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 weathersp:


Not funny... even though some of us know its a joke... Some lurkers here may have thought you wern't kidding...

Please consider your actions before you post.


I'm not joking. You should always be prepared!
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Quoting antonio28:


That's is my greeatest fear with this one. Has been over 70 years...since last cat 5.


a juyil ... as we say in pr .. we have too many structures in 100 x 35 miles island.. plus the rain in the mountainss causing landslides everywhere .. and do not forget that we have urban areas both built on the coast and in places not appropriate..
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according to the AVN ir sat convection is starting to go around the COC of ex-TD2


Link
Member Since: June 13, 2009 Posts: 2 Comments: 12140
Quoting CaneWarning:


AKA Lower Alabama.
Ummmm I think you need a map. Panama City Beach, Fl is nowhere near Lower AL
Quoting CaneWarning:


YES
Sure! lol
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Quoting CaneWarning:


YES


Not funny... even though some of us know its a joke... Some lurkers here may have thought you wern't kidding...

Please consider your actions before you post.
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Ouch...again.
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Quoting Stormchaser2007:
18z

Wind

can u give me the link to that chart, thanks a lot.
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Quoting DM21Altestic:
UTC (also known as z time and GMT) is like, 4 hours ahead of Eastern Time, 5 ahead of CST. For instance, it's 00z but here it's 6:00.

Also, why aren't the oozy (00Z) runs out yet? It's 00z. I've always wondered why they were always six hours behind.

GFS has 3.5 hours of data assimilation. That way the first ~3 hours of any run are "perfect" (in so far that our obs are perfect)...makes a better more-than 5 day forecast. Number crunching time needed after that.
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Quoting TampaMishy:
Should I be preparing for a direct here in Tampa? J/K


YES
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hit*
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Quoting ALCoastGambler:
Doesn't show Lower Al. It shows PCB, FL


AKA Lower Alabama.
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Should I be preparing for a direct here in Tampa? J/K
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Quoting Drakoen:
90L is a very large circulation.
Is there any chance TD2 gets more organized overnight or is it completely kaput ?
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Quoting CaneWarning:
What is the GFS showing? What part of Florida does it hit before hitting lower Alabama?
Doesn't show Lower Al. It shows PCB, FL
Quoting CaneWarning:
What is the GFS showing? What part of Florida does it hit before hitting lower Alabama?


it goes straight up JFVWS' nose...
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What is the GFS showing? What part of Florida does it hit before hitting lower Alabama?
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18z

Wind

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Quoting Drakoen:
90L is a very large circulation.


Looks better organized.
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1862. BtnTx
delete comment
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Quoting KEEPEROFTHEGATE:
just after 8 pm edt taz



thank you
Member Since: May 21, 2006 Posts: 5091 Comments: 115256
Quoting louisianaboy444:
What is Dmax?

Early in the morning when the ocean temperature is greater than the air temperature it causes a temperature gradient and warm air rises from the gulf(because it is less dense) causing an unstable atmosphere which in turn causes thunderstorms or in other words convection


Thanks:)
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1858. KEEPEROFTHEGATE (Mod)
it will be 0034 or 0037 utc normally
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Quoting IKE:


And I get 15 inches of rain.

I don't trust these systems...I guess that's why I keep up on them.
Yeah, either way your screwed. Better send it 100mi. East of you
1856. KEEPEROFTHEGATE (Mod)
Quoting Tazmanian:
when dos this update next???


000
WHXX01 KWBC 131901
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1901 UTC THU AUG 13 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL902009) 20090813 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090813 1800 090814 0600 090814 1800 090815 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 11.7N 23.3W 12.5N 26.1W 13.0N 29.7W 13.1N 33.5W
BAMD 11.7N 23.3W 12.0N 25.9W 12.0N 28.7W 11.8N 31.5W
BAMM 11.7N 23.3W 12.1N 25.9W 12.5N 29.0W 12.6N 32.2W
LBAR 11.7N 23.3W 11.9N 25.5W 12.2N 28.5W 12.5N 31.7W
SHIP 25KTS 29KTS 37KTS 48KTS
DSHP 25KTS 29KTS 37KTS 48KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090815 1800 090816 1800 090817 1800 090818 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 12.9N 38.0W 12.1N 46.9W 10.8N 54.5W 9.5N 60.1W
BAMD 11.9N 34.5W 12.4N 41.1W 13.2N 47.3W 14.4N 52.8W
BAMM 12.7N 35.9W 12.4N 43.7W 11.5N 49.5W 12.5N 52.5W
LBAR 12.7N 35.6W 13.2N 44.1W 13.2N 48.0W .0N .0W
SHIP 60KTS 79KTS 89KTS 98KTS
DSHP 60KTS 79KTS 89KTS 98KTS

...INITIAL CONDITIONS...
LATCUR = 11.7N LONCUR = 23.3W DIRCUR = 280DEG SPDCUR = 7KT
LATM12 = 11.5N LONM12 = 21.9W DIRM12 = 278DEG SPDM12 = 7KