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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2437. Skyepony (Mod)
Quoting Tazmanian:
has any one noted how big 90L is ???


Yes Taz, I brought this up 2 nights ago. We may see another well defined tight swirl Felicia type suck dry a too big & blobby to get turning Enrique type. TD2 still has a nice swirl, keeping just enough convection to get by but now slowing the forward speed as 90L gets closer because it's forward speed is faster. By tonight's quikscat 90L has a ways to go to a closed low. Looked like 02L was tapping into 90L, the pic up top that Masters hung shows it well. Hard to tell now since the sun went down. I haven't ruled it out as a good possibiblity. Something with defined lower spin & structure ramps up way faster than a huge, cumbersome, wet blob. Remember too that many models don't do well when 2 storms are close together, combined with how weak they are & it's best to not use models as gospel..
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Quoting TampaSpin:
Looks like TD2 or the Low which ever one want to refer to it is heading into the Caribbean.....


If it stays weak like that, yes, this is going in the caribbean. If it intesifies, east coast watch out!
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Quoting reedzone:
Good evening everyone,

90L is gaining convection and a good DMAX tonight should upgrade it to Tropical Depression 3. ALL models now form "Ana" .. Bill apparently was sick and couldn't develop right now so Ana left TD2 which is why it was downgraded to help Bill out and take his place for 90L. ;)
Bill will have the next storm.


Lol! well said
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i think this is a big problem for central gulf states maybe uppper mid texas...it will be a freaking typical gulf monster as of late...

Which one (wave)are you referring to? I definitely will be keeping an eye out....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
2433. jdjnola
Wow the blog comments get nasty when the tropics are playing mind games with us...

ANYWAY, I'm not calling RIP on the artist-formerly-known-as-TD2 yet. I think it has stayed far south enough to barely survive short-term and is facing less and less dry air. Shear may be the final nail in its coffin but I get the feeling it's going to survive.

90L is a beast and I don't even want to think about it yet.
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2432. BrandiQ
Quoting KoritheMan:


http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/DUST/WESTERNAFRICA/


Thank you!
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The convection in the carribean disturbance appears to be enhanced by its proximity to the afternoon thunderstorms produced over Hati. It also appears that there is actually a lower level divergence, instead of convergence necessary to form a low.

Dat Hokie dude is paying attention, y'all.

I haven't seen any lower level convergence there, yet.
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What up with the blob on hispaniola
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Quoting Tazmanian:
if 90L dos not become TD 3 or a name storm


this hurricane season will be dead


No it won't.
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Good evening everyone,

90L is gaining convection and a good DMAX tonight should upgrade it to Tropical Depression 3. ALL models now form "Ana" .. Bill apparently was sick and couldn't develop right now so Ana left TD2 which is why it was downgraded to help Bill out and take his place for 90L. ;)
Bill will have the next storm.
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2426. KEEPEROFTHEGATE (Mod)
Quoting DM21Altestic:
11 PM saturday night is a little too late, the SHIPS has it as a moderate to strong TS by then.

I'm still going with midday, Friday.
thats 13hrs 35 mins from now to midday tomorrow its first convective cycle will be in waning phase by then
Member Since: July 15, 2006 Posts: 176 Comments: 55543
What's the most recent GFS run at the moment?
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Quoting zoomiami:


at last, a voice of reason, i'll keep close - don't leave me here


disturbing in here sometimes
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My beef is when people shut down other folks that are suggesting where they think a storm may go and the only reason someone is shutting them down is the same excuse we hear all the time, it is too far out to say that. This is not an offical forecast so who cares if they say they think the storm is GOM bound or east coast bound. More power to them for trying. Not everyone has to explain in detail why they feel how they feel, it would help the rest out but it is not needed.
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Quoting atmoaggie:

That requires some scripting. Some folks might have it turned off intentionally...or visiting from a smart phone with scripts disabled.


That's fine, but at least say who you are referring to.
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No more convection in my neighborhood:



CRS
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting BrandiQ:
I haven't seen any images of 90L in a while. Is it due to the fact that it is dark right now over there?


http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/DUST/WESTERNAFRICA/
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Quoting Hhunter:
i think this is a big problem for central gulf states maybe uppper mid texas...it will be a freaking typical gulf monster as of late...


Are you talking about 90L, TD2, or the disturbance in the carribean?

In my opinion, for TD2, we want it to strengthen (60 knots?), and move into cooler waters where it can die as a fish storm. This should allow it to gain lattitude (observe HWRF on TD2 as the most aggressive increase in intensity, and also the most latitude gain)

90L is more of a concern since the models are consistent on track out to a couple of days, even with the variance in forcast intensity.

The convection in the carribean disturbance appears to be enhanced by its proximity to the afternoon thunderstorms produced over Hati. It also appears that there is actually a lower level divergence, instead of convergence necessary to form a low.
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Quoting Tazmanian:
if 90L dos not become TD 3 or a name storm


this hurricane season will be dead

If Barry Bonds (who is LEGIT by the way) didn't break Hank Aaron's home run record, then Hank Aaron would still be the home run king ;)
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Hmmmmmm.....


