TD 2 nearly dead; African disturbance 90L gathering strength

By: Dr. Jeff Masters , 2:38 PM GMT on August 13, 2009

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Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.

Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.


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

African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. 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 has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.

I'll have an update Friday morning.

Jeff Masters

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2187. Walshy
This is interesting. Look at this loop from weather-underground.

Did Tropical Storm Guillermo have a eye earlier? Or were the clouds just rotating fast?

Link
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2186. TX2FL
Quoting FLGatorCaneNut:
Baromter Bob and StormW are on and talking about 90L... Saying that somewhere in the U.S. in the next 10 days Hurricane Watches will probably be issued....

This weekend folks.... everyone should brush up and get those supplies, check those shutters IF this comes your way



Nice...just in time for my move back to Florida.... Tetrapak milk is on sale for $1.00 here..guess I'll bring some with!
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Looking at the latest GFS and a number of choice words come to mind, unprintable of course.

Jeez.
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Compared to 12z runs, 18z HWRF and GFDL look slightly south and closer to the northernmost islands. right?
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There will always be a limit on how good the models can be based on the limitations of the input data. Not to mention chaos theory. Even if you have good measurements everywhere, there's always some error/uncertainty associated with any measurement. These errors propagate through the model.
Member Since: June 12, 2002 Posts: 0 Comments: 1589
2182. KEEPEROFTHEGATE (Mod)
Quoting caneluver:
90L is oer 600 miles wide...Massive storm per stormw. Says it could pull a Floyd or plow straight into the gulf
may be just possible a very high but lets hope not
Member Since: July 15, 2006 Posts: 174 Comments: 54398
2181. 19N81W
all I see is yellow and red and TD ....on the sat I dont see anything that looks like what I used to see when it comes to Hurricane season! I picked up Cayman over 50 miles away today!! and I think I saw Aruba:) At least the dust seems to have died down a bit...the last 6 weeks have looked like downtown Toronto in the summer!
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KOTG, Got a question. I know you the right one, so I will trust your answer....lol
Was always told, higher foward speed storms are harder to "recurve". Right or Wrong?
Quoting louisianaboy444:
Baromter Bob and StormW are on and talking about 90L... Saying that somewhere in the U.S. in the next 10 days Hurricane Watches will probably be issued....

This weekend folks.... everyone should brush up and get those supplies, check those shutters IF this comes your way


How do i tune into that?
hurricanehollow.com
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Quoting aquak9:


What happened to "WE KNOW EVERYTHING"??

He is chewing out everyone on the Barometer Bob show...
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not to rain on anyone's parade - but since when do we even look at the intensity of a model for a storm that hasn't formed for a period of more than three days?

Every thing we know about all the models is that the least predictable factor is intensity.

Geezz
Member Since: August 13, 2007 Posts: 10 Comments: 4158
Quoting Rodek:
I usually lurk but post on rare occasions. I wanted to take a second to thank everyone for keeping the information flowing throughout the day and night on this blog. Without you, I'd be bored and ill-informed.

Now, a couple of questions.

How old are the models that are used to attempt to predict possible storm tracks?

Also, are there plans for new, more accurate systems in the future?


Some of the models go back 10 years or more, but they have been improved along the way and are still being improved.

For the future, NOAA has a project, NOAA’s Hurricane Forecast Improvement Project
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has invest 90 become better organized since this morn? if so, the computer models are not all ovr the place then?
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Baromter Bob and StormW are on and talking about 90L... Saying that somewhere in the U.S. in the next 10 days Hurricane Watches will probably be issued....

This weekend folks.... everyone should brush up and get those supplies, check those shutters IF this comes your way


How do i tune into that?
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2172. aquak9
Quoting KEEPEROFTHEGATE:
yeah aquak there has even been an imposter of me back earlier in the week even may have tried to hack me but i turn ed out to be more than he bargin for nothing but empty space now


good for you, keeper. That version of stormtop (not stormno, he's the real one this year) that version of stormtop that just posted showed up here right before Katrina.

Fully loaded and ready, keep. Good for you.
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Quoting stormno:
this is a special weather statement issued by my weather office for la mississippi and alabama..people need to to just keep tuned to your weather officials this weekend..there is a very good chance with the ssp falling in the northern gom and sst as high as 95 degress something could form and strengthen rapidly...so im asking everyone who live on the northern and ne gom to keep abreast of the weather information..my data out of my office indicated to me conditions or ripe for a depression to form late sat or sunday..im giving this forecast a 60% chance we will be dealing with anna in the gom sat or sunday..please stay tuned and i will broadcast the minute i see any threatening weather conditions for the gulf coast...i will be getting new data shortly after 2am ..i want to stress its nothing to worry about now its just something i want everyone to watch over the weekend...this has been a special weather statement issued by stormnos weather office out of new orleans..Stormno
absolutely no model support on this theory besides high pressure in the gulf
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I told him through my hysterical laughter. Your comment is as funny as the pic.

Quoting ALCoastGambler:
Tell your husband no. That is the improved version. FEMA made him raise it after Katrina
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Quoting DM21Altestic:
It's dangerous to play darts with a naked system.

It's dangerous to play darts with a naked anything.
L8R.
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Thank you all for the information and entertainment!
I have learned a lot and have enjoyed doing so over the course of the last few years.
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Link
latest models
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2165. KEEPEROFTHEGATE (Mod)
Quoting aquak9:


not the real stormtop, notice the zero instead of the O in the T0P part
yeah aquak there has even been an imposter of me back earlier in the week even may have tried to hack me but i turned out to be more than he bargain for nothing but empty space now
Member Since: July 15, 2006 Posts: 174 Comments: 54398
2164. jdjnola
Quoting centex:
agree, but I think 90L got it's own moisture and the talk about TD2 clearing the way is not correct. TD2 not clearing anything.


