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 atmoaggie:

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.


I tell that to everyone, and most people Ive talked to think Katrina was the worst case scenario. Boy are they wrong! Not to mention the we have lost plenty of wetlands since Katrina effected the area in 2005. We are becoming more vulnerable each day, and that is the scary part.
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2383. mkmand
Quoting atmoaggie:

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.

Similar track as Gustav of last year. If Gustav was 20 mph stronger and 40 miles more north, it would have been the worst case scenario.
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Quoting atmoaggie:

I went from Covington to Slidell for that one...but into a cold war-era bunker.
Actually had more damage from Ike than Gustav at my house. Rain band pushed 60 mph gusts and took down a couple of trees.


the center of gustav passed over my house and my neighbors and some dumb friends stuck around to watch..
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spit wads in the east atlantic are not as important as the spit wad that could, by a slim chance, be an immediate threat to the gulf coast residents flood, wind, whatever.
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Actually had more damage from Ike

i remember the flooding was bad from ike, could see it along the river on 12.
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Official intensity brings 90L to 90knots in 120 hours.
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Saints and Weather fan here in Destrehan. I agree about that not being a fumble. It's preseason for officials too. Saints 7 Bengles 0. Also think 90L headed for GOM.

Hey Patrap did you see the out of bounds challenge lol
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2376. jipmg
I think the models are starting to underestimate 90L intensity wise in the short term.. I see it developing into something fairly quick right now, that convection erupting near the center is indicitive of that
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guys according to avn ir sat it is getting cooler and cooler ( stronger and stronger)
Link
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Quoting Ameister12:
Hey guys, I saw on the Weather Channel earlier today that 90L could be an Andrew storm,meaning It might hit Florida and turn towards Louisiana, but it's way to early to tell.


I've been carefully watching the forecast steering pattern, and I do think that it could eventually wind up near the Bahamas. Of course, things can change that far out. We will see.
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Early 0z runs for ex TD2

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2372. java162
Quoting Weather456:
90L has an official track (black line)




why is the official track the most north of all the tracks? is it old?
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2371. tbrett
Quoting Patrap:
06 GFS run

Not a pretty picture
Member Since: July 20, 2007 Posts: 0 Comments: 107
2341 ws it takes a bser to know one good job you have redeemed your self in my eyes probably only.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
Quoting reedzone:
If that isn't a TD, then shoot me... seriously, recon reports winds at 30 knots, deep convection bursting, outflow is good.. I think a re-classification is in order by 11 p.m. tonight. We'll see...



REED look at the red outburst ......Heck it might even be close to being ANA....
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Quoting reedzone:


What would that mean then?


Those who are not living along that line hope that it will follow it.
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Quoting CandiBarr:


you know there are a lot of peeps i know in the madisonville area that didnt not evac for gustav :-(

I went from Covington to Slidell for that one...but into a cold war-era bunker.
Actually had more damage from Ike than Gustav at my house. Rain band pushed 60 mph gusts and took down a couple of trees.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting FloridaTigers:


Camille, passing in the same spot Katrina did would be the worst case.

I still think New Orleans is a city people shouldn't repopulate, no offense. Its still a bowl.


I strongly agree.
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Quoting ALCoastGambler:
Patrap, everytime you post something it looks bad for you. Ohh, and me...lol


can someone post this... i try the links but they never work :(
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Quoting atmoaggie:

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.


Yep, so true!
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Quoting Weather456:
90L has an official track (black line)



What would that mean then?
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Quoting FloridaTigers:
Ok Kori...

you know what to do >_>


>_>

My brother has the PS2, so ok.
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2361. GatorWX
Quoting jasoniscoolman10:
i was talking to the national hurricane center on the phone we will have a tropical depression 2 back by 11pm tonight..


