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 WeatherStudent:



Adrian, both of these features are gonna fizzle out and that's final. Very A typical of an El Nino Hurricane Season.


Hmm can't believe I've waited this long to say this, but time to put ya on ignore. Too much flip flopping around.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5482. IKE
Quoting tharpgomex:
what I'm worried about in the Florida Panhandle.. this wave dumping a lot of rain on us.... and then what might come with Ana or future Bill


Same here...
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Quoting Vortex95:


That dry air patch has been following it since the begining.


Theres an ull just northwest of tiny ana produing southwesterly shear and combined with some dry air iam just not sure ana will survive.Models have done a poor job forcasting upper conditions.
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If Dr. Masters doesn't take a bit of time on his busy schedule to update his blog soon the post here will reach the 200 mark.
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Extreme:

HWRF intensity predictions have never materialized!! Of course I cannot remember every storm but just last year it had IKE at 170mph in the Gulf, and one time over Miami too...IKE was barely a Cat 2!
Of course HWRF mey get it right once in a while but I for one DO NOT believe its intensity guidance!
Look at TD3 right now - not much deep convection anywhere espacially at its center!!
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Quoting WeatherStudent:



Adrian, both of these features are gonna fizzle out and that's final. Very A typical of an El Nino Hurricane Season.


???
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5477. jpsb
Hurricanes are only in the Atlantic basin and E. Pacific. So, S. Fla would definiately be in the running for Hurricane Capital of the world. Personally I think the Keys would beat ya, but I don't have any figures to back that up.
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Quoting Seastep:


Yes it is. Wilma ate something if I remember.
Wilma ate alpha
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Quoting TexasHurricane:
Anyone have a link to the GOM? Please....

I don't think the GOM has web servers.
If it did, the link would be in my blog with all of my other favorite tropical/severe links.
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5473. Melagoo
Ana looks like Jack and TD3 looks like the Giant from the bean stalk
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It looks like the ensemble models still take TD3 away from Florida.
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5469. Seastep
Quoting sopla2o:


Is that even possible, that TD3 takes over Ana...


Yes it is. Wilma ate something if I remember.
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5468. sfla82
Quoting superweatherman:



GOM is in trouble


I agree! Everyone keeps saying S Fla...Nope!!! Its the GOM's storm!
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NHC shows 03L continuing W/WSW through tomorrow.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5465. CJ5
This could be some concern later:


Link
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5464. sopla2o
Quoting MrSea:


highly unlikey, they are both their own circulations


Is that even possible, that TD3 takes over Ana...
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Thanks extreme236. With this activity of storms, it seems anything can happen.
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5462. ackee
I just think the longer TD#3 move WSW less chance this will be NE Carbb system
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5461. KBH
Quoting btwntx08:

90L IS now td 3

Is it possible that these three systems will be interacting with each other, for better or worst..
I am guessing where one goes the others will follow.
and the add one more system to the fray, look behind the wave exiting Africa, another system in a few days
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5460. KEEPEROFTHEGATE (Mod)
Quoting HurricaneKyle:
Where is Jeff's new post.. its almost noon.
be here when he is good and ready lots to talk about putting it all together takes some time sometimes
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5459. jipmg
Quoting P451:


I don't know...but it seems to be south of west.



thats the forecast
Quoting IKE:
TD3 keeps going WSW, maybe South America feels it.

Ana looks terrible.


Take a glance @ this water vapor image note the large patches of dry air across the tropical atlantic.

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Anyone have a link to the GOM? Please....
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Quoting philliesrock:

Almost no chance for South America to affect TD3. The weakness in the ridge will eventually pull it WNW.


LOL... r u sure, I sure wouldnt mind it hitting Chavez's mansion in Venezuela
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Quoting Chiggy007:
Extreme:

HWRF intersity guidance has never materialized - always over cooking it - you know that!
TD3 will be barely a Hurricane before the Islands - my prediction! :)


Based on? The HWRF, SHIPS, and all of their basis is on 27-28C waters and light shear...once it gradually organizes and gets an inner core those conditions make it ripe steady intensification, especially when an eye forms. We've seen this time and again.

And if the HWRF was always wrong they wouldn't use it.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5453. Melagoo
Link

RBG shows awesome firing of the storm activity surrounding TD 3
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5452. MrSea
Quoting gbTracker:
Hey everyone. Could Bill eventually take over (absorb) Ana's energy and change track?


highly unlikey, they are both their own circulations
The key system is getting good spin.
Member Since: August 31, 2008 Posts: 0 Comments: 833
Quoting JupiterFL:


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.
Yeah I was quoting vortex who said hurricane capital of the world.
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If it pass GFDL path there will be nothing to weaken it... unless shear
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As for the GOM system...it has been really windy and rainy all day in S. Florida.
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what I'm worried about in the Florida Panhandle.. this wave dumping a lot of rain on us.... and then what might come with Ana or future Bill
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Quoting gbTracker:
Hey everyone. Could Bill eventually take over (absorb) Ana's energy and change track?


None of the models currently suggest this.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Extreme:

HWRF intersity guidance has never materialized - always over cooking it - you know that!
TD3 will be barely a Hurricane before the Islands - my prediction! :)
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Quoting IKE:
TD3 keeps going WSW, maybe South America feels it.

Ana looks terrible.

Almost no chance for South America to affect TD3. The weakness in the ridge will eventually pull it WNW.
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Gone for 2 hours and there are 20 more pages!!

If Ana goes toward the south of the cone it will be bad for both Hispaniola and Ana.
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12Z GFS coming out.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5439. IKE
Quoting Nolehead:
5415. IKE 3:28 PM GMT on August 15, 2009
GOM system looks invest worthy.



Ike i agree...GOM is way too hot....


Has more convection then Ah-nah.
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Hey everyone. Could Bill eventually take over (absorb) Ana's energy and change track?
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Quoting jpsb:
I am watching that one. We really need the rain in Texas, hoping nothing develops but a big Texas rain maker.


Uh no I'll just take frontal storms lest we incur 2001 all over again...
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Quoting extreme236:


By one mph

Within the possible measurement error of vortex fixes...even if we had HHunters in there.
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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...


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

Ana looks terrible.
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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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