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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5434. IKE
TD3 keeps going WSW, maybe South America feels it.

Ana looks terrible.
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Quoting hurricanelover236:
Is everyone with me that florida is 100 percent in the clear right now? Like I said, much ado about nothing. Ana a gulf storm that hits the islands and fizzles. And td 3 if it forms will head out to sea.


ummmmm... no
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called my mom in p'cola yesterday to see if she had seen anything about the wave over the keys; she said that the local mets had mentioned nothing of it. Although I do not think it become anything crazy, I do think it could be a td or so and cause lots of rain. If one of the other storms do get in the gulf, good luck keeping those trees up after a td soaking loosens up that soil.
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GOM is in trouble
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5430. ackee
Quoting Funkadelic:
On this visible you can really see TD3 moving WSW. What if he takes a nose dive lol..


Link
agree wonder how long it will continue move WSW
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5429. jipmg
Quoting Vortex95:


Still seems due west


it was moving WSW a moment ago, seems to be moving just south of due west now, if not due west.. the forecast was for it to move WSW for 6 hours then move W to WNW
5415. IKE 3:28 PM GMT on August 15, 2009
GOM system looks invest worthy.



Ike i agree...GOM is way too hot....
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Quoting foggymyst:
Orca, I saw you forecast picture.. not good. Will Ana open the path for a stronger "Bill"?


That would be a safe assumption... and you live a little to close to Zoo...
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5425. sfla82
Now with these two looking more and more like they wont come my way I will now have to watch what is coming off the African coast!
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Quoting robie1conobie:
I agree with you in terms of these storms, but overall hurricane capital of the world? I think the folks in west pacific may have a tough time swallowing that.


That depends if you are talking Country or State. If you are comparing to the W. Pacific then you have to use the USA as a whole. I am sure someone on here knows the most likely country to be hit.
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guys dont ues the word fish in tell TD 3 gets too 50W
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Is everyone with me that florida is 100 percent in the clear right now? Like I said, much ado about nothing. Ana a gulf storm that hits the islands and fizzles. And td 3 if it forms will head out to sea.
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Quoting Chiggy007:
Kyle:

Yes Models are in good agreement but to me TD3 is barely a TD; I have seen much beter looking TDs before - this one has still has a broad circualtion moving WSW, center of which I make to be at 11.2N - 34.5W at the moment!
Just my opinion, ofcousre, but intesinty 3-5 days out is overdone - greatly may I add...!! We shall see...


Satellite estimates indicate its almost a TS already. Its not overdone, if anything it could be underdone if the conditions are as favorable as the HWRF shows it.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting HurricaneKyle:
Where is Jeff's new post.. its almost noon.


boarding up......lol..j/k
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So here it is. We are all waiting to see to outcome of the dance of the ts and trough.
Ana fast or trough slow, then Ana south of MIA.
Ana slow or trough fast, then Ana misses FL entirely.
Trough weakens...(likely) prob FL somewhere and a recurve...(with very little chance of emerging into GoM.)

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5418. Seastep
Quoting BiloxiGirl:
What prevents the keys area from becoming an invest?


No convergence.
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Quoting BiloxiGirl:
What prevents the keys area from becoming an invest?


A couple of margarita's and a shot of Jager
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5415. IKE
GOM system looks invest worthy.
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Quoting HurricaneKyle:
Where is Jeff's new post.. its almost noon.


He's got A LOT to update, lol.
5412. jpsb
Quoting philliesrock:
Don't forget about the thing near the Florida Keys right now! That has potential to be a sleeper storm that catches us all by surprise.
I am watching that one. We really need the rain in Texas, hoping nothing develops but a big Texas rain maker.
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Kyle:

