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 weathersp:
Born of the same mother...



Would that be Mother Eff?
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that gfdl model run is scary. i have a bad feeling it might pull a Katrina and go across Florida and into the gulf and hit Louisiana and Mississippi. according to the models it is going to be a hell of a storm. gfdl says it'll be a cat. 3 before it hits the islands. i think its going to go right along the northern edge of the islands and not meet much to bring the strength down. gut feeling its a gulf storm, or bad nerves. lol! Texas may be in its path too. well its far away, but what do you all think about it being a gulf storm. does it look or feel that way to you? what about the steering currents? what and where are they and how can i read them to see where the steering currents might take it?
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Quoting Chiggy007:
Canesrule:

That graphics you show re the position of 90L was at 12Z - that was some 4 hours ago now! On latest Sat images loop to me at least it look like 12N - 28W
i think its at 12.3-ish and 28.1-ish, close yo ur guess.
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Quoting HIEXPRESS:
Apologise for wasting blog space to say this but
Has any model really told us what we didn't know from climo - this time of year, anybody down wind could get a storm? If it forms watch it, if you find yourself in the cone (or near it), and you don't have a safe place to hunker down considering the worst case of possible rapid intensification, move out of the way.
Back to work.


Lol. Sure throw logic and common sense into the mix. ;)
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Quoting RitaEvac:
Somewhat shocked to see models in the Gulf like this...



The good thing, or bad thing depending on your perspective, is if this gets in the gulf these models have it going through PR, DR, and Cuba before getting there. Going up the spine of Cuba and the other islands would greatly diminish it.
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Born of the same mother...

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Quoting canesrule1:
Just click add all at the bottom of the model list and you good to go:Link


Thanks!
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Somewhat shocked to see models in the Gulf like this... this far out?

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Quoting SavannahStorm:


Quite the spread.
Yep, pretty consensus 5 days out, then the spread begins.

Quoting PcolaDan:


Cue Jaws music.

LOL - Thanks for the giggles.
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1 - 2 punch brewing for someone? That's not good.
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324. jpsb
Quoting MrSea:


Lol im not exactly sure why it happens, but its been happening to me every once in a while for the past 2 years.. so i doubt its a virus
I would be willing to bet that is the weather underground error message for a page not found error. Not sure how weather underground generates it pages, but sometimes a busy web server can error, when it does it defaults to an error page. No big deal, not a virus, just a busy server tring to keep up with demand.
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Quoting canesrule1:
LOL, i love going through hurricanes, and i remember andrew, when i went outside, we were receiving winds over 130MPH, and i was still loving it, i recorded it as-well, very breathtaking, but then u have to deal with the sadness of the death and devastation other people suffer.


Gee I hope you don't let a little death and destruction rain on your picnic...
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Canesrule:

That graphics you show re the position of 90L was at 12Z - that was some 4 hours ago now! On latest Sat images loop to me at least it look like 12N - 28W
Quoting scott1968:
Hi, looking for a link to any of the LONG RANGE models. Thanks in advance!
Just click add all at the bottom of the model list and you good to go:Link
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Quoting canesrule1:


That image is almost 4 hours old.
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Quoting TheCaneWhisperer:
Very possible to have 2 tropical depressions @ 5pm
agreed, i think we might have Ana by tomorrow.
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Member Since: August 2, 2007 Posts: 19 Comments: 19234
Hi, looking for a link to any of the LONG RANGE models. Thanks in advance!
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Quoting hurricanehanna:

I think he loves the thrill of a storm, then panics thinking they are all going to hit him....too much time on his hands if you ask me.
LOL, i love going through hurricanes, and i remember andrew, when i went outside, we were receiving winds over 130MPH, and i was still loving it, i recorded it as-well, very breathtaking, but then u have to deal with the sadness of the death and devastation other people suffer.
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Very possible to have 2 tropical depressions @ 5pm
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Quoting Grothar:
Hi guys...been away for awhile. Considerable activity in such a short time. DRAKOEN. Question: It would appear very little shear will interfere with 90L. From my limited observation it does not seem apparent that any weaknesses in the high would be strong enough to steer 90L to higher latitudes until after it reaches the islands. Is my assumption correct? Also, are you in ageement with the models (GFDL) showing such a strong system that soon. I would appreciate any other's comments. This is all quite interesting for a novice!


What the GFDL and other intensity model is a real possibility. Most of the models have significant strengthening of the system once it gets going.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
Extreme: thank you Sir!

