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 farhaonhebrew:
is true they will adjust to the left..but tha hurricane will be hit here in Puerto Rico then move to the Carolina's like Hugo'89
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TD3 moving like Ivan. If it get too far south then I believe I will be in for some trouble. These models have been very poor so far.
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TWC always flip-flops. Hopefully these systems lose some speed so a recurve can occur quicker.
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5580. Michfan
About damn time Ana formed. She took long enough.

Looks like the east coast hit pattern is setting up. The longer it takes for these systems to strengthen the more likely they are to hit the US.
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Quoting InTheCone:


According to what I read on Hurricane City a few years ago Grand Cayman is hit the most by tropical systems in the Atlantic basin. They did go into the Pacific.

That makes sense they hit hit often. Like Paloma last year. Although that hit cayman broc

When will Dr. Masters post
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Quoting stormwatcherCI:
He said he would be back later with an update.

Where and when did he say that?
Member Since: September 30, 2007 Posts: 9 Comments: 15979
Quoting hurricane23:
In regards to ana trackwise everything has to be in place for a system to impact southern florida coming from this direction.


True does not happen much, from a local met only 2 times at that latitude where TD#2 began did a system hit the U.S.


but who knows right?
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Quoting AussieStorm:

StormW doesn't post on weekends. Its family time.
He said he would be back later with an update.
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Train is a rolling

Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting AussieStorm:

StormW doesn't post on weekends. Its family time.


Thanks Aussie and props to him for that.
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5571. jpsb
Quoting stoormfury:
Steve Lyons on the recent tropicalmupdate said that ANA would reach south Florida as a 70 mph storm in seven days time
No way! A 7 day prediction on track and strenght? lol, he's going to be eating serious humble pie.
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Quoting hurricane23:
In regards to ana trackwise everything has to be in place for a system to impact southern florida coming from this direction.


Though, a small shift to the south in 72 hours would put it over Haiti (poor folks, they had enough last year) and probably tear her apart.
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I live in grassy key just a little east of marathon right now we have a light rain and 10 to 15 mph breeze from the south east. nothing exciting happening. just keeping me from working on my porch. But it seems maybe in a few days things could get interesting with Ana looming on the horizon. water is really hot in the area right now we'll see what happens
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Claudette is a-comin

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Quoting ftpiercecane:
Any sign of stormw this morning?

StormW doesn't post on weekends. Its family time.
Member Since: September 30, 2007 Posts: 9 Comments: 15979
Quoting WPBHurricane05:
Ana looked pretty good early this morning:



she needs more Dmax =D well not really
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Be back later...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting BiloxiIsle:
I feel better today with the GFS turning TD3 more to the north. Hopefully, it will continue and it turns before anyone can be affected. Didn't like how it kept slapping the central GOM yesterday!


Remember this though, they could shift right on back. Its moving at a pretty fast pace, if its going to curve out to sea it better slow down.
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5561. Dakster
I see that we have Ana and soon to be Bill now. It will be interesting to see just how accurate that long range GFS turns out to be!
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is true they will adjust to the left..but tha hurricane will be hit here in Puerto Rico then move to the Carolina's like Hugo'89
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In regards to ana trackwise everything has to be in place for a system to impact southern florida coming from this direction.
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5557. Melagoo


Looks like a lot of action coming from Africa now!
Member Since: July 31, 2006 Posts: 19 Comments: 1607
Quoting WPBHurricane05:
Ana looked pretty good early this morning:



Ana doesn't seem to be a morning person. Its looked terrible in the morning ever since it formed originally.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
I feel better today with the GFS turning TD3 more to the north. Hopefully, it will continue and it turns before anyone can be affected. Didn't like how it kept slapping the central GOM yesterday!
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5554. CJ5
Since it is very busy, let's all refrain from usless posts like "finally a new blog", "finally", "bout time", "first, etc and to a lesser degree, "Thanks, Dr" when the new blog gets posted. :)
Member Since: July 4, 2007 Posts: 0 Comments: 1755
Ana looked pretty good early this morning:

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Quoting gbTracker:
Question: Doesn't the MJO have something to do with the pop up of three features we're watching right now.

Yes, a pretty good spike. I think it will be moving along soon...hopefully.

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Uh Ah-nah, Bill doesn't find those outflow boundaries very attractive.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
5550. 7544
wow td3 looks like a hurricane symbol in the visable
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Quoting seflagamma:
Good morning again,

been reading back on some posts..

folks.. no one is "a target or not a target" at this point. be real... for the next 5 days those models will change every 3 hours.

it will sway way to the north and south so many times over the next few days you all will make yourself nuts.

These systems will strengthen and weaken and die and come back etc. This is an El Nino year so lots of shear out there to blow the tops off these systems.

It is fun, but don't be making Declarations about it hitting or not hitting your area.

Best place to be 3-4 days out is in the center of the cone, because then it is for sure it will not hit your area. LOL




knock yourself out, nice try tho ...

:)
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Quoting jasoniscoolman10:
WHAT IS THIS NEXT TO KEY WEST..I DO NOT LIKE THIS AT ALL.


That my friend is a soon to be Humberto like cousin
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Any sign of stormw this morning?
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Quoting futuremet:


Shear is effecting this system (10-20kts) from the base of an upper level low, not dry air. It has been like this ever since Ana formed. Dry air intrusion is not too evident.
Quoting futuremet:


Shear is effecting this system (10-20kts) from the base of an upper level low, not dry air. It has been like this ever since Ana formed. Dry air intrusion is not too evident.


?? you can clearly see its ingested some dry air as there are is no CU.Dry air is also disrupting its inflow to its southwest .
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Question: Doesn't the MJO have something to do with the pop up of three features we're watching right now.
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Quoting KEEPEROFTHEGATE:
you are the only thing that may fizzle out

don't take your eye off the ball or it could smack you in the face


Thats a pretty good one KOG.
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Quoting cchsweatherman:


Good perspective. Was gonna post something like that but yours is better.
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5540. jipmg
Ana starting to move just north of due west, very exposed though
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Quoting stoormfury:
Steve Lyons on the recent tropicalmupdate said that ANA would reach south Florida as a 70 mph storm in seven days time



Well, I guess we can mail out the warnings then.
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Quoting InTheCone:


According to what I read on Hurricane City a few years ago Grand Cayman is hit the most by tropical systems in the Atlantic basin. They did go into the Pacific.
I don't think Grand Cayman is "hit" the most but quite a few very close encounters.
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90Knots in 120 hours...TD3 is going to be a mean one...and the nhc has it taking pretty much the sane course as ANA, for now. Gonna be an interesting week.
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I hope Dr Master's gets here with a new blog soon.
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Quoting Nolehead:
AussieStorm 3:44 PM GMT on August 15, 2009
Quoting WeatherStudent:



Adrian, both of these features are gonna fizzle out and that's final. Very A typical of an El Nino Hurricane Season.

Do you have proof of this comment or you been taking the wrong medicine again list the other morning?



is there a Dr. in the house??

Send the doctor over to WeatherStudent's place, check if his brain and hands are connected and functioning properly, sorry mate,,, your Ignored Name #11
Member Since: September 30, 2007 Posts: 9 Comments: 15979

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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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