Potentially dangerous 92L steadily developing; Igor nears hurricane strength

By: Dr. Jeff Masters , 3:04 PM GMT on September 11, 2010

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A tropical disturbance (92L) over the Eastern Caribbean, a few hundred miles south of Puerto Rico, is steadily organizing and appears likely to develop into a tropical depression by tonight or Sunday morning. Satellite loops show an impressive and expanding region of heavy thunderstorms, with good spiral banding and respectable upper-level outflow on all sides. Long range radar out of Puerto Rico shows that heavy rains are now affecting that island, but there is no rotation to the radar echoes evident. However, the rain bands are becoming more intense and more organized. San Juan, Puerto Rico reported a heavy rain squall at 8:44 am this morning, and radar estimates suggest two inches of rain fell in this squall just southeast of San Juan. Wind shear over 92L is low, 5 - 10 knots. The waters beneath are at near-record warmth, 30°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-northwest at 11 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 Mexico's Yucatan Peninsula on Wednesday. The HWRF model has a more northwesterly track, taking 92L over the Dominican Republic, Haiti, and Cuba, but this model has been trending too far north in its tracks. I expect 92L will follow a path south of the islands, bringing it near or just south of Jamaica on Monday, then into the Yucatan Peninsula on Wednesday. On this track, the southern Dominican Republic can expect heavy rains of 3 - 6 inches tonight through Monday morning; southern Haiti can expect similar rains Sunday through Monday, and Jamaica and the Cayman Islands can expect heavier rains of 4 - 8 inches Monday and Tuesday. Eastern Cuba will probably escape 92L's heaviest rains in this scenario (Figure 2.)

Intensity forecast for 92L
I can't find any reason to doubt this will be a tropical storm by Sunday or Monday, and potentially a Category 1 or 2 hurricane by Wednesday, if 92L avoids passage over Hispaniola and Cuba. The SHIPS model predicts wind shear will remain low, 5 - 10 knots, through the period, and makes 92L a Category 1 hurricane by Monday night. 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. The first Air Force Hurricane Hunter mission into 92L is scheduled for Sunday afternoon, but there will be a research mission by the National Center for Atmospheric Research G-V jet today that will give us valuable information on 92L's large scale environment and potential for development.


Figure 2. Forecast rain amounts from 92L from the 2am EDT Saturday run of the GFDL model. This model predicts most of 92L's heaviest rains will miss Haiti, but will affect Jamaica, the Cayman Islands, and the Yucatan Peninsula. Image credit: Morris Bender, NOAA/GFDL.

Igor
Tropical Storm Igor is very close to hurricane strength, and appears destined to become a large and powerful major hurricane over the Central Atlantic in the days to come. Wind shear is moderate, 15 - 20 knots, waters are warm, 28°C, and Igor has moistened its environment enough to keep the dry air of the Saharan Air Layer (SAL) at bay. Igor will track west under the influence of a strong ridge of high pressure for the next three days, then turn more to the west-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 has a slight chance of making landfall on the U.S. East Coast or Canada. Climatology shows that about 10% 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 5% for Canada. The forecast steering pattern for the coming two weeks from the GFS model 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. The odds of Igor hitting land in the U.S. or Canada are probably close to their climatological 10% and 5% probabilities, respectively.

Elsewhere in the tropics
A new tropical wave (Invest 93L) emerged from the coast of Africa yesterday, and is already showing signs of organization. Most of the models predict 93L will develop into a tropical depression 2 - 4 days from now, and NHC is giving 93L a 30% chance of developing by Monday.

Next post
This may be my only post today; I'll have a new post Sunday morning.

Jeff Masters

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Quoting dracko19:
Hey, do you remember that movie "The Perfect Storm"? It was about a fishing ship that was lost at sea off the NE USA coast in a "storm of the century", which turned out to be a Cat 4 Hurricane merging with a low pressure system creating a ..."Super Subtropical Storm".

Take a look at this:
Link

This is the GFS Long Range Model. Take a look how it handles IGOR in the long term (8+ days out) It blows it up to a cat 5 and then takes it right over Bermuda!! (That would destroy Bermuda) Then, it merges with a low over New Foundland and creates a Super-SubTropical storm on Sep 23rd. Very interesting...


18z GFS.

108 knots.

