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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(ex) TD 2 is looking much better and is wrapping around nicely, we may have a regeneration on hand.
Member Since: Posts: Comments:
Quoting hurricanehanna:
*Press, hand me a Thorazine shot....now, JFV, hold real still...."


LOL!
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1182. Patrap
The G-4 Departs at 2000 UTC or in 32 minutes
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1181. Michfan
Quoting hurricanehanna:
*Press, hand me a Thorazine shot....now, JFV, hold real still...."


Hahahahaha
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Quoting Drakoen:
Interesting ensembles which is why i'm not sold on the southern solution just yet.


Ya, we got 20 more model runs untill it gets in the vicinity of the Leewards.
Member Since: September 23, 2005 Posts: 14 Comments: 11215
1179. WxLogic
Quoting nrtiwlnvragn:


Hehe... the typical flip-flop on long range. At least we can feel with a high degree of certainty that the Northern Leeward Islands will need to watch out for this one... that include you 456... hehe...
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A recurve looks more likely according to the latest ensemble models.
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1177. Patrap
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*Press, hand me a Thorazine shot....now, JFV, hold real still...."
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Quoting WxLogic:


I won't be surprised that it might be starting to feels some of that octane already.


We got the G-IV jet going out in about an hour and half.. Hopefulle we get some good sondes..
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Quoting Dakster:


I keep thinking that way too... The last place this thing will hit is where the long range models show it...


amen. in Tampa, the safest place to be is in the center of the Cone of Uncertainty 5 days out.
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1173. Michfan
Apocolypticane....LOL
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Quoting Drakoen:
When O2L get past 50W is when we might start seeing things ramp up:


It is certainly getting close there
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1171. Drakoen
Interesting ensembles which is why i'm not sold on the southern solution just yet.
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1170. WxLogic
Quoting Drakoen:
When O2L get past 50W is when we might start seeing things ramp up:


I won't be surprised that it might be starting to feels some of that octane already.
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1169. Dakster
Quoting FloridaTigers:
I'm glad the models are aiming in the general direction of Florida. It means it won't be anywhere near here a week from now :P


I keep thinking that way too... The last place this thing will hit is where the long range models show it...
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Quoting leftovers:
president clintons wife is there today cape verde islands wonder if bill and her ever see each other anymore
Is she?

I find that kinda ironic considering that wave by the CVs could end being called... Bill.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
1166. Patrap
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Member Since: September 23, 2005 Posts: 14 Comments: 11215
1163. Drakoen
When O2L get past 50W is when we might start seeing things ramp up:
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Quoting canesrule1:
wow, definitely a southward shift, SFLA might now get a hurricane.


*sigh* Yes, noticed the shift as well. It looks worse and worse for us here in Puerto Rico each passing hour. :-s
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1161. WxLogic
Quoting wunderkidcayman:
000
NOUS42 KNHC 141400
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT FRI 14 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 15/1100Z TO 16/1100Z AUGUST 2009
TCPOD NUMBER.....09-078

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: PSBL LOW LEVEL INVEST
FOR 16/1800Z NEAR 17.0N AND 55.0W ON THE REMNANTS
OF TD-02. 3. NOTE: 1- THE G-IV WILL FLY A RESEARCH MISSION AROUND
THE REMNANTS OF TD-02 TODAY DEPARTING TBPB 14/2000Z.

2- BOTH NOAA43 AND G-IV WILL FLY RESEARCH MISSIONS
IN AND AROUND THE REMNANTS OT TD-02 DEPARTING TBPB
15/2000Z.
can someone when they say today do they mean 14/8/08/2000z


Yeap... departing Barbados @20HR on 8/14. So they should be out in 1 hour to 2 hours or so.

CORRECTION: 30 Min since I was looking at an outdated clock
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Quoting hurricane23:


HPC link...How you been? Its been a while since ive seen on here.Iam Tired long day @ work.


I've been good, very busy with sports and school.
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1158. Drakoen
Quoting wunderkidcayman:
000
NOUS42 KNHC 141400
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT FRI 14 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 15/1100Z TO 16/1100Z AUGUST 2009
TCPOD NUMBER.....09-078

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: PSBL LOW LEVEL INVEST
FOR 16/1800Z NEAR 17.0N AND 55.0W ON THE REMNANTS
OF TD-02. 3. NOTE: 1- THE G-IV WILL FLY A RESEARCH MISSION AROUND
THE REMNANTS OF TD-02 TODAY DEPARTING TBPB 14/2000Z.

