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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5233. SoFla
I don't think I would call South Florida the safest place. That is a bit naive.
Member Since: Posts: Comments:
5232. ackee
Quoting wunderkidcayman:
guys I have a BAD feeling about TS ANA and TD 3 I think both will be caribbean systems kinda like dean and felix
I think TD#3 might be carrb system my view too
Member Since: July 15, 2008 Posts: 0 Comments: 1346
5231. CJ5
Quoting Drakoen:
Still posting advisories and track...


nothing changes here
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Quoting Weather456:


i edited my post, dead on track, not dead one


Woops, scratch my last post then I thought you were talking about land interaction.
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5228. centex
I'm going to stick with slow development and both systems and further south. Sometimes xtrap best forecast when status quo persisting.
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Right now if it continues its forward speed, this isn't going to go out to sea, 17 Mph is very fast.
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It looks like Florida could be hit by Ana and TD3.
The good thing is that there's about a week to prepare for these two storms.
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TD 3 on weather channel
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Quoting coffeecrusader:
Now that we have 2 Tropical systems. I am anxiously awaiting expert analysis from Dr. Masters and Storm W. Wake up guys!!

StormW doesn't post on weekends.
Member Since: September 30, 2007 Posts: 9 Comments: 15932
Quoting Funkadelic:


You think its dead?


A track that close to Hispaniola could have severe consequences on the circulation.
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Quoting Weather456:


I'm not riping anything, I was talking about the dead on forecast track of ana right over me.


Oh sorry...yeah..."dead on" track...gotcha! :)
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Quoting Funkadelic:


You think its dead?


i edited my post, dead on track, not dead one
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Quoting Weather456:


the big difference is though, 2007's ridge was a monster. Dean has the most consistent path of anything storm I ever track. It is unlikely TD 3 will follow.


i got your back 456

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5217. SoFla
Quoting SeniorPoppy:


Rather be in the center of the cone now. Look what happened with Ike last year. It just kept trending south until South Florida was out of the cone.


I completely agree.
Member Since: Posts: Comments:
TS Ana, another dead on track

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Quoting SeniorPoppy:
South Florida might be the safest place to be right now because any deviation will cause a recurve down the road or a more westerly track into Gulf. I am not a forecaster. I am just speculating.
Not at all.
That will show ya,a 800 mile difference from 00 Z GFS and the 6 Z (when that system was forecast to reach 30N).
About Destin for the 0 Z.


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Quoting mobilegirl81:

NHC keeps riding the curve westward.
Keep it up...Fl bound you are....LOL
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guys I have a BAD feeling about TS ANA and TD 3 I think both will be caribbean systems kinda like dean and felix
Member Since: Posts: Comments:
Funny that they posted a clarification on pronunciation of ANA in the headline for the fourteenth advisory. Reminds me of one of the discussions for Noel ("pronounced exactly like the word KNOLL") in 2007.

...ANA...PRONOUNCED AH-NA...MOVING QUICKLY WESTWARD WITH LITTLE
CHANGE IN STRENGTH...
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Quoting CycloneOz:
Hey 456...

Are you R.I.Ping Ana, or was that a sarcastic post? :)


I'm not riping anything, I was talking about the dead on forecast track of ana right over me.
Member Since: Posts: Comments:
Quoting Stormchaser2007:
The NHC brings TD3 to 90knots in 120 hours. It shows rather rapid strengthening.

72HR VT 18/1200Z 14.0N 50.5W 60 KT
96HR VT 19/1200Z 16.5N 57.0W 75 KT
120HR VT 20/1200Z 19.0N 63.0W 90 KT



Also in 2007 for TD4's first advisory.
72HR VT 16/1200Z 13.0N 51.0W 60 KT
96HR VT 17/1200Z 14.5N 57.5W 75 KT
120HR VT 18/1200Z 16.0N 63.5W 90 KT


Astonishing.
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5208. CJ5
Quoting WeatherStudent:


In a quick nutshell, Ana is dying, while TD3 is getting stronger.


