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 jipmg:


Katrina did so much damage and it was an 80MPH hurricane.


It was also a 80mph hurricane that pulled a Cat. 5 storm surge with it.
Member Since: Posts: Comments:
Quoting DM21Altestic:
the Onion is the Weird Al Yankovic/The Lonely Island of news.
ROFLMAO, i love "im on a boat" lol
Quoting TampaSpin:


Hate to say this but, that was what happened with Andrew.


TampaSpin... Is it me or is it Looking like ana?

Member Since: June 17, 2006 Posts: 44 Comments: 5010
Quoting DaytonaBeachWatcher:

I thought you promised not to ask that...
He can't help himself.
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Quoting DM21Altestic:

lol

Link


lol lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting jipmg:


Katrina did so much damage and it was an 80MPH hurricane.

I was saying in terms of affecting 90Ls track lol.
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Well here in the panhandle we have had quite enough for a lifetime. I don't want to even think about comparing any of this to 2004 season.
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Quoting Weather456:


it did,


2-3 days ago. lol
lol
2525. Jerrob
Quoting FLHurricaneChaser:


That area of Florida would get no more than Cat 1 winds, if that.

Well, Cat 1 winds?????? That did a number on my house in central fl in 04.. would still make me worry.
Member Since: Posts: Comments:
it did,


2-3 days ago. lol


Lol ok wise guy...I will stick my neck out here and say that TD2 is already back but the NHC hasn't made it official yet...90L has also started building some convection near its center
Member Since: August 29, 2006 Posts: 22 Comments: 1352
Quoting Weather456:
Its amazing how west TD 2 has been going since it emerged off africa.


Why is that amazing.....The Azores/Bermuda highs is forcing everything that way.....no surprise really.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Somehow the SAL found a way to affect 90L. It always does....

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2521. jipmg
Quoting Stormchaser2007:


The official intensity forecast has it near 65 mph in the Bahamas. That wouldn't do much.


Katrina did so much damage and it was an 80MPH hurricane.
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Quoting WeatherStudent:
True Adrian, but then TD2 would head straight towards us, while the other heads out to sea, wouldn't they?

I thought you promised not to ask that...
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Quoting atmoaggie:

It is called Tammany Hills...for a reason. Between Covington and Mandeville somewhat in the Abita springs direction (honestly, same drive time, really, to all 3 of those)


OO i know where abouts! the bay was new find though. we are pretty close. tallow creek area. i'm glad to hear you didnt have any damage.
Hey, Tucan Sam!
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Quoting louisianaboy444:
IMO 02L will form into a tropical depression before 90L


it did,


2-3 days ago. lol
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting DM21Altestic:

lol

http://www.youtube.com/watch?v=nFM1X0o2pnc


That isn't copying an official document. The video is clearly comedy, not coming out as official information.
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True Adrian, but then TD2 would head straight towards us, while the other heads out to sea, wouldn't they?
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IMO 02L will form into a tropical depression before 90L
Member Since: August 29, 2006 Posts: 22 Comments: 1352
00z Early runs for 90L

Heres a view @ both Statistical/Simple Models & Dynamic Models (More sophisticated models) for 90L.
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Quoting DM21Altestic:
ONION NEWS NETWORK BULLETIN

Dude, not everyone knows what the Onion is...you might be misleading some folks.
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Quoting DM21Altestic:
ONION NEWS NETWORK BULLETIN
TROPICAL DEPRESSION THREE SPECIAL ADVISORY NUMBER 1 KONN/ONION WEATHER CENTER HOUSTON TX AL032009
1100 PM EST TUE AUG 11 2009

...THIRD TROPICAL DEPRESSION OF THE ATLANTIC HURRICANE SEASON FORMS...

SATELLITE IMAGES INDICATE THAT A TROPICAL DEPRESSION HAS FORMED OVER THE FAR EASTERN TROPICAL ATLANTIC.

AT 11 P
THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 13 MPH...20 KM/HR...AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...45 KM/HR...WITH HIGHER GUSTS. STRENGTHENING IS FORECAST...AND THE DEPRESSION COULD BECOME A TROPICAL STORM EARLY ON SATURDAY.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.71 INCHES.

...SUMMARY OF 1100 PM EST INFORMATION...
LOCATION...12.2N 30.8W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 270 DEGREES AT 13 MPH
MINIMUM CENTRAL PRESSURE...1005 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE ONION WEATHER CENTER AT 500 PM EST.

$$
FORECASTER KEVIN FISCHER

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| Ignore User





lol nice try
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Ummm...we aren't that DUMB.

The Onion would NEVER do that.
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Quoting canesrule1:
i doubt that a lot, because well 02L is not going to strengthen rapidly and i don't think that 02L will have an affect on 90L's track,imo.


The official intensity forecast has it near 65 mph in the Bahamas. That wouldn't do much.
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Quoting reedzone:
I know everybody is concerned about South Florida, but what about where I live.. Northeastern Central Florida? We need to be watching it to.