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Quoting TampaSpin:
My dang WU setting for some reason is set for show average and i can't see much of anyones post. Are you all below average......LOL


Hey Tim! I know that I probably am. I doubt if anyone has ever clicked a + or - for me. lol
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1621. help4u
show me the pattern change that was suppose to happen for last 6 weeks,talked about everyday on this blog and nothing happened,Major storms were supposed to be steered into US, nothing!i will stay a troll rather than a fantasy caster of make believe storms.
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Beell, what's your take on the diving jet stream's effect on 92L's future steering, or Igor for that matter? TIA
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My dang WU setting for some reason is set for show average and i can't see much of anyones post. Are you all below average......LOL
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1616. xcool
KoritheMan i agree".
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1615. xcool
traumaboyy hey sir.
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1614. xcool
Krycek1984 okay anyway did i asking you personal attacks me noo thank bye.
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goodnight everyone. The days ahead should be interesting.
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Quoting xcool:
we moveing in to Caribbean season soon .i meaning more storms going start development in Caribbean that put highrisk for usa...sorry about miss spell i just goting home from work.


exactly right......Evening/Morning XCOOL!!

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Quoting xcool:
we moveing in to Caribbean season soon .i meaning more storms going start development in Caribbean that put highrisk for usa...sorry about miss spell i just goting home from work.


Just curious, is English your first/main language or no?
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Quoting beell:
Entrance of the jet stream-upper left of frame.

ATL WV Loop



Yep, Beell, we're on the same page. The weakness is closing, not as pronounced. And, it only takes eyeballs to see 92L react quickly to the low-level flow, shooting it westwards.

It's alright, Levi, you do really good. But, all of these dynamics can sometimes fool the best of us, least of which is me. Oh, and yes, good luck on your studies - all the best!
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1607. pcola57
Hey atom..
Thanks for posting that link on lightening and storm intensity corrolation.
Very interesting.
Here's a link for another phenomenom you may like.
It's from Scientific American

Link
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Quoting help4u:
Igor is a fish,and so are the other 2 storms in atlantic,nothing is coming close to east coast and anything in gulf will head toward mexico.Troughs are taking everything out to sea.There is no pattern change coming,people have been talking about this for 6 weeks.Nada!!
wrong
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Quoting xcool:
we moveing in to Caribbean season soon .i meaning more storms going start development in Caribbean that put highrisk for usa...sorry about miss spell i just goting home from work.


Correct. The US will be hit eventually. I'm no wishcaster, but the chances are quite high that something will eventually find US soil. Hermine already did so.
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1604. xcool
we moveing in to Caribbean season soon .i meaning more storms going start development in Caribbean that put highrisk for usa...sorry about miss spell i just goting home from work.
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Quoting dracko19:
Hey, do you remember that movie "The Perfect Storm"? It was about a fishing ship that was lost at sea off the NE USA coast in a "storm of the century", which turned out to be a Cat 4 Hurricane merging with a low pressure system creating a ..."Super Subtropical Storm".

Take a look at this:
Link

This is the GFS Long Range Model. Take a look how it handles IGOR in the long term (8+ days out) It blows it up to a cat 5 and then takes it right over Bermuda!! (That would destroy Bermuda) Then, it merges with a low over New Foundland and creates a Super-SubTropical storm on Sep 23rd. Very interesting...


The guy who actually forecasted that "Perfect Storm" out of Boston WS was Dr. Bob Case. He was a forecaster at the NHC back in the 80's. A real nice guy, who also took a liking to a very young Avilla at the time, often commenting "he really knows his stuff. It looks like he was right.
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1602. beell
Entrance of the jet stream-upper left of frame.

ATL WV Loop
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1601. help4u
Igor is a fish,and so are the other 2 storms in atlantic,nothing is coming close to east coast and anything in gulf will head toward mexico.Troughs are taking everything out to sea.There is no pattern change coming,people have been talking about this for 6 weeks.Nada!!
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1600. Levi32
Quoting moonlightcowboy:



There's nothing about the speed of that flow "slow" - lol. Dang thing has taken off westwards like its been shot out of a cannon.

Good obs, Beell. Respect, Levi, but you missed that one.


Don't think so, but to each his own opinion.
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Few comments on recurving tc's this year...

The primary reason is the negative torque anomalies that have persisted across the last 90 days in the 20-40N band around the hemisphere. This can be seen as the blue shaded areas here.The GLAAM negative anomalies are correlated to increased meridional flow, or flows that have more south to north, or north to south components. When zonal prevails, the anomalies tend to reverse - but there is also a velocity component to the total budget. In this case, however, this has marked an increased potential for incurring trough into ambient subtropical ridges, which in turn increased(s) the background probability for earlier polarward migration of TCs due to the effect that has on the steering levels.

There can be exceptions, however. Earl was a long track with a lot of resistance to recurving ...similar I believe to what Igor's destiny will be. I consider Earl a successful impact on the U.S. despite the lack of direct strike. And, in terms of "Eastern North America", he did have a direct strike on NS where one fatality was registered.
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Quoting FloridaTigers:


Definitely, we've been really lucky. Lets hope it lasts...


Relatively speaking, this pattern would turn around and bite you in the behind come October / November. Good for now though.
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Quoting Stormchaser2007:
Here she comes....




