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 SELAliveforthetropic:


That would wipe Terrebonne Parish off the map


I personally would prefer that not happen...
Member Since: Posts: Comments:
LOL @ food on the TV....sounds like you need a roll of Bounty near the TV like I do near my computer display :))

It's had MORE COFFEE spit at it than carter has pills :))
Member Since: September 25, 2007 Posts: 53 Comments: 8533
Quoting WeatherStudent:


Wow, a repeat of 04, perhaps? OUCH, let's hope not my friend.
but worse, i hope not too.
What are the model consensus with exTD2?
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Its amazing how west TD 2 has been going since it emerged off africa.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting jipmg:


lol I remember yesterday you were going crazy on how it was a dead naked low
yea yea yea, that was the past! lmao
2478. Patrap
Hurricane Preparation Entry
Member Since: July 3, 2005 Posts: 426 Comments: 128654
I think i might be sounding like Al Gore=The Boy who cried hurricane.

I believe TD2 will get near the Bahamas and then head back west because of the developing Bermuda High
Member Since: August 29, 2006 Posts: 22 Comments: 1352
2474. jipmg
Quoting canesrule1:
agree 100%


lol I remember yesterday you were going crazy on how it was a dead naked low
2473. tbrett
Quoting atmoaggie:

No thanks. I am in a fairly decent mood and just cleaned the food off of the TV I threw at it the last I did that.


ROTFLMAO
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Quoting leftovers:
236 i guess after all these yrs following these storms we finally agree going to give my baby 18 yr old alittle extra time tonight. if you all have kids give them time talk to them dont let what happen to my wifes friends kid. "give them love" but no gas money. early tomorrow this rooster will be here.

Yup I guess there is always room for agreement.
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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.
for sure.
I know everybody is concerned about South Florida, but what about where I live.. Northeastern Central Florida? We need to be watching it to.
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2469. mkmand
Quoting MississippiWx:


02L Rainbow Loop

If that's not a T Depression, then I don't know what is.

So it looks like former TD2 will become Ana after all !!!
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Quoting Patrap:
06 GFS run


this dang thing sure has my attention, one lil' twitch to the north and it's all over southern Florida and affecting me. The poor Haitians look to be getting another big rain event if not a wind one too.. those folks just haven't had much of a break lately
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Quoting hurricane23:


Nah not really,ive not been impressed with 90L 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 agree completely.
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2466. alcomat
Quoting leftovers:
236 i guess after all these yrs following these storms we finally agree going to give my baby 18 yr old alittle extra time tonight. if you all have kids give them time talk to them dont let what happen to my wifes friends kid. "give them love" but no gas money. early tomorrow this rooster will be here.
you are so right and very very good advice.my babies are my life,I get chills just thinking of something happening to one of them.I am so sorry for your wifes friend,we need to listen to what our kids have to say,and we need to ask questions to.god bless
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Quoting extreme236:
TD2 looks impressive.
agree 100%
the 18Z GFS opens TD 2 as it heads west.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting WeatherStudent:



Oh God, your kidding, right Adrian? :(


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.
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TD2 looks impressive.
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2421 atomaggie

lol I have to look up where that is, im still kinda new to the area. thanks though :)
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Quoting CandiBarr:
Actually had more damage from Ike

i remember the flooding was bad from ike, could see it along the river on 12.

Thankfully we had none of the wet stuff. Only 6 miles inland from the Lake, but at 48 feet above sea level...on a hill...12 feet higher than anywhere else in a 2 mile radius.
I didn't buy flood insurance and a month later 12 inches of rain in one day...yard was still rock-hard and the ditches empty. Love my location.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting chevycanes:

can you post the link or post the image?


Link
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Another reminder as we approach the 20th anniversary of Hurricane Hugo.
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Quoting Weather456:


we were talking about 90L
oh im sorry.
Quoting AllBoardedUp:
It would have been if it were 50 to 100 miles west of where it came ashore. Correct?


That would wipe Terrebonne Parish off the map
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Quoting DM21Altestic:
Adrian, do you think TD 2 will become Hurricane Ana and threaten Florida?
im not adrian but im about 98% sure it will.
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



still, 7 to nothing...with bad calls. And you guys have Derrick Brooks
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I think that ExTD2 should become Ana before 90L

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Quoting canesrule1:
but how could it get renumbered if it is already "02L"


we were talking about 90L
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2448. Patrap
Quoting CandiBarr:


is that basically right up lake p-train?


Yall creeping me out..now



I guess we picked a Bad week to stopping Blogging.


