Igor an impressive Cat 4; 92L running out of time to develop; Julia forms

By: Dr. Jeff Masters , 1:47 PM GMT on September 13, 2010

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There are few sights in the natural world more impressive than a hurricane near maximum intensity. Hurricane Igor certainly fits that description this morning, as it flirts with Category 5 strength in the Central Atlantic. Igor's rapid intensification burst brought the mighty hurricane's winds to 150 mph, just shy of the 156 mph threshold for Category 5 status. Igor is the strongest hurricane in the Atlantic in three years. The last hurricane stronger that Igor was Category 5 Hurricane Felix of 2007.


Figure 1. Morning satellite image of Igor.

Intensity forecast for Igor
Wind shear is low, 5 - 10 knots, and is expected to remain low for the next four days. Waters are warm, 28.5°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. These conditions should allow Igor to remain at major hurricane status for the next four days. The hurricane will probably undergo one of the usual eyewall replacement cycles intense hurricanes commonly have, where the eyewall collapses and a new eyewall forms from an outer spiral band. This will weaken the hurricane by 10 - 20 mph when it occurs, but Igor will probably regain its lost intensity when the cycle completes. There's no evidence that an eyewall replacement cycle is imminent today, so Igor could potentially strengthen a bit more. However, I believe Igor has peaked, and will not reach Category 5 status today. By Saturday, when Igor should be nearing Bermuda, the trough of low pressure steering Igor northwestwards should bring moderate wind shear of 10 - 20 knots to the storm, weakening it.

Track forecast for Igor
The track forecast for Igor remains unchanged. Igor will move west under the influence of a strong ridge of high pressure until Tuesday morning, 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 appears likely to be a threat to Bermuda, and that island can expect tropical storm force winds as early as Friday. Igor 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 - 10 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 hitting the U.S. or Canada. While the trough expected to recurve Igor out to sea is not as sharp as the troughs that recurved Danielle, Earl, and Fiona, it should still be strong enough to keep Igor from hitting the U.S. However, Newfoundland, Canada could see a close pass. An examination of the tracks of the ten major September hurricanes that have passed closest to Igor's current location (Figure 2) reveals that one of these hurricanes went on to hit the Bahamas and Florida as a Category 2 storm, and another hit Newfoundland as a Category 1 storm. The other eight missed land. One wild card may be the intensification of Julia behind Igor. If Julia develops into a hurricane and moves close to Igor, as some of the models are suggesting, the two hurricanes could interact, affecting the track of Igor unpredictable ways. However, it currently appears the Julia will be much weaker than Igor, and will probably have little impact on her big brother's track.


Figure 2. Historical plot of the tracks of the ten major September hurricanes that have passed closest to Igor's current location.

Caribbean disturbance 92L
Tropical disturbance (92L) over the Central Caribbean, centered about 100 miles south of Jamaica, has changed little over the past day. The storm remains a threat to develop into a tropical depression, but time is running out for it to do so. Satellite loops this morning do not show a surface circulation, but 92L does have a moderate area of intense disorganized thunderstorms that are bringing heavy rain to Jamaica this morning. Kingston, Jamaica has picked up 0.67" of rain thus far this morning from 92L.


Figure 3. Morning satellite image of 92L.

Forecast for 92L
Wind shear over 92L is low, 5 - 10 knots, and is expected to remain low to moderate for the next five days. The waters beneath are hot, 29.8°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 has been interfering with development of 92L. NHC is putting the odds of 92L developing into a tropical depression by Wednesday at 40%. Given the current disorganized state of 92L, it would be difficult for it to intensify quickly enough to become any stronger than a tropical storm with 50 mph winds by Wednesday, when it will move over Belize and Mexico's Yucatan Peninsula. 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 several hundred miles south of the Texas border. A Hurricane Hunter aircraft is scheduled to investigate 92L this afternoon.

Julia
Tropical Storm Julia formed between the Cape Verdes Islands and coast of Africa yesterday, bringing some heavy rain squalls and gusty winds to the Cape Verdes, but no sustained winds of tropical storm force. Julia is headed northwest, out to sea, and it is unlikely that this storm will trouble any land areas . Shear is low enough over the next few days to allow Julia to become a hurricane, but shear will rise sharply 4 - 5 days from now, limiting the potential for Julia to become a major hurricane.

Elsewhere in the tropics
The NOGAPS model is calling for a new tropical depression to form off the coast of Africa 6 - 7 days from now.

Next post
I'll have a new post Tuesday morning.

Jeff Masters

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Unbelievable!
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Quoting VAbeachhurricanes:


Heres another view!
Rapid Scan


Both were killer, but look at the eye in the last half of images on the second link! It's beautiful.
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Quoting VAbeachhurricanes:


Heres another view!
Rapid ScanAction: Quote | Ignore User
Member Since: September 6, 2007 Posts: 0 Comments: 1791
Excellent! Thanks for the post VAbeachhurricanes & Seastep!
Member Since: August 17, 2010 Posts: 21 Comments: 6939
my path for both system on fri is working both systems are in my path still even close in the middle
Member Since: July 13, 2008 Posts: 6 Comments: 10796
821. Vero1
btwntx08

This looks like last week.