Seems like it's moved lot more West than the models had them only few hours ago at 26W!?
310. 786
exactly, all of this is speculation up until the last minute the steering changes. Dean was supposed to come right through Grand Cayman and within the hour it was due to hit it ended up going well South of us, we didn't even get rain! Paloma was supposed to be a direct hit and last minute went North of us. On the other hand Ivan was supposed to go North of us and last minute came right over. So really everyone should be prepared (that's never a bad thing) but there is NO telling where it will go - even when it is 5 days out. The tracks will continue to shift N and S.
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Quoting StormW:


You are? Are are you asking if I'm gonna be on?

I'm listening to the podcast of this morning/last night's show.
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting ftpiercecane:


He's probably putting up his storm shutters.

lol!
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TD2: The Little Engine That Could?

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Quoting AussieStorm:

I get it all the time... I just refresh the page again.

Thanks Aussie - it worked!
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Apologise for wasting blog space to say this but
Has any model really told us what we didn't know from climo - this time of year, anybody down wind could get a storm? If it forms watch it, if you find yourself in the cone (or near it), and you don't have a safe place to hunker down considering the worst case of possible rapid intensification, move out of the way.
Back to work.
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Quoting Chiggy007:
Can someone confirm LLC of 90L - I clearly it at 12N - 28W!!
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Troughs here in the east have been pretty deep most of the summer,but now things are more summerlike,with troughs not very deep.
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Quoting StormW:


Hey!

Hey StormW, Do you think the next few weeks is going to be overly active?
Member Since: September 30, 2007 Posts: 9 Comments: 15935
Quoting canesrule1:
ROFLMAO!!! I live in Miami and a lot of models are pointing here im not worried, i dunno what is his problem, lol.

I think he loves the thrill of a storm, then panics thinking they are all going to hit him....too much time on his hands if you ask me.
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Quoting Chiggy007:
Can someone confirm LLC of 90L - I clearly it at 12N - 28W!!


I had 28.1 but close enough
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As Dr. Masters said, shear should decrease further over 90L later today and allow the center to become more involved with the main convection.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Hi guys...been away for awhile. Considerable activity in such a short time. DRAKOEN. Question: It would appear very little shear will interfere with 90L. From my limited observation it does not seem apparent that any weaknesses in the high would be strong enough to steer 90L to higher latitudes until after it reaches the islands. Is my assumption correct? Also, are you in ageement with the models (GFDL) showing such a strong system that soon. I would appreciate any other's comments. This is all quite interesting for a novice!
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Quoting hurricanehanna:
I know this is off topic, but why does this keep happening when I refresh? Is it part of the virus from a few days ago? Thanks.

JeffMasters does not have any blog entries.


no it happens to me too every once in a while gotta just refresh again
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Quoting Chiggy007:
Can someone confirm LLC of 90L - I clearly it at 12N - 28W!!


Thats just about where it is at.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Drakoen:
Good thing JFV isn't here. He would go into cardiac arrest looking at that long-range CMC


Please don't blow the dog whistle. LOL j/k
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I still think the Hurricane effects the Islands, heads to the Bahamas and heads north maybe just east of Florida like Floyd in 1999 due to a trough and heads slightly east of due north, hits the Northeast. Conditions are setting up for an East Coast hit, also mentioned by some meteorologist besides Joe Bastardi, the pattern is setting up for an East Coast storm, not a GOM storm.. Though this thing is still at least a week away before it impacts anybody, so it's gonna take time and patience.
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The T-Numbers update every 6 hours next update will be 1:45EDT
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Quoting Drakoen:
Good thing JFV isn't here. He would go into cardiac arrest looking at that long-range CMC


He's probably putting up his storm shutters.
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Quoting TheCaneWhisperer:


Current Time is 15:33

prob back to 1.5 now or very very soon and or 2.0
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Can someone confirm LLC of 90L - I clearly it at 12N - 28W!!
Quoting StormW:


ROFLMAO Drak!

Hey StormW, Just listening to you on the show tonight?
Member Since: September 30, 2007 Posts: 9 Comments: 15935
286. MrSea
Quoting hurricanehanna:
I know this is off topic, but why does this keep happening when I refresh? Is it part of the virus from a few days ago? Thanks.

JeffMasters does not have any blog entries.


Lol im not exactly sure why it happens, but its been happening to me every once in a while for the past 2 years.. so i doubt its a virus
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banding has become more evident as of the 15:15 UTC on former td2
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Quoting weatherfan92:


I've been getting that too. Is anyone else getting an error message that closes the webpage?


I have been as well. I haven't logged in for most of the season, and I did two days ago, right after that my computer started going ape sh**. Not sure!
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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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