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 WeatherStudent:
I think that it'll eventually head on out to sea; however, not before it gives South Floridians a REAL SCARE. A similiar Hurricane Floyd situation I'd say.


Maybe if it gets close enough it will scare your hat back straight.
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1584. Skyepony (Mod)
Quoting Vortex95:


Okay but how do you know its assosiated with the distrubance there?


Well it was right in the wave. Looking at RGB earlier looked like vorticy at the surface was displaced just south of Hispanolia & well south of the bigger blow up of convection. Wierd thing is when it refreshed again the barb was gone completely. & it was something that had been reporting on land the whole afternoon, so it wasn't just some ship that up & left. Very odd.
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1583. java162
Quoting Weather456:
good afternoon to all


what is your opinion on your invest 90
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may be TD 2 will pull a TD 10
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
Quoting Vortex95:
Ted a red alert and a TCFA alert.


Yea I looked back, wasn't expecting a 'red' so quickly. I was at the doctors today, getting my ear checked out.
Member Since: July 8, 2005 Posts: 259 Comments: 24262
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Quoting Vortex95:
Ted a red alert and a TCFA alert.


Yup there's a lot of reason to think this will develop into something, not to mention an increasingly condutive environment. Still, these things take time to organized. Systems can take on a convection-less appearance just after emerging from Africa since temperatures over land are higher and more unstable than over water.
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Quoting RitaEvac:


lol


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good afternoon to all
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Keep an eye on the remnants of 02L...you never know what will spin up in the Bahamas (cough TD 10/12 cough).
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting WPBHurricane05:


I hope Ritaevac was just joking.


I am just getting aggravated with the tropics
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Quoting Vortex95:


Okay but how do you know its assosiated with the distrubance there?
i live on yhr east end of hati i just turned my ceiling fan on that must be what your seeing
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What is that big yellow for?
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Quoting WPBHurricane05:


I hope Ritaevac was just joking.


Eh...hes been doing the same thing for 2 years. I dont have time for it.
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Hi to TampaSpin
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Quoting DM21Altestic:

I'll jump right on it!!

DEAN

DEAN


Both of my own creation in Aug 2007.


Hm I have both of your old handles on ignore from the old days. You must have really done something. Good to see that your different from then.
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Quoting P451:


Link

If you're wondering about the GIF loop I've been making them so I can post them on the blog to be seen. Just feel it's easier to do that then send people on a link to 5MB+ java loops.


Thanks!
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looks like they went red at 5pm.
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Quoting Stormchaser2007:


Flag
Ignore
And move on


I hope Ritaevac was just joking.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Definitely a SFLA SOAKER!
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Quoting TampaSpin:
I bet Old TD2 makes a comeback just looking at it...
I'm with you on that TS!
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Quoting WPBHurricane05:


LOL!


lol
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1561. cg2916
Quoting chevycanes:

no it's not.

the time that says 7:044 is when it was taken. that's during the 3am time edt.

the time you listed is the data buffer time.

So it was taken at 7:04 AM? That was the lastest one I could find, though.
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Quoting RitaEvac:
Hype Hype Hype, aint nothing going on out there.... clouds swirling away and aint nothing materializing, Gulf coast residents, go take a sailboat to the Bahamas, beautiful out there


LOL!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting WPBHurricane05:


LOL!


Flag
Ignore
And move on
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Quoting KEEPEROFTHEGATE:
we have to stop with the polls to many its becoming annoying i will request admins assistance if needed please stop with so many of them
Here we go agian with the lack of the freedom of speech! The polls ask about storms. so if you don't like it use your ignoe button!!
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Ensembles again.

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1552. KEEPEROFTHEGATE (Mod)
Quoting kingzfan104:
When does everyone expect 90l to start developing convection?
it will fire some tonight and early morning try and tigthen up the coc then wane tommorow in evening till late sat afternoon before waxing up again it has to built itself so it will come in cycles till it gets its self together

its kinda like gettin dressed before going out to the party
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Hype Hype Hype, aint nothing going on out there.... clouds swirling away and aint nothing materializing, Gulf coast residents, go take a sailboat to the Bahamas, beautiful out there
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Quoting RitaEvac:
TD2 and 90L look un impressive folks. Once again no named storm for 2009! Time keeps on tickin....tickin...tickin into the futuuuuure.


LOL!
Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting RitaEvac:
TD2 and 90L look un impressive folks. Once again no named storm for 2009! Time keeps on tickin....tickin...tickin into the futuuuuure.


I really hope your joking.
Member Since: July 8, 2005 Posts: 259 Comments: 24262
I bet Old TD2 makes a comeback just looking at it...
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Quoting Skyepony:
I've got the nowCOAST up on the big monitor all blown up on the wave N of Hispanolia, got the wind barbs on. It's set to refresh every 4 mins. A weak west wind has just appeared on the south end of Haiti.

interesting...
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Quoting DM21Altestic:
POLL: What kind of storm will 90L resemble most, as far as track and intensity?


A) Hurricane Bertha (2008)
B) Hurricane Georges (1998)
C) Hurricane Isabel (2003)
D) Hurricane Ivan (2004)
E) Hurricane Andrew (1992)
F) Hurricane Floyd (1999)
G) Hurricane Helene (2006)
H) Hurricane Allen (1978)
Z) 90L won't become a hurricane at all.

...Bold your choice...



I'm going with I) Hurricane Dean. ;)

Afternoon everyone! We have a red alert eh?
Member Since: July 8, 2005 Posts: 259 Comments: 24262
Quoting cg2916:

it was from 3:12 PM EST.
Now that you mention it, it is. It does still need to tighten the circulation and build and organize convection.

no it's not.

the time that says 7:044 is when it was taken. that's during the 3am time edt.

the time you listed is the data buffer time.
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Life stinks, got laid off thid morning....uggggghhhh
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TD2 and 90L look un impressive folks. Once again no named storm for 2009! Time keeps on tickin....tickin...tickin into the futuuuuure.
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Quoting Drakoen:
The graphics from StormVista contradict the graphics from Earl Barker


NOAA has some CFS graphics: Link
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Quoting Ameister12:
My god, do my armpits smell!!!
Deodorant time!


Btw, I got to go!



that photo is not posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself.
Member Since: May 21, 2006 Posts: 5091 Comments: 115255
1538. JRRP
this is 90L 2007(Dean)

90L 2009
Member Since: August 16, 2007 Posts: 0 Comments: 5998
About to head out of here for the evening, hope everyone has a nice night!

Final thoughts:

TD2 bears watching as indicated by the NHC. As long as some convection continues to fire - that is mass that is being pulled from the center of the low and should act to keep the central pressure lower than the environment around it. This in turn will help sustain the nice low level circulation and keep it poised to possibly strengthen somewhat if shear conditions improve.


90L looked better this afternoon and has regressed a bit in organization. However, as NRT posted, the pressure was falling pretty sharply this afternoon. This should help pull the circulation together over the next 24 hours and get us closer to a depression or storm. Also, the easterly shear over 90L is forecast to relax slowly to more favorable conditions tomorrow.

Finally, the SSTs will warm a bit tomorrow which will make the environment more unstable and support additional convection.

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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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