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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3484. Patrap
Quoting StormW:


Looks that way my friend. I'll probaly post sometime tomorrow afternoon.

Thank you and those who joined in the show last night.


Shucks StormW,.thats was a good experience for many as everyone enjoyed it all Im sure.
Member Since: Posts: Comments:
Quoting Stoopid1:
NHC is doing 8p.m. and 2a.m. updates now since there are no organized systems. Once a TD forms they do 11 and 5 updates.


Half they time they are issuing these things whenever they want now lol...look at all these special advisories this year so far in the EPAC too.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
I know the problem, both storms are going to be declared at TS status and they can't figure out which storm to name Ana and which to name Bill.....

but seriously, if both are declared at the same time how do they figure out what to call each one?
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Quoting Patrap:



Id say watch your Local Sources and NWS and NHC for updates throughout the week but Im 100% sure the Media will be on these Like Milk Gravy on Biscuits at a Georgia Truck Stop..
thanks Pat...love all your little sayings..cute...and hope you enjoyed the game
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3480. GatorWX
Quoting TampaSpin:
Has anyone ever seen the case of an 11pm update come out this late before..i haven't....


no, not this late!! I've noticed it being 15-20 mins, but it's going on midnight, lol, maybe hit f5
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impressive

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Patrap:



Id say watch your Local Sources and NWS and NHC for updates throughout the week but Im 100% sure the Media will be on these Like Milk Gravy on Biscuits at a Georgia Truck Stop..


You got a book of those or something?
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Quoting sammywammybamy:


Tampa... Look at all that Heat...

TD2 Could Become a Hurricane


I think it has a good chance and it could become more than people would ever would have believed 12hrs ago.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
link
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I SAY WE ALL JOIN TROPICS TALK!!!!!!!!!
Quoting HurricaneTracker1956:
It's my imagination or I can see a low developing south of Cuba,most of the models are showing a small system,TD or TS forming South of the tip of Florida or just to the East in GOM,any comments???

our local meteoroligist just spoke of the low south of cuba scenario said it may merge with the other...said they are watching it closely
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NHC is doing 8p.m. and 2a.m. updates now since there are no organized systems. Once a TD forms they do 11 and 5 updates.
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Just came in to the blog, how close should we, on the gulf coast, be paying attention to the weather coming between FL and Cuba?
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Quoting TampaSpin:
Has anyone ever seen the case of an 11pm update come out this late before..i haven't....
no update at 11 maybe at 2?
oops.
Its a good bet Td 3 is forming or atleast has form.....5am
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3464. Patrap
Quoting KATRINABILOXIGIRL:
so Pat what are the chances that I won't be delivering the mail on the MS gulf coast in the next coming week or so?



Id say watch your Local Sources and NWS and NHC for updates throughout the week but Im 100% sure the Media will be on these Like Milk Gravy on Biscuits at a Georgia Truck Stop..
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It's my imagination or I can see a low developing south of Cuba,most of the models are showing a small system,TD or TS forming South of the tip of Florida or just to the East in GOM,any comments???
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the models have been like a 'YO YO' all day
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g'night ya'll.
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Has anyone ever seen the case of an 11pm update come out this late before..i haven't....
Member Since: September 2, 2007 Posts: 178 Comments: 20439
tampaspin u there?
No TD at 12:00Midnight, guess we got to wait till 1 or 2 am.
3456. Patrap
Quoting jipmg:


a little spin is seen on the radar,either a mid level low or a weak surface low



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Quoting weatherboykris:
GFS ensembles not as tightly clustered. The main group nudged a bit north and their are now a few southern outliers. The overall average seems to have shifted north, IMO.



I would think a northern shift puts Florida more at danger, while a southern shift puts the rest of the gulf at more danger.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
On NightLine they are about to talk about the drought in Texas that is so bad. Do you think we may get any rain soon? Not hurricane, just rain?
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GFS ensembles not as tightly clustered. The main group nudged a bit north and their are now a few southern outliers. The overall average seems to have shifted north, IMO.

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Quoting Relix:
PR Media Insider Info! Seriously, I know quite a few people that work in Univision PR and Telemundo. Technicians mostly! The thing is I got in contact with them and they all replied that they are ready for the storms coming over. They have the title banner, the music, etc etc and that they are getting ready to expect a direct hit to PR soon so they could be signing hazard contracts, etc etc soon. Media taking this serious here!
They should be. Besides, if it is not this storm, I'm sure we will see at least one in our area before the end of the month.
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Quoting Funkadelic:
Cycloneoz, My cousin is still going out if 90L, and x td 2 pose a threat to land. As of right now what is the best place to set up shop in the Conus?


Stay put.

No one can answer that question yet.

Disclaimer: Hurricanes are extremely dangerous storms that ravage entire regions. Airborne debris and storm surge is deadly to human beings. Evacuate if ordered to do so, or hunker down in a safe shelter until the storm abates.
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Quoting Patrap:


That's a good Idea as well,its the first of a series of frays from the Atlantic,..the next two behind are bad,and worse.

I got my eye on it like a phat tick on a tired bloodhound...
so Pat what are the chances that I won't be delivering the mail on the MS gulf coast in the next coming week or so?
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00Z GFS 48 hrs

Member Since: July 24, 2005 Posts: 407 Comments: 19076
3446. Patrap
Quoting StormW:
Hi Patrap...456!



Hiya Chief,..looks like a Long brew week with the coffee and the Atlantic..
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Well guys, I'm gonna call it a day.
Maybe 90L and 02L will develop by the time I wake up.
Member Since: August 9, 2009 Posts: 10 Comments: 4888
If I read this:
http://www.nco.ncep.noaa.gov/pmb/nwprod/prodstat/index.html#TARGET

correctly,

The 00 UTC GFS 24hr PRODUCTS

Should be done in just a very few minutes.


[edit] now it says "Complete"
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3443. jipmg
TD 3 looking amazingly good on satellite
Hey StormW, I hailed you earlier but the blogs were moving fast.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3441. Patrap
Quoting Nolehead:
patrap...that's what i'm watching...once it gets in the gom...watch out for the boom....


That's a good Idea as well,its the first of a series of frays from the Atlantic,..the next two behind are bad,and worse.

I got my eye on it like a phat tick on a tired bloodhound...
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3440. Jerrob
StormW.... LOL!
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3439. Relix
PR Media Insider Info! Seriously, I know quite a few people that work in Univision PR and Telemundo. Technicians mostly! The thing is I got in contact with them and they all replied that they are ready for the storms coming over. They have the title banner, the music, etc etc and that they are getting ready to expect a direct hit to PR soon so they could be signing hazard contracts, etc etc soon. Media taking this serious here!
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This is how things changes fast, every thing shifts west

LINK
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Weather456:
Thats how Dean and Georges evolved, lopsided convection became more symmetric. This is so similar to those 2 storms, that its hard to ignore the models



Dean and Georges where both beasts too, espeically Dean.
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3435. jipmg
Quoting Patrap:


a little spin is seen on the radar,either a mid level low or a weak surface low
3434. Patrap
Quoting Funkadelic:
Cycloneoz, My cousin is still going out if 90L, and x td 2 pose a threat to land. As of right now what is the best place to set up shop in the Conus?




.."WS's front yard Im sure is available"..
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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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