SATELLITE PICTURES INDICATE THAT THE VIGOROUS TROPICAL WAVE AND
ASSOCIATED LOW PRESSURE SYSTEM ABOUT 375 MILES EAST-SOUTHEAST OF
THE CAPE VERDE ISLANDS IS BECOMING BETTER ORGANIZED. IF CURRENT
TRENDS CONTINUE...ADVISORIES COULD BE INITIATED TONIGHT OR SUNDAY.
INTERESTS IN THE CAPE VERDE ISLANDS SHOULD CLOSELY MONITOR THE
PROGRESS OF THIS SYSTEM IN CASE WATCHES OR WATCHES ARE REQUIRED.

THERE IS A HIGH CHANCE...90 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH.



LOVE THIS! We've recently begun DVR'ing Julia Child... and trying our best to cook what she teaches... it'll be nice to have a tropical storm that isn't the same name as somebody that works for me (katrina, danielle)... :)
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Quoting CyclonicVoyage:


Loving this pattern we got sticking like duct tape.


Definitely, we've been really lucky. Lets hope it lasts...
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1582. Legion 11:36 PM EDT on September 11, 2010

That's a prime example of something called the "trochoidal oscillation".
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Quoting barotropic:


The EC has to keep an eye on Igor however I think at this point there is some confidence in their forecast. From the discussion;


"THE OFFICIAL NHC FORECAST TRACK HAS BEEN ADJUSTED TO
THE RIGHT...FOLLOWING THE TREND IN THE GUIDANCE... BUT IS NOT AS FAR RIGHT AS THE MULTI-MODEL CONSENSUS.

It also notes that the trough is "significant". So I do believe they have somewhat of a handle on it and right now it looks as though (hopefully) it will miss the islands. Hopefully, somehow it will miss Bermuda also but it may be quite close.


Loving this pattern we got sticking like duct tape.
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Quoting dracko19:
Hey, do you remember that movie "The Perfect Storm"? It was about a fishing ship that was lost at sea off the NE USA coast in a "storm of the century", which turned out to be a Cat 4 Hurricane merging with a low pressure system creating a ..."Super Subtropical Storm".

Take a look at this:
Link

This is the GFS Long Range Model. Take a look how it handles IGOR in the long term (8+ days out) It blows it up to a cat 5 and then takes it right over Bermuda!! (That would destroy Bermuda) Then, it merges with a low over New Foundland and creates a Super-SubTropical storm on Sep 23rd. Very interesting...


OMG here we go with the panic and hysteria...I figured it would start either tonight or tomorrow...
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Hey, do you remember that movie "The Perfect Storm"? It was about a fishing ship that was lost at sea off the NE USA coast in a "storm of the century", which turned out to be a Cat 4 Hurricane merging with a low pressure system creating a ..."Super Subtropical Storm".

Take a look at this:
Link

This is the GFS Long Range Model. Take a look how it handles IGOR in the long term (8+ days out) It blows it up to a cat 5 and then takes it right over Bermuda!! (That would destroy Bermuda) Then, it merges with a low over New Foundland and creates a Super-SubTropical storm on Sep 23rd. Very interesting...
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Jeez, 92L really shriveled up. I do see a bit of broad spin but other than that...it has moistened up the area quite a bit.
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Good night all. It's been an interesting day of reading and learning. I expect tomorrow will be a busy day here.
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Quoting moonlightcowboy:



There's nothing about the speed of that flow "slow" - lol. Dang thing has taken off westwards like its been shot out of a cannon.

Good obs, Beell. Respect, Levi, but you missed that one.


And, evidently the weakness was "weaker" as well.
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1588. xcool
AL, 93, 2010091200, , BEST, 0, 128N, 185W, 25, 1006, DB
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Quoting beell:


Last look at the RGB may allow for another interpretation.
:)

Link



There's nothing about the speed of that flow "slow" - lol. Dang thing has taken off westwards like its been shot out of a cannon.

Good obs, Beell. Respect, Levi, but you missed that one.
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Quoting TheDawnAwakening:
I see Kori, but I will side with the EURO lead consensus south of Jamaica over a consensus lead by the HWRF any day, but again that is JMO. Reasoning is the NAO staying positive will reinforce the ridging north of 92L throughout its lifetime across the western Caribbean Sea. Wind shear is very low as well as models agree on a continued upper level anticyclone staying with this system. Satellite blackouts will soon occur and therefore means time for bed. Good night everyone and I would not be surprised we see 93L become tropical storm Julia by the time I wake up tomorrow morning, probably around 8am EDT.


