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 Halon056:


41041 is closest, at last update was still 257 nm away....


Interesting note though, ships report 106 miles away WVHT was 16.4 ft....
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4145. luigi18
Quoting Relix:
Some people in PR are in panic XD! They say the trough will fail and we'll get a direct impact. It should turn WNW in the next 12 hours or so.


Yo ya me estoy preocupando lol!
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Meteorology is interesting to say the least...that's why we are on this blog but consistant patterns that seem to never change can be quite boring. Does anyone realize how many weeks have been spent analyzing whether these CV storms will go west or re-pcurve? It seems like it is not meant to happen this year. No one wants disaster but from a weather enthusiast standpoint it is quite bizarre to see this happen over and over again!
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Quoting 1fromnovasscotia:
Anyone know if there is a buoy that is close enough to Igor to record wave heights close to the center, must be around 80 foot waves that would be my guestimate.


41041 is closest, at last update was still 257 nm away....
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4139. Relix
LATCUR = 17.6N LONCUR = 49.2W DIRCUR = 265DEG SPDCUR = 9KT
Member Since: August 3, 2006 Posts: 0 Comments: 2647
Quoting Cotillion:


Igor has no advisories posted.

---

Yeah, unreasonable would be a better word, KanKunKid. Also agree with the November observation.

---



It happens a fair amount.

2007 is a good example of that. 15 storms, but below average in ACE.

2005 eclipsed 1950 by 5 in ACE... despite having 14 more storms (15, but one was ST, therefore not counting) and 5 more hurricanes.

A big Cape Verde season tends to mean a big ACE season.

Thanks, I was wondering if it had something to do with the longevity and strength of the storm. And since it's been an active Cape Verde, I can see why we will surpass some of those yrs.
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Quoting 1fromnovasscotia:
Anyone know if there is a buoy that is close enough to Igor to record wave heights close to the center, must be around 80 foot waves that would be my guestimate.
Link
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The big question on everyone's mind is where is IGOR going to end up? Let's look at the models this morning and see what's happening.

The NOGAPS model, which predicted some strong ridging over the NE USA coast has relented a bit this morning and is now predicting a VERY strong ridge over the Central Atlantic and a weaker ridge over the Great Lakes. There is a weakness in between the ridges and IGOR "Shoots the gap". This is really bad news if you like Bermuda to look like a habital island.



The ECMWF shows that same strong ridge in the Central ATL, but it extends it all the way to the Great Lakes ridge and essentially BLOCKS IGOR from going North. This would be bad news if you own Beachfront Property along the central East Coast.



Then there's the GFS. The GFS says YES to that strong ridge in the central ATL. It says the Great Lakes Ridge will be a bit further west and it says there isn't much in between, so IGOR shoots right up north. Bermuda gets a taste of IGOR, but will survive.



Now we get into the "who do you believe" category. Even the NHC forecasters hedge their bets here, talking about "model consensus" and even throwing it back at us to make our own guesses. Check it out! This is from the 5am AST update from the NHC discussion on IGOR:

...ALTHOUGH MOST OF THE GLOBAL MODELS SHOW THE
TROUGH FLATTENING IN 3 TO 4 DAYS...THERE ARE DISAGREEMENTS IN HOW MUCH...IF ANY...SUBTROPICAL RIDGING BUILDS IN THE WAKE OF THE TROUGH. THE ECMWF AND UKMET MODELS CONTINUE TO BUILD MORE RIDGING NORTH OF IGOR...RESULTING IN A TRACK FARTHER WEST THAN THE OTHER MODELS. OVERALL...THE MODEL GUIDANCE HAS SHIFTED SLIGHTLY TO THE RIGHT FROM THE LAST CYCLE AND THE OFFICIAL FORECAST IS NUDGED IN
THAT DIRECTION...BUT REMAINS ON THE SOUTH SIDE OF THE GUIDANCE ENVELOPE.

So, they aren't sure which model to believe either..

The GFS has a historical cold bias for fronts/troughs. They tend to overdo them and their effects. However, the GFS is the only model that properly initializes IGOR's power at the onset. Still, it comes down to those ridges over the Great Lakes and Central ATL. That is the key to IGOR's eventually destination. I doubt anyone here can conclusively tell us as even the models are in disagreement. Perhaps we can get some historical data on flattening troughs and ridging off the NE USA coast by other posters?

