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 Patrap:



Im hurt,really hurt,..man...a lil humor and the Place goes up In A Glenn Beck Moment

LOL


LMAO...that made me laugh.
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I am getting really tired of seeing things like this:

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/18/images/gfs_ten_252l.gif

At this point I'm definitely rooting for the Euro solution.
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Quoting Dropsonde:
That is the 12Z. The 18Z is another Gulf storm, the third out of today's four runs. :(

all the runs also take it very close or over S. FL.

it can very easily hit both.
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Wow Patrap! That was really uncalled for.
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Quoting Patrap:



Im hurt,really hurt,..man...a lil humor and the Place goes up In A Glenn Beck Moment

LOL


Was that directed at you?
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Quoting Ldog74:
Kinda surprised that I'm not hearing any "OMG Td 2 is going to regenerate in the Bahamas and be Katrina's big sister!!", but thats a welcome subtraction to this blog.

90L needs to get smaller, if it could shed some of its weight it'd make it a lot easier to wind up.

And for the possibility that 90L is going to rapidly intensify, i doubt it. At least over the next couple of days. Rapid intensification, being a technical term of a decrease of 42 millibars in less than 24 hours, has a low chance of occurring in such cool (relatively speaking) waters. Not to mention that currently 90L is much too large of a system for a "normal" rapid intensification situation to occur. As for when its closer to the East Coast/Caribbean, sure, it could happen.


SHIPs RI index for 25kt increase in 24 hours suggests only a 30% chance for rapid intensification.
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1777. Patrap
Quoting DDR:

What does this have to do with weather?
I putting you back where you belong,my S**t list.



Im hurt,really hurt,..man...a lil humor and the Place goes up In A Glenn Beck Moment

LOL
Member Since: July 3, 2005 Posts: 414 Comments: 125591
Quoting WeatherStudent:


Yup, eleven counts of the GFS taking the storm to Florida. More to follow suite. A trend? clearly.


Its not even a TD yet. Far as you know five days from now they will be pointed elsewhere.
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Quoting weatherboykris:
18z GFS takes it through Miami area...remember, this far out exact track doesn't really matter.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_ten_204l.gif
That is the 12Z. The 18Z is another Gulf storm, the third out of today's four runs. :(
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Quoting Drakoen:


Not even close
Looks more like 12.5 and 30.0 to me.
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1772. Ldog74
Kinda surprised that I'm not hearing any "OMG Td 2 is going to regenerate in the Bahamas and be Katrina's big sister!!", but thats a welcome subtraction to this blog.

90L needs to get smaller, if it could shed some of its weight it'd make it a lot easier to wind up.

And for the possibility that 90L is going to rapidly intensify, i doubt it. At least over the next couple of days. Rapid intensification, being a technical term of a decrease of 42 millibars in less than 24 hours, has a low chance of occurring in such cool (relatively speaking) waters. Not to mention that currently 90L is much too large of a system for a "normal" rapid intensification situation to occur. As for when its closer to the East Coast/Caribbean, sure, it could happen.
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yea but I have seen them keep a system up for 2-3 days w/o any convection just to have it come back and become a hurricane
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Quoting jaxairportman:
Here is a new poll how many here think it has become a dictatorship?


No dictorama here, just be ready to back what you type.It's better to let the info guys battle(which they usually end up agreeing at the end) then to jump in the middle of it.
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1769. IKE
Quoting weatherboykris:
18z GFS takes it through Miami area...remember, this far out exact track doesn't really matter.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/images/gfs_ten_204l.gif


Put them shutters up WS!
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1768. DDR
Quoting Patrap:




What does this have to do with weather?
I putting you back where you belong,my S**t list.
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1766. Patrap
GOM 60 Hour Surface Current,Loop Eddy Included,area specific
Member Since: July 3, 2005 Posts: 414 Comments: 125591
.
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goes just south of S. FL on this run of the GFS and hits New Orleans.
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Quoting Patrap:





True Patrap. We are no where close to the horrors of Hitler and Stalin.
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Quoting DestinJeff:
Would like to comment that the current tone on the blog is great. Not over-dramatic, not tit-for-tat ... just a bunch of tropic-geeks doing their thing.

