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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Quoting rwdobson:
The thing is, small differences in the track now (compared to the models) then lead to large differences in the track later. I mean, we don't even know where the center of 90L will be when/if it becomes a TD or TS.


Exactly, a 100 mile difference now can mean a 500 mile difference down the road. Or, just far / close enough to a trough that will re-curve it. The possibilities are in the hundreds of thousands right now.
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Quoting TampaSpin:


Probably going to be to close to each other i would think.......the outflow from 90L will shear anything that close i would think.


By the time the wave would leave the coast 90L is forecast to have cleared -40W in the CATL, which would be a bigger seperation between the two than what 90L currently is from TD2 (and none seem to be interacting with each other as far as wind shear goes). Although GFS isn't nearly as aggressive with that wave as with 90L.
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Quoting Chicklit:
You cannot have it 'your way' here.
Or should I say, "ur?"


YOUR pretty smart chicklit...:-)

heh heh, your for you're is one of my favorite internet typos.

although "no thrat" from yesterday made me laugh too.
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Quoting FloridaTigers:


Yeah, I'm done with JFster. I'm ignoring him now. Its obvious he's now purposely misspelling his posts. Its almost troll-ish.


WHO cares????? Gezzzz all of the remarks is pretty troll-ish...
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1183. KEEPEROFTHEGATE (Mod)
Quoting TerraNova:
A TCFA how now been issued.

WTNT02 KNGU 131900
SUBJ/TROPICAL CYCLONE FORMATION ALERT 131900Z AUG 09//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 11.7N 23.3W TO 12.9N 30.1W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT IM-
AGERY AT 131800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 11.7N 23.3W. THE SYSTEM IS MOVING WESTWARD AT 8 TO 13 KNOTS.
2. REMARKS:
A. SEA SURFACE TEMPERATURES ARE RANGING FROM 24 TO 27 DEGREES
CELSIUS ACROSS THE TROPICAL ATLANTIC. UPPER LEVEL WINDS OVER THE
SYSTEM ARE EASTERLY 20 TO 25 KTS. HOWEVER WINDS ARE DECREASING
WEST OF THE WAVE. AS THE WAVE CONTINUES TO TRACK TO THE WEST,
ENVIRONMENTAL CONDITIONS BECOME MORE CONDUCIVE FOR DEVELOPMENT
.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED
BY 141900Z.//

i see ya found the best info next to NHC there TN
Member Since: July 15, 2006 Posts: 178 Comments: 56007


1090. Prgal 7:45 PM GMT on August 13, 2009
1107. seminolesfan 7:48 PM GMT on August 13, 2009


Not sure where you get ten min from Tampa. Where did you learn subtraction?
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1181. Prgal
Quoting seminolesfan:
Your engrish is fine. The models are usually pretty good for 72hrs, then ok for longwave patterns out to about five days, but progressively getting poorer from the 3 day mark on. After five days it's very questionable output.


Alright! So that means that by Sunday we should have a high probability that whatever the models are showing at the moments is right. I shouldnt be so worried today...just wait until Saturday or Sunday. Thank you!
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The thing is, small differences in the track now (compared to the models) then lead to large differences in the track later. I mean, we don't even know where the center of 90L will be when/if it becomes a TD or TS.
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Quoting Orcasystems:

Or the blog just east of Cuba



I resemble that remark
CRS
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting fire635:


REALLY!?? Just once PLEASE... I want to see you type T H E In a row. That would be the word THE

You'll drive yourself crazy with that.
Just pretend it isn't happening.
I'm a certified English teacher and blog.
You cannot have it 'your way' here.
Or should I say, "ur?"
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1177. Patrap
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Quoting Drakoen:


Good post


Thanks Drak, I appreciate that.
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Quoting TerraNova:


That blob over Africa is going to be another one to watch; both GFS and ECMWF have been showing a second system developing out behind 90L toward the middle of next week. The Caribbean/N of Hispaniola wave may merit watching when it moves into the Gulf and hence better conditions...


Probably going to be to close to each other i would think.......the outflow from 90L will shear anything that close i would think.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1174. Patrap
Earth Full Disk Atlantic 2Sept 08

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1173. trey33
Quoting Orcasystems:
I am suprised... no mention of what is following 90L

Fox National mentioned it at noon - nothing mentioned on TWC, or local Tampa weather (note to Paul).
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i agree terra....any surfer in the GOM or eastcoaster for sure ...fix your dings and wax that board...looks like we are going to get a swell for sure......
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Quoting canesrule1:
Hey guys the curve all u people keep talking about was stated on the news as "highly unlikely" so i wouldn't be saying that SFLA is out of the picture.


