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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Raw T# on Igor have jumped up to 5.8.
Member Since: July 8, 2005 Posts: 259 Comments: 24574
Quoting atmoaggie:
Not much lightning near Igor's eyewall. Not an indication that intensification isn't going to happen, but would strongly affirm it, if lightning were present.



Okay, the double (triple?) negative thing has me confused. Lightning indicates strengthening or not strengthening? (Brain dead, football all day)
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1519. JLPR2
Quoting WeatherNerdPR:
NHC Issued a Special TWO Stating that 93L has a 90% of becoming a TD and advisories would be initiated later tonight or early tomorrow morning. Now I'm out.


Looks like TD 12 is about to form, a special two usually means that, plus the 90% just gives it away. LOL

Night!
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1517. help4u
with the next couple cape verde systems curving way out to sea,and the high pushing anything south into mexico and troughs coming one after the other on east coast could the threat of anything hitting US about over.
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Quoting KoritheMan:


Anytime. If you have any additional questions regarding interpretation of that product, I'll be more than happy to answer.


Ok. If i understand it correctly, take the pressure from the storm and find the corresponding layer and that map will give you the general steering of the storm?
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1515. Drakoen
Quoting beell:
Hey, Levi,
Before you and Drak pummel me into submission, lol-gotta get in a "best wishes and good luck" as you dive into your college studies.


Thank You :)
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Quoting Levi32:


Given the tendency for strong ridging over the southeastern US all summer, I don't think this is the last credible threat. Even October could hold some storm tracks that continue to the west a lot longer than they're "supposed to" according to climatology.


Thanks for the insight.
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NHC Issued a Special TWO Stating that 93L has a 90% of becoming a TD and advisories would be initiated later tonight or early tomorrow morning. Now I'm out.
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1512. Levi32
Quoting beell:
Hey, Levi,
Before you and Drak pummel me into submission, lol-gotta get in a "best wishes and good luck" as you dive into your college studies.


Lol, thanks Beell :) Appreciate it.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
1511. Levi32
Quoting dan77539:


The NW Caribbean has SO MUCH TCHP, it really has me concerned. Climatology starts to work in our favor here on the Tx coast in about 3 weeks. Makes me feel that 92L is the last credible major storm threat for Tx. Thoughts?


Given the tendency for strong ridging over the southeastern US all summer, I don't think this is the last credible threat. Even October could hold some storm tracks that continue to the west a lot longer than they're "supposed to" according to climatology.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
1510. beell
Hey, Levi,
Before you and Drak pummel me into submission, lol-gotta get in a "best wishes and good luck" as you dive into your college studies.
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1508. beell
Quoting Drakoen:


I'm not convinced. The actual data doesn't support a fast low level flow in the Caribbean.


Ok, maybe "brisk" or "fast" is too agressive.
15 knots at 850mb as a guess.

For now, if you assume the center along 15N the movement has been pretty much due west.
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Quoting tropiccian:
Well fellow Texans and all you intelligent teachers, good nite. I'll lurk a little later.


see ya on here tomorrow
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Quoting KerryInNOLA:
I'll 2nd that!


I totally agree, all of them are very knowledgable and whether they agree or disagree with eachg other, they know how to keep it civil. And we learn alot from them. Thanks guys !
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Quoting Levi32:


If it [92L]were to gain enough latitude, then possibly, and they should keep an eye on it, but with the strong ridge remaining solidly in place near Texas for the next few days a hit on Mexico is more likely, if the system develops. It is still a ways off though.


The NW Caribbean has SO MUCH TCHP, it really has me concerned. Climatology starts to work in our favor here on the Tx coast in about 3 weeks. Makes me feel that 92L is the last credible major storm threat for Tx. Thoughts?
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Well fellow Texans and all you intelligent teachers, good nite. I'll lurk a little later.
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Not much lightning near Igor's eyewall. Not an indication that intensification isn't going to happen, but would strongly affirm it, if lightning were present.

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Best guess is that 93L is Julia and 92L is Karl, and I am not going out on a large limb, but more like a twig instead.
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1500. Levi32
Quoting beell:


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

Link


Another look at it from CPC analysis says slow, and so does the RGB loop. It may appear faster because the mid-upper clouds are also moving in a westerly direction, but it's still pretty slow.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
Thanks Koritheman. Better organization tonight of 92L, definite low level circulation finally taking shape. Tomorrow should reveal a much better system to watch finally develop into a tropical cyclone. Can't wait.
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Quoting want2lrn:


Thank you Kori!