While many people are yet unaware, those here have at least an understanding of what the next several days might entail.

Keep of the good work fellas and ladies.


I noticed this also today. Very nice , very nice; hope this keeps up when it gets even more "exciting" around here!

Good job everyone; lurking today has been pleasant.
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1758. Drakoen
Quoting Chiggy007:
Anyone see the center of 90L around 11.5N - 29.5W! To my eyes it's pretty evident...


Not even close
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Quoting jaxairportman:
Here is a new poll how many here think it has become a dictatorship?


Show me a big boat filled with frankfurter-shaped potatoes and...

Anyway, no, it's democratic here. Use the blog tools and everything will be A-OK.
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.
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Quoting jaxairportman:
Here is a new poll how many here think it has become a dictatorship?


Who's the dictator?

It's more like an oligarchy...
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1752. Patrap
GOM 60 Hour SST Model,area Specific
Member Since: July 3, 2005 Posts: 414 Comments: 125591
Anyone see the center of 90L around 11.5N - 29.5W! To my eyes it's pretty evident...
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Quoting jasoniscoolman10:







Aug. 14, 2009 6:18 pm ET
A juicy but fading front coupled with a tropical disturbance coming out of the Bahamas and Hispaniola with trigger thunderstorms from the Carolinas to the northern Gulf Coast states this weekend. Some of the thunderstorms will contain flash flooding rains.with all his rain from FL TO NC if a big hurricane hit land there will be lots of tree coming down.





That map looks so 90s...XD
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Here is a new poll how many here think it has become a dictatorship?
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Quoting jlp09550:
Local meteorologist said there are two scenarios: 1) it heads towards an area along the Louisiana coast; or 2) it hits Florida and heads North. Both depend on a low pressure trough just north of Florida.

Is this correct? o.O


I'd say those are two of many possibilities. Too early to tell.
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Quoting jaxairportman:
She says it so well! the lack of freedom of specch here is like being in dictorship.


Freedom of speach goes both ways and there is a Clique on here.Give your opinion,take critisism and back it up-you be bloggin now
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Quoting jlp09550:
Local meteorologist said there are two scenarios: 1) it heads towards an area along the Louisiana coast; or 2) it hits Florida and heads North. Both depend on a low pressure trough just north of Florida.

Is this correct? o.O


Have heard the same.
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Quoting jlp09550:
Local meteorologist said there are two scenarios: 1) it heads towards an area along the Louisiana coast; or 2) it hits Florida and heads North. Both depend on a low pressure trough just north of Florida.

Is this correct? o.O


Louisiana coast :/
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Quoting Thundercloud01221991:
Why isnt TD2 a tropical depression still I have seen worse ones that that thing


It looked more amorphous earlier before 5 thats why. Organization was only a T1.0.
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Local meteorologist said there are two scenarios: 1) it heads towards an area along the Louisiana coast; or 2) it hits Florida and heads North. Both depend on a low pressure trough just north of Florida.

Is this correct? o.O
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Why isnt TD2 a tropical depression still I have seen worse ones that that thing
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1738. Patrap
csi - 16
Location:Chevron MP41M platform, Coordinates:89 02.128',29 24.07



Latest Obs


9.01 knots (10.36 miles/hour)

Sea Surface Temperature:
87.78 F




Member Since: July 3, 2005 Posts: 414 Comments: 125591
I don't know if that is a pinhole Taz, but look at the beautiful tails (don't know the technical term...I am new) That looks like one of those perfect little symbols that the weather stations use and put on top of a hurricane. The blender blade look. Awesome view!
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Quoting WeatherStudent:
Max Mayfield just said on Local 10 News here in SF. That he would advise South Floridians to look over their hurricane plans this weekend.


The best advice you can give right now. Anyone in those Caribbean islands should as well, as San Juan NWS said today.
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1734. JLPR
Interesting...
Ada Monsón here said that 02L should clear the dry air for 90L

02L should pass to the north of PR
and 90L is a bigger threat since it could pass according to her anywhere from 50 - 100 miles to our north or south or end up affecting us directly, she sounded a little worried =\
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.