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 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
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5533. CJ5
Quoting WeatherStudent:



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


Come on, Dude. There is a big difference in educated speculation and plain old misinformation. The later can be very dangerous.
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5500....Do I here 6000???
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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 just kidding.. that is a joke not a statement! :o)


Member Since: August 29, 2005 Posts: 302 Comments: 40955
Quoting HurricaneKyle:


uhh.. huh? Your joking right?

Seems like some people think El Nino is an absolute guarantee that they are safe and that everything will either poof or curve out to see. Which as you can ask 23 this too, its totally untrue.
how bout andrew that was en el nino year?
Quoting sopla2o:


Is that even possible, that TD3 takes over Ana...


evrything is possible, but in this case is not likely due to thes systems a very apart each other and ana is increasing it speed..
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West shifting winds in Florida Keys system. Perhaps a surface low has formed.

Conditions at SANF1 as of
(11:00 am EDT)
1500 GMT on 08/15/2009:

Continuous Winds TIME
(EDT) WDIR WSPD
11:00 am SW ( 227 deg ) 23 kts
10:50 am SSW ( 195 deg ) 26 kts
10:40 am S ( 178 deg ) 25 kts
10:30 am SSE ( 164 deg ) 25 kts
10:20 am SSE ( 155 deg ) 21 kts
10:10 am SE ( 145 deg ) 18 kts

Station SANF1 - Sand Key, FL

NWS Long Range Reflectivity Key West, FL
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Afternoon everyone! Seems we got some people here writing off Ana and calling TD3 a fish (JFV as usual of course.) Remember Ana is a fighter, its going to be hard to kill it off. TD3 is pretty down south too, it is going to be hard for that to curve out to see without threatening the islands.
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5526. KEEPEROFTHEGATE (Mod)
Quoting WeatherStudent:



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

Do you have proof of this comment or you been taking the wrong medicine again list the other morning?
Isn't his opinion good enough ? LOL
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Quoting all4hurricanes:

I think the tip of cuba or even Cozumel would be the Hurricane Capital


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.
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OMG!!! log off at 1am still the same ole thing.. Just got back on and WOW.. How the H E double hockey sticks did 3 get in there?
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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??
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To bad its not a typical El Nino...its a reactive one.
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12Z GFS 12 hours...showing that new African system:



Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Chiggy007:
What if TD reaches 10N - realistic scenario since NHC surface maps has it moving WSW quite a while...


It becomes a "sudden death match" to move more north?
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Quoting AussieStorm:

Do you have proof of this comment or you been taking the wrong medicine again list the other morning?
roflmao
yeah, that GOM water is saying come to momma.....
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5514. centex
The reason models show W or WSW in short term is because that is what it's currently doing. Not really a forecast track.
Member Since: August 10, 2007 Posts: 0 Comments: 3293
Last retired B hurricane was Bob 1991
hopefully Bill won't be as bad
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5512. CJ5
There seems to be some good agreement (albiet long term) on Ana going Miami or S and TD3 going Miami or N. Then there is the african wave behind TD3...could be a long few weeks.

Link
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Quoting KBH:

Is it possible that these three systems will be interacting with each other, for better or worst..
I am guessing where one goes the others will follow.
and the add one more system to the fray, look behind the wave exiting Africa, another system in a few days

Those system seem to feed each other. as of now not so much, but there is clearly a visible counter mirror circulation going on. And in such process i belive the stronger one gains more. Which might influence storm speed and the rise of the chance to absorb even more.
Also the pattern suggest that these circulating patterns improve each other, hence increase the conditions for incoming systems.

For our scenario rightnow it would require substantial slowing or temporary stalling of 1 system.
It will be intresting to see this in the coming days when a storm interacts with land or higher SST.
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Steve Lyons on the recent tropicalmupdate said that ANA would reach south Florida as a 70 mph storm in seven days time
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Quoting sfla82:


Yeah which we all knew was going to happen!!!! They always curve away!


uhh.. huh? Your joking right?

Seems like some people think El Nino is an absolute guarantee that they are safe and that everything will either poof or curve out to see. Which as you can ask 23 this too, its totally untrue.
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5508. Melagoo
Quoting HurricaneKyle:


exactly.. ???
People that are calling out TD3 don't know what they are talking about in my opinion. This thing has the potential to become a serious threat.