"Ana is dying" is misinformation.
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456 what is crucial here is timing. TD3 is moving at a fast clip and would be in the islands sooner than was expected. the big quetion is will the trough be strong enough to cause that forecast weakness? then to create that turn
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5205. KBH
Quoting canesrule1:
Miami in the center:
Now I understand why FL is called bullseye!
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South Florida might be the safest place to be right now because any deviation will cause a recurve down the road or a more westerly track into Gulf. I am not a forecaster. I am just speculating.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
WTNT43 KNHC 151440
TCDAT3
TROPICAL DEPRESSION THREE DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 AM AST SAT AUG 15 2009

SATELLITE IMAGERY AND QUIKSCAT DATA INDICATE THAT THE BROAD AREA OF
LOW PRESSURE OVER THE EASTERN ATLANTIC HAS FORMED A WELL-DEFINED
CIRCULATION AND SUFFICIENTLY ORGANIZED CONVECTION TO BE DESIGNATED A
TROPICAL DEPRESSION. THE INITIAL INTENSITY IS 30 KT BASED ON THE
QUIKSCAT DATA...AS WELL AS SATELLITE INTENSITY ESTIMATES OF 30 AND
35 KT FROM SAB AND TAFB.

THE SYSTEM IS CONSOLIDATING SOUTH OF WHERE THE CENTER WAS BEING
TRACKED YESTERDAY...AND THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN
265/15. SOME ERRATIC MOTION IS POSSIBLE TODAY AS THE DEPRESSION
INTERACTS WITH THE ELONGATED MONSOON/TROPICAL WAVE CIRCULATION THAT
SPAWNED IT. OVERALL...DEEP-LAYER HIGH PRESSURE OVER THE CENTRAL
AND EASTERN ATLANTIC SHOULD STEER THE CYCLONE GENERALLY WESTWARD
FOR THE NEXT COUPLE OF DAYS...FOLLOWED BY A TURN TOWARD THE WEST-
NORTHWEST. THE TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT WITH
THIS SCENARIO.
..AND THERE IS A FAIRLY TIGHT CLUSTER OF THE MODELS
AROUND THE 5 DAY FORECAST POINT. ONE EXCEPTION IS THE ECMWF...
WHICH FORECASTS SIGNIFICANTLY MORE NORTHWARD MOTION THAN THE OTHER
MODELS AND AT THIS TIME IS A RIGHT OUTLIER.

THE CYCLONE IS IN DEEP-LAYER EASTERLY FLOW WITH LIGHT/MODERATE
VERTICAL WIND SHEAR FORECAST FOR AT LEAST THE NEXT 4 DAYS. ALL
INTENSITY GUIDANCE FORECASTS THE SYSTEM TO BECOME A HURRICANE BY
THE END OF THE FORECAST PERIOD
...WITH THE HWRF FORECASTING A MAJOR
HURRICANE. THE INTENSITY FORECAST THUS CALLS FOR GRADUAL
STRENGTHENING TO A TROPICAL STORM IN 12 HR AND A HURRICANE IN 72-96
HR IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 15/1500Z 11.5N 34.0W 30 KT
12HR VT 16/0000Z 11.3N 36.1W 35 KT
24HR VT 16/1200Z 11.3N 38.9W 40 KT
36HR VT 17/0000Z 11.8N 41.7W 45 KT
48HR VT 17/1200Z 12.4N 44.4W 50 KT
72HR VT 18/1200Z 14.0N 50.5W 60 KT
96HR VT 19/1200Z 16.5N 57.0W 75 KT
120HR VT 20/1200Z 19.0N 63.0W 90 KT


$$
FORECASTER BEVEN
Member Since: Posts: Comments:
5201. Drakoen
Still posting advisories and track...
Member Since: October 28, 2006 Posts: 57 Comments: 29886
5199. Relix
Quoting Drakoen:


Pull up the steering layers.


Are these the ones:



????
Member Since: Posts: Comments:
Now that we have 2 Tropical systems. I am anxiously awaiting expert analysis from Dr. Masters and Storm W. Wake up guys!!
Member Since: Posts: Comments:
The NHC brings TD3 to 90knots in 120 hours. It shows rather rapid strengthening.

72HR VT 18/1200Z 14.0N 50.5W 60 KT
96HR VT 19/1200Z 16.5N 57.0W 75 KT
120HR VT 20/1200Z 19.0N 63.0W 90 KT

Member Since: Posts: Comments:
000
WTNT43 KNHC 151440
TCDAT3
TROPICAL DEPRESSION THREE DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032009
1100 AM AST SAT AUG 15 2009

SATELLITE IMAGERY AND QUIKSCAT DATA INDICATE THAT THE BROAD AREA OF
LOW PRESSURE OVER THE EASTERN ATLANTIC HAS FORMED A WELL-DEFINED
CIRCULATION AND SUFFICIENTLY ORGANIZED CONVECTION TO BE DESIGNATED A
TROPICAL DEPRESSION. THE INITIAL INTENSITY IS 30 KT BASED ON THE
QUIKSCAT DATA...AS WELL AS SATELLITE INTENSITY ESTIMATES OF 30 AND
35 KT FROM SAB AND TAFB.

