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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StormW I like the runs myself. Yesterday it was heading for Mobile Bay. Now PCB, Fl. Maybe next further East, and so on. We know these models always change from run to run. So everyone from TX to ME need to watch for the time being
2086. Drakoen
GFDL:
Member Since: October 28, 2006 Posts: 57 Comments: 30832
Quoting DM21Altestic:
165 mph is too bullish for an African wave, right Drak?
Hurricane Dean in 2007 was a classic Cape Verde storm originating on Aug 11. Peak winds at 145kts(approx 165 mph)
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From what I'm seeing on CIMSS, 90L doesn't look like it has everything together yet...
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I've been gone for the last few hours. 90L sped up? Or slowed down?
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Quoting StormW:


If you're speaking of 90L, only thing I can say right now, if what I was just looking at in the steering layers forecast, it won't be a fish anytime soon. In fact, I prefer the 18Z GFDL track.


which is?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
2080. Drakoen
Quoting DM21Altestic:
When I get my myspace friend Drak to join, there'll be two Drak's, lol.

No offense, Drak, you're the better meteorogist easily...it will just be funny.


Also, if 90L speeds up a lot in the next 120 hours, is there still some hope that it will be a fish/Bermuda storm?


Drak or Drakoen is not even my real name.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
2078. Skyepony (Mod)
90L
Member Since: August 10, 2005 Posts: 226 Comments: 39434
Man, I am just such an impatient person...I just want to know , is my area going to be affected by a tropical storm or hurricane? It can't be that hard to answer can it? :)

I know, I know - Wait and Watch!!
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting Drakoen:


Yes.
what does taking a divemean? South? And where do you think south is? Would it go south of Florida?
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Quoting Drakoen:
The faster the system is the better chance it has at hitting the SE U.S.


That would be correct.
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Quoting DM21Altestic:
165 mph is too bullish for an African wave, right Drak?
that would be insane, I'd be so intrigued to see what that would do to my neighborhood in northern broward. Wilma was pretty horrible and if I'm not mistaken was only a cat1 and it was going very fast
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2070. Drakoen
Quoting DM21Altestic:

And the slower the system goes, the better chance it has of taking a dive?


Yes.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
Barometer Bob is starting please join us in storm chat at irc.hurricanehollow.org

we will be discussing 90L former TD 2 and the 5th Aniversary of HUrricane charley come join us

STORMW will be on the show. come join us
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Quoting DM21Altestic:
So what category do you guys think this system will eventually end up peaking as?

I say Category Four.


If it gets under the right conditions, Cat 5 isn't out of the question.
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I'm guessing we'll have to get our hurricane evacuation plans ready next week. :x
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Barometer bob show is on.
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Quoting DM21Altestic:
So what category do you guys think this system will eventually end up peaking as?

I say Category Four.
Two
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2062. Drakoen
The faster the system is the better chance it has at hitting the SE U.S.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
2060. Patrap
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Oh, I know, QBO = Quasi Beer Offering when being offered non-alcoholic brew.
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Quoting StormW:


Hello Mishy!
Hey! So what is your prediction?
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2057. JRRP
Quoting weathersp:
HWRF 18z

it shows the center 14n
Member Since: August 16, 2007 Posts: 0 Comments: 6213
Barometer Bob is starting please join us in storm chat at irc.hurricanehollow.org

we will be discussing 90L former TD 2 and the 5th Aniversary of HUrricane charley come join us
Member Since: Posts: Comments:
2054. jipmg
I suspect based on the latest satellite images 90L is seemingly gaining some convective activity near the center.. also the models are somewhat more consistent this time around.. but still very far off from being anywhere near accurate in my honest opinion. Lets hope for the best, but a very interesting system to track
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2053. Drakoen
HWRF takes it to 935mb with 144knt winds at 900hpa
Member Since: October 28, 2006 Posts: 57 Comments: 30832
2052. Drakoen
HWRF 18Z:
Member Since: October 28, 2006 Posts: 57 Comments: 30832
Quoting StormW:


Hello Mishy!


Hi,

Can you fill us in on the GOM?? Any thing of interest coming up or a no go?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
2050. tbrett
Quoting WPBHurricane05:



Umm...965 knot is NOT a cat 3...its more like a cat "Holy Crap Al Gore Was Right Run For Your Life!!!"


LOL
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well this action has brought me outta lurk mode. First time posting since Hurricane Hanna
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Quoting DM21Altestic:
965 knots, that was a typo lol. Also, MJO means major in my book...I'm not talking about the Oscillation with the Green Pulses...

Ummm, MJO means Madden-Julian Oscillation all the time in tropical met discussions. What's yer own personal meaning for the QBO, if you don't mind me asking.
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Quoting hurricane23:
18z HWRF isn't up yet on fsu.


Yup...didn't look at the times. My bad.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting Drakoen:


The run is not out fully on there.


Yea.
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2043. jipmg
Finally I can comment lol Hello there, ive been a lurker for some time, I really enjoy reading the analysis you guys make on 90L. I hope I can contribute to the discussions =D
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HWRF 18z
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Barometer Bob in 2 minutes join us in storm chat at irc.hurricanehollow.org

we will be discussing 90L former TD 2 and the 5th Aniversary of HUrricane charley come join us
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2040. Drakoen
Quoting hurricane23:
ah never mind just go it on penn state.


The run is not out fully on there.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
Quoting Orcasystems:




Ooops.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
may be has we are linking the mode runs too you can you may try this try too bookmark them?
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
2037. Drakoen
Quoting atmoaggie:

965 mb, 108knots @ 35 m...more sensical than the last run.
That one had cat 4 pressure with cat 2 winds.


lol
Member Since: October 28, 2006 Posts: 57 Comments: 30832

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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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