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As i said earlier chiggy with this kind of pattern that involves timing models will go all over the place because just a slightly different view on timing can have a huge impact on track when it comes to patterns like this
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Quoting TexasHurricane:
As of right now, the 90 isn't looking like it will be an east coast storm. Seems to be going west......hmmmmm
uhhhhh, it has been forecasted to go west for a while.
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Quoting hahaguy:


Your not the only one :)


and now there are three - perhaps we need a corner, one we could protetct....
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2413. JRRP
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Quoting weatherblog:


Yup.


Yeah, cause models out two weeks tell you this? Yeah, next week the models will give us a better idea... until then, it is just your opinion.
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2411. BrandiQ
I haven't seen any images of 90L in a while. Is it due to the fact that it is dark right now over there?
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Quoting TexasHurricane:
As of right now, the 90 isn't looking like it will be an east coast storm. Seems to be going west......hmmmmm
Let hope you are wrong
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Quoting KEEPEROFTHEGATE:
iam here your never alone zoo


As am i :)
if 90L dos not become TD 3 or a name storm


this hurricane season will be dead
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HaboobsRsweet:

Like I said; if you have formally studied weather then my previous comments wan't targeted to you - not sure where your beef is with me... :)
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Quoting BILOXISAINT2:
As i said earlier. this person is clueless


You don't even know me so your assumptions mean nothing. I could say the same thing about you, but it's not like you actually contribute anything to the blog for me to care.
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Quoting presslord:
zoo...be not afraid...you are not alone...


at last, a voice of reason, i'll keep close - don't leave me here
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2404. hahaguy
Quoting zoomiami:
I have fallen into the blog of banned, cloned, related, definitely trolls, and who know what other characters, and I'm all by myself here...


Your not the only one :)
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Quoting KEEPEROFTHEGATE:
anytime after nov 30 is good

lol


lol well apparently for obvious reasons... sorry what i meant was that I didn't know if your winters or springs were rainy seasons
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As of right now, the 90 isn't looking like it will be an east coast storm. Seems to be going west......hmmmmm
Member Since: July 2, 2009 Posts: 0 Comments: 2811
2401. KEEPEROFTHEGATE (Mod)
Quoting zoomiami:
I have fallen into the blog of banned, cloned, related, definitely trolls, and who know what other characters, and I'm all by myself here...
iam here your never alone zoo
Member Since: July 15, 2006 Posts: 176 Comments: 55543
No more convection in my neighborhood:

Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting TampaSpin:
Looks like TD2 or the Low which ever one want to refer to it is heading into the Caribbean.....

that is what I said
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Havn't seen that much concurance in the ensembles in some time. Kinda spooky.
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guys we are all start too get off key here what get back on key and move on too 90L
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Quoting zoomiami:
I have fallen into the blog of banned, cloned, related, definitely trolls, and who know what other characters, and I'm all by myself here...

All I see are the mis-fit toys...think toy story next door neighbor.
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11 PM saturday night is a little too late, the SHIPS has it as a moderate to strong TS by then.

I'm still going with midday, Friday.
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Quoting Chiggy007:
HAHA, is that what taught you in weather school - stick your neck out and forecast the weather!
I am all for educated guesses and you have to agree with me that lot of people on here are not that educated when it comes to metereology - they've probably learned a few things from watching the TWC...!
IF you have formally studied weather than obviously this wasn't targeted to you...so YOU CHILL mate lol... PEACE!

Whatever dude...think what you want. People know what I do and where I went to school. I do 2 week forecasts all the time and have to say 100% or 0% that something is going to happen. If you make a forecast right now...pick a spot using sound reasoning on where 90L is going to hit, track it and see what factors caused you to be right or wrong, you might actually learn something and get better at it.
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zoo...be not afraid...you are not alone...
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Looks like TD2 or the Low which ever one want to refer to it is heading into the Caribbean.....
Member Since: September 2, 2007 Posts: 179 Comments: 20448
Lot of the 00Z models have moved south and none show recurve!
00Z GFS Ensemble runs look very different than 6 hours ago; which goes to show that even the models don't know squat!!
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Quoting CaicosRetiredSailor:


Only recommendation I would have is to avoid July, August, & September.

CRS


LOL
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Quoting DM21Altestic:
LOL, 90L won't even sight the East Coast.

I'm starting to believe that this storm will take a dive into the Caribbean, allah Dean.


I don't. Dean was much farther south. Plus, there was a huge high in 2007 that forced all storms due west into the Caribbean; it's basically the oppisite this year.
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2388. JLPR
Quoting KEEPEROFTHEGATE:
with everything isee and all info i have read sat imagest and other sources i am thinking 48 hrs from now which will be approaching 11 pm sat night for first advs. on td 03l


yeah that sounds right
big system needs time to develop
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2376. Chiggy007 9:14 PM CDT on August 13, 2009
HAHA, is that what taught you
Well said
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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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