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

By: Dr. Jeff Masters , 2:02 PM GMT en Agosto 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 jasoniscoolman10:
WHAT HAPPERN TO 90LNOW ITS 03L WHY??
Don't worry, it's a TD now.
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4833. jipmg
well im going to take a nap, a little tired
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You know, I understand that Ana and TD3 are interesting CV storms...

But wow, they're still days away from affecting anything...

I would like to see a focus on what the GoM blob is doing. P451 posted a floater-type image of it some posts back and it is firing up.

Models are not developing it, so that's why it is not going to develop? Are you kidding me?

Since when did a developing TC need model support in order to come around?

What's stopping this thing right now? Shear? SSTs? Some other unfavorable condition? What?

If there are no unfavorable conditions, why doesn't it develop into something very very bad?
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Quoting HurricaneKyle:
Anyone that calls 90L a fish or a US landfall this far out doesn't have a clue what they are talking about.
With Current model support everyone is calling it a fish, come on, its not been classified as a TD yet, and its over 3000 miles away from us in Miami, wait till' it gets to the Leeward Islands, then we talk track.
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4830. jpsb
Quoting jipmg:


some models are picking up on it, and pressures are falling, heck CMC turns it into a storm in the eastern gulf
hmmm, well we sure could use a good hard rain here in Galveston County, but after Ike a real storm would be very bad news. Thanks for the info, I will try to keep an eye one that blob.
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4829. ackee
90L does look that organize maybe NHC will wait a while before may it TD#3
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Quoting canesrule1:
wow, but Ana isn't worrying me I think 03L might do a much larger effect, what r chanced of that hitting me here in SFLA?the models does not go that far yet, it depends how big it is. a high is predicted to get stronger to the nw of it and if invest 3 gets stronger then it is influenced more by the upper level winds than if it stays weaker. i would get ready now to be the rush if either comes your way. ana could get stronger in a few days. dont overlook the closer one, there is still a few days between ana and invest 3.
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Back later
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4826. RM706
Quoting extreme236:


Ana needs to go back to the dmax store and get some more clothes...


LOL
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Tropical Depression 3


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Who thinks TD3 will form by 11am?
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4823. jipmg
guys dont trust the models for TD3 until its become a tropical storm/drepression officialy so that the models get the data for a more accurate prediction
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Masters is probably waiting until after 11 to update his blog.
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Quoting jasoniscoolman10:
WHAT HAPPERN TO 90LNOW ITS 03L WHY??


Again I repeat, 90L has been upgraded to TD3 on the navy site and on the model runs.
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Quoting jasoniscoolman10:
WHAT HAPPERN TO 90LNOW ITS 03L WHY??


TD
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Quoting Stormchaser2007:


Ana needs to go back to the dmax store and get some more clothes...
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Quoting Tazmanian:
4800 commets


olny 100 more too go


dang! 4800 comets? you talkin bout the oort cloud right?

:D
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Quoting Stormchaser2007:
Anas exposed yet again.



Yup lol.
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Quoting WeatherStudent:


Geeze, why did they upgarde it then. RIP. Ana, your giving the NHC a bad name here.
Rip Ana, are u insane???? This has a rather high possibility of affecting us here in SFLA as a possible Cat 1 and u r saying Rip ana, WTF?
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Quoting stormsurge39:
Aussie that might be ANA going in GOM. Look to the right and see what looks like Bill recurving to NE. The models look like there putting Ana in the GOM. I think its going to hang on and blow up in the GOM. Just a guess. What do i know? LOL

That's what I am not liking about it. It did occur to me it was Ana and Bill
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Anyone that calls 90L a fish or a US landfall this far out doesn't have a clue what they are talking about.
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It is just too eary to tell with these systems. The general trend of these systems is to follow the disturbance that is under the Keys right now. The speed of the systems and weakening of the ridge that is forecasted to occur will be the deciding factors.
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Quoting IpswichWeatherCenter:


Don't ask - in my 3 or 4 seasons of being here, I never understood it. (under various not used handles)


we're talking about the "crow" deal - what gives?

do a brother a favor and kindly explain haha!

what is crow? why do people have crow served? lol is it tasty?
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4809. fire635
Quoting AussieStorm:

OMG. look at the size of it compared to Ana and TD3


If you recall... TD3 was that large before it came off... I wouldnt be too too concerned
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.
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Quoting AussieStorm:


What's that developing in the GOM?