That area of Florida would get no more than Cat 1 winds, if that.
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Quoting louisianaboy444:
I believe TD2 will get near the Bahamas and then head back west because of the developing Bermuda High


Hate to say this but, that was what happened with Andrew.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting canesrule1:
I'm in big s#!t if that happens, lol


the models dont seem to like TD 2. some dont develop it and others show a moderate tropical storm
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting tharpgomex:
canesrule1 I knew your real name was AL!
lol, no it's actually Robert.
2503. Patrap
Quoting WindNoise:
Saints need to put Jason David in Crab Boil and ship him to China. He stinks.


So much for Blogging and Being Behind 15 minutes with the DVR.

I look forward to that play now..LOL
Member Since: July 3, 2005 Posts: 426 Comments: 129089
Quoting indianrivguy:


they got SO lucky that Katrina hooked to the right just before landfall.. thousands could have died

Thousands (well, more than jus one thou) did die, but I know what you mean and agree completely.
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2500. Jerrob
Quoting WeatherStudent:


Wow, a repeat of 04, perhaps? OUCH, let's hope not my friend.

I agree! 04 was not a fun ride at all!!!
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Quoting Stormchaser2007:
Interesting that the official has it right off the coast.

00Z

ExTD2





Shet... If it Follows the Yellow Line.. itll Be a guest at my House...

The Models have been consistent too....


Please Tell me theres shear?
Member Since: June 17, 2006 Posts: 44 Comments: 5010
Quoting hurricane23:
If extd2 strengthens significantly it could help to turn Invest 90 to the north quicker than thought right now.
i doubt that a lot, because well 02L is not going to strengthen rapidly and i don't think that 02L will have an affect on 90L's track,imo.
Quoting CandiBarr:
2421 atomaggie

lol I have to look up where that is, im still kinda new to the area. thanks though :)

It is called Tammany Hills...for a reason. Between Covington and Mandeville somewhat in the Abita springs direction (honestly, same drive time, really, to all 3 of those)
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2496. hahaguy
Quoting WeatherStudent:


I see, but what type of potential implications might these two cyclones have on our long term weather here in SF, Adrian?


Nobody knows yet .
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I have to agree with 23...ex TD 2 > 90L.

Long term...90L might become a big threat for the Caribbean.
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2494. jipmg
Im so glad I found this blog/forum, its greatly improved my knowledge on tropical systems.
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canesrule1 I knew your real name was AL!
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Quoting Patrap:


The Booth Officicial must be at the Bar,an that Game Ref need a Lasix procedure.

Im 4 Miles west here from the Dome and I made a better call,LOL
Saints need to put Jason David in Crab Boil and ship him to China. He stinks.
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Quoting Stormchaser2007:
Interesting

00Z

ExTD2

I'm in big s#!t if that happens, lol
Quoting atmoaggie:

Right up Barataria Bay and the counterclockwise winds on a bigger storm fill the lake, stack water to the west, and then slosh it back to the southeast (to the city) as the storm passes. Very much like what happened in Slidell during Kat. No 2-day fill-the-city event...2-hour-fill-the-city.


they got SO lucky that Katrina hooked to the right just before landfall.. thousands could have died
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Quoting hurricane23:


Nah not really,ive not been impressed with 90L today as it looks like its still being impacted by easterly shear.Regardless i stll expect this to slowly but surely develope into a pretty significant cyclone.Dont forget about extd2.


I see, but what type of potential implications might these two cyclones have on our long term weather here in SF, Adrian?
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If extd2 strengthens significantly it could help to turn Invest 90 to the north quicker than thought right now.
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Quoting pcolasky:



still, 7 to nothing...with bad calls. And you guys have Derrick Brooks


the officials had one too many hand grenades in the quarter before reporting to work!but i can't blame them..
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AL 02 2009081500 03 OFCI 0 147N 448W 30
AL 02 2009081500 03 OFCI 12 150N 479W 35
AL 02 2009081500 03 OFCI 24 153N 512W 39
AL 02 2009081500 03 OFCI 36 158N 547W 44
AL 02 2009081500 03 OFCI 48 166N 583W 48
AL 02 2009081500 03 OFCI 60 175N 618W 51
AL 02 2009081500 03 OFCI 60 175N 618W 51
AL 02 2009081500 03 OFCI 72 185N 652W 53
AL 02 2009081500 03 OFCI 72 185N 652W 53
AL 02 2009081500 03 OFCI 84 198N 685W 56
AL 02 2009081500 03 OFCI 96 212N 718W 58
AL 02 2009081500 03 OFCI 108 226N 750W 61
AL 02 2009081500 03 OFCI 120 242N 783W 63
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Interesting that the official has it right off the coast.

00Z

ExTD2

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Quoting SELAliveforthetropic:


That would wipe Terrebonne Parish off the map


I personally would prefer that not happen...
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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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