Disturbance 90L close to tropical depression strength; TD 2 may rise again

By: Dr. Jeff Masters , 2:02 PM GMT on August 14, 2009

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A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.

Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.


Figure 1. The remnants of Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.

I'll have an update Saturday morning, or earlier, if significant developments occur.

Jeff Masters

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Quoting Vortex95:


I thought you would be more upset of him calling you pressy.
At least he spelled it correctly....lol
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The models cant agree on US landfall of 90L but are in are in much consensus in our area. The chances of knowing a US impact is slim to none.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
My gut feeling is I'm going to win the lottery tonight.
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629. DVG
St Simon...those are now old gfs model runs.
New ones bring it up along and on the east Fla coast. I live in Jax. It centers Jax on this run as it moves north.

If it does this next week, then we worry.
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Quoting WeatherStudent:
Afternoon Drak. Do you forsee this critter hitting us? Afternoon Pressy.


WS, you have to be patient, it is impossible to tell at the moment. However, a Florida landfall is likely, depending on the strength of the trough.
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Quoting fatmike:
Hey guys, new to watching the tropics, but a long time reader. By watching the following GFS model animation, doesn't it have 90L going north of Cubs, brushing S. Florida, then hitting New Orleans head on? Or am I missing something?

http://www.wunderground.com/modelmaps/maps.asp?model=GFS&domain=TA

And where do I see the models that show what the estimated category of the storm is in the future? Specifically, people are talking about a CAT 5 for Florida/GA possibly. THANKS!


Link
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Quoting louisianaweatherguy:
IF there are models showing a New Orleans strike this early... chances are very high that it WILL NOT hit New Orleans...



Zactly..and the fuss over the Homecasters east of us is always fun to gander over,..LOL


Keep wishing what you want to happen,..


..ya may get yer Wish,but Id start gathering those Items you may want to evac North with,..
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My brother is living in St.Croix,he better watch this thing,some models take it right over him.
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Quoting WeatherStudent:
Afternoon Drak. Do you forsee this critter hitting us? Afternoon Pressy.



Seriously ?!?!?!?! Are you seriously asking him that?!?!?!?!?!?!
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Hello,

Just took a quick look at the 12z GFS and it was nice knowing you miami lol.This system is still quite a distance away BUT one thing is for sure the models are pretty tightly clustered just north of the islands. Track on the 12z is somewhat similar to the 1926 miami cane.
Member Since: May 14, 2006 Posts: 8 Comments: 13749
Quoting Sting13:
Well i know this is an odd question, because models keep changing, but yesterday the GFS had 90L coming right up to me in eastern canada, nova scotia to be exact. I know model has changed now and they arnt very reliable, but my question is, if it WERE to come up the coast, would it still be a hurricane when it got here, we don't get many hurricanes up this way, but hurricane juan is still talked about, that was only category 2 when it hit and destroyed everything, can still see the effects in some places and that was back in '04. Registered just to post this question :P, been reading for a while :)



It's a legitimate fear but an unlikely one at that. Who KNOWS where this storm could be going days from now, anything could direct it your way, but there are so many factors in steering these storms. If a frontal system comes off the east coast or some sort of blocking high steers it you could be in the clear pretty easily. Even if it reaches you, judging by the Sea surface temperatures right now, if it rides the east coast Floyd style, it could make it up there at Hurricane strength, especially if it has some speed behind it. This is only my opinion of course. And dont get too worried yet, We are days and days away from knowing where it's headed!
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Quoting presslord:
pat....the one question that shows up here frequently...and just irks the snot outta me...is: "What's your gut feeling about...."

Who cares what somebody's "gut feeling" is?!?!?!?!?!


I had a gut feeling you'd feel that way.
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Quoting presslord:
pat....the one question that shows up here frequently...and just irks the snot outta me...is: "What's your gut feeling about...."

Who cares what somebody's "gut feeling" is?!?!?!?!?!


Well,press.to Quote a Movie scene,and I'll catch some flak about this one,Go figure,

..."Moods and feelings are for Women and Cattle,..up on yer feet and watch the storm,sport"..
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Quoting canesrule1:
I always agree with the CMC:

you'd be wrong 80% of the time then.
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TD2 to hit FL
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Quoting canesrule1:
can u please post the link for it, thanks.
post 604
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IF there are models showing a New Orleans strike this early... chances are very high that it WILL NOT hit New Orleans...
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Link

Looks to be pretty big to, wonder how strong...
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I always agree with the CMC:
What support is there for a Gulf strike? There is none at the moment.

