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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18z takes it to around the PCB area
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting SouthALWX:
You WANT to be in a cat5? You're crazy =]



welll if he wants to be in a cat 5 i get a row boat for him and next time we have a cat 5 some where he can row out in a row boat
Member Since: May 21, 2006 Posts: 5091 Comments: 115104
this reminds me of ike
Member Since: Posts: Comments:
1832. IKE
18Z NOGAPS......

heads 90L toward the islands...similar to the GFS.

Takes the blob north of DR/Haiti into the western Florida panhandle...

EX-TD2 shows up nicely east of the Bahamas...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting louisianaboy444:
Look at the Divergence aloft on 90L i have a feeling this is going to pop tonight for Dmax


What is Dmax?
Quoting Stormchaser2007:
18Z

do those continue onto Florida or go out to sea of through Cuba into the caribbean? Thanks in advance
Member Since: Posts: Comments:
1829. tbrett
DM2altestic - Doesn't help, I live on the border of the Windwards & leewards but am classified as Leewards so I guess I am 50/50 LOL
Member Since: July 20, 2007 Posts: 0 Comments: 107
If you look close the GFS has it thrreading the needle through the straits so it might not necessarily be weaker. More than looking at the model per it's track, I think the screaming message here is "timing".
Member Since: August 27, 2008 Posts: 0 Comments: 1497
1827. Drakoen
90L is a very large circulation.
Member Since: October 28, 2006 Posts: 57 Comments: 30490
Interesting Run.

CMC Model: Watch out Houston, TX!!
Member Since: Posts: Comments:
1825. KEEPEROFTHEGATE (Mod)
mail sent 456
Member Since: July 15, 2006 Posts: 171 Comments: 53838
Quoting Relix:

No! Though to be honest we are quite overdue from receiving the full brunt of a Cat 5. It's been what... nearly 70 years? Statistically we are about to be hit by one soon. I am honestly ready for that one with the sole exception I live 1 mile away from the beach =P


I think that in Puerto Rico will not sustain a cat.5 hurricane that we are too urbanized and overcrowded ... the wind damage, plus the amount of rain (because of our topography) would be unprecedented compared to ... Andrew and Katrina together


Member Since: July 14, 2008 Posts: 0 Comments: 248
Look at the Divergence aloft on 90L i have a feeling this is going to pop tonight for Dmax
Member Since: August 29, 2006 Posts: 22 Comments: 1352
1821. Dakster
Quoting Tazmanian:



its dead


Thanks for the opinion...

Now to watch 90L... Hopefully it falls apart too.
Member Since: March 10, 2006 Posts: 0 Comments: 10291
Quoting Relix:

No! Though to be honest we are quite overdue from receiving the full brunt of a Cat 5. It's been what... nearly 70 years? Statistically we are about to be hit by one soon. I am honestly ready for that one with the sole exception I live 1 mile away from the beach =P


I think that in Puerto Rico will not sustain a cat. 5 hurricane, that we are too urbanized and overcrowded ... the wind damage, plus the amount of rain (because of our topography) would be unprecedented compared to ... Andrew and Katrina together...


Member Since: July 14, 2008 Posts: 0 Comments: 248
Also on the 18 Z GFS "forecast" track, I would expect the storm to much weaker than shown, especially if it rakes across the islands and mountainous Cuba
Member Since: August 27, 2006 Posts: 0 Comments: 1763
Quoting Stormchaser2007:
18Z



Looks pretty consistent.
You WANT to be in a cat5? You're crazy =]
Member Since: August 27, 2008 Posts: 0 Comments: 1497
1816. tbrett
WxLogic: I am a firm believer in "better safe then sorry" I have lived with an active volcano for 4 1/2 years so my family has a very good evacuation plan. I have already started preparing for this system, if t does not come then I am that much more prepared for the next one. It's Mother Nature, no one knows for sure what is she has planned.
Member Since: July 20, 2007 Posts: 0 Comments: 107
1815. IKE
Trough doesn't make it as far south and as far east at 10 days on this run.

That's why it's impossible to say on ANY runs from ANY model.

The islands have a chance of being hit. Beyond that impossible...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Stormchaser2007:
18Z



A shift south?
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1812. Drakoen
Member Since: October 28, 2006 Posts: 57 Comments: 30490
Member Since: Posts: Comments:
18Z

Member Since: June 9, 2007 Posts: 4 Comments: 15891
i think that wave N of PR has some sight turing with it
Member Since: May 21, 2006 Posts: 5091 Comments: 115104
1805. WxLogic
Quoting FirstCoastMan:
Does anyone have the link for the 18z gfs..TIA


Here you go:

Link
Member Since: August 14, 2008 Posts: 4 Comments: 4972
1804. WxLogic
Quoting Drakoen:
GFS is way too inconsistent with the speed of this system to be considered credible.


