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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90L no doupt appears to be currently impacted by shear easterly shear that is and if this continues it may very well track into the caribbean as the GFDL suggest.
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GFDL run is not much different from the GFS run.
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GFDL is coming more in line with the GFS though.
Member Since: October 28, 2006 Posts: 57 Comments: 30601
hanna- you're more sophisticated than my parents. We just grab a sheet and drill it up. Rinse & repeat. Mom made Dad leave her a little "peep hole" at the tops of the windows so she could at least see out. Bless her heart.
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779. Skyepony (Mod)
Quoting Drakoen:
If TD2 becomes a tropical cyclone again you can bet on those model changing even just a little. Some of the computer models suggest regeneration of the system.


Totally agree~ weak systems, kinda close together. TD2 is tapping into 90L's convection a little here & there. Ways to go with these two.

East coast seabreeze is firing up here in Melbourne.
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Quoting Mclem1:



It's a legitimate fear but an unlikely one at that. Who KNOWS where this storm could be going days from now, anything could direct it your way, but there are so many factors in steering these storms. If a frontal system comes off the east coast or some sort of blocking high steers it you could be in the clear pretty easily. Even if it reaches you, judging by the Sea surface temperatures right now, if it rides the east coast Floyd style, it could make it up there at Hurricane strength, especially if it has some speed behind it. This is only my opinion of course. And dont get too worried yet, We are days and days away from knowing where it's headed!


Awsome, i figured it would be something like this, usually the storms turn into depressions by the time they get up here, but every few years we get a hurricane, and its been 5 years so it's getting about time. =(
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Someone hide the crayons....NHC is at it again!
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00Z Runs Will have the data
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Quoting hurricanehanna:

Ours still is! lol and they are labeled for each window.
Ours is ducktape. It's cheaper and we don't have to label them....lol
774. slavp
Quoting MandyFSU:


Ha- my parents' idea of hurricane shutters was plywood over the windows lol
LOL I see people out here still use duct tape
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Wow just checking in to see what is going on with 90L and I see that Old TD2 is making a come back.... I'm more concerned about 90L than any other but I do see we will be wet this sunday due to the Tropical wave moving thru.... I'm wondering if we have any eddy's in the gulf???? can someone help me out....

Taco :0)
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Quoting Patrap:
And if a BIG threat comes up our way,..IM gonna be sipping Whiskey with Press out on Sunny Johns Island,S Carolina..too


Would you be willin to ship some out to Tampa for your ole pal ted?
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I'd watch the east coast and NE Gulf area...wouldn't be surprised to see something pop up here as well. Be back in a little bit.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
What models will be the first to incorporate the data from the reconnaissance flights below?


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.


-------------------

CRS
Member Since: July 12, 2007 Posts: 0 Comments: 6064
12Z GFDL is south of HWRF. Into the Caribbean

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Quoting MandyFSU:


Ha- my parents' idea of hurricane shutters was plywood over the windows lol

Ours still is! lol and they are labeled for each window.
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Quoting hurricane23:
Caribbean cruiser?


The problem for me with that run is it has it moving to the WSW. What is going to do that.
Member Since: October 28, 2006 Posts: 57 Comments: 30601
Member Since: August 9, 2009 Posts: 10 Comments: 5070
765. Skyepony (Mod)

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And if a BIG threat comes up our way,..IM gonna be sipping Whiskey with Press out on Sunny Johns Island,S Carolina..too
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763. 7544
attention post 742 eveytime you post those aminatied imagesyou frezze the blog please link them ty
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Quoting hurricane23:
Caribbean cruiser?


Interesting, reminds me more of Dean. Will watch to see if the models will follow the GFDL and also track it through the Caribbean.
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Quoting futuremet:


LOL my family never put up hurricane shutters. We have been hit directly by three canes, and still don't care.


Ha- my parents' idea of hurricane shutters was plywood over the windows lol
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http://www.nhc.noaa.gov/gtwo_atl.shtml
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Quoting alaina1085:


We dont bother either. lol. If you shutter up then you


My kid hit the enter button before I was done lol. Anywho, we like to see whats going on and go outside like idiots.
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Quoting Drakoen:
If TD2 becomes a tropical cyclone again you can bet on those model changing even just a little. Some of the computer models suggest regeneration of the system.