One that run of the cmc it takes Ana in the gulf.
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Quoting WeatherStudent:


Geeze, why did they upgarde it then. RIP. Ana, your giving the NHC a bad name here.


They upgraded it because the data at that time warranted it. Systems can come and go very quickly. Remember Kyle from some years ago that lasted no more than a day or so ?.

The NHC calls it as they consider appropriate given all the data available to them which includes a lot we do not have ready access to.
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Anas exposed yet again.

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Aussie that might be ANA going in GOM. Look to the right and see what looks like Bill recurving to NE. The models look like there putting Ana in the GOM. I think its going to hang on and blow up in the GOM. Just a guess. What do i know? LOL
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4802. jipmg
yea you cant say RIP until the swirl completely dies out, I think we all learned that when our TD 2 died off and came back as Tropical storm Ana
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Quoting mossyhead:

looking at the discussion on ana, they are calling for ana to weaken a little, so a longer westward track could take place before it turns wnw. if ana does not weaken, then it could turn wnw quicker. it also depends how strong the ull to the west is and how fast it moves away from ana. a lot of variables to hapeen.
wow, but Ana isn't worrying me I think 03L might do a much larger effect, what r chanced of that hitting me here in SFLA?
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Quoting jipmg:


some models are picking up on it, and pressures are falling, heck CMC turns it into a storm in the eastern gulf
No sir. I believe what you are seeing in the models, as someone just mentioned is the CMC driving whatever is left of Ana into the gulf.
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.
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Quoting WeatherStudent:


Geeze, why did they upgarde it then. RIP. Ana, your giving the NHC a bad name here.


Omg I give up. There is no RIP. NHC has favorable conditions throughout the forecast period it could just be a fluctuation in the organization aided by the drier air.
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Quoting ackee:
Do u guys think TS watch will be issue for the leeward Island at 11pm ?


possible, if ana remains as it is
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Don't mean to be rude or of an annoyance but what about that blob in the Floridian straits going to the GOM? That concerns me more than the African wave that just came.
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4579 JRRP:
yes
TD3
Link


I clicked your link and got this
This Connection is Untrusted
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Quoting jipmg:
GFS was turning that wave into a storm and hurricane rapidly and right behind TD 3
wow!
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4793. rxse7en
Quoting jipmg:
I feel a tropical depression ana coming in at 11..
There are meds for that.
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4792. ackee
Do u guys think TS watch will be issue for the leeward Island at 11pm ?
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4791. jipmg
Quoting jpsb:
At while back Ike posted a link of a blob in the Keys. Sure looked like something tropical to me. Then he REMOVED the link! What's up with that blob? I get worried about tropical things in the GoM since I live right on Galveston bay. thanks in advance.


some models are picking up on it, and pressures are falling, heck CMC turns it into a storm in the eastern gulf
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Quoting CaneWarning:
Well, if I had to guess, I would say TD3 would roughly follow the same track as Ana.


They all will

Ana is following the tropical wave near Florida right now.

All are embedded within this flow that takes everything west northwest.
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Quoting canesrule1:
So i see we have T.S Ana, wow!, which might be a threat to SFLA. and 03L is there still the possibility of a SFLA hit?

looking at the discussion on ana, they are calling for ana to weaken a little, so a longer westward track could take place before it turns wnw. if ana does not weaken, then it could turn wnw quicker. it also depends how strong the ull to the west is and how fast it moves away from ana. a lot of variables to hapeen.
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Quoting CaneWarning:
Well, if I had to guess, I would say TD3 would roughly follow the same track as Ana.
I agree but then I would be screwed here in Miami.
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4785. jpsb
At while back Ike posted a link of a blob in the Keys. Sure looked like something tropical to me. Then he REMOVED the link! What's up with that blob? I get worried about tropical things in the GoM since I live right on Galveston bay. thanks in advance.
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4784. jipmg
GFS was turning that wave into a storm and hurricane rapidly and right behind TD 3
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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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