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 ackee:
It just seem to me that some poeple make it seem like the GFS is the only model frankly not big fan of GFS my view


It is one of the few that go out that far. It is tightly clustered with all the others in the 5 day range.
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Thank you for the information,I just got the feeling that this wave North of Cuba can be a problem in the next 48-72 hours.
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forecast. lol.
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Quoting Patrap:
How frigging Hard is it to Google Tropical Models,,last time I checked it took,1.785 seconds. And I had to wait ,and sweat all that time.

LOL

But in that 1.785 seconds, things could change? (no comments about how a blog posting will take 5-10 minutes for a reply)
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Dean



90L

Member Since: July 24, 2005 Posts: 407 Comments: 19076
I believe this could possibly be a Rita or Katrina type path with south florida getting hit first and making a second hit somewhere on the Northern Gulf coast but thats just IMO right now...
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Quoting nrtiwlnvragn:


AMS Glossary

recurvature—The change in direction of tropical cyclone movement from westward and poleward to eastward and poleward, under the influence of midlatitude westerlies.
Such recurvature of the path frequently occurs as storms move into midlatitudes and is a major concern in tropical cyclone forecasting.


/clap!!!
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Quoting StSimonsIslandGAGuy:
Good afternoon, all! I'm back home from FIU. So, any new and or recent developments regarding 90L's future strength and trayectory this afternoon? :)


WEatherStudent, so sorry you are home from having the flu! Is it swine flu?


LOL you are joking right StSimons????
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The only real forecsat will come after it is a depression.
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Quoting Hurricane1956:
I just notice that most of the models,develop some how the tropical wave north of Cuba just below the tip of Florida or just on the East coast into a tropical depression or storm and take it to New Orleans.Any comments?.To me I can see in the satellite presentation some minor bandings?,can this be developing slowly into something?.

It is embedded in an ULL, it will take a bit to organize into a TC (if at all). It still bears close watching, though.
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How frigging Hard is it to Google Tropical Models,,last time I checked it took,1.785 seconds. And I had to wait ,and sweat all that time.

LOL
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Quit speculating on a model run 216 hours out. It shows Florida now, might go back to the GOM or out to sea next run. Through hour 180 it has been consistent with being northwest of Haiti, after that its a crapshoot.
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Quoting Skyepony:
StSimon~ WU long run GFS Takes out SFL about 200hrs.


Not to mention NOLA.
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I just notice that most of the models,develop some how the tropical wave north of Cuba just below the tip of Florida or just on the East coast into a tropical depression or storm and take it to New Orleans.Any comments?.To me I can see in the satellite presentation some minor bandings?,can this be developing slowly into something?.
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Quoting BenBIogger:
GFS 216 hours

your going to kill the poor JFV.
Thats a big shnooter
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Well i know this is an odd question, because models keep changing, but yesterday the GFS had 90L coming right up to me in eastern canada, nova scotia to be exact. I know model has changed now and they arnt very reliable, but my question is, if it WERE to come up the coast, would it still be a hurricane when it got here, we don't get many hurricanes up this way, but hurricane juan is still talked about, that was only category 2 when it hit and destroyed everything, can still see the effects in some places and that was back in '04. Registered just to post this question :P, been reading for a while :)
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561. Skyepony (Mod)
StSimon~ WU long run GFS Takes out SFL about 200hrs.
Member Since: August 10, 2005 Posts: 225 Comments: 39381
Quoting StSimonsIslandGAGuy:
Why is it called recurvature and not curvature?


AMS Glossary

recurvature—The change in direction of tropical cyclone movement from westward and poleward to eastward and poleward, under the influence of midlatitude westerlies.
Such recurvature of the path frequently occurs as storms move into midlatitudes and is a major concern in tropical cyclone forecasting.
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Quoting reedzone:
This is NOT good for me here in Northeast/Central Florida



Not good for Georgia either!
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GFS 216 hours

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There is Plenty evidence of PAST Hurricanes in the geologic recorded of the Basin.