Yes, and it will be a bigger threat to the east coast than 90L.
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Yeppars Drak,

..were gonna need Lotsa Lil Pins fer da Tracking Map here in Big Duke NOLA Sevens Living room Command Post,..
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yes extreme it is still popping off some deep convection but i'm sure D max tonight can get them to get in a more organised manner. Structure is improving by the hour now its convection needs to catch up.
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Yes I can also see the curvature of the clouds over the Bahamas,like something is trying to get going in there, I made a comment about that too a while ago, some of the models develop a tropical system TD OR TS,at the south tip of Florida or just East of the South Tip.
Check the NOGAPS link:
http://www.nwmangum.com/NOGAPS.phtml
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Quoting futuremet:


LOL my family never put up hurricane shutters. We have been hit directly by three canes, and still don't care.


We dont bother either. lol. If you shutter up then you
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Quoting extreme236:
Not the first time they've said a little less organized and a TD formed within 1-2 advisories (i.e. TD /Gert in 05)


Its just because of the shear thats effecting it, plus its getting close to DMIN. Convection wise, its sustaining itself though.
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Caribbean cruiser?
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If TD2 becomes a tropical cyclone again you can bet on those model changing even just a little. Some of the computer models suggest regeneration of the system.
Member Since: October 28, 2006 Posts: 57 Comments: 30601
Quoting hurricane23:


Nope...Infact if i had to bet the models might shift into the caribbean.12z GFDL just came in futher south.


LOL my family never put up hurricane shutters. We have been hit directly by three canes, and still don't care.
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Don't see any reason why we won't see a blowup tonight and a TD by 5 PM tomorrow, other than shear which is decreasing.
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Biggest TWO we've had all year I believe.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Not the first time they've said a little less organized and a TD formed within 1-2 advisories (i.e. TD /Gert in 05)
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting WeatherStudent:
Plz, Pressy, plz! Are you gonna be looking over your hurricane kit this weekend, Adrian?


I think you may want to look into moving to Nebraska. It may keep you from having a heart attack.
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FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWER ACTIVITY HAS BECOME A LITTLE BETTER ORGANIZED IN ASSOCIATION
WITH THE REMNANT LOW OF FORMER TROPICAL DEPRESSION TWO...LOCATED
ABOUT 1225 MILES EAST OF THE LESSER ANTILLES. WHILE UPPER-LEVEL
CONDITIONS ARE ONLY MARGINALLY FAVORABLE FOR DEVELOPMENT...
REGENERATION OF THIS SYSTEM INTO A TROPICAL CYCLONE IS POSSIBLE AS
IT MOVES WESTWARD AT ABOUT 15 MPH OVER THE NEXT COUPLE OF DAYS.
THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
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Quoting WeatherStudent:
Plz, Pressy, plz! Are you gonna be looking over your hurricane kit this weekend, Adrian?


Nope...Infact if i had to bet the models might shift into the caribbean.12z GFDL just came in futher south.
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RyanFSU HWRF 12Z hypercane forecast deluxe again! 90L to Category 5 once more...


Got to love the HWRF. After a weird initialization it takes a while for 90L to get really going, and given it's present organization with shear being a culprit, that's pretty believable
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742. P451
TD2 & 90L

VIS, WV, AVN





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Quoting Drakoen:


Interesting NOGAPS. Perhaps it could be a player. Models are differing on its track though


CMC also keeps TD2 alive and strengthens it a bit (but still weak) but has it going through Cuba and into the SE Gulf of Mexico around when 90L is approaching the islands.
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Quoting WeatherStudent:
Plz, Pressy, plz! Are you gonna be looking over your hurricane kit this weekend, Adrian?


omg
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Quoting hurricane23:
Heres comes the shift?

12z GFDL into the caribbean.


It has 90L moving WSW for a period of time. Satellite imagery shows the system moving north of due west.
Member Since: October 28, 2006 Posts: 57 Comments: 30601
738. A4Guy
looks to me like HWRF shifted south...am I missing something?
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Quoting Chiggy007:
12Z GFDL in now futher south...models have no idea beyond 55W...


713. hurricane23 1:34 PM EDT on August 14, 2009
Heres comes the shift?

12z GFDL into the caribbean.
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Plz, Pressy, plz! Are you gonna be looking over your hurricane kit this weekend, Adrian?
90L closing out LLC at or near 11.5N 29.5W will be a named storm tonight or earlier tomorow I buy the GFS forrescast, as been so far preaty accurate a Major over PR in August 20, 2009 142 hours from now and counting hope the local goverment is on top of this tropical cyclone and activate the Emergincy agency at least 72 hrs before the storm arive next thursday.
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They're saying 90L is slightly less organized, but that doesn't surprise me seeing how large it is and its getting close to DMIN. I'll say TD on Saturday for 90L and TD2 might regenerate on Sunday.
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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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