I don't like this as much as you don't like it but for now i am leaning towards the last couple runs of the GFS model...it shows the high building in Florida getting hit then a trough picking it up and taking it to the Northern Gulf Coast...I'm hoping that doesn't pan out it just seems reasonable right now based on my past knowledge and events
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Quoting louisianaweatherguy:
90L is looking very impressive. Is there a closed area of circulation with 90L yet?


Yes Indeed,a Broad one at that,which will take some time to spin Up,but slow and steady wins the race.


90L Multiplatform Satellite Surface Wind Analysis,Wind Field. Time of Latest Image: 200908141200
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Quoting Drakoen:
CMC 12z tracks the system just north of the Lesser Antilles.
can u please post the link for it, thanks.
Hey guys, new to watching the tropics, but a long time reader. By watching the following GFS model animation, doesn't it have 90L going north of Cubs, brushing S. Florida, then hitting New Orleans head on? Or am I missing something?

http://www.wunderground.com/modelmaps/maps.asp?model=GFS&domain=TA

And where do I see the models that show what the estimated category of the storm is in the future? Specifically, people are talking about a CAT 5 for Florida/GA possibly. THANKS!
Member Since: Posts: Comments:
pat....the one question that shows up here frequently...and just irks the snot outta me...is: "What's your gut feeling about...."

Who cares what somebody's "gut feeling" is?!?!?!?!?!
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12Z CMC
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90L resembles H Dean in invest number, organization, date and latitude.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting jasoniscoolman10:



what are you talking about......

. A trough digging down from the N of Ex TD2 that may increase shear over it depending on the relative speeds of the two. the jet steam is way to the north right now..this is no trough here unit end of next week..


Either you didn't watch the loop or don't understand it.
Member Since: August 19, 2006 Posts: 0 Comments: 15812
CMC 12z tracks the system just north of the Lesser Antilles.
Member Since: October 28, 2006 Posts: 57 Comments: 30248
Quoting louisianaweatherguy:
90L is looking very impressive. Is there a closed area of circulation with 90L yet?


since yesterday. but it remains broad but becoming tighter
Member Since: July 24, 2005 Posts: 407 Comments: 19076
90L is looking very impressive. Is there a closed area of circulation with 90L yet?
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Quoting louisianaboy444:
I believe this could possibly be a Rita or Katrina type path with south florida getting hit first and making a second hit somewhere on the Northern Gulf coast but thats just IMO right now...


You had to bring up Rita..... :)

I saw a model somewhere on here bringing the 90 to LA...We are about 15 minutes away from the LA border -
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Below average rainfall here in St Kitts is threatening our reservoirs. Water levels are low, leading to water interruptions. We desperately deend the rain.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
12CMC - Northern Leeward Islands and TD#2 Remnants into the GOM.

Link
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Quoting louisianaboy444:
I believe this could possibly be a Rita or Katrina type path with south florida getting hit first and making a second hit somewhere on the Northern Gulf coast but thats just IMO right now...


What support is there for a Gulf strike? There is none at the moment.
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Atlantic Basin 2 Sept 2008


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Quoting Hurricane1956:
I just notice that most of the models,develop some how the tropical wave north of Cuba just below the tip of Florida or just on the East coast into a tropical depression or storm and take it to New Orleans.Any comments?.To me I can see in the satellite presentation some minor bandings?,can this be developing slowly into something?.


The Canadian GEM regional 15km model thinks so...Sunday morning weak vertical circulation at 500 and 700 mb over the N central gulf and plenty of convective QPF (model precipitation estimate).No sign of a surface circulation yet...but a suggestive upper pattern.

Link
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Quoting Skyepony:
StSimon~ WU long run GFS Takes out SFL about 200hrs.


Yes and look where it puts it at 06Z on Tuesday. Still far too early since it hasn't even formed yet. It's hurricane season, I'm always as prepared as I can/should be. Lets hope it goes fish.
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Quoting StSimonsIslandGAGuy:
It says he is home from Flu, right?

Oh wait, Florida International University

FIU.

Hmmmm is there a difference between FIU and FLU? :)


HAHAHAHAHAHA!
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Quoting ackee:
It just seem to me that some poeple make it seem like the GFS is the only model frankly not big fan of GFS my view


It is one of the few that go out that far. It is tightly clustered with all the others in the 5 day range.
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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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