TD 2 nearly dead; African disturbance 90L gathering strength

By: Dr. Jeff Masters , 2:38 PM GMT on August 13, 2009

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Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.

Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.


Figure 1. Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).

African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. 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 has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.

I'll have an update Friday morning.

Jeff Masters

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Quoting Funkadelic:
I suppose that we will start to hear all the hype on the news channels starting early next week. I guess warning the people early is a good thing. Because I know many people have forgotten about hurricane season due to the slow start.

And the situation is really bad here in south Florida, because every 10 feet there is a forclosed house that is abandoned.


If a major hurricane were to hit an area with a high forclosure (empty homes) rate it would be a nightmare. After Andrew, every contractor was begging to stay (with crew) in damaged homes. With so many homes empty, I think we would see allot of people living in homes that they never got permission to stay in.
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3236. cg2916
The LLC is closed around the COC, but we have east winds running through the center.
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3235. IKE
Quoting jipmg:


can you post a gif here, for some reason I cant access the page


What is gif?
Member Since: June 9, 2005 Posts: 23 Comments: 37885
Morning All.

Which way is the pendulum swinging today?
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Quoting breald:


Hi guys, do Bermuda highs keep storms to the south/GOM or pull them north?

From most of the models I see on this page it has the storm pulling up the east coast. I know they constantly change but was wondering.
Thanks.




The high keeps them to the south and travelling due west.

The northward tracks up the east coast are due to the high pressure system petering out there.
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Quoting cg2916:

It shows TD2 becoming probably a hurricane and heading for the US, and is slow to develop 90L.
;

Yea I think the NOGAPS got it backwards,
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3231. IKE
Quoting 92Andrew:
Question guys:

I know i can go look for the model runs but it would be time consuming, therefore, i prefer to ask all of you.

I am due to leave Miami this upcoming Thursday, and head over to Tallahassee before classes begin... do you think I will be able to leave south florida before 90L threatens the South East?


I'd say yes..
Member Since: June 9, 2005 Posts: 23 Comments: 37885
3230. jipmg
Quoting IKE:
6Z NOGAPS...


can you post a gif here, for some reason I cant access the page
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3229. cg2916
Quoting IKE:
6Z NOGAPS...

It shows TD2 becoming probably a hurricane and heading for the US, and is slow to develop 90L.
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3228. jipmg
Quoting breald:


Hi guys, do Bermuda highs keep storms to the south/GOM or pull them north?

From most of the models I see on this page it has the storm pulling up the east coast. I know they constantly change but was wondering.
Thanks.



Depends on the intensity of the HIGH, if its weak its likely a stronger system would curve out to see due to a weakening in the ridge, if its strong its likely to keep a tropical system on a continual west path until it reaches a break in the ridge
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Question guys:

I know i can go look for the model runs but it would be time consuming, therefore, i prefer to ask all of you.

I am due to leave Miami this upcoming Thursday, and head over to Tallahassee before classes begin... do you think I will be able to leave south florida before 90L threatens the South East?
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3225. IKE
6Z NOGAPS...
Member Since: June 9, 2005 Posts: 23 Comments: 37885
3224. breald
Quoting jasoniscoolman10:
two very big highs to the north of 90L...WOW.


Hi guys, do Bermuda highs keep storms to the south/GOM or pull them north?

From most of the models I see on this page it has the storm pulling up the east coast. I know they constantly change but was wondering.
Thanks.

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3223. russh46
Quoting Funkadelic:
I suppose that we will start to hear all the hype on the news channels starting early next week. I guess warning the people early is a good thing. Because I know many people have forgotten about hurricane season due to the slow start.

And the situation is really bad here in south Florida, because every 10 feet there is a forclosed house that is abandoned.



Most cities and counties don't even have a plan for these homes in the event of a cane.
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3222. cg2916
Quoting jasoniscoolman10:
wow

I'm surpsrised by how much TD2 has made a comeback. I wouldn't be surpsrised if we have code red for that at 8, because I think it looks better now than it did during a least most of its TD status.
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Morning everyone! Looking at satellite imagery we may very well have a depression soon.

