak were discussing earlier. He is just trying to entice people into arguing. He's a troll that's a master at bating people into disagreements.


agreed
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2825. xcool


uppdatee
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Goldenblack:
I do not agree, 200-700 is exactly the right level at this time. That is deep level steering.

"Less intense hurricanes are steered mostly by winds in the lower to middle layers of the atmosphere; higher-level wind currents also factor into the steering of the more intense storms. This is one way in which track and intensity may be understood as mutually causative: a storm could become more intense for whatever reason, and its track could then change from what it might have been, as a result of having come under the influence of the higher-level steering currents."

Excerpt from Hurricane Steering Layer myths



Goldenblack,
You posted the right chart. Its the same chart that Levi and Drak were discussing earlier. He is just trying to entice people into arguing. He's a troll that's a master at bating people into disagreements.
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Does anyone have a sattelite image that updates more often than 30 minutes? tia
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Quoting pottery:

It's every man for himself, if we were out there...
150 mph winds. Can you imagine the sea conditions in the center of that thing?


NO I CAN NOT.....my boat is 43' and I have been in 15-20 one time and my BP goes up with the memories of that day.....I can not imagine just the seas....and with the wind you would not be able to see at all.
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2821. shawn26
Half of the models have it coming bsck towards the U.S. now
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Quoting MoltenIce:

Category 5 14% chance in 36 hours
You may want to get a new sheet...hm... according to some of these well informed posts its on the edge of a 5 now.
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Quoting Flyairbird:
Bah! Whats a little puff of wind and rain?


A little puff of wind and rain...LOL.
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2818. mbjjm
Quoting Goldenblack:
I do not agree, 200-700 is exactly the right level at this time. That is deep level steering.

"Less intense hurricanes are steered mostly by winds in the lower to middle layers of the atmosphere; higher-level wind currents also factor into the steering of the more intense storms. This is one way in which track and intensity may be understood as mutually causative: a storm could become more intense for whatever reason, and its track could then change from what it might have been, as a result of having come under the influence of the higher-level steering currents."

Excerpt from Hurricane Steering Layer myths


okay.. we'll see time will tell
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Quoting pottery:

Good Evening, and LOL.
What a fierce storm our Igor has become.
Really glad he aint coming anywhere near here!
The waves in the Northern Leewards are going to be something to see...
Agreed, the "big wave" surfers could be paying them a visit. Swells will propagate for quite some time.
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Quoting Stormchaser2007:
Heeeeere's Julia!

AL, 12, 2010091300, , BEST, 0, 133N, 229W, 35, 1005, TS



Lets not forget about Julia!
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Quoting pilotguy1:


Your social skills are awesome.


???

he is right and why is it that 90% of your posts are made to pick on other peoples comments?
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Quoting Inactivity:
You guys DO realize that Igor almost intensified as much as Wilma in 12 hours.An amazing achievement.


I do. When I last posted around 0600, Igor had surface winds of 80mph. When I came back at 1730, he was a Cat 4 with winds of 140mph. I was in awe.
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Category 5 14% chance in 36 hours
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Evening everyone.

Did you all come to a consensus* as to whether our big boy is moving a bit south of west or if it was a wobble?


*well, as close to a "consensus" as possible with this many people........and on this particular blog. lol
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Quoting Stormchaser2007:
Heeeeere's Julia!

AL, 12, 2010091300, , BEST, 0, 133N, 229W, 35, 1005, TS

I wonder if they will have a hurricane named Klutz...I have seen a few of those in my day!.
Member Since: Posts: Comments:
I do not agree, 200-700 is exactly the right level at this time. That is deep level steering.

"Less intense hurricanes are steered mostly by winds in the lower to middle layers of the atmosphere; higher-level wind currents also factor into the steering of the more intense storms. This is one way in which track and intensity may be understood as mutually causative: a storm could become more intense for whatever reason, and its track could then change from what it might have been, as a result of having come under the influence of the higher-level steering currents."

Excerpt from Hurricane Steering Layer myths

Quoting mbjjm:
Goldenblack looking at the wrong chart, and wrong levels of the atm
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2809. pottery
Quoting traumaboyy:


Good evening Sir!!

Yes sir....definately have to put out the sea anchor with this one..lol

It's every man for himself, if we were out there...
150 mph winds. Can you imagine the sea conditions in the center of that thing?
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Quoting Inactivity:
You guys DO realize that Igor almost intensified as much as Wilma in 12 hours.An amazing achievement.
Bah! Whats a little puff of wind and rain?
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You guys DO realize that Igor almost intensified as much as Wilma in 12 hours.An amazing achievement.
Member Since: Posts: Comments:
Quoting pottery:

Good Evening, and LOL.
What a fierce storm our Igor has become.
Really glad he aint coming anywhere near here!
The waves in the Northern Leewards are going to be something to see...


Good evening Sir!!

Yes sir....definately have to put out the sea anchor with this one..lol
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2791, thanks, I don't feel so crazy now. Couldn't believe what I was seeing on the deep layer steering.

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Hmmm...and they took 92L off the CIMSS page:

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Quoting muddertracker:

Somebody tell the tropics that the cold war is over!


LOL.....the wall is Gone!!
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2799. mbjjm
Quoting Seastep:


Irresponsible statement.


Very responsible statement,irresponsible in what regard?
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2798. pottery
Quoting PSLFLCaneVet:
Good evening, Pottery.
Quoting traumaboyy:


Monster eat good master...lol

Good Evening, and LOL.
What a fierce storm our Igor has become.
Really glad he aint coming anywhere near here!
The waves in the Northern Leewards are going to be something to see...
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Quoting MZT:


Katrina is a very common Russian name too.

SHHHHHHH!!!!!
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2776...ROFLMAO!!!!
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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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