Anytime. If you have any additional questions regarding interpretation of that product, I'll be more than happy to answer.
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Quoting KoritheMan:


Here you go, amigo.


Thank you Kori!
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Quoting earthlydragonfly:
Got a new shot tonight .... Let me know what you guy think of it....

Lightning
Beautiful.
Member Since: August 3, 2005 Posts: 10 Comments: 5684
Quoting btwntx08:

a potential threat to the western carribean possibility hurricane by then cant rule out RI with those record tchp it could be a dangerous situation after that the two areas that need to watch are tx and mx (more tx if it gains more lattude)(mx stays at a low lattude but could be a alex track if that)


Thanks, i am sure you are getting pretty tired of looking out your back door down into the BOC..
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Quoting want2lrn:


Speaking of Hermine, we only had 2.2 in of official rainfall here from the storm. it was really weird, it appeared watching satelite loops a slot of dry air got in and it kept us pretty dry. We did not have any rain after about 11am.


We had 7 1/2 here at the house....I was shocked when I woke up and noticed the large eye was just to the SW of CC...thought it was going to be SW of San Antonio
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Quoting TheDawnAwakening:
Link

Please, I beg you to check out my latest post and forecasted track of Igor and 92L and discussion of 93L. Please read my blog. And comment as well.


I'll get right on that! I've always appreciated your insight.
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1492. Drakoen
Quoting beell:


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

Link


I'm not convinced. The actual data doesn't support a fast low level flow in the Caribbean.
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Quoting TXCaneCrasher:


Good evening "Want" and "Tropic".....nice to meet you both. Yes you are right Tropic, you all have been hit pretty good. At least they you all haven't had the real high winds with all the saturated grounds. Keep an eye on 92L....you never know


Speaking of Hermine, we only had 2.2 in of official rainfall here from the storm. it was really weird, it appeared watching satelite loops a slot of dry air got in and it kept us pretty dry. We did not have any rain after about 11am.
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Quoting Neapolitan:
Two reds, a yellow, and a hurricane...


Walk into a bar.....

Igor living up to its name....first cat 5 of the season??
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1489. beell
So, Kman bails on me!
Thanks, Moonlight!
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Quoting want2lrn:
Levi, would you mind pointing me to a place where i can lern to read the map from post 1462? TY


Here you go, amigo.
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Quoting earthlydragonfly:
Got a new shot tonight .... Let me know what you guy think of it....

Lightning


Absolutely fantastic picture.... Thanks for sharing.

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1485. Drakoen
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Quoting tropiccian:
I'm down in Harlingen. We've had three already. Hermine slapped us good on Monday. Really getting tired of this.


Good evening "Want" and "Tropic".....nice to meet you both. Yes you are right Tropic, you all have been hit pretty good. At least they you all haven't had the real high winds with all the saturated grounds. Keep an eye on 92L....you never know
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Link

Please, I beg you to check out my latest post and forecasted track of Igor and 92L and discussion of 93L. Please read my blog. And comment as well.
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1482. beell
Quoting Drakoen:


The low level flow is very weak in the Caribbean


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

Link
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Levi, would you mind pointing me to a place where i can lern to read the map from post 1462? TY
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Quoting cyclonekid:
Oh. I was just wondering. Since after all his last blog post was the first of August. It just seems weird, not seeing him around.


Yeah, I can understand that. His input is certainly missed on this end.
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Man, Igor sounds like a name you'd hear in a Frankenstein monster movie, quite ironic since it will probably become a monster storm in the future.
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Quoting zoomiami:


And has a new little one. That will keep anyone busy.


Oh, he has a child too? Good for him. :)
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I'm down in Harlingen. We've had three already. Hermine slapped us good on Monday. Really getting tired of this.
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Quoting TXCaneCrasher:


Victoria area....what about you?




Corpus here...Hi neighbors!
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Quoting kmanislander:
I'm out for now folks. May be back later but if not in the morning before golf LOL


Good night. Enjoy golf; the 11th is still my least favourite!
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Quoting Stormchaser2007:


Busy with family and other things.
Quoting KoritheMan:


I'm wondering this too. I imagine he's just busy with life. He's married after all, I think.
Oh. I was just wondering. Since after all his last blog post was the first of August. It just seems weird, not seeing him around.
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Quoting tropiccian:
Hey TXCaneCrasher. What part of Tx are you in?


Victoria area....what about you?


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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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