That's what happens when you dissect every model run for an undeveloped system that is 5 days or more from the islands and over a week away from the states. It's like a boat rocking back and forth. I think some enjoy it.
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Quoting Orcasystems:
I am suprised... no mention of what is following 90L



Or the blog just east of Cuba



everyone is preoccupied w/ the td2 & 90l, but it looks like the next wave behind 90l has just as good of a chance to develop (if not better)as the aforementioned disturbances
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Quoting Prgal:


Hmm, maybe its my english Tampa, no worries. Let me try to rephrase it. The models are more accurate for 1 day...2 days? 90L is about 7 days away from PR...but how accurate is that (considering that I am aware that it might change due to other conditions in the atmosphere). How far in time can the models be trusted?
Your engrish is fine. The models are usually pretty good for 72hrs, then ok for longwave patterns out to about five days, but progressively getting poorer from the 3 day mark on. After five days it's very questionable output.
Member Since: Posts: Comments:
1168. Patrap



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Quoting Orcasystems:
I am suprised... no mention of what is following 90L



Or the blog just east of Cuba




That blob over Africa is going to be another one to watch; both GFS and ECMWF have been showing a second system developing out behind 90L toward the middle of next week. The Caribbean/N of Hispaniola wave may merit watching when it moves into the Gulf and hence better conditions...
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btwntx - I don't see a disclaimer from him. I actually just "hid" him for now, but if I don't feel like reading someone cursing other posters because they simply disagree I'd say that's my prerogative. Trolls typically use "like" handles. I will give him that someone may have hacked him, but it wasn't a troll.
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Link I just finished my expert anlysis on td2 and 90l blog.This is the link to my blog.
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Quoting KEEPEROFTHEGATE:
T.C.F.A.



90L/XX/X3X
MARK
11.7N/23.3W


We knew this was coming...
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Quoting seminolesfan:
I may not always be the sharpest knife, but I did deduce:
1)from PR
2)not male

(j/k :p Tampa)


I see as Nole you figured that out after studing it for 10mintues...LOL....SORRY i had to do that.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
lol..sorry seminolesfan
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1161. Prgal
Quoting TampaSpin:


In my best Opininon....the steering flow with the highs are not going to change to much over the next 3-4 days....after that its hard to tell......it could go north of you or it could go south and it could go straight over you.....watch the next 4 days and by then you will have at least a window to see where it might be moving.


Good advice! Thank you TampaSpin!
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Quoting WeatherStudent:
hey tehre, timster.


ehllo WSster how rae yuo todae? Watt do yuo thikn aboot htis stmor? Is hte hting gonig two nrut?
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1158. Patrap
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I am suprised... no mention of what is following 90L



Or the blog just east of Cuba


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A TCFA how now been issued.

WTNT02 KNGU 131900
SUBJ/TROPICAL CYCLONE FORMATION ALERT 131900Z AUG 09//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 11.7N 23.3W TO 12.9N 30.1W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT IM-
AGERY AT 131800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 11.7N 23.3W. THE SYSTEM IS MOVING WESTWARD AT 8 TO 13 KNOTS.
2. REMARKS:
A. SEA SURFACE TEMPERATURES ARE RANGING FROM 24 TO 27 DEGREES
CELSIUS ACROSS THE TROPICAL ATLANTIC. UPPER LEVEL WINDS OVER THE
SYSTEM ARE EASTERLY 20 TO 25 KTS. HOWEVER WINDS ARE DECREASING
WEST OF THE WAVE. AS THE WAVE CONTINUES TO TRACK TO THE WEST,
ENVIRONMENTAL CONDITIONS BECOME MORE CONDUCIVE FOR DEVELOPMENT
.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED
BY 141900Z.//

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1155. trey33
Quoting StormBeast:
jasoniscoolman10,

Now perhaps you just had a bad day at your law firm.

.. just let's get back to being the REAL, TRUE, Jason... that so transparently is you.


Hey.... no lawyer bashing! lol
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it looks like a good size of ocean swell is going to 'hit' the Islands & East Coast...no matter how direct of an impact either of the potential disturbances provide..
Link
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Quoting Nolehead:
HEAD ON....."Apply directly to the forhead"
Now why did you have to go and do THAT?!? If that is stuck in my head all afternooon...
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1152. KEEPEROFTHEGATE (Mod)
T.C.F.A.



90L/XX/X3X
MARK
11.7N/23.3W
Member Since: July 15, 2006 Posts: 178 Comments: 56007
1151. Drakoen
Quoting TerraNova:
12z GFS has this system nearing the Leewards in the Wednesday-Thursday timeframe, however, it may just as well miss these islands entirely if a trof off the East coast begins to pull it northward before then (12z ECMWF). Both are good possiblities, but my honest opinion is that this will threaten a landmass whether it be an island or a continent) somewhere down the road. Too far out to tell exactly where.


Good post
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Quoting Prgal:


Hmm, maybe its my english Tampa, no worries. Let me try to rephrase it. The models are more accurate for 1 day...2 days? 90L is about 7 days away from PR...but how accurate is that (considering that I am aware that it might change due to other conditions in the atmosphere). How far in time can the models be trusted?


