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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Well one thing is for sure, anywhere from the eastern GOM and the eastern seaboard are in the cone


actually...what is certain..is that at this moement..no one in the conus is in the cone
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Quoting Drakoen:
thats the intensity most models are showing, over 125mph+
Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit


Don't include me in that bandwagon. I favored recurvature yesterday. I go by the models and climatology.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
Quoting ricderr:
ok....a serious post in a forum that i try never to be seroius on...

while you guys are speculating over gut feelings and unsubstantiated tracts...please note the close alignments of the models...for those that have been here for awhile....can you remember when this early into a systems cycle...when the models have been so closely aligned so soon?


I have NEVER seen the models converge like this 5+ days out.
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Here is an interesting loop for anyone who wants to look at the bigger picture. It is a WV loop showing several interesting features such as :

1. The ULL over Cuba that is helping to support the flare up from the Twave in that area.

2. Ex TD2 heading into air that is completely void of moisture other than what it can generate itself.

3. A trough digging down from the N of Ex TD2 that may increase shear over it depending on the relative speeds of the two.

While Ex TD2 has been trying to mount a comeback this morning it is still struggling with a less than ideal environment where it is and cloud tops have warmed some in the last 2 hours.

Still a wait and see with this feature.

WV Loop
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Quoting heliluv2trac:
why do i have a feeling everyone on here wants to get hit


Well you might be on to something... :)
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Quoting Elena85Vet:


Does this mean they potentially had SUV's in A.D. 500?

It just means that today we humans are responsible. Rightnow we put alot of fuel into the air system. Though the oceans take up 50% of the emitted Co-2 - just have a look on SST records.

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Quoting melwerle:


Ok Patrap, now THAT was funny!
Good to hear from you ... how goes it?
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Quoting KimberlyB:


Holy Hell! Was he drunk?? Did he get a HUI?

What about Ivan from the same year.
Member Since: September 30, 2007 Posts: 9 Comments: 15750
Quoting futuremet:
Well one thing is for sure, anywhere from the eastern GOM and the eastern seaboard are in the cone. If the trough is adequately strong, it could curve this bad-boy out to sea.


It might be a bad girl...
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Quoting reedzone:


Or an east coast event on this run.. Troughs can make storm recurve of course, but sometimes they can make storm go up the east coast. people are just not getting the idea that this could do that.


Yeap... is another possible solution in the event the trough is again depicted to be stronger.
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Member Since: October 28, 2006 Posts: 57 Comments: 29714
why do i have a feeling everyone on here wants to get hit
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Well one thing is for sure, anywhere from the eastern GOM and the eastern seaboard are in the cone. If the trough is adequately strong, it could curve this bad-boy out to sea.
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467. 7544
Quoting futuremet:
GFS shows FL landfall



been keeping track this is the 10th run the gfs shows fla innits path stay tuned
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ok....a serious post in a forum that i try never to be seroius on...

while you guys are speculating over gut feelings and unsubstantiated tracts...please note the close alignments of the models...for those that have been here for awhile....can you remember when this early into a systems cycle...when the models have been so closely aligned so soon?
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GFS hits SFL like the CMC maybe just a tad south but still a hit.
Member Since: October 28, 2006 Posts: 57 Comments: 29714
Quoting CaneWarning:


At least it doesn't look like a Cat 5.
im surprised because a lot of other models have a CAT 3+ landfall.
South Florida and it looks like there's enough room between the 2 highs to take it up the coastline.
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Quoting Patrap:



Its only insight thru the Long term,and completely discount these Nutz who willy nilly about "finishing",only a fool would wish calamity on another.

Folks been washing us away for Centuries,way before they were here as a family,.

And as one who Lost Loved ones in the storm,they Know not what they say, As many found out with Ike,you can easily become "They",..overnight

Amen!
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Quoting CaneWarning:


At least it doesn't look like a Cat 5.


Are you seriously concerned with how strong the 200 hour GFS shows the system?
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Quoting Seflhurricane:
quick mid afternoon poll

A) Ex TD2 regerates at 5PM
B) Ex TD 2 regenerates tonight
C) Ex TD2 Regenerates near the islands
D) Ex TD 2 never regenerates



C)
and continue with a WNW track....
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Quoting futuremet:
GFS shows FL landfall



At least it doesn't look like a Cat 5.
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Quoting reedzone:


no lol, but the pattern is setting up for an east Coast event. Everybody is screaming GOM when the pattern just doesn't favor it. A trough will lift this up eventually and either move it out to sea WEST of Bermuda, or take it up the Eastern Seaboard. Not just South Florida either, us people here in Central/Northeast Florida have to watch it to. Bastardi even mentioned that he knows he always predicts Northeast storms but he showed evidence proving that the pattern is quite similar from a week before Floyd hit in 1999. He also showed some NAO charts and tracks from the 1950s thru 80s. He's not just wishcasting this, more METS are also saying this could be more of an East Coast event.


