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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Former TD 2 Enhanced Infrared (IR) Imagery (4 km Mercator)

Time of Latest Image: 200908141200
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TD2 coming back and sustaining itself.
Member Since: August 31, 2008 Posts: 0 Comments: 833
Quoting wunderkidcayman:

yes a star but not a fish storm


When puns are outlawed only only outlaws will use puns :)
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JFV may have already evacuated.
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Quoting canesrule1:
im calling it! red for ex-02L at the TWO!!!

so am I
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Quoting Drakoen:


I cannot say how strong that system is based on looking at the GFS. The GFS cannot adequately represent the strength of a system. Conditions look favorable and there is some hot Bahamian waters. You can only speculate.


One can draw conclusion from the GFDL that has a rapidly strengthening cyclone just north of the leewards moving into increasingly warmer waters. Last ships had 107mph at the leewards.
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Quoting drg0dOwnCountry:
Study Finds Big Storms on a 1,000-Year Rise


The North Atlantic Ocean has spawned more hurricanes and tropical storms over the last decade than it has since a similarly stormy period 1,000 years ago, according to a new study.

The research, published yesterday in the journal Nature, tries to trace the pattern of storms along North America's Atlantic and Gulf coasts back to A.D. 500, well before humans were recording weather observations.

Taken together, he said, they suggest that warmer temperatures produce more storm activity -- meaning that coming climate change could increase the frequency of hurricane activity.

"The paleoclimate evidence seems to reinforce the notion that, all other things being equal, when you have warm sea surface temperatures in the tropical Atlantic, you see more activity," he said.

Kerry Emanuel, a climatologist at the Massachusetts Institute of Technology who has published studies linking climate change to stronger hurricanes, called the new research "an impressive piece of work, melding two completely independent approaches to estimating past hurricane activity."

Emanuel said the Nature study "shows that hurricane activity is indeed quite sensitive to climate, and although we are still not completely sure about global warming effects, the paper raises again the flag that potentially they could be large."
NyTimes

On this NY Times Article on storm pattern from
500 or 1000 years ago:
Wow, now That takes some serious audacity
to say they know what really happened back then for storm frequency and strength, haha.
We are not so sure about storms 100 years ago,
so I have to take this article with a grain, or a whole darn shaker of salt.
It's also easy to claim to be scientific about something that distant and vague and declare to have knowledge of this sort, due to one being "a scientist". We do have Ice Cores and Tree Rings etc for reference, but these things are not too specific or accurate, giving only general clues.
I would love to know what kind of Actual Data they have and how they use that data to extrapolate their conclusions.
What is their methodology, and control over error, how subjective is the analysis??
The New York Times also has an obvious editorial slant that makes some of their articles a bit suspect (my opinion here).
Interesting food for thought however.
Al Gore would be proud...
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Quoting CaneWarning:


I think into the gulf...
i think over florida into he gulf then the trough kicks in and then into Loisiana, imho.
Quoting Progster:


ex TD2 - a "star" fish storm?

yes a star but not a fish storm
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I don't want to get hit here in Okeechobee, but I must admit it would be great for the economey.
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im calling it! red for ex-02L at the TWO!!!
Quoting StSimonsIslandGAGuy:
So where does the GFS put the big wave in 200 hours? I gotta go soon and don't have models bookmarked here at work.


I think into the gulf...
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lol you are the more stable one on here
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Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit

Take me off the list as well. I am tired of evacuating and worrying about what I will come home to. BUT, I do like to keep up so that I can make plans early IF I need to.
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on avn ir loop of ex-TD2 looks like a star
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Quoting Patrap:
What some seem to fail to realize is this,and Drak will confr
irm what I say next. When a Large CV Hurricane becomes embedded in the Easterlies ,they can,and sometimes do..plow thru LARGE or medium sized synoptic Challenges. No one wants a CONUS strike,nor a Island strike,that would be ones own Madness.
Never discount what May occur,and prepare NOW for in the event a Large CV storm comes into your area. Thats being Pro-active instead od re-active,

And remember,Calamity Knows no Borders,only Mens Minds and Maps do.

Exactly. Large hurricanes tend to create their own weather around them. I could rattle off examples, but overall, with very deep pressures, they are steered around by an extremely high air current, primarily around 200mb.
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Quoting Patrap:
What some seem to fail to realize is this,and Drak will confrirm what I say next.

When a Large CV Hurricane becomes embedded in the Easterlies ,they can,and sometimes do..plow thru LARGE or medium sized synoptic Challenges. No one wants a CONUS strike,nor a Island strike,that would be ones own Madness.

Never discount what May occur,and prepare NOW for in the event a Large CV storm comes into your area. Thats being Pro-active instead od re-active,

And remember,Calamity Knows no Borders,only Mens Minds and Maps do.


Yes everyone should review their Hurricane plans this weekend - just in case.
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No renumber on the CIMSS site, so probably no 02L or 03L at 2 PM EST.
what appears to me is that we are jumping the gun on the models, yes we can analyse them but they have always changed back and forth i for one do not want a hurricane hitting florida or any land area we are in a horrific economic situation in florida and if we get hit the S**t is going to hit the fan
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Quoting breald:


What people tend to forget is that hurricanes do come up the east coast once in a while.

Aside from South Fl and the Carolin's, New England has been hit more than any other region on the East Coast. Including North Florida.