Convection appears to be waning with ex-02L but as the SHIPS predicted would occur a few days ago the circulation is entering a region of relatively light shear (hence the orange circle) and bears watching.

The Greater Antilles wave shouldn't get too far along in terms of development this week but may be worth watching if/when it enters the GOM.
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3219. IKE
EX-TD2 is falling apart again with convection.
Member Since: June 9, 2005 Posts: 23 Comments: 37885
Ridge showing signs of strenghening so recurvature might just be out of the quetion!!!!
Member Since: August 22, 2006 Posts: 0 Comments: 2832
Quoting PSLHokie:


That must be when all the middle school children on summer break get woken up by their mothers...


I don't know what it is, but the last week it's been very difficult to read the blog because of all the posts that seem fake or make no sense.
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3215. jipmg
Based on satellite imagery it seems TD 2 has lost alot of its strong circulation.. still a nice spin to it, but its fairly week compared to 12-16 hours ago.. despite the convective blow up over the COC last night, I think it barely has a chance to regenerate.. but the convection currently blowing up may wrap around now that the shear has lightened up a bit compared to 24 hours ago.
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The other thing to think about is that former TD2 and 90L are fairly close proximity (and it appears that 90L is gaining on former TD2). If one develops, it will suppress and redirect the other (really you will get mutual interaction).

If 90L intensifies to TS or stronger This will suppress development of former TD2, and keep TD2 toward the south. At the same time, a little increase in organization of former TD2 could cause a big shift north for 90L.
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3212. IKE
Quoting stoormfury:
IKE
where is the exact centre of 99L? iam seeing two vortices one at 10.6N 28.8W and the other at 11.7N 28.8W


Looks close to 12N and 27W to me.
Member Since: June 9, 2005 Posts: 23 Comments: 37885
3211. cg2916
I've been watching the GFDL since it's my favorite model, and the most reliable. At the 00Z run, it takes the remnants of TD 2 to 75 MPH at the end of its run, and 90L to 100 MPH before it even gets close to the Antilles.
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Should continue towards the west for the next 36-72 hours.

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3209. WxLogic
As IKE already mentioned... ECMWF is the outlier as its developing 90L too quickly and deepening it and under estimating the Bermuda High strength.

This is a trend I've been seeing ever since the HURR season started with models in their long range runs.

Currently 90L almost has a closed circulation and just needs to tighten up a bit more on the W quadrant but QS already reveals TD strength winds happening as well as TS wind gusts... so I do expect 90L to become a TD between 5PM and 11PM if it keeps improving:

Member Since: August 14, 2008 Posts: 4 Comments: 5166
3207. cg2916
Quoting IKE:


Like sporteguy03 said...

Also, the way it looks for 90L, there will be so many posts on here soon, you won't be able to keep up with them.

That explains my time on the blog yesterday. Everytime I refreshed, three new ones pop up.
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The gfs ensemble members from the 00Z run indicate 90L may have some recurvature. Long way out on the ensembles (they run out to 384 hours).

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IKE
where is the exact centre of 99L? iam seeing two vortices one at 10.6N 28.8W and the other at 11.7N 28.8W
Member Since: August 22, 2006 Posts: 0 Comments: 2832
3204. IKE
Quoting PSLHokie:


That must be when all the middle school children on summer break get woken up by their mothers...


Like sporteguy03 said...

Also, the way it looks for 90L, there will be so many posts on here soon, you won't be able to keep up with them.
Member Since: June 9, 2005 Posts: 23 Comments: 37885
Quoting PSLHokie:


That must be when all the middle school children on summer break get woken up by their mothers...
HA HA..have a good day all..off to work to deliver the lovely mail be back later happy weathering until then
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Morning everyone! 90L is looking far more impressive. I will right up an analysis and post it on Jeff's next blog.