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Quoting Cotillion:


Sorry, what?

The eye isn't shrinking at all. Some of it is illusionary based on the visible, the IR shows barely any change whatsoever. In addition, there are no current indications of an impending EWRC, let alone one that is just about to start.


drako is a troll, i think (he's tries to look like the real drakoen) in slang terms, he's a poser
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Quoting Drakoen:


No.


Just to play devil's advocate here, would you have said the same of Ike?
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T# are going back up.
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Quoting stormwatcherCI:
Hi Drak. With Igor current south of west movement any chance he gets in the Caribbean ?


No.
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Quoting mcluvincane:


Third trough???


That's what I've been seeing. Maybe misinterpreting something.
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Quoting Drakoen:
Igor Rapid Scan!


WOW!
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Quoting Drakoen:
Igor Rapid Scan!


Heres another view!
Rapid Scan
Member Since: September 6, 2007 Posts: 0 Comments: 6670
Quoting angiest:


Child #2 is now firmly entrenched in the Yo-Gabba-Gabba, Upside Down Show, etc., stuff. Oh well, I survived the first time.


my number 3 is captivated by Sid the science Kid at the moment. lol
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Quoting angiest:


I think the second trough is supposed to lift it some so a third trough can turn him out.


Third trough???
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Quoting dracko19:


Nope. Don't think so. Lots of reasons why. Let's take a look at some....

1. Right now, IGOR is going through an EWRC (Eye Wall Replacement Cycle). The eye is shrinking and winds are down across the board on sattelite estimates:

SATCON = 116 kts / 945 hPa
CIMSS = 104 kts / 953 hPa
ADT = 127 kts / 937 hPa

IGOR should complete the eyewall cycle tonight. This should make IGOR bigger. Bigger storms usually have slower max wind potential, but not always.

2. Take a look at this picture. This is the current sea surface temperature (SST) crossed with archival data suggesting a hurricane can only reach so high in maximum winds based on the temperature. Notice that IGOR is in the 140kts max area.



Also note the projected path of IGOR. Its forecast to stay over the "140 max" slot. However, if IGOR continues to move WEST of the forecast track as it has continued to do, there is a swath of 160 kt max wind temeratures in front of it. If it enters that area, then all bets are off!!


Sorry, what?

The eye isn't shrinking at all. Some of it is illusionary based on the visible, the IR shows barely any change whatsoever. In addition, there are no current indications of an impending EWRC, let alone one that is just about to start.
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Igor is staying south of the first forecasted point that is supposed to make him turn WNW....
Member Since: August 2, 2010 Posts: 21 Comments: 9874
like i said the two shouldve look like this on post 789
Member Since: July 13, 2008 Posts: 6 Comments: 10796
807. unf97
Quoting hydrus:
Here is Wilma with her world record pinhole eye.....I remember years ago saying to myself" I will never live to see a hurricane WILMA..Not only did I live long enough, but to my utter astonishment, it became a Cat-5..The "W" storm becoming a 5 is amazing to me.


Good image of Wilma at her strongest in 2005. You can definitely put Wilma right there with Gilbert with those classic "pinhole" eyes certainly for sure. Thanks for posting that Wilma image.
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806. Vero1
Quoting btwntx08:
if i wrote my own two it would be something like this
SHOWERS AND THUNDERSTORMS ARE BECOMING BETTERORGANIZED IN ASSOCIATION
WITH A BROAD AREA OF LOW PRESSURE OVER THE WEST-CENTRAL CARIBBEAN
SEA. SOME DEVELOPMENT OF THIS SYSTEM IS POSSIBLE AT IT MOVES
WEST-NORTHWESTWARD AROUND 15-20 MPH...AND THERE IS A HIGH CHANCE...
60 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL
IS POSSIBLE OVER PORTIONS OF HISPANIOLA...JAMAICA...CUBA...THE
CAYMAN ISLANDS...AND THE YUCATAN PENINSULA DURING THE NEXT DAY OR
TWO. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN


And if you drew it it would look like this:

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maybe the nhc didnt notice the change yet if it continues then they will up the chances
Member Since: July 13, 2008 Posts: 6 Comments: 10796
Quoting GetReal:


It appears that Igor is on the verge of bypassing that second trough that has been forecasted to turn it WNW and then out to sea...

Glad you brought this up -- can anyone tell me based on current speed when we may know whether it bypasses this trough/turn?
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Quoting GetReal:


It appears that Igor is on the verge of bypassing that second trough that has been forecasted to turn it WNW and then out to sea...