That's pretty cool dude!
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Hey guys, I saw on the Weather Channel earlier today that 90L could be an Andrew storm,meaning It might hit Florida and turn towards Louisiana, but it's way to early to tell.
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Quoting alaina1085:


Ya, not liking that run

I know im not...lol
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2358. jipmg
Quoting louisianaboy444:
We're both still Padawan learners

I can remember back in the good ol days on here i was like 16 you was 15 and we were the young ones asking all the dumb questions lol...Glad that we can both finally contribute to the blog


interestingly enough Im 16 =O
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Quoting atmoaggie:

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.


you know there are a lot of peeps i know in the madisonville area that didnt not evac for gustav :-(
Latest Observation:
Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)
Transmitted: 15th day of the month at 00:08Z
Aircraft: Gulfstream IV-SP (G-IV) (Reg. Num. N49RF)
Mission: Non-Tasked Mission, possibly not tropical (originating in the North Atlantic basin)
Mission Identifier: Td2
Observation Number: 06

Part A...

Date: Near the closest hour of 23Z on the 14th day of the month
Highest Mandatory Level For Which Wind Was Reported: 150mb
Coordinates: 17.5N 47.3W (View map)
Location: 876 miles (1409 km) to the ENE (70°) from Bridgetown, Barbados.
Marsden Square: 041 (About)

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1013mb (29.91 inHg) Sea Level (Surface) 26.0°C (78.8°F) 23.9°C (75.0°F) 55° (from the NE) 19 knots (22 mph)
1000mb 117m (384 ft) 25.2°C (77.4°F) 23.4°C (74.1°F) 60° (from the ENE) 23 knots (26 mph)
925mb 801m (2,628 ft) 21.0°C (69.8°F) 18.5°C (65.3°F) 65° (from the ENE) 24 knots (28 mph)
850mb 1,530m (5,020 ft) 17.0°C (62.6°F) 16.5°C (61.7°F) 55° (from the NE) 20 knots (23 mph)
700mb 3,171m (10,404 ft) 9.2°C (48.6°F) 4.8°C (40.6°F) 75° (from the ENE) 18 knots (21 mph)
500mb 5,880m (19,291 ft) -6.9°C (19.6°F) -11.0°C (12.2°F) 95° (from the E) 17 knots (20 mph)
400mb 7,600m (24,934 ft) -16.1°C (3.0°F) Approximately -49°C (-56°F) 90° (from the E) 10 knots (12 mph)
300mb 9,700m (31,824 ft) -31.1°C (-24.0°F) -34.2°C (-29.6°F) 155° (from the SSE) 6 knots (7 mph)
250mb 10,970m (35,991 ft) -40.9°C (-41.6°F) Approximately -57°C (-71°F) 185° (from the S) 16 knots (18 mph)
200mb 12,440m (40,814 ft) -53.7°C (-64.7°F) Approximately -68°C (-90°F) 160° (from the SSE) 22 knots (25 mph)
150mb 14,250m (46,752 ft) -65.9°C (-86.6°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 175° (from the S) 21 knots (24 mph)

Information About Radiosonde:
- Launch Time: 22:49Z
- About Sonde: A descending radiosonde tracked automatically by satellite navigation with no solar or infrared correction.

Remarks Section...

Splash Location: 17.51N 47.37W
Splash Time: 23:03Z

Release Location: 17.5N 47.32W (View map)
Release Time: 22:49:01Z

Splash Location: 17.51N 47.37W (View map)
Splash Time: 23:03:32Z

Mean Boundary Level Wind (mean wind in the lowest 500 geopotential meters of the sounding):
- Wind Direction: 65° (from the ENE)
- Wind Speed: 25 knots (29 mph)

Deep Layer Mean Wind (average wind over the depth of the sounding):
- Wind Direction: 110° (from the ESE)
- Wind Speed: 11 knots (13 mph)
- Depth of Sounding: From 145mb to 1013mb