In my best Opininon....the steering flow with the highs are not going to change to much over the next 3-4 days....after that its hard to tell......it could go north of you or it could go south and it could go straight over you.....watch the next 4 days and by then you will have at least a window to see where it might be moving.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Member Since: Posts: Comments:
1148. Prgal
Quoting rwdobson:


The accuracy of an NHC forecast at 5 days out is +/- 300 miles. This is as good a forecast as you can get, because it includes all models plus expert human interpretation.

So if you're talking about only 1 model, no human interpretation, and more than 5 days, you can see that the "cone of uncertainty" is absolutely huge.


Thanks! That was what I was looking for. Thanks to the other guys as well.
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1147. slavp
Quoting WeatherStudent:


yup, as well as a direct conus hit
Well, It stands to reason, if it develops, that it will do one or the other
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Yes, 18 years.
Quoting CaneWarning:


Is that the one that was missing for the past 15-20 years?
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Quoting StormBeast:
jasoniscoolman10,

I must tell you that am SHOCKED by such immature, and poor grammatical posting. If one were to guess anything about you, based on the pic you provided.. it would say "Jason clearly has his life together. He is well educated, and doesn't live in his mother's trailer" Now perhaps you just had a bad day at your law firm, or your trophy wife overspent on your black AMEX card....

.. just let's get back to being the REAL, TRUE, Jason... that so transparently is you.


Damn! lol
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What is with the blob above Hispaniola? www.ssd.noaa.gov/goes/east/tatl/loop-rb.html
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Good afternoon. Just a quick stop in for now.

The Navy site has the coordinates for TD2 at .2 degrees further North than earlier today. Previously it had been running pretty much straight due West along the 14 degree N lat. line but visible loop imagery confirms that it has now lifetd N of that position.

I suspect that the reason for this is that the low level steering that is controlling the system has pulled up to the North a bit and the flow to the WSW has now eased off some.

This is allowing TD2 to pull up on a course that is probably around 280 degrees ( with due West being 270). By tonight we will have a good sense of whether that estimate is more or less correct. It is too early to say if this means it is headed out to the N Atl. or simply on a track to the N of the Islands.

I still do not think it will enter the Caribbean but time will tell about that.

In the mean time 90L has flattened out some from 280 degrees this morning to 275 or just barely N of due West. The NHC consider this a W heading.

Here is the current steering flow showing how the winds have relaxed above TD2
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1141. Prgal
Quoting seminolesfan:
I may not always be the sharpest knife, but I did deduce:
1)from PR
2)not male

(j/k :p Tampa)

LOL! You are quite right! ;-)
Member Since: Posts: Comments:
TD2 seems to be trying to moisten its environment and get some of the dry air out of the way. Moreover, it is tapping some moisture from 90L, to its SE.

However, TD2 still has a long way to go before it can survive this environment. Tonight will be important cause it needs to take advantage of DMAX if it is going to strengthen.
Member Since: July 6, 2005 Posts: 5 Comments: 580
CIMSS wind shear shows an anticyclone developing to the north of the system. Models have it expanding over 90L and providing ventilation.

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Quoting Vortex95:
Guys he is doing it on purpose now best to not respond.


Yeah, I'm done with JFster. I'm ignoring him now. Its obvious he's now purposely misspelling his posts. Its almost troll-ish.
Member Since: May 17, 2009 Posts: 0 Comments: 559
Expect possible missing/delayed satellite images. GOES east station keeping maneuver.

On Thursday, August 13, the following exclusive schedule will be
employed to support maneuver operations: (*PLEASE NOTE the scheduled
GOES-11 (GOES-West) Full Disk scan period to support the primary
GOES-12
(GOES-East) outage during the maneuver.*)

GOES-12 (GOES-East) Maneuver Schedule starts at 1905 UTC on Thursday,
August 13, 2009.
(Southern Hemisphere Scan at 1909 UTC is canceled)

>From 13/1915 UTC through 14/0059 UTC -- GOES-12 (GOES-East) Routine
Imaging and Soundings.

*From 14/0100 UTC through 14/0214 UTC -- No GOES-12 (GOES-East) Imaging
or Soundings*

**From 14/0100 UTC through 14/0229 UTC -- GOES-11 (GOES-West) Full Disk
Imaging**

>From 14/0215 UTC through 14/0914 UTC -- GOES-12 (GOES-East) Post
Maneuver Recovery Including (updated for KOZ interference):
* Full Disk Images (19 minute scan) at XX15 and XX45
* CONUS Soundings at XX46
* 0415, 0445, 0515 & 0545 Short Full Disk Images will be canceled.
* The following images have been scheduled in place of the Short Full
Disk Images:
- 0445 - Northern Hemisphere Extended Image
- 0456 - CONUS image
- 0515 - CONUS image
- 0522 - CONUS image
- 0545 - CONUS image
- 0556 - CONUS image

0915 UTC August 14 -- GOES-12 (GOES-East) Routine Scan Operations
Resume

Expect GOES-12 (GOES-East) imager and sounder gridding offsets for
up to
6 hours following the maneuver.



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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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