Rising Tide 4 is the 22nd here.

Geeezum.

www.risingtidenola.net
Member Since: July 3, 2005 Posts: 426 Comments: 128654
Quoting WeatherStudent:



Oh God, your kidding, right Adrian? :(
no we will probably have a 1 2 punch a possible Cat 1, one day, and a possible Cat 3+ three days later. But i'm not evacuating! lol.
Quoting hurricane23:
Iam far more impressed at this hr with extd2 then the sheared large octopus behind it.


Yep
Member Since: September 2, 2007 Posts: 178 Comments: 20443
Quoting Stormchaser2007:
New intensity models bring ExTD2 to a strengthening Category 1 hurricane in the very warm Bahamas.



Track.


can you post the link or post the image?
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Quoting canesrule1:
but how could it get renumbered if it is already "02L"


I believe he was talking about 90L in which he is right.
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Quoting DM21Altestic:

Andrew was expected to become a hurricane and head out to sea


Actually it was headed towards central Florida. Melbourne was the target when I went to bed that night. Woke up and it had turned straight towards Homestead.
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2441. jipmg
Quoting stormdude77:
What if TD2 develops further, wouldn't that have an impact on 90L?


its way too small in my opinion to have an impact on such a large circulation, both are strengthening right now though, 90L is getting more organized convectively speaking, and TD 2 is getting stronger
Well of course, TD 2 will still be more interesting even if it remains a TD while 90L becomes Ana, even hurricane ana
Member Since: July 24, 2005 Posts: 407 Comments: 19076
2439. MrSea
Quoting stormdude77:
What if TD2 develops further, wouldn't that have an impact on 90L?


Well first off TD2 could over-turn and cool the waters out ahead of 90L if it got really strong. Also if Td2 got strong then heights would built back behind it and it would be unlikely for 90L to follow the exact same path.
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Quoting DM21Altestic:

Andrew was expected to become a hurricane and head out to sea
Quoting KoritheMan:


Andrew was initially forecast to recurve due to a split in the subtropical ridge to the north caused by an upper-level low. This did not materialize, as the upper vortex was too far north for Andrew to feel it.


Thanks. I dont remember cause I was like 7 and im to lazy to look it up atm. :)
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Quoting extreme236:


My concern is if it can become a hurricane and develop an eye, over those warm waters and high TCHP we could see it rapidly intensify. Big IF's but, something to think about.


Very different story since we were tracking this thing off the African coast eh? lol
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Quoting KoritheMan:


The 0-0-0 talk never had even a single percent of merit.


I disagree. Until something is named, it is the exact condition of the 2009 Hurricane season.

What, in my opinion, never had merit was the initial projections for an active season.

Those have been rolled back, so the first ones were meritless.
Member Since: August 26, 2006 Posts: 10 Comments: 3753
18Z

AL 90 2009081418 3 OFCL 0 125N 288W 25
AL 90 2009081418 3 OFCL 12 125N 316W 30
AL 90 2009081418 3 OFCL 24 125N 343W 35
AL 90 2009081418 3 OFCL 36 125N 371W 40
AL 90 2009081418 3 OFCL 48 126N 402W 45
AL 90 2009081418 3 OFCL 72 135N 470W 60
AL 90 2009081418 3 OFCL 72 135N 470W 60
AL 90 2009081418 3 OFCL 96 155N 535W 75
AL 90 2009081418 3 OFCL 120 175N 605W 95


00Z (interpolated 18Z)

AL 90 2009081500 3 OFCI 0 125N 305W 25
AL 90 2009081500 3 OFCI 12 125N 333W 30
AL 90 2009081500 3 OFCI 24 125N 360W 35
AL 90 2009081500 3 OFCI 36 126N 390W 40
AL 90 2009081500 3 OFCI 48 128N 422W 46
AL 90 2009081500 3 OFCI 60 133N 456W 53
AL 90 2009081500 3 OFCI 60 133N 456W 53
AL 90 2009081500 3 OFCI 72 140N 489W 61
AL 90 2009081500 3 OFCI 72 140N 489W 61
AL 90 2009081500 3 OFCI 84 150N 522W 68
AL 90 2009081500 3 OFCI 96 160N 556W 77
AL 90 2009081500 3 OFCI 108 170N 591W 87
AL 90 2009081500 3 OFCI 120 180N 627W 98
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Quoting stormdude77:
What if TD2 develops further, wouldn't that have an impact on 90L?


Still think 90L will ultimately win out, because it has a circulation much larger than TD2.
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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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