Average Wind Over Lowest Available 150 geopotential meters (gpm) of the sounding:
- Lowest 150m: 159 gpm - 9 gpm (522 geo. feet - 30 geo. feet)
- Wind Direction: 60° (from the ENE)
- Wind Speed: 22 knots (25 mph)

Sounding Software Version: AEV 20801

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point
1013mb (Surface) 26.0°C (78.8°F) 23.9°C (75.0°F)
962mb 23.4°C (74.1°F) 19.8°C (67.6°F)
850mb 17.0°C (62.6°F) 16.5°C (61.7°F)
768mb 13.6°C (56.5°F) 11.3°C (52.3°F)
753mb 13.0°C (55.4°F) Approximately 8°C (46°F)
706mb 9.6°C (49.3°F) 6.7°C (44.1°F)
682mb 8.2°C (46.8°F) Approximately -1°C (30°F)
665mb 6.4°C (43.5°F) 4.2°C (39.6°F)
603mb 1.8°C (35.2°F) 1.5°C (34.7°F)
559mb -0.9°C (30.4°F) Approximately -13°C (9°F)
555mb -1.3°C (29.7°F) Approximately -13°C (9°F)
540mb -2.7°C (27.1°F) -5.2°C (22.6°F)
517mb -4.9°C (23.2°F) -8.0°C (17.6°F)
510mb -5.5°C (22.1°F) Approximately -12°C (10°F)
497mb -7.1°C (19.2°F) -11.3°C (11.7°F)
494mb -7.1°C (19.2°F) Approximately -13°C (9°F)
488mb -5.9°C (21.4°F) Approximately -41°C (-42°F)
483mb -5.9°C (21.4°F) Approximately -55°C (-67°F)
427mb -11.7°C (10.9°F) Approximately -51°C (-60°F)
376mb -19.9°C (-3.8°F) Approximately -49°C (-56°F)
366mb -21.3°C (-6.3°F) Approximately -34°C (-29°F)
357mb -22.5°C (-8.5°F) Approximately -40°C (-40°F)
348mb -24.3°C (-11.7°F) -29.0°C (-20.2°F)
341mb -25.3°C (-13.5°F) Approximately -30°C (-22°F)
330mb -26.9°C (-16.4°F) -26.9°C (-16.4°F)
310mb -30.3°C (-22.5°F) -34.0°C (-29.2°F)
297mb -31.5°C (-24.7°F) -34.5°C (-30.1°F)
279mb -34.9°C (-30.8°F) -38.4°C (-37.1°F)
262mb -38.1°C (-36.6°F) Approximately -50°C (-58°F)
198mb -53.9°C (-65.0°F) Approximately -70°C (-94°F)
145mb -66.9°C (-88.4°F) -70.5°C (-94.9°F)

Significant Wind Levels...
Level Wind Direction Wind Speed
1013mb (Surface) 55° (from the NE) 19 knots (22 mph)
957mb 65° (from the ENE) 28 knots (32 mph)
850mb 55° (from the NE) 20 knots (23 mph)
830mb 75° (from the ENE) 18 knots (21 mph)
786mb 85° (from the E) 21 knots (24 mph)
706mb 70° (from the ENE) 17 knots (20 mph)
642mb 100° (from the E) 22 knots (25 mph)
520mb 100° (from the E) 22 knots (25 mph)
496mb 90° (from the E) 17 knots (20 mph)
487mb 75° (from the ENE) 11 knots (13 mph)
444mb 80° (from the E) 11 knots (13 mph)
433mb 55° (from the NE) 10 knots (12 mph)
399mb 90° (from the E) 10 knots (12 mph)
335mb Unavailable
287mb 185° (from the S) 11 knots (13 mph)
279mb 205° (from the SSW) 14 knots (16 mph)
252mb 185° (from the S) 16 knots (18 mph)
233mb 160° (from the SSE) 12 knots (14 mph)
209mb 155° (from the SSE) 15 knots (17 mph)
181mb 190° (from the S) 10 knots (12 mph)
169mb 170° (from the S) 22 knots (25 mph)
153mb 185° (from the S) 23 knots (26 mph)
90L has an official track (black line)

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2354. java162
looks like 90l is becoming more arganised by

the minute. i can see that it is tightening up and bands are begining to
forn all around the system
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Just a guess, but I'm betting they live on East Coast
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Quoting atmoaggie:

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.