Don't be afraid to disagree with me. This field wouldn't be any fun if we all came out with the same forecasts. :)

Also, despite our current disagreement, I still very much value your insight. You're right up there with people like Drak, Levi, myself, 456, etc.
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1585. xcool
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2010 Time : 021500 UTC
Lat : 17:37:47 N Lon : 42:10:38 W


CI# /Pressure/ Vmax
4.3 / 982.2mb/ 72.2kt


Final T# Adj T# Raw T#
4.2 4.6 5.8

Latitude bias adjustment to MSLP : +0.0mb

Estimated radius of max. wind based on IR : 17 km

Center Temp : -9.8C Cloud Region Temp : -65.6C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

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

Tno/CI Rules : Constraint Limits : 0.5T/hour
Weakening Flag : ON
Rapid Dissipation Flag : OFF

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Should be a tremendously exciting day tomorrow for tropical cyclone weather enthusiasts. JMO. Good night everyone. Igor is a menace now and can't wait until what he looks like tomorrow morning, hopefully not what he looked like this morning.
Member Since: October 21, 2008 Posts: 246 Comments: 3970
Should be a tremendously exciting day tomorrow for tropical cyclone weather enthusiasts. JMO. Good night everyone. Igor is a menace now and can't wait until what he looks like tomorrow morning, hopefully not what he looked like this morning.
Member Since: October 21, 2008 Posts: 246 Comments: 3970
Quoting atmoaggie:
A quick google answer: http://wattsupwiththat.com/2009/06/07/a-new-study-on-predicting-maximum-hurricane-intensity-using-l ightning/
Thanks for the link. I read the comments as well. If it helps improve forecasting even a little, I'll gladly shovel some of my tax dollars their way. Baby steps, as was stated here earlier.
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Quoting KoritheMan:


Yes, there can sometimes be discrepancies in the CIMSS steering maps, when you compare them to water vapor imagery.

However, most of the time it's accurate. What you really need to do when using these steering layers, is view the steering currents from at least 12 hours back to present. That way, you will be able to tell the evolution of the steering flow over a longer period, making your forecasts more accurate.


Thank you...that makes sense. I appreciate your time tonight!
Member Since: July 28, 2010 Posts: 0 Comments: 285
1579. Ron5244
Maybe its just me, but I happen to see some slight bending toward the west at the very end of the 00z dynamical runs.

Perhaps foreshadowing something like this?
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1578. Patrap
Quoting KimberlyB:


Oh ya, it happens all the time for sure. It just thought it was doing a lot of North~South skippin' & jumpin' back & forth on the last few frames.

I'll make sure to take some Dramamine tomorrow before getting on the blog! lol


Also,,as a Storm nears a coastal area,,the wobble direction is usually biased toward the relative observer's relationship to that storm.

Or Wish-itis.
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Quoting crashingwaves:
If Igor continues on the w to wnw track, I don't see how the EC will dodge this monster storm. I keep hearing curvature but the NHC mentions nothing about it. I would think by the end of the forecast, which would be next week.The NHC should have a better handle on Igor. Its hard to concentrate on 92L & 93L.


The EC has to keep an eye on Igor however I think at this point there is some confidence in their forecast. From the discussion;


"THE OFFICIAL NHC FORECAST TRACK HAS BEEN ADJUSTED TO
THE RIGHT...FOLLOWING THE TREND IN THE GUIDANCE... BUT IS NOT AS FAR RIGHT AS THE MULTI-MODEL CONSENSUS.

It also notes that the trough is "significant". So I do believe they have somewhat of a handle on it and right now it looks as though (hopefully) it will miss the islands. Hopefully, somehow it will miss Bermuda also but it may be quite close.
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I see Kori, but I will side with the EURO lead consensus south of Jamaica over a consensus lead by the HWRF any day, but again that is JMO. Reasoning is the NAO staying positive will reinforce the ridging north of 92L throughout its lifetime across the western Caribbean Sea. Wind shear is very low as well as models agree on a continued upper level anticyclone staying with this system. Satellite blackouts will soon occur and therefore means time for bed. Good night everyone and I would not be surprised we see 93L become tropical storm Julia by the time I wake up tomorrow morning, probably around 8am EDT.
Member Since: October 21, 2008 Posts: 246 Comments: 3970
Quoting Patrap:


Dats what dey do..they never follow a straight line as the forces involed make um wobble.

Kinda like us blogger types.

So expect the wobble-itis to increase as Igor trends west thru time.


Oh ya, it happens all the time for sure. I just thought it was doing a lot of North~South skippin' & jumpin' back & forth on the last few frames.

I'll make sure to take some Dramamine tomorrow before getting on the blog! lol

*edited to correct my spelling*
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1574. xcool
heyyy
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Blog Update
Puerto Rico tropical forecast
Hurricane Igor and Tropical Storm Julia ?
Link
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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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