My bet is (and this is just a guess....I'm only an amature forecaster....don't hate me) is we are going to have a weakness strong enough to spare the USA east coast. Bermuda on the other hand is still very much in trouble. If I lived on Bermuda, I might want to take that 2 week long vacation to Chicago I've been saving up for.
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4133. luigi18
Quoting lovejessicaa9:


where did you get it Jessi
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wht i m seeing from the storm history and igors historical corodinates is that hes been traveling along 17,70 since yesterday and hasnt moved in longitude apart from one were he went to 17,60 then back to 17,70 im only ameture but from what ive just seen on satilite loops hes taken a... smalll slightttt budge to 17,80 and the trough is starting to affect him but im only a ameture but i think hes going to keep heading due west and scrape the northen lesser antties then head wnw or nw and hit bermuda but yeah like i said i am a ameture im not always right but thats what i belive is going to happen ... if im wrong and he goes strait thru the lesser antties then hell get to were 92l was encounter low windshear and very warm seas intensify to cat 5 go thru EWRC and come back to a much larger cat 5 igor near yuctan and the gulf and.. .. yeah... all hell but lets dream let us pray that dont happen and that im wrong :( ps... sorry for the bad spellings im not going to make a excusse i just dont spell good and am a complete numpty
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And there's still no guarantee that the Caribbean will light up.

Cue the 1995 map again:



Is it likely? Yes. Is it certain beyond any doubt? No.

(For the record, I do believe something will occur in the Caribbean. Thinking next month.)
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Quoting KanKunKid:


It's still a little early for me (CST) but not by much. The little town here on the beach (Puerto Moreles, just 30 KM south of Cancun) was Jimmy Buffet's inspiration for the song "Marguaritaville".
There are other things to do here such as snorkeling and fishing. Marguaritaville wasn't a fishing song. Tequila and mix is available at the 7-11 on the corner and it's cheap (Jose Cuervo Especial 6 bucks 500ml) and you can have beer delivered with your pizza. It is a "moisture rich" (alcohol) environment. So, it was no coincidence that I was staring at the open top of a blender full of marguarita(s).

And yes, there is a woman to blame.

There always is.



Yup! ;) And, not much further is the Blue Parrot down in Playa del Carmen, pictures of him there. Been there several times. Hoping 92L stays disorganized and no grief comes your way.
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4129. Relix
Quoting RecordSeason:
Well, the first trough missed so far N it's a joke. It never even got close enough to tap the outflow, nevermind steering Igor...

The second one doesn't really look any deeper just yet...


it does. Way deeper as well
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Anyone know if there is a buoy that is close enough to Igor to record wave heights close to the center, must be around 80 foot waves that would be my guestimate.
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4126. Grothar
Quoting stormchaserDAZ:
from that loop it seems that igor takes a small shift to the wnw in the last 3 images s he crosses the like


SHHH! The westcaster may hear you. I do agree with Storm that it will go a little further west than predicted though, before the turn. Here is a confusing little map, that shows just that.

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4125. bjdsrq
Quoting portcharlotte:
It seems like we are in a pattern etched in stone...The maps looks the same they did in late July....The break between highs in the Atlantic which all started with the first re-curve and I believe that contibuted to the lingering weakness there. Also we have the riding over the north Gulf. If this continues you can have 40 storms and they will all miss which is okay but it seems like our luck shoulod run out...any comments


So far, if you aren't a fish or a mexican, you aren't going to see a storm at your door step. Looks like the same story for the rest of the month. Don't forget the analog year is 1998, and that brought Georges through the keys in early October.
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4124. Relix
Quoting Halon056:


The moisture spot WNW of Igor, has been there for sometime. What is it?


Weakness spot
Member Since: August 3, 2006 Posts: 0 Comments: 2647
Quoting StormW:
Food for thought...

Here are two graphics...with a good weakness outlined...if you go to the site and loop it, you can clearly see it. This is why I think the turn will occur a little further west. Look how close he is to both trofs, and the weakness. Which way is he still going?



Fantastic explanation. Goes to show that troughs don't always turn em, don't always protect you from a hit. Sometimes the steering wins the battle.
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Quoting angiest:


It took 10 years to reclassify Andrew. Gustav was just two years ago.


Yes, correct. Could Floyd end up being revised in years to come? He did hit 155mph, just shy of Category 5 status.

Earl was a lot further away. 11mph may not seem much, but when put next to storms like Floyd and Gustav, it's a sizeable increase in the difference between actual speed and Cat 5 classification. Personal opinion that Earl was not even close. If I'm wrong, happy to take a big wedge of crow with lemon.