Camille, passing in the same spot Katrina did would be the worst case.

I still think New Orleans is a city people shouldn't repopulate, no offense. Its still a bowl.
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Quoting nishinigami:


Is this the most recent run??


Nope. This is though. Very similar, huh?

18z
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2350. 7544
Quoting RitaEvac:
Post the 06 GFS run please....


Link
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Quoting louisianaboy444:
Sorry to bring up sports but who are the Saints Fans in here...no way was that a fumble just now
Saints and Weather fan here in Destrehan. I agree about that not being a fumble. It's preseason for officials too. Saints 7 Bengles 0. Also think 90L headed for GOM.
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2348. Patrap
Quoting alaina1085:


Patrap just posted it above.




Sorry,I was watching Saints Game,and didnt look and see yas there.
Member Since: July 3, 2005 Posts: 428 Comments: 129903
2347. GatorWX
Quoting Patrap:
06 GFS run


Staying pretty true to the last few runs eh?
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Quoting atmoaggie:

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.


I agree it wouldn't be rapidly..but I feel it has good potential of getting up to a lower-end category 3. Almost all local news channels around here keep saying they think it will be a very strong one.
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Quoting alaina1085:


Ya, not liking that run

And you know that worst-case NOLA storm that has been talked about? Katrina wasn't it. A storm making landfall and passing west of NOLA would be it. We'll see what GFS comes up with...hopefully none of that once we get closer.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting Patrap:
06 GFS run


Is this the most recent run??
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If that isn't a TD, then shoot me... seriously, recon reports winds at 30 knots, deep convection bursting, outflow is good.. I think a re-classification is in order by 11 p.m. tonight. We'll see...

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Quoting louisianaboy444:
Ya, not liking that run

Thats not the most current one...


True, but the most current run is very similar to that one.
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2340. GatorWX
I think at the moment, I'd put my money on ex-td2 over 90L. That is, in the short term. 90L is going to take longer to develop than it'll take 02L to redevelop in part because of it's large size, but I agree with what Drak said earlier and like 02's small tight structure. Its circulation has kept entirely intact. Some commented on 90L helping to elongate it, but I don't see this. The one inhibiting factor will be the increase in shear brought on by the upper low to its north and water temps being only marginally warm. 90L is impressive with its large size, but this wont help its chances of developing any faster. In the long term however, I'd keep a close eye on 90L from Virginia to LA/TX. It seems a trof may work its way south around the time 90L may be entering the gulf or western caribbean, thus a sharp turn to the north would be expected. I would certainly hate to see what it could do in the gulf with good conditions aloft. Temps are in the upper 80's to near 90 throughout most of the gulf. Everyone just keep tabs on the forecasts and be safe if something does develop out this. Hard to believe the model consensus with this one and they haven't changed drastically since it was still over Africa!
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okay im starting to get a little confused b/c the gfs and other models have 90L as the "bad" one right? so is this a temporary flare up of X-td2? or should we expect to see a change in the models soon (hopefully)?
Quoting canesrule1:
can u give me the link, thanks a lot!


Patrap just posted it above.
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We're both still Padawan learners

I can remember back in the good ol days on here i was like 16 you was 15 and we were the young ones asking all the dumb questions lol...Glad that we can both finally contribute to the blog
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Post the 06 GFS run please....
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Quoting TampaSpin:


CanesRule1 you are killing me tonite..you are on a roll my friend...LOL
thank u!
Ok Kori...

you know what to do >_>
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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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