2- BOTH NOAA43 AND G-IV WILL FLY RESEARCH MISSIONS
IN AND AROUND THE REMNANTS OT TD-02 DEPARTING TBPB
15/2000Z.
can someone when they say today do they mean 14/8/08/2000z


They are departing in 38 minutes
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Quoting WeatherStudent:


Meaning?


meaning it might curve before it reaches south florida.
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Quoting WeatherStudent:


Pat, folks like over there? I didn't know that. Talk about the middle of no where, LOL.

Some people don't like the hustle and bustle of living in a city. Also, the weather there is like southern California, without the earthquakes.
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I predict a TD out of 90L later tonight. DMAX plus lower shear should get things going quick.
000
NOUS42 KNHC 141400
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT FRI 14 AUGUST 2009
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 15/1100Z TO 16/1100Z AUGUST 2009
TCPOD NUMBER.....09-078

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: PSBL LOW LEVEL INVEST
FOR 16/1800Z NEAR 17.0N AND 55.0W ON THE REMNANTS
OF TD-02. 3. NOTE: 1- THE G-IV WILL FLY A RESEARCH MISSION AROUND
THE REMNANTS OF TD-02 TODAY DEPARTING TBPB 14/2000Z.

2- BOTH NOAA43 AND G-IV WILL FLY RESEARCH MISSIONS
IN AND AROUND THE REMNANTS OT TD-02 DEPARTING TBPB
15/2000Z.
can someone explane when they say today do they mean 14/8/08/2000z
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Quoting weatherboykris:


What's up Adrian? And what r u thanking me for?


HPC link...How you been? Its been a while since ive seen on here.Iam Tired long day @ work.
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Quoting Patrap:
Current Image from That Cape Verde Webcam



It would be eerie living Cape Verdes, you get to experience rain showers that would morph into behemoths down the road.
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ex TD2 still has a very nice circulation on visible floater at the ssd site.
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A lot of models predicting the curve right before it reaches SFL.
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1146. Patrap
Current Image from That Cape Verde Webcam

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Quoting 92Andrew:
So what used to be Tropical Depression 2 is no longer an invest? How could that be? The storm, as it stands right now, looks relatively healthy and should at least be declared an invest.


It is an invest in a way. Its just 02L
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Quoting Patrap:


Yeah, seems these keep getting a little more south..is it just me?

Seems like some of those other storms where they were saying it will turn more northerly and it just never happened....time will tell I guess.
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Quoting jeffs713:

Take out CLP5 (climatology), and you have an insanely tight spread of models, especially for something that hasn't been fully initialized yet.


Reminds of Gustav, the model consensus was impressive. Shortly after it made landfall in Haiti, the model consensus were focused on a NOLA hit.
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1142. fmbill
Quoting bwi:
HPC's 3-7 day outlook final issuance for today now up.

Although HPC isn't going to go out on a limb on intensity, their discussion says the track ideas are coordinated with TPC. Looks like they estimate 90L just north of Haiti Day 7.


...and TD2 is an open wave.

Sure looks like back-to-back landfalls are a real possibility for Florida.

I'm looking forward to some HH data getting into the models.
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Quoting leftovers:
if l lived in tampa i'd be concerned about the new yellow circle


I live in st. petersburg, fl and its not that concerning. right now just a lot of rain no wind. If it was to turn into anything probably wouldnt have much time before coming ashore.
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P451 - I like your graphics and please keep posting them, they are not big files and are very relevant.
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Quoting hurricane23:
Thanks kris.


What's up Adrian? And what r u thanking me for?
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Quoting nrtiwlnvragn:
wow, definitely a southward shift, SFLA might now get a hurricane.
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1135. viman
Quoting Cotillion:


Link

That might be what you're looking for.
Thanks, I gotta go for now but I've saved the link and I'll explore it later
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Quoting nrtiwlnvragn:

Take out CLP5 (climatology), and you have an insanely tight spread of models, especially for something that hasn't been fully initialized yet.
Member Since: Posts: Comments:

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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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