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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Ok Kori...

you know what to do >_>
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Quoting louisianaboy444:
Ya, not liking that run

Thats not the most current one...


Then show me the current one :p
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Quoting jasoniscoolman10:
i was talking to the national hurricane center on the phone we will have a tropical depression 2 back by 11pm tonight..


I'm going to remember this quote.
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Quoting Patrap:
06 GFS run
Patrap, everytime you post something it looks bad for you. Ohh, and me...lol
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Quoting louisianaboy444:


You learned from me! haha just playing


:P

We're both still Padawan learners.
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Quoting cg2916:

Lol.

I g2g, I'll be back in the morning.
later.
Quoting canesrule1:
i'm just telling u what recon reported, and why are u making it rain on my picnic, i was half-way threw my PB&J and now its soggy, lol.


CanesRule1 you are killing me tonite..you are on a roll my friend...LOL
Member Since: September 2, 2007 Posts: 179 Comments: 20448

The more west it will come. Caribbean bound MAY be a good call.
That would be sad if it became significant and hit those that have been hit/affected repeatedly nearly every season SAD.
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Quoting tbrett:

Yes I know Angelo's, in fact my daughter works there until schools starts again


Cool
Say hello to Mahesh from me
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Quoting alaina1085:


Ya, not liking that run
can u give me the link, thanks a lot!
2324. cg2916
Quoting canesrule1:
i'm just telling u what recon reported, and why are u making it rain on my picnic, i was half-way threw my PB&J and now its soggy, lol.

Lol.

I g2g, I'll be back in the morning.
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2323. SLU
02LTWO.30kts-1007mb-147N-448W
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SO every GFS run so far over the past days has it over Florida somehow someway from the Keys to Miami to palm beach by Tampa.
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Quoting KoritheMan:


I wouldn't have ever made it this far though, if it were not for the extremely knowledgeable people like Drak, StormW, futuremet, and hurricane23, etc. I learn a lot from them, and hope to continue to do so.


You learned from me! haha just playing
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Quoting tharpgomex:
lmao...canerules...poor PB&J
lmao!
Ya, not liking that run

Thats not the most current one...
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Quoting leftovers:
korieth your good no doubt hope to hear from you early tgif over and out


I wouldn't have ever made it this far though, if it were not for the extremely knowledgeable people like Drak, StormW, futuremet, and hurricane23, etc. I learn a lot from them, and hope to continue to do so.
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If that did happen...GFS that you referenced....it would be very very bad...AGAIN
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Quoting Patrap:
06 GFS run


Ya, not liking that run
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lmao...canerules...poor PB&J
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Quoting CaneAddict:


Uh..so your saying everyone else doesn't? Buddy, I do the same, take last season for example. This season I've not been doing much forecasting and analyzing but I felt you may of left a few of us out.

Get riled up, much?

Seriously, looking at the different wind field data sources, I have to think that 90L will be slow to intensify just due to the size of the windfield...unless it does an amazing job of consolidation.
I am of the opinion that SHIPS is too strong too early:

Not to say that the system couldn't get up to major status, but I think it would be doing so slowly, if so.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
2282. KoritheMan 7:55 PM CDT on August 14, 200
thanks, I need to keep hearing that...I seem to be having nightmares of Katrina...need to quit thinking about it
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2311. Skyepony (Mod)
Gonzo sampled the N edge of TD2

1012mb (29.88 inHg) Sea Level (Surface) 25.4°C (77.7°F) 24.5°C (76.1°F) 65° (from the ENE) 25 knots (29 mph)
1000mb 104m (341 ft) 24.4°C (75.9°F) 24.0°C (75.2°F) 60° (from the ENE) 31 knots (36 mph)
925mb 786m (2,579 ft) 20.6°C (69.1°F) 20.6°C (69.1°F) 80° (from the E) 40 knots (46 mph)
850mb 1,517m (4,977 ft) 17.8°C (64.0°F) 17.8°C (64.0°F) 85° (from the E) 34 knots (39 mph)
700mb 3,160m (10,367 ft) 10.2°C (50.4°F) 6.0°C (42.8°F) 80° (from the E) 32 knots (37 mph)
500mb 5,870m (19,259 ft) -5.5°C (22.1°F) -6.6°C (20.1°F) 95° (from the E) 24 knots (28 mph)
400mb 7,590m (24,902 ft) -16.9°C (1.6°F) -20.5°C (-4.9°F) 90° (from the E) 17 knots (20 mph)
300mb 9,700m (31,824 ft) -30.5°C (-22.9°F) Approximately -36°C (-33°F) 130° (from the SE) 20 knots (23 mph)
250mb 10,970m (35,991 ft) -41.1°C (-42.0°F) Approximately -48°C (-54°F) 160° (from the SSE) 12 knots (14 mph)
200mb 12,450m (40,846 ft) -53.7°C (-64.7°F) Approximately -70°C (-94°F) 130° (from the SE) 16 knots (18 mph)
150mb 14,240m (46,719 ft) -65.5°C (-85.9°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 140° (from the SE) 8 knots (9 mph)
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Quoting extreme236:


No tropical depression confirmed yet.
i know
Quoting cg2916:

OMG!! CAN YOU BELIEVE THERE ARE MORE QUALIFICATIONS A LOW HAS TO GO THROUGH BEFORE BEING CLASSIFIED??? WOW ZOMG!!!