Does the term MONSTER mean anything ... It looks very powerful already!
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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?
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What if TD reaches 10N - realistic scenario since NHC surface maps has it moving WSW quite a while...
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Quoting jipmg:


interesting.. there is a definate counter clock wise spin on the radar, possibly at the surface too.. very breezy over miami right now
yup
5504. jipmg
Quoting stoormfury:
TD3 is moving south of west, which will make that turn projected turn by the NHC even way off target. the longer it takes for the system to move north the more threatening it becomes for the central winward islands. i will not be surprise if the track is shifted to the left in the next advisory


The forecast was for it to move WSW for a while.. then curve WNW, dont think this sudden WSW movement is strange at all
5503. centex
These things going W longer than models showing. They have proven this year that they are poor predictors with developing systems.
Member Since: August 10, 2007 Posts: 0 Comments: 3293
Quoting sfla82:


I agree! Everyone keeps saying S Fla...Nope!!! Its the GOM's storm!


I agree. If Ana hits S. FL, it should still move into the Gulf to reorganize.
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5501. jipmg
Quoting P451:




interesting.. there is a definate counter clock wise spin on the radar, possibly at the surface too.. very breezy over miami right now
Quoting Orcasystems:


???


exactly.. ???
People that are calling out TD3 don't know what they are talking about in my opinion. This thing has the potential to become a serious threat.
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Quoting hurricane23:


Theres an ull just northwest of tiny ana produing southwesterly shear and combined with some dry air iam just not sure ana will survive.Models have done a poor job forcasting upper conditions.



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5498. sfla82
Quoting CaneWarning:
It looks like the ensemble models still take TD3 away from Florida.


Yeah which we all knew was going to happen!!!! They always curve away!
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TD3 is moving south of west, which will make that turn projected turn by the NHC even way off target. the longer it takes for the system to move north the more threatening it becomes for the central winward islands. i will not be surprise if the track is shifted to the left in the next advisory
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I'm off to Punta Gorda now. I'll be back later tonight to see what the models are saying! Everyone stay safe!
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Quoting jpsb:
Hurricanes are only in the Atlantic basin and E. Pacific. So, S. Fla would definiately be in the running for Hurricane Capital of the world. Personally I think the Keys would beat ya, but I don't have any figures to back that up.

I think the tip of cuba or even Cozumel would be the Hurricane Capital
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NOLA Forecast re GOM


However...the heaviest and most prolific period of rainfall looks
to be Monday into Tuesday. The tropical wave will begin to pull to
the west of the region...allowing for the strongest lift and deep
moisture to sweep into the area. This moisture will be fed by deep
southerly flow off the Gulf of Mexico. With little convective
inhibition in place...have went with likely probability of precipitation across the
forecast area for Monday. Temperatures will remain below
normal...due to the rainfall and cloud cover expected to be in
place. The heaviest rains look to pull to the west and farther
inland Monday night into Tuesday. However...fairly strong and deep
Omega values on the eastern side of the inverted trough
axis...combined with ample moisture will allow for another round
of likely probability of precipitation for Tuesday afternoon. Given the likelihood of
heavy rainfall...some flooding issues may develop...and will have
to monitor for the need to issue a Flash Flood Watch for Monday.
In addition...some minor coastal flooding may develop due to an
expected higher than average tide and some swells emanating in
from the central Gulf of Mexico.

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SFLA82 are you serious, your posts are so complacent, you are brushing off the NHC tracks like they are nothing, by the way you do realize as easily as the models and NHC track can shift south they can easily move North why you feel your out of the woods is beyond me.
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5478. Orcasystems 3:40 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.


???


LOL...you kill me WS....
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Quoting Seastep:


Yes it is. Wilma ate something if I remember.


Yup Alpha due to the Fujiwara Effect however Ana is expected to pick up forward speed so dunno if that'll happen
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Quoting hurricane23:


Take a glance @ this water vapor image note the large patches of dry air across the tropical atlantic.



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.
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Quoting Seastep:


Yes it is. Wilma ate something if I remember.

Wilma ate what was left of TS Alpha.
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5485. jipmg
winds are picking up across SFLA

is that thing over the keys getting any stronger?
Quoting WeatherStudent:



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


Hmm can't believe I've waited this long to say this, but time to put ya on ignore. Too much flip flopping around.
Member Since: August 2, 2007 Posts: 19 Comments: 19234

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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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