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 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...
Member Since: August 31, 2009 Posts: 0 Comments: 5628
However, in 7 or 8 days...it's Sept. 21st..I would think the set-up is right but the CV storms should decrease...Also, if the ridging is in place at that time, then the typical late season storms will not go north but head west. It's all timing and there may be no hits from La to Florida if this continues which would be fine. Before you know it...the pattern change will take place but guess what it's Christmas!


Quoting StormW:


Well, it's been much slower to occur...all the information keeps getting pushed back in time.

On it's way though. The current MJO index shows that the MJO may be making that path back over our way



And the majority of forecast models indicate it should be in or near octants 1&2 in around 7-8 days

When this occurs, we should see that troffing off the east coast go bye bye, and see more ridging in place.









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Jeff,

what was that that you were commenting below about having possibly 5 to 6 storms in just the next few weeks with recurving towards Florida? just wondering, thanks
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Quoting Jeff9641:


Here is my proof.

http://en.wikipedia.org/wiki/File:Typical_North_Atlantic_Tropical_Cyclone_Formation_in _September.pn g

http://en.wikipedia.org/wiki/File:Typical_North_Atlantic_Tropical_Cyclone_Formation_in _October.png


Not sure that is PROOF....Those are likely scenarios...what about storms that HAVE developed in these two months, what have they done?? In Sept it shows more Likely to hit TX or La before Fl. Your opinion is fine, just would like to see TRUE facts of what storms HAVE done not what they would LIKELY do during these months, that's all!!
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Quoting Grothar:
from that loop it seems that igor takes a small shift to the wnw in the last 3 images s he crosses the like
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4088. bird72
Quoting RecordSeason:
Honestly folks, the track is still balancing on the edge of a razor.

The little peak in the ridge is still oriented in a way that is not at all favorable for any WNW or NW turn any time soon.


I think that's a key variable to know, why Igor still going west.
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4087. angiest
Quoting TropicalAnalystwx13:


Others, as well as I, still believe we haven't hit the peak of the season yet.


Count me, don't think we've hit peak and I think we will continue at least until the end of the official season.
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Quoting TropicalAnalystwx13:


Others, as well as I, still believe we haven't hit the peak of the season yet.


Others also believed Earl was going to be a Category Five.
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4085. angiest
Quoting NOSinger:


That wave/ hurricane that it is predicting is taking the same path that all of the Carribean storms have been taking this year, straight into Mexico.


I'll buy into the formation of the system at this range, but not the track.
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4083. Grothar
Quoting cat5hurricane:
That's a great picture. Would you happen to have the link for that?


Yes. Just follow directions on posting.

Link
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Morning folks! Holy Cow! Let me get a coffee before I try to digest this!!
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Quoting Cotillion:
There's going to be a lull at some point. Every season does. Even 2005 did to an extent.

I expect we're probably in the peak. This could be a classic active season.

A quietish June to July, a very active mid August to late September, a bit of a lull, before a secondary peak in mid October, with a storm thrown in November.

16-17/8-9/4-5.


Others, as well as I, still believe we haven't hit the peak of the season yet.
Member Since: July 6, 2010 Posts: 113 Comments: 32835
Destin always talks about the feebleness of the chart, but maybe... just maybe... he did a 'Storm Whisperer' trick of his own.

Now, wouldn't that be ironic.
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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?





West. And as you (I think it was you) pointed out last night on the show, Igor seems to be compressing that dry air underneath the trof. Doesn't seem like it's affecting him at all.
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Come October, the Gulf states really need to watch the Caribbean. This is when more storms will form in the Caribbean, and this is when more will move North and target the Gulf states, or move north, then recurve, targetting Florida.
Member Since: July 6, 2010 Posts: 113 Comments: 32835
4076. bassis
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?





He is still moving due west
Member Since: September 8, 2008 Posts: 0 Comments: 423
There's going to be a lull at some point. Every season does. Even 2005 did to an extent.

I expect we're probably in the peak. This could be a classic active season.

A quietish June to July, a very active mid August to late September, a bit of a lull, before a secondary peak in mid October, with a storm thrown in November.

16-17/8-9/4-5.
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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.


That wave/ hurricane that it is predicting is taking the same path that all of the Carribean storms have been taking this year, straight into Mexico.
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4071. angiest
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 have been considering that. GFS hasn't been developing to a true CV system behind Julia. I suppose it could be a miss, but right now the thing is still over land...
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4069. Grothar
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Quoting earthlydragonfly:
Repost:

I dont know about anyone else but the appearance of the disturbance in the carib (invest 92) is putting together a classic S feature. Normally when I see this happen the Depression is about to develop. and convection seems to be on the rise... Any other thoughts on the carib developing (92)????