Yeah and that is where this one will probably end up heading. If the NHC says East Coast or recurve you can pretty much bank on it. I learned my lesson going against those guys especially during the last few years and up to now.
Member Since: Posts: Comments:
Quoting Patrap:
What some seem to fail to realize is this,and Drak will confr
irm what I say next. When a Large CV Hurricane becomes embedded in the Easterlies ,they can,and sometimes do..plow thru LARGE or medium sized synoptic Challenges. No one wants a CONUS strike,nor a Island strike,that would be ones own Madness.
Never discount what May occur,and prepare NOW for in the event a Large CV storm comes into your area. Thats being Pro-active instead od re-active,

And remember,Calamity Knows no Borders,only Mens Minds and Maps do.


Sure. It takes a large strong Cat 4 or 5 to do that. Gilbert or Wilma sized.
Member Since: October 28, 2006 Posts: 57 Comments: 30841
510. Skyepony (Mod)
Quoting ricderr:
ok....a serious post in a forum that i try never to be seroius on...

while you guys are speculating over gut feelings and unsubstantiated tracts...please note the close alignments of the models...for those that have been here for awhile....can you remember when this early into a systems cycle...when the models have been so closely aligned so soon?




Hard to trust models with a weak undeveloped circulation, especially when located kinda close to another trying to pull it together storm..
Member Since: August 10, 2005 Posts: 227 Comments: 39457


ex TD2 - a "star" fish storm?
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KEH - doing well out here. Love it. Still have that house in Savannah though so keeping my eyes glued to the weather...

How's by you?
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What some seem to fail to realize is this,and Drak will confrirm what I say next.

When a Large CV Hurricane becomes embedded in the Easterlies ,they can,and sometimes do..plow thru LARGE or medium sized synoptic Challenges. No one wants a CONUS strike,nor a Island strike,that would be ones own Madness.

Never discount what May occur,and prepare NOW for in the event a Large CV storm comes into your area. Thats being Pro-active instead od re-active,

And remember,Calamity Knows no Borders,only Mens Minds and Maps do.
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Quoting StSimonsIslandGAGuy:
Why is it called recurvature and not curvature?
:)
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Quoting hahaguy:


That's what a lot of people have been asking lol.


I think it is because it first curves when it starts heading from a Westerly direction towards WNW and NW then "recurves" once the heading starts towards the NNE and points further East.

Not sure but my best guess LOL
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Quoting FLHurricaneChaser:


I have NEVER seen the models converge like this 5+ days out.

In the 3 years I've watched the tropics closely, I can count the times the models have been this close this far out on one hand.
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Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit


Take me off that list, 3 is more than enough for me.
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Goodnight all,
Stay safe, Play safe, Blog safe.
Cheers
AussieStorm
Member Since: September 30, 2007 Posts: 9 Comments: 15979
Quoting 7544:



hi drake how strong does that model show ti a


I cannot say how strong that system is based on looking at the GFS. The GFS cannot adequately represent the strength of a system. Conditions look favorable and there is some hot Bahamian waters. You can only speculate.
Member Since: October 28, 2006 Posts: 57 Comments: 30841
Quoting RobbWilder:
Not discounting the model run but this is still an invest right? Its still in the middle of the atlantic? model runs arnt that great on weaker storms? it needs to develop more before you can get a good reading?


Indeed... the main point to take out of this is not where the storm is going to hit but how the Upper level pattern are trending... so if indeed something develop you'll get an idea where it might be heading.
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496. ackee
Quoting RobbWilder:
Not discounting the model run but this is still an invest right? Its still in the middle of the atlantic? model runs arnt that great on weaker storms? it needs to develop more before you can get a good reading?
good point
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495. A4Guy
Quoting FLHurricaneChaser:


Are you seriously concerned with how strong the 200 hour GFS shows the system?


Are YOU seriously concerned about WHERE the 200 hour GFS shows the system?

Maybe in 5 days from now, we will have a better idea as to the general vicinity of where the storm will be 10 days from now.

IKE was pointed straight at SoFla 4 days before expected landfall...we know how that story ended.

Before anyone mobilizes FEMA trailers, lets let another day..or 8 go by.
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Quoting StSimonsIslandGAGuy:
Why is it called recurvature and not curvature?


That's what a lot of people have been asking lol.
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Quoting ricderr:
Well one thing is for sure, anywhere from the eastern GOM and the eastern seaboard are in the cone


actually...what is certain..is that at this moement..no one in the conus is in the cone


LOL.
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Looking at the ensembles...... could it be another Andrew?
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Quoting Vortex95:



RIGHT OVER JFV, AND us as well...
and me.
Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit


Nope, I want it to stay far away. I wouldn't mind a hurricane day at work though. We had one last year for Fay. I saw a couple of drops of rain and a gust of wind around 20 mph.
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Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit


Their opinion doesn't change the storms track anyway...
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Not discounting the model run but this is still an invest right? Its still in the middle of the atlantic? model runs arnt that great on weaker storms? it needs to develop more before you can get a good reading?
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486. 7544
Quoting Drakoen:



hi drake how strong does that model show ti a
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Well one thing is for sure, anywhere from the eastern GOM and the eastern seaboard are in the cone


actually...what is certain..is that at this moement..no one in the conus is in the cone
Member Since: Posts: Comments:

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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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