Personally I think 90L will likely become a Hurricane, and will go north or directly to the Lesser Antilles, anything else now is speculation but the models are close with the exception of the ECMWF which obviously underestimates the speed of 90L as Ike pointed out.
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This Atlantic wide view image shows it as more organised than the others I've seen. Heck, there's even the semblance of an eye, there. I know it isn't an eye, but it does make it look the part.


When I previewed the comment, the wide view image messed up the blog by widening it, so I left it out, but you know where to find it.
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Quoting IKE:


This blog losses it about 9-10 am...almost unbearable.



That must be when all the middle school children on summer break get woken up by their mothers...
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morning WXLogic
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3198. IKE
Quoting sporteguy03:


They'll be here soon enough, give it a few hours. That is why I lurk all day mostly here now other than in the am. Most of the time it is way too childish in here now.


This blog losses it about 9-10 am...almost unbearable.

Member Since: June 9, 2005 Posts: 23 Comments: 37885
Quoting IKE:


ECMWF is an outlier, curving it north near 60W. It's too slow on 90L's movement. Showing it only near 37W on Monday. It'll be around 50W by then.

Maybe it's right on track, but I would discount it. Most of the rest of the models take it to the northern islands or just north of there within 4-5 days.

GFS has backed off on the strength of the eastern USA trough. Maybe it goes back the other way, but it's August.

I would say the odds of the USA feeling 90L at 30-40% for now.

Ok then, prayers will officially start now.
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3196. WxLogic
Good Morning...
Member Since: August 14, 2008 Posts: 4 Comments: 5166
Quoting cg2916:
Good morning everybody!

Well, can't say I'm not surpsrised. I thought the Hispaniola wave would be back, but I can't believe that the remnants of TD 2 are code ORANGE! Didn't expect much else with 90L, thought it would stay red. The models are scaring me a little with 90L. Usually the CMC is about the only one that's in constant apocalyptic mode. This will be an interesting day.


The Hispanola wave was being enhanced by an ULL at the right distance from the wave casuing increased upper level divergence (enhancing convection).

The wave does have some mid level turning (500mb), but nothing at the surface. In addition, the wave is now being disrupted by an ULL over cuba. This could totally wipe out the wave, or just cut it off from the ITCZ. Either way, with the lack of organization currently with the system, it probably needs several days to even get to TD status... Probably going to be over Texas or Mexico by then.
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Quoting stoormfury:
i notice all the downcasters have fled the blog
reality is here


They'll be here soon enough, give it a few hours. That is why I lurk all day mostly here now other than in the am. Most of the time it is way too childish in here now.
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3193. IKE
Quoting ALCoastGambler:
Ike have the models still been jumping around all over or are they starting to generalize into a more profound area? albeit probably for the time being.


ECMWF is an outlier, curving it north near 60W. It's too slow on 90L's movement. Showing it only near 37W on Monday. It'll be around 50W by then.

Maybe it's right on track, but I would discount it. Most of the rest of the models take it to the northern islands or just north of there within 4-5 days.

GFS has backed off on the strength of the eastern USA trough. Maybe it goes back the other way, but it's August.

I would say the odds of the USA feeling 90L at 30-40% for now.

Member Since: June 9, 2005 Posts: 23 Comments: 37885
Tropical Update

BBL
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3190. cg2916
What's the difference between the GFS's "Ten" model run and "SLP" model run?
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i900 miles east of the lesser antilles that's a long way off
Member Since: August 22, 2006 Posts: 0 Comments: 2832
Ike have the models still been jumping around all over or are they starting to generalize into a more profound area? albeit probably for the time being.
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Quoting tikikopamsxm:
hello everybody,
can you tell me how stong will be 90L around the northern islands


models greatly differ but average out a strong TS or minimal hurricane
Member Since: July 24, 2005 Posts: 407 Comments: 19076

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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