With the drier air to the NW, Id guess what your seeing is the interference of the drier air and at the end of the frame it looks like a S but really its just the drier air breaking apart some of that NW side.

However, this all based on the latest WV imagery, I see some instensification in the center of the storm and maybe some slight convection. The dry air is really making 92 into a smaller storm. Although other conditions are extremly favorable, that drier air needs to go before giving this system any real chance of intensification.
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4067. angiest
Quoting mobileshadow:


That's 384 hrs out and just another GFS fantasy


Like when it had Danielle at that timeframe?
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Quoting DDR:
Quoting AstroHurricane001:


GFS consistently predicted (for 36 hours) a hurricane in the Gulf or one moving from the Caribbean toward the East Coast by the end of the run. This time it shows two components.


The gfs has also been persistent in showing a large area of disturbed weather over the island by weeks end,things could get intersting here once again!.


That's 384 hrs out and just another GFS fantasy
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hi this is my first time on here i just wanted to say this is just about the best weather site i have ever seen.
just one question where do the invests get there number from as they always seam to be either 90,91,or 92 is there a reason for this?

i am sat on a sail boat in puerto rico which up to now has been good this year with no major storms coming here
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This is another Julia, in terms of how fast she developed...You can already see the well-defined circulation:

Member Since: July 6, 2010 Posts: 113 Comments: 32835
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.



Actually we are not tied with 2007 we have surpassed 2007

2007:71.7
2010:72.285
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Good morning, folks.

Igor looking awesome, steering gradually changing. 92L's got some convergence going on now, popping convection. And, the wavetrain is still coming!
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Quoting GTcooliebai:
2005 had an ACE of 248.1. 2004 had an ACE OF 225, AND 1995 had an ACE of 227.4. And as of Sept. 13 2010 we have an ACE OF 70.5. So still have a lot of catching up to do.


I think it'd be unfair to presume or expect this season to surpass those seasons.

Right now, the 2008 season is a good and fair target. It may be revised later on (I expect so), but for the time being. That ACE was 145 or so, around 24th on the provisional all time list.
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92L
Member Since: October 9, 2008 Posts: 0 Comments: 8436


AOI

AOI

AOI

AOI

AOI

AOI

AOI
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I know you've all seen this before, but holy blobova!!!

off to the salt mine.
have a great day everyone.
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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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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?





West
Member Since: July 6, 2010 Posts: 113 Comments: 32835
4053. angiest
Good morning. I see GFS continues to be interesting at the very long range. Once again we have a hurricane crossing the Yucatan into the BOC, and now it would appear another storm in the central and western Atlantic.

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Quoting Jeff9641:


Well you might want to keep checking because after mid Sept comes it's very hard to have system hit TX. It's normally FL or MX that gets it.


I would have to disagree....according to the map Ike just put up of storms that developed and landed in the last 100 yrs ( from this date thru Oct.15th I think). Fl didn't have much of anything. Matter of fact the Gulf really had nothing for the most part. I would love to see your facts to back that statement up. I've been wrong many times.....
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4048. bassis
Quoting DestinJeff:


Morning DJ

Just got here. any idea if he went through ewrc last night
Member Since: September 8, 2008 Posts: 0 Comments: 423
4047. Vero1
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON SEP 13 2010

ATLANTIC OCEAN...
A DEEP LAYER TROUGH IS MOVING THROUGH THE WATERS OF THE CENTRAL
ATLANTIC OCEAN...THROUGH 32N52W TO 25N54W TO 23N60W. A COLD
FRONT PASSES THROUGH 32N53W TO 28N60W 28N67W. RAINSHOWERS ARE
WITHIN 30 NM TO 60 NM ON EITHER SIDE OF THE LINE THAT PASSES
THROUGH 32N47W 30N51W 28N60W 27N70W 25N80W. A SURFACE TROUGH IS
ALONG 22N58W TO 19N59W 17N57W. ISOLATED MODERATE RAINSHOWERS ARE
WITHIN A 30 NM RADIUS OF 20N59W. AN UPPER LEVEL TROUGH PASSES
THROUGH 32N24W TO A 27N33W CYCLONIC CIRCULATION CENTER...TO
19N35W. BROKEN TO OVERCAST MULTILAYERED CLOUDS AND POSSIBLE
RAINSHOWERS ARE FROM 27N TO 30N BETWEEN 25W AND 30W. A SURFACE
RIDGE PASSES THROUGH 32N37W TO 26N43W.

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I believe the NHC believes that Igor will track just to the west of Bermuda. That would mean that Bermuda gets the eastern eyewall.

As a major hurricane, also...
Member Since: July 6, 2010 Posts: 113 Comments: 32835

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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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