Michael K. Crosby
Carl A. Reese
Geologic Evidence of Hurricane Rita Recovered from Texas Point, TX
Southeastern Geographer - Volume 49, Number 1, Spring 2009, pp. 41-48

The University of North Carolina Press

Abstract:

Hurricane Rita made landfall at the Texas/Louisiana border on 24 September 2005 as a category 3 hurricane. In November 2006, four cores were recovered along a north-south transect from the marsh at Texas Point, TX. Loss-on-ignition and grain size analysis identified the inorganic storm layer (consisting of fine-grained sands and silts) deposited as a result of this event. Results show that the sediment pushed inland by the 3 m storm surge was unevenly distributed along the transect. Areas of open water (i.e. small lakes) along the transect provide a different depositional environment than the vegetated marsh surface and affect the characteristics of the storm layer, and thus potentially the interpretation of the hurricane history. This variability suggests that great caution is required when reconstructing past hurricane activity in marsh environments, especially when storm layer thickness is being used for the estimation of past hurricane strength.



Link
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Quoting Patrap:
Fortunately Gut feelings have no Basis In Fact or forecasting,if that were true,JFV would have Obliterated S Fla,10 Times over since June I 2007


roflmao, BAWHAHAHAHAHAHA

Pat, that is funny!!!
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KEH - good idea - I never thought of having entertainment packed in the hurricane kit...makes sense though!
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I just notice that most of the models,develop some how the tropical wave north of Cuba just below the tip of Florida or just on the East coast into a tropical depression or storm and take it to New Orleans.Any comments?.To me I can see in the satellite presentation some minor bandings?,can this be developing slowly into something?.
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Quoting HurricaneKyle:


As long as ex-TD2 generate convection, it will serve pretty much as a dust sweeper for 90L.
very true!
Quoting WeatherStudent:
Good afternoon, all! I'm back home from FIU. So, any new and or recent developments regarding 90L's future strength and trayectory this afternoon? :)


Don't look at the GFS. I mean, really don't look at the GFS saying it is coming right to SEFL, and going to stall directly over your house. ;)
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Short term it would be bad for a SEFLA economy long term it could actually help. Construction Jobs, Housing filling up Etc... Buying materials to repair rebuild... The instant boon from purchasing supplies pre hurricane... Floridians know how to get on there feet FAST! Of course everyone preforclosure might be opening there windows and doors for it...

im not wishing it here because I love my reduced rate homeowners insurance right now..
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Quoting Progster:


ex TD2 - a "star" fish storm?


As long as ex-TD2 generate convection, it will serve pretty much as a dust sweeper for 90L.
Member Since: August 10, 2009 Posts: 3 Comments: 672
This is NOT good for me here in Northeast/Central Florida

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Quoting StSimonsIslandGAGuy:
Thanks CaneWarning for what you told me. You'd think SOMEONE around here would post a model page when asked.


I would if I wasn't at work! I don't have all my bookmarked stuff here.
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Quoting Weather456:
Good Afternoon

Tropical Update


Hi 456...
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Quoting WeatherStudent:
Good afternoon, all! I'm back home from FIU. So, any new and or recent developments regarding 90L's future strength and trayectory this afternoon? :)
A cat 5 to SFLA, not kidding.
543. ackee
It just seem to me that some poeple make it seem like the GFS is the only model frankly not big fan of GFS my view
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Good Afternoon

Tropical Update
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Current 02L models suggest it will make landfall from either SFLA threw Northern North Carolina.
Quoting WeatherStudent:
Good afternoon, all! I'm back home from FIU. So, any new and or recent developments regarding 90L's future strength and trayectory this afternoon? :)


Yes, it looks to be headed your way.
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The GFS is not updating on the NCEP site.. only up to 174 hours!!
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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.
Different strokes for...
Best to not have your neighbor's tin roof take away your last breath!
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Quoting melwerle:
KEH - doing well out here. Love it. Still have that house in Savannah though so keeping my eyes glued to the weather...

How's by you?
Keeping an eye to weather. Unfortunately, I have cannibalized my hurricane shelf twice since March, LOL! (Still have the most important stuff - books included)
Prayers and Preparation, per usual
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Former TD 2 Enhanced Infrared (IR) Imagery (4 km Mercator)

Time of Latest Image: 200908141200
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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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