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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2634. jipmg
Quoting sammywammybamy:
I have a Decent Question:

IF the Models Runs do hold true.. and IF.. When will South florida be feeling the effects of 02L?

Thank you .... The answer will be used if needed later on to alert friends and family..


02L mid week next week, if it comes to SFLA based on computer models, the other one late weekend.. right before school starts =O
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2633. IKE
Quoting extreme236:


My "illegal" site lol Link


LOL!
Member Since: June 9, 2005 Posts: 23 Comments: 37860
I just got home, and I do not like the model projections I am seeing. Have any of the 00 UTC runs been released?

I certainly look forward to these storms getting to 50W, (About 1,200 miles from me here on Providenciales) so I can have a better idea of where they most likely will go.

...more waiting.

CRS

[edit]... I now see the 8pm / 00 Z run above and still don't like it.
Member Since: July 12, 2007 Posts: 0 Comments: 6069
91L?
Member Since: June 9, 2007 Posts: 4 Comments: 15950
Quoting sammywammybamy:
I have a Decent Question:

IF the Models Runs do hold true.. and IF.. When will South florida be feeling the effects of 02L?

Thank you .... The answer will be used if needed later on to alert friends and family..
i think the 19th is possible
Quoting canesrule1:
yup, we already got one TD tonight lets see if we get another one, what site did u get the TD thing.


My "illegal" site lol Link
Member Since: August 2, 2007 Posts: 19 Comments: 19234
THERE IS NOTHING ABOUT 91L ON NAVY SITE - QUIT PUTTING FALSE INFO ON HERE PLS
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Quoting MelbourneTom:
I do not see 91L on the Navy site. What link are you using please?
it says 91w which is pacific he read it wrong
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Quoting atmoaggie:

You and he are not talking about the same landfall. And those 2 numbers above never did both happen together for any of the 3 landfalls.


Gotcha, I thought he was talking about the final landfall, which was higher than 80mph anyway...
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Quoting Weather456:
Invest 91L lol



What the heck? Are they going to call TD2 TD3 now (like Katrina's TD10 was named TD12)
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Quoting TightLines305:
I can’t believe it, two ants just walked across my laptop screen.


Oh no...time for the exterminator!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Almost every model now takes 90L in the vicinity of PR (north and south)

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Navy Site Link
Member Since: September 25, 2007 Posts: 53 Comments: 8533
Quoting jasoniscoolman10:


where is 91L I DO NOT SEE IT.
me either
Quoting MelbourneTom:
I do not see 91L on the Navy site. What link are you using please?


Navy Tropical Cyclone Page
Member Since: July 31, 2006 Posts: 56 Comments: 8112
2617. jipmg
Quoting TampaSpin:
Although TD2 is smaller in size, the outflow from TD2 could create some shear for TD3!


I really really doubt that.. its wayy too small for it to affect TD 3 in any "significant" manner
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Hey Tampaspin, What do you think of the two areas in the Gulf coast. I don't see much happening with the area nearest the coast, but what about the one over Cuba/Hispanolia?
Invest 91L lol

Member Since: July 24, 2005 Posts: 407 Comments: 19076
lol..on that other navy site that pat sent taz today, they do have a 91L.
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I can’t believe it, two ants just walked across my laptop screen.
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GFS Ensemble still clustered up the East Coast, but a few more outliers plow through the Caribbean.
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I do not see 91L on the Navy site. What link are you using please?
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Quoting extreme236:
Watching for any renumbering of 90L...
yup, we already got one TD tonight lets see if we get another one, what site did u get the TD thing.
Quoting Weather456:
They (TWC) are saying we may have 2 TDs at 11pm


We may, they just made 02L a TD again in their files so they may do the same for 90L now that its becoming better organized.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2605. sctonya
Quoting CycloneOz:
CELEBRATE!!!
0,0,0 CONDITION STILL EXISTS!!!


WOOHOO!!!! Enjoy it while ya can, cause it ain't gonna last long :(
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Quoting DM21Altestic:
TWC says TD 2's pressure is 1012 mb.



When it is actually 1007 mb.
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Quoting SavannahStorm:


It was also a 80mph hurricane that pulled a Cat. 5 storm surge with it.

You and he are not talking about the same landfall. And those 2 numbers above never did both happen together for any of the 3 landfalls.
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2600. Patrap
Irony always wins..

Mr. Bill PSA from 2003-4 from Creator ,He's from Louisiana.

In this public service announcement created before Katrina, Mr. Bill of SNL fame demonstrates the dangers of a hurricane hitting New Orleans.




Member Since: July 3, 2005 Posts: 428 Comments: 129781
NAVY NRL Tropical Cyclone
Member Since: July 31, 2006 Posts: 56 Comments: 8112
They (TWC) are saying we may have 2 TDs at 11pm
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Although TD2 is smaller in size, the outflow from TD2 could create some shear for TD3!
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting Weather456:
Frankly both 90L and TD 2 looks impressive, which one will fizzle will be interesting.


Don't think either one will fizzle, the models still indicate 90L will be much more powerful than newly Re-generated Tropical Depression Two.
But TD2 is far enough away unlike Felicia and Enrique in the EPAC that they wont effect each other.
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I believe the chances of 90L curving out to sea or up the Eastern Seaboard have decreased dramatically i just ain't seeing it...
Member Since: August 29, 2006 Posts: 22 Comments: 1352
2594. 7544
Quoting boatmanoki:
Can someone seen me the link to the Navy site


there is no 91l hahah

2009 Storms
All Active Year

Atlantic
90L.INVEST
02L.TWO



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Quoting DestinJeff:


one of which is Abrahms


HA!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
.


Member Since: July 24, 2005 Posts: 407 Comments: 19076
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
The onion = fake news
Member Since: July 19, 2008 Posts: 1 Comments: 229
Watching for any renumbering of 90L...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Can someone seen me the link to the Navy site
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I know that we could have 2 tropical storms this close together.....but, i really doubt that we will see 2 hurricanes that close to each other......1 of them will win out and more the likely the larger of the 2 probably TD3
Member Since: September 2, 2007 Posts: 179 Comments: 20448
2584. mkmand
Quoting extreme236:
Funny how we all thought TD 2 would become Ana and 90L would be Bill. Then TD2 became a remnant low then 90L was Ana. And now were back where we started.

I know thats funny!
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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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