Each successive run with the GFS has been flattening out the trough and also a little faster with it. This does point to more of a westerly course with 90. Placement of troughs and ridges is actually a strong point of the GFS. We're still a week away, but it seems when this trough was first advertised it was a little too amplified for August. I think a weaker trough will be the solution.
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Quoting Patrap:


"Hebert",..in a Box


LOL. Bravo.
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Quoting futuremet:
GFS shows FL landfall



Great timing...
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455. ackee
Quoting extreme236:


Not sure T
Quoting Seflhurricane:
quick mid afternoon poll

A) Ex TD2 regerates at 5PM
B) Ex TD 2 regenerates tonight
C) Ex TD2 Regenerates near the islands
D) Ex TD 2 never regenerates
my answer is B
Member Since: July 15, 2008 Posts: 0 Comments: 1341
SFL hit:

Member Since: October 28, 2006 Posts: 57 Comments: 29714
As expected... the right shift due to the weaker Western extent of the Bermuda high... but yet still strong enough to almost make it look like a Charley.

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GFS shows FL landfall

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Quoting WxLogic:


Indeed... with a bit weaker High extent into the US from before... which would mean a right shift to the re-curvature.


Or an east coast event on this run.. Troughs can make storm recurve of course, but sometimes they can make storm go up the east coast. people are just not getting the idea that this could do that.
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449. afj3
Hello everybody.
Question. Some ensemble models are moving 90L south. But if TD2 develops, can it weaken the ridge and eventually bring 90L north with it? Sorry if tihs question seems silly or evens stupid as I am no expert at all! So be nice.
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Quoting WxLogic:


Indeed... with a bit weaker High extent into the US from before... which would mean a right shift to the re-curvature.


not necessarily
Member Since: October 28, 2006 Posts: 57 Comments: 29714
Quoting canesrule1:
can someone tell me what CMC means, thanks a lot!


Canadian Meteorological Centre (CMC)


The NHC has updated their description of the models, includes a lot more information and links:

http://www.nhc.noaa.gov/modelsummary.shtml
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Quoting Seflhurricane:
quick mid afternoon poll

A) Ex TD2 regerates at 5PM
B) Ex TD 2 regenerates tonight
C) Ex TD2 Regenerates near the islands
D) Ex TD 2 never regenerates

I'm thinking B.
Member Since: August 9, 2009 Posts: 10 Comments: 4504
Thats why I never predict anything,I observe,..and now we observe the Model trends in 12 Hour increments and compare to How the System is doing in real time.

Only the uninformed make predictions,willy nilly.
And over time,if you go back in the archive here,well that becomes painfully obvious.
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Quoting reedzone:


Also there's a good possibility it doesn't enter the GOM but heads up the East Coast, maybe even up to Long Island, NY.. That's my gut feeling.


What people tend to forget is that hurricanes do come up the east coast once in a while.

Aside from South Fl and the Carolin's, New England has been hit more than any other region on the East Coast. Including North Florida.

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443. Prgal
Quoting FLHurricaneChaser:
People you need to stop worrying about the Gulf. The islands and Florida are first up.

Thank you Chaser. Living in PR I agree 100%!
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Has 456 been on today? I wonder if he's getting prepared.
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Quoting Seflhurricane:
quick mid afternoon poll

A) Ex TD2 regerates at 5PM
B) Ex TD 2 regenerates tonight
C) Ex TD2 Regenerates near the islands
D) Ex TD 2 never regenerates


Not sure which but I'd say a, b, or c as I think we will see regeneration at some point.
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Quoting WxLogic:


Hehe... I don't pay too much attention to the Herbert box.


That setup plays out on the GFS SFL will be target with a path into the GOM
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I notice the NHC has a track out there now...slightly to the north of most models.

Link
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Quoting Patrap:
Fortunately Gut feelings have no Basis In Fact or forecasting,if that were true,JFV would have Obliterated S Fla,10 Times over since June I 2007


I understand that but the pattern also is setting up for an East Coast event. We really won't know about the track until it reaches the islands, then we should have an idea of what area it will go to (East Coast, GOM, or out to sea)
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Quoting Drakoen:


Look at the trough


Indeed... with a bit weaker High extent into the US from before... which would mean a right shift to the re-curvature.
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Quoting Seflhurricane:
quick mid afternoon poll

A) Ex TD2 regerates at 5PM
B) Ex TD 2 regenerates tonight
C) Ex TD2 Regenerates near the islands
D) Ex TD 2 never regenerates

A or B if it don't at A then it will at B
Member Since: June 13, 2009 Posts: 2 Comments: 9598
Quoting FLHurricaneChaser:
People you need to stop worrying about the Gulf. The islands and Florida are first up.


Link

CMC (Canadian Meteorological Centre) 48 hr forecast initialized 12Z this morning. 15 km resolution.

Incipient cyclogenesis Sunday morning Northern Gulf....?
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.