LMAO.
2309. jipmg
Quoting Weather456:


dude thats 11 years old, thats an image of pre Georges in 1998 which was 92L


LOL then it looks similar to how 90L looked 6 hours ago
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Quoting Twinkster:



ATTENTION YOU DON'T HAVE AUTHORITY TO SAY IT IS TD #2 YET. WAIT TILL NHC SAYS SO
i'm just telling u what recon reported, and why are u making it rain on my picnic, i was half-way threw my PB&J and now its soggy, lol.
Quoting Weather456:


how is that good?


Good = accurate, in this case I believe
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Quoting canesrule1:
***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!!


No tropical depression confirmed yet.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting cchsweatherman:


Just glad to know that you, StormW, Weather456, and I all perform our own analysis and we all stick by our own methods and approaches. You continue to do an amazing job.


CCHS there is alot of very dam good forecast bloggers on this blog including yourself. Sometimes you just have to look what is in front of you and throw away all data and models.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
2303. Patrap
06 GFS run
Member Since: July 3, 2005 Posts: 428 Comments: 129762
2302. cg2916
Quoting canesrule1:
***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!! I AM NOT LYING THIS IS FOR REAL!!!

OMG!! CAN YOU BELIEVE THERE ARE MORE QUALIFICATIONS A LOW HAS TO GO THROUGH BEFORE BEING CLASSIFIED??? WOW ZOMG!!!
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Quoting hurricane23:


The more west it will come. Caribbean bound MAY be a good call.


Yes, that too, Adrian. I for one am hoping that it develops quickly and becomes powerful enough to recurve. This could really be a monster if it hits that TCHP in the Caribbean.
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Quoting Chiggy007:
Ameister12:

Can you tell me where exactly do you see a 90L LLC - need coordinates! I am seeing it around 11.5N - 30W or so... please confirm!! thx

I think you might be right about it being around 11.5N - 30W, but I am not the greatest at coordinates.
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Quoting canesrule1:
***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!!



ATTENTION YOU DON'T HAVE AUTHORITY TO SAY IT IS TD #2 YET. WAIT TILL NHC SAYS SO
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2296. 7544
Quoting canesrule1:
***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!!


rebirth
Member Since: Posts: Comments:
Quoting Weather456:


dude thats 11 years old, thats an image of pre Georges in 1998 which was 92L


LMAO!!
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Quoting hurricane23:


The more west it will come. Caribbean bound MAY be a good call.


how is that good?
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting canesrule1:
***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!!


Circulation appears to be becoming less elongated also. Good sign for regeneration. We'll probably have TD2 tonight or tomorrow morning.
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Quoting jipmg:


thats an old image


dude thats 11 years old, thats an image of pre Georges in 1998 which was 92L
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting KoritheMan:
Given that the circulation of 90L is still broad, I'm not expecting it become a tropical depression until around 18-24 hours.


The more west it will come. Caribbean bound MAY be a good call.
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Quoting cchsweatherman:


Just glad to know that you, StormW, Weather456, and I all perform our own analysis and we all stick by our own methods and approaches. You continue to do an amazing job.


I'm so happy to be knowledgeable enough about tropical meteorology in order to analyze things for myself, and make my own forecast. :)
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***********ATTENTION************

RECON HAS JUST REPORTED 27KNOT WINDS AND 42KNOT GUSTS AT THE SURFACE!!!!!!!!!WE HAVE TD#2!!!!!!PRESSURE IS 1009MB!!!!!!!!!!! I AM NOT LYING THIS IS FOR REAL!!!
2287. cg2916
Quoting extreme236:
2255. Didnt show up on mine

Click help, then click Welcome Message. If it's not there, then open it in windows Explorer, then do it.

It's hilarious that the welcome message is a theat to being legally punished.
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Given that the circulation of 90L is still broad, I'm not expecting it become a tropical depression until around 18-24 hours.
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2285. 7544
Quoting TampaSpin:


Don't know i just logged on also...looks like TD2 is nearly a Storm just looking at it an RECON appears to have confirmed nearly the same.


thanks for that info
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Quoting cchsweatherman:


Just glad to know that you, StormW, Weather456, and I all perform our own analysis and we all stick by our own methods and approaches. You continue to do an amazing job.


Uh..so your saying everyone else doesn't? Buddy, I do the same, take last season for example. This season I've not been doing much forecasting and analyzing but I felt you may of left a few of us out.
Member Since: October 5, 2007 Posts: 3 Comments: 2151

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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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