However, still a lot of 'coulds'. 145mph, 155mph is beyond bad enough.

I think I've ended up detracting from my original point, though. Never mind.
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The moisture spot WNW of Igor, has been there for sometime. What is it?
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It seems like we are in a pattern etched in stone...The maps looks the same they did in late July....The break between highs in the Atlantic which all started with the first re-curve and I believe that contibuted to the lingering weakness there. Also we have the riding over the north Gulf. If this continues you can have 40 storms and they will all miss which is okay but it seems like our luck shoulod run out...any comments
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Quoting lovejessicaa9:


Just does not want to go above the 18.....

Heck I don't blame him.
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4113. Relix
Some people in PR are in panic XD! They say the trough will fail and we'll get a direct impact. It should turn WNW in the next 12 hours or so.
Member Since: August 3, 2006 Posts: 0 Comments: 2647
4111. RJT185
Quoting Neapolitan:
A brief rundown:

--2010's ACE now stands at 72.285. That puts this year ahead of current "active" season years '97, '09, and '02, and ties it with '07.

--Depending on what Igor and Julia do, this season's ACE will surpass 2006's sometime tomorrow.

--The mean average ACE for the active period is 101. Again, depending on a few factors, 2010 may surpass that sometime late this week. (next up is 2001).

--Igor has now been a hurricane for six TWOs, and a major hurricane for three. By way of comparison, Alex was a hurricane for six TWOs, Danielle was a hurricane for 27 (and a major for four), and Earl was a hurricane for 22 TWO (a major for 14).

--Since 8/22 (a 23-day span), seven storms have been named, or one every 3.29 days. (Contrast this to 1995, which saw ten in a 35-day span, or one every 3.5 days.)

--Also since 8/22, only one day--September 5th--had no named storms. Average daily ACE over that period has been 2.7474.

--2010 has now seen more named September storms than '95, '96, '97, '99, and '09, and it's seen as many as '01, '03, '04, '06, and '08.

--To-date, HDP (Hurricane Destruction Potential) stands at 54.1275.


Thanks
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thanks
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Quoting NWWNCAVL:
Shouldn't there be a 8 am update?


Igor has no advisories posted.

---

Yeah, unreasonable would be a better word, KanKunKid. Also agree with the November observation.

---

Quoting GTcooliebai:

I'm just rather amazed at how 2004 only had 15 named storms yet it surpassed 1995 in terms of ACE. It may be crazy, but I have this seasons total named storms at 20, and the ACE may be lower than all three of those yrs. So I guess it's irrelevant to the fact that the higher the number of storms does not mean the ACE will be as high either...


It happens a fair amount.

2007 is a good example of that. 15 storms, but below average in ACE.

2005 eclipsed 1950 by 5 in ACE... despite having 14 more storms (15, but one was ST, therefore not counting) and 5 more hurricanes.

A big Cape Verde season tends to mean a big ACE season.
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4105. angiest
Quoting Cotillion:


People also said that for Gustav.


It took 10 years to reclassify Andrew. Gustav was just two years ago.
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4103. calder
Beautiful storm, here's hoping that he doesn't hit anything. By the way, seems to be some confusion - Igor isn't and never was annular.
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yikes
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Shouldn't there be a 8 am update?
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Quoting RecordSeason:
4086:

Wait for post-season analysis.

In all likelihood, Earl actually was a category five briefly.


People also said that for Gustav.
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Quoting Halon056:
Ok I am curious that spot of Moisture West of Igor, it doesn't seem to even move, it changes form but is nearly stationary. Thoughts?
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where do you and Tropical Analyst see this trend? do you have a website?
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Quoting Cotillion:


Others also believed Earl was going to be a Category Five.


I'm pretty sure Earl was briefly a Category 5 hurricane.

If not, It came really close.
Member Since: July 6, 2010 Posts: 113 Comments: 31453
Quoting Jeff9641:


We should pass 1995 by mid October. Really feel we haven't anything yet. Once these Caribbean waters get tapped then watchout and could start getting tapped later next week by the wave that coming off Africa tomorrow. I do believe it's that wave that the GFS has been blowing up in the Caribbean for the past 5 or 6 runs.

I'm just rather amazed at how 2004 only had 15 named storms yet it surpassed 1995 in terms of ACE. It may be crazy, but I have this seasons total named storms at 20, and the ACE may be lower than all three of those yrs. So I guess it's irrelevant to the fact that the higher the number of storms does not mean the ACE will be as high either...
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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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