I think the second trough is supposed to lift it some so a third trough can turn him out.
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Convective pulse is happening within the nw quadrant of Igor.
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Quoting Drakoen:
Igor going to pass to the south of his next forecast point.
Hi Drak. With Igor current south of west movement any chance he gets in the Caribbean ?
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I disagree with the NHC and they should have given 92L a 50% chance of development or even 60% chance. He is developing a low level circulation.
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Quoting Drakoen:
Igor Rapid Scan!


That's one heck of inny belly button!!!
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Ah, here is the info on the buoy. It's a floater
Water temp is 28.7.

Link
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Quoting ADCS:


Visual-spatial thinkers are naturals at understanding vector calculus (though it can be hard to get basic algebra down, lol). As a result, it's not surprising that many with a meteorological interest would think this way! I bet most of the pros do, too.


i get a real nerdy kick out of architecture too.
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UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 13 SEP 2010 Time : 164500 UTC
Lat : 17:33:55 N Lon : 49:53:35 W


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


Final T# Adj T# Raw T#
6.4 6.5 6.5

Latitude bias adjustment to MSLP : +2.0mb

Estimated radius of max. wind based on IR : 27 km

Center Temp : +18.8C Cloud Region Temp : -68.2C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF
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Quoting Cotillion:


Yet? Nah, still 150mph. If it isn't now, when will it be? It probably has until this time tomorrow if it does.

Still, if it doesn't, my thoughts look better by the day, eh? ;)



Nope. Don't think so. Lots of reasons why. Let's take a look at some....

1. Right now, IGOR is going through an EWRC (Eye Wall Replacement Cycle). The eye is shrinking and winds are down across the board on sattelite estimates:

SATCON = 116 kts / 945 hPa
CIMSS = 104 kts / 953 hPa
ADT = 127 kts / 937 hPa

IGOR should complete the eyewall cycle tonight. This should make IGOR bigger. Bigger storms usually have slower max wind potential, but not always.

2. Take a look at this picture. This is the current sea surface temperature (SST) crossed with archival data suggesting a hurricane can only reach so high in maximum winds based on the temperature. Notice that IGOR is in the 140kts max area.



Also note the projected path of IGOR. Its forecast to stay over the "140 max" slot. However, if IGOR continues to move WEST of the forecast track as it has continued to do, there is a swath of 160 kt max wind temeratures in front of it. If it enters that area, then all bets are off!!
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It appears that Igor is on the verge of bypassing that second trough that has been forecasted to turn it WNW and then out to sea...
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Quoting DestinJeff:


might say it gets into your...Noggin.

[I KNOW IT ISN'T NOGGIN ANYMORE]

gonna make it Big Time!


Child #2 is now firmly entrenched in the Yo-Gabba-Gabba, Upside Down Show, etc., stuff. Oh well, I survived the first time.
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Quoting Cotillion:


Any way to discard the Lat/Lon lines?

Aside that, simply breathtaking.


No
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Quoting Drakoen:
Igor Rapid Scan!


Any way to discard the Lat/Lon lines?

Aside that, simply breathtaking.
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Here's one of the best vapor images of the incoming trough that I've seen. As you can tell, it's not nearly as deep as the one that recurved Earl. Regardless, it will open up a window in the steering high pressure aloft, but I have to agree that it's not very clear if Igor will be far enough north for the westerlies to pick it up and get it out of there. The forward speed is what concerns me right now. If it slows down enough, this trough could pass right over it, opening a window further west.

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Igor Rapid Scan!
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785. 7544
igor wobble dobble wsw again ?
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40% on 92L.

Nothing else on TWO.
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Do not count out 92L. It has the whole NW carribean to feed off of!
Member Since: June 13, 2009 Posts: 0 Comments: 6886
SSD site not updating?
Member Since: September 6, 2007 Posts: 0 Comments: 6670
781. ADCS
Quoting KimberlyB:


Hey, don't knock it. There is zero reason to make anything more complicated then it needs to be. Simple is fantastic.


Visual-spatial thinkers are naturals at understanding vector calculus (though it can be hard to get basic algebra down, lol). As a result, it's not surprising that many with a meteorological interest would think this way! I bet most of the pros do, too.
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i disagree nhc
Member Since: July 13, 2008 Posts: 6 Comments: 10796
Quoting rareaire:
I know but we have seen this before... It can really spin up fast and many have. If not for the HEAT i would not be worried but its bathwater out there and a minor change and its on!!


agreed
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...JULIA A LITTLE STRONGER...
2:00 PM AST Mon Sep 13
Location: 15.1°N 26.7°W
Max sustained: 45 mph
Moving: WNW at 13 mph
Min pressure: 1002 mb
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Quoting angiest:
BTW, I believe Igor's eye is larger than all of TS Marco was.
Yeah definitely, Marco's gale force winds only extend to up to 20 km I think.
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I see a new station id popped up about 60 miles from the center of Igor. It's registering a 995.7 I can't get any info on the buoy though

It is listed as 41958
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Quoting DestinJeff:


No, I don't...like...candy corn.

No, I don't...like...candy corn.

Noggin gets in your brain doesn't it. Stoopid moose A moose.
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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.