Yes Models are in good agreement but to me TD3 is barely a TD; I have seen much beter looking TDs before - this one has still has a broad circualtion moving WSW, center of which I make to be at 11.2N - 34.5W at the moment!
Just my opinion, ofcousre, but intesinty 3-5 days out is overdone - greatly may I add...!! We shall see...
there is a live chat available on the xtremehurricanes.com live hurricane webcam page, but no one uses it...so very private
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5409. sfla82
Good morning all! Just logged on and again its looking better for us here in S Fla! I know we are in the middle of the bullseye with Ana, but thats a good thing because it keeps shifting futher south so she shouldnt be an issue. Plus its only forecasted to be a Tropical storm if it comes this way which it wont. And IMO it looks more and more that TD3 which will be stronger will be a fish for sure. I think Bermuda will have to deal with it but overall a fish! We just keep dodging them down here in S. Fla!!!!
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Wow the wave over Africa looks as big as T.D. 3!
What prevents the keys area from becoming an invest?
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Where is Jeff's new post.. its almost noon.
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Quoting atmoaggie:

Nice control. Many here would have blow up on that police guy at some point.
Thanks Aggie, But I don't lose my control with people here. I just say what I need to say and move on. What I said was more to the truth than what he said. Polls are worthless. If I get banned. Ohh Well. But I will never lose control. I'm way too much above that...LOL
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Orca, I saw you forecast picture.. not good. Will Ana open the path for a stronger "Bill"?
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Quoting FreelanceHistorian:
Wow, sleep in late and look what happens!

So, the "dead" TD2 came back with a roar and is now Ana? Invest 90L is still Invest 90L, but the wave behind it ramped up last night and grabbed the TD3 moniker before 90L could?

Boy, gonna need a scorecard here soon...


90L is TD3....
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Quoting FreelanceHistorian:
Wow, sleep in late and look what happens!

So, the "dead" TD2 came back with a roar and is now Ana? Invest 90L is still Invest 90L, but the wave behind it ramped up last night and grabbed the TD3 moniker before 90L could?

Boy, gonna need a scorecard here soon...


No Invest 90L is now TD3. Wave behind 90L/TD3 hasn't been designated an invest or TD yet.
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5399. Seastep
Quoting HurricaneKyle:


NHC seems to agree with the models though, 90 kts at the end of the period, and they've brought TD3 to Hurricane status/ Major all week. So it's pretty probable that it will end up being one.


NHC actually puts it at 77% for hurricane by 120hrs. 68% by 96.
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Quoting jipmg:
you guys know our large TD3 is moving a bit faster than ANA right


By one mph
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5397. jipmg
you guys know our large TD3 is moving a bit faster than ANA right
It's going to take some deep trough to haul this TD3 to WNW and to NW - Do anyone this through coming? Models are in good agreement though!!
I'm surprised people aren't using the tropics chat utility in the information box above where you would type a comment. Usually when the blog is this busy the live chat is pretty useful.
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Are there any trofs or weakening in the high that allows for Ana to recurve?
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NHC notes there still north of the guidance with ana which in my view means more southern shifts to the track are forth coming.Again iam not so sure ana will ever develope into anything significant based on shear/dry air in the vicinity noted on water vapor loops which as the nhc noted has been badly forcased by some large scale models.You never know TD3 may also run into the same issue as it tracks along.
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models are suggesting that a wave located in the Indian ocean will cross all of Africa and as soon as it enters the Atlantic will become a TC
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Quoting Chiggy007:
Some of the models take TD3 so far north is that the also develop it into a Cat 2/3 hurricane!! My feeling is that TD3/Bill will be no where near that strength -
Strangely enough lot of the models have been in agreement for over a day now but they have been wrong with TD currently moving WSW - one can clearly see that on the NHC Sat loops....


NHC seems to agree with the models though, 90 kts at the end of the period, and they've brought TD3 to Hurricane status/ Major all week. So it's pretty probable that it will end up being one.
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Quoting ALCoastGambler:
LOL

Nice control. Many here would have blow up on that police guy at some point.
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Quoting tharpgomex:
Mobilegirl...please don't mention Ivan! That was a rough storm to ride through.

Sorry, just trying to make a comparison to get a bead on TD3
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Quoting Drakoen:
GFS shows the Africa wave developing almost immediately after coming off the coast.


Start to emerge now.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Don't forget about the thing near the Florida Keys right now! That has potential to be a sleeper storm that catches us all by surprise.
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Quoting AussieStorm:

Where?


Under Community Chat on the left side of the page.

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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.