THE SYSTEM IS CONSOLIDATING SOUTH OF WHERE THE CENTER WAS BEING
TRACKED YESTERDAY...AND THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN
265/15. SOME ERRATIC MOTION IS POSSIBLE TODAY AS THE DEPRESSION
INTERACTS WITH THE ELONGATED MONSOON/TROPICAL WAVE CIRCULATION THAT
SPAWNED IT. OVERALL...DEEP-LAYER HIGH PRESSURE OVER THE CENTRAL
AND EASTERN ATLANTIC SHOULD STEER THE CYCLONE GENERALLY WESTWARD
FOR THE NEXT COUPLE OF DAYS...FOLLOWED BY A TURN TOWARD THE WEST-
NORTHWEST. THE TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT WITH
THIS SCENARIO...AND THERE IS A FAIRLY TIGHT CLUSTER OF THE MODELS
AROUND THE 5 DAY FORECAST POINT. ONE EXCEPTION IS THE ECMWF...
WHICH FORECASTS SIGNIFICANTLY MORE NORTHWARD MOTION THAN THE OTHER
MODELS AND AT THIS TIME IS A RIGHT OUTLIER.

THE CYCLONE IS IN DEEP-LAYER EASTERLY FLOW WITH LIGHT/MODERATE
VERTICAL WIND SHEAR FORECAST FOR AT LEAST THE NEXT 4 DAYS. ALL
INTENSITY GUIDANCE FORECASTS THE SYSTEM TO BECOME A HURRICANE BY
THE END OF THE FORECAST PERIOD...WITH THE HWRF FORECASTING A MAJOR
HURRICANE. THE INTENSITY FORECAST THUS CALLS FOR GRADUAL
STRENGTHENING TO A TROPICAL STORM IN 12 HR AND A HURRICANE IN 72-96
HR IN BEST AGREEMENT WITH THE INTENSITY CONSENSUS MODELS.

FORECAST POSITIONS AND MAX WINDS

INITIAL 15/1500Z 11.5N 34.0W 30 KT
12HR VT 16/0000Z 11.3N 36.1W 35 KT
24HR VT 16/1200Z 11.3N 38.9W 40 KT
36HR VT 17/0000Z 11.8N 41.7W 45 KT
48HR VT 17/1200Z 12.4N 44.4W 50 KT
72HR VT 18/1200Z 14.0N 50.5W 60 KT
96HR VT 19/1200Z 16.5N 57.0W 75 KT
120HR VT 20/1200Z 19.0N 63.0W 90 KT

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Hey 456...

Are you R.I.Ping Ana, or was that a sarcastic post? :)
Member Since: Posts: Comments:
Quoting HurricaneKyle:
You guys want to know something stunning?
Tropical Depression 3.

Tropical Depression 4 in 2007. (4th advisory)



woah thats a little too much, almost the same day,position and track
Member Since: Posts: Comments:
Quoting CycloneOz:
Dr. Masters has wisely waited until the 11AM advisory and updates.

He's working on his new blog now, I'm sure.

I am sure too
Member Since: September 30, 2007 Posts: 9 Comments: 15932
i liked it better when nothing was going on. at least i could halfway keep up with you guys! now my head is spinning. hey, it is the anniversary week of hurricane camille, on this day she was about where td3 is i think. camille is the first hurricane i saw devastation afterward in person. i saw the kmart was a polished clean concrete slab. not even any tiny debris was left. you coulda ate off it.
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Td3 could be the 1st hurricane of the season!!!
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5190. rxse7en
Quoting serialteg:


feeding outflow - fujiwara - clarification?
I'd be careful with the use of the "F" word--you may be called "Silly" by certain bloggers. :D On a serious note, both systems are large enough, but are they close enough to have some effect on each other. I had suggested yesterday that their proximity to each other may be one of the factors keeping them on a flatter, westerly course as opposed to turning poleward. Perhaps an expert can comment?

And good morning all...

B
Member Since: Posts: Comments:
Quoting centex:
The south trend continues.If it keeps up through tomorrow, I think they will be GOM in the end.

NHC keeps riding the curve westward.
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Quoting Ameister12:
NHC has issued the 1st advisory on TD3

Member Since: September 30, 2007 Posts: 9 Comments: 15932
we can expect a blog update very soon.
.
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Quoting TerraNova:
First forecast advisory takes newly designated TD3 to 105 mph, Category 2 status, on day 5 after reaching hurricane strength on day 4.


In line with the SHIPs, basically.
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Quoting MrSea:


that was Dean?


Yessir. Dean.
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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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