Hehe yeah... but I did noticed that the Bermuda high was stronger as I would have expect... not in the long range but once it start heading into the Carib... seem the Bermuda High is holding its own. Which would explain the minimized effect of the trough.
Member Since: August 14, 2008 Posts: 4 Comments: 4972
Quoting DM21Altestic:
lol, every storm is the next Andrew. Why don't they just give the name, Andrew Jr. or, Andrew XXXVIII? You take a crack at why the NHC didn't do that.


[spoiler=because not every CV storm hits Florida and goes into the Gulf like Andrew did, hint hint [/spoiler]


And every storm doesn't harmlessly curve out to sea. The point is, be prepared regardless.
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Does anyone have the link for the 18z gfs..TIA
Member Since: August 7, 2009 Posts: 0 Comments: 251
1801. SouthALWX
10:42 PM GMT on August 13, 2009
18Z Gfs ... Always bucking the other runs =P Not that I believe it, but it definitely shows the complexity of the steering even 2-3 knots per hour faster over 10 days makes a huge difference here.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
1800. Chucktown
10:41 PM GMT on August 13, 2009
18 Z GFS is just last like last nights 18 Z. Trough not as amplified so 90 heads further west across Florida. Its gonna be all timing next week - wait until reconnaisance can get in there which will probably be Sunday at the earliest.
Member Since: August 27, 2006 Posts: 0 Comments: 1763
1799. IKE
10:41 PM GMT on August 13, 2009
It goes over 3,600 miles in 10 days...that's 240 hours...that's 15 mph average.....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1798. Cavin Rawlins
10:41 PM GMT on August 13, 2009
NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 12 HOURS
FORECAST POSITION AT T+ 12 : 11.4N 24.3W

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 14.08.2009 11.4N 24.3W WEAK
12UTC 14.08.2009 11.3N 26.9W WEAK LITTLE CHANGE
00UTC 15.08.2009 12.3N 29.3W MODERATE INTENSIFYING RAPIDLY
12UTC 15.08.2009 12.1N 32.0W MODERATE INTENSIFYING SLIGHTLY
00UTC 16.08.2009 12.5N 35.3W STRONG INTENSIFYING SLIGHTLY
12UTC 16.08.2009 12.6N 38.6W STRONG LITTLE CHANGE
00UTC 17.08.2009 13.3N 42.0W STRONG LITTLE CHANGE
12UTC 17.08.2009 14.2N 45.8W STRONG LITTLE CHANGE
00UTC 18.08.2009 14.8N 49.3W STRONG INTENSIFYING SLIGHTLY
12UTC 18.08.2009 15.3N 52.7W STRONG LITTLE CHANGE
00UTC 19.08.2009 16.4N 56.1W STRONG LITTLE CHANGE
12UTC 19.08.2009 16.7N 59.5W STRONG LITTLE CHANGE
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1797. antonio28
10:41 PM GMT on August 13, 2009
Quoting farhaonhebrew:


estoy de acuerdo....i agree with you.. even with an Invest we have a lot of troubles here in pr..remeber last year...



Yeap an Invest bring a lot of troubles here in PR the window seems to be little to escape from a hit from this potencialy huricane. Fingers Crossed since last week.
Member Since: July 15, 2008 Posts: 0 Comments: 799
1795. Relix
10:40 PM GMT on August 13, 2009
Hey I didn't know the NHC killed off TD2 already.
Member Since: August 3, 2006 Posts: 0 Comments: 2723
1793. Seastep
10:40 PM GMT on August 13, 2009
Haven't had a chance to read back, but looking at RGB and visible, definite spin with the new blow up of the wave N or PR.

Link
Member Since: September 9, 2008 Posts: 6 Comments: 3414
1792. louisianaboy444
10:40 PM GMT on August 13, 2009
You see the minute i say something positive like "it could go out to sea" the GFS spits something out like that..thats why i dont say anything
Member Since: August 29, 2006 Posts: 22 Comments: 1352
1791. WxLogic
10:40 PM GMT on August 13, 2009
Quoting farhaonhebrew:


both comments are very insightful..i wanna know to be ready here in puerto rico...



I have family in both PR and DR... so definitely keeping an eye on this one myself... guaranteed.
Member Since: August 14, 2008 Posts: 4 Comments: 4972
1790. Dakster
10:39 PM GMT on August 13, 2009
Quoting Drakoen:
GFS is way too inconsistent with the speed of this system to be considered credible.


more like INcredible...
Member Since: March 10, 2006 Posts: 0 Comments: 10291
1789. Tazmanian
10:39 PM GMT on August 13, 2009
Quoting Dakster:
Wassup WeatherStudent.

What's your take on the ex-TD2? Is it completely dead or up for revivial?




its dead
Member Since: May 21, 2006 Posts: 5091 Comments: 115104
1788. IKE
10:39 PM GMT on August 13, 2009
Back in the GOM...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
1787. Drakoen
10:38 PM GMT on August 13, 2009
GFS is way too inconsistent with the speed of this system to be considered credible.
Member Since: October 28, 2006 Posts: 57 Comments: 30490

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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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