Didn't say TD2 is clearing anything, I said 90L was clearing the way for TD2 to stop sucking in so much dry air.
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Baromter Bob and StormW are on and talking about 90L... Saying that somewhere in the U.S. in the next 10 days Hurricane Watches will probably be issued....

This weekend folks.... everyone should brush up and get those supplies, check those shutters IF this comes your way

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I was saying earlier how i was feeling at ease that models were trending more and more Northward but now it looks like the models are trending further south with an increase in forward speed for 90L...makes sense but these patterns that are all about timing like when you have a trough involved for example can be subject to massive model swings...so you can pretty much throw a dart right now with this system
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Quoting jaxbeachbum:
LMAO! I'm glad I didn't have a drink in my mouth for I would have surely fried my mac. My husband asked if that was stormno's "real" office. LOL!
Tell your husband no. That is the improved version. FEMA made him raise it after Katrina
2158. Rodek
Quoting ALCoastGambler:
As for Question #2 unlss Mother Nature fills out an application we have to go with what we have


LOL!!! Guess you're right about that!
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2157. K8eCane
on a side note good evening everybody
tropics heating up so i decided i better pay yall a visit since this blog keeps me informed very well
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Quoting Rodek:
I usually lurk but post on rare occasions. I wanted to take a second to thank everyone for keeping the information flowing throughout the day and night on this blog. Without you, I'd be bored and ill-informed.

Now, a couple of questions.

How old are the models that are used to attempt to predict possible storm tracks?

Also, are there plans for new, more accurate systems in the future?

Some of the models, like GFS, have been our primary operational model for more than 5 years, but are constantly undergoing tweaks.
HWRF is one big tweak waiting to happen, as well.

There have been some new models, especially by the Japanese mets, that have been able to competently simulate cyclogenesis, the track, and intensity of an observed TC. It will take years before research level technology is incorporated into our operational models. They must be numerically stable, reliably offer an skill improvement over more than one hurricane season, and other testing before they will be used.
That Japanese model, NICAM, is the most promising one I have seen lately.
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2153. K8eCane
Quoting atmoaggie:
The stormno forecast office, parked on the Orleans Ave canal:


ROFLMAO on that one for sure and i am darned glad my mouth wadnt full too!
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Hey everyone hows the evening going pretty pleasant here in Louisiana just went for an evening jog...I see 90L hasn't changed much in organization if anything i think its massive size is the inhibiting factor right now
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Member Since: March 19, 2009 Posts: 0 Comments: 1421
2150. aquak9
Quoting STORMT0P:
There will be a record deadly storm this year...in Sept...


not the real stormtop, notice the zero instead of the O in the T0P part
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2149. aquak9
Quoting KerryInNOLA:
No one really knows where 90l is going. Lots of speculatiion and bias, but thats it.


What happened to "WE KNOW EVERYTHING"??
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2147. KEEPEROFTHEGATE (Mod)
Quoting atmoaggie:
KOTG,

Am I looking those right?

BAMD vs BAMS and former td-2 get further north with BAMS (as opposed to BAMD), but 90L gets further north with BAMD (which makes perfect sense)?

Why would the 2 systems so close to one another have such divergent BAMS and BAMD runs...as in the general behavior?
thats what ya call a model clitch it will work itself out with future runs

models are meant to be used as guidance only and do not depict final outcome for any one event

things can and will change
Member Since: July 15, 2006 Posts: 174 Comments: 54398
LMAO! I'm glad I didn't have a drink in my mouth for I would have surely fried my mac. My husband asked if that was stormno's "real" office. LOL!
Quoting atmoaggie:
The stormno forecast office, parked on the Orleans Ave canal:
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2144. IMA
Now y'all be sure and heed that special weather statement! I'm sure glad you don't have to have any grammar or spelling skills to issue those or we might not have that valuable info. Of course, tonight's is so much better than yesterday's that I have to wonder if someone has hacked stormtops, uhm, I mean stormno's computer!

{Ima's goin' back into hiding again now, but those of you who know me know that I couldn't let that go for a second day w/out the smart-alec in me gaining control of the keyboard)
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2142. KEEPEROFTHEGATE (Mod)
that there be the flush model DM21
Member Since: July 15, 2006 Posts: 174 Comments: 54398
Quoting Rodek:
I usually lurk but post on rare occasions. I wanted to take a second to thank everyone for keeping the information flowing throughout the day and night on this blog. Without you, I'd be bored and ill-informed.

Now, a couple of questions.

How old are the models that are used to attempt to predict possible storm tracks?

Also, are there plans for new, more accurate systems in the future?
As for Question #2 unlss Mother Nature fills out an application we have to go with what we have
KOTG,

Am I looking those right?

BAMD vs BAMS and former td-2 get further north with BAMS (as opposed to BAMD), but 90L gets further north with BAMD (which makes perfect sense)?

Why would the 2 systems so close to one another have such divergent BAMS and BAMD runs...as in the general behavior?
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Hello! just dropped in. what going on? Big flare up around hispaniola.
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Quoting atmoaggie:
The stormno forecast office, parked on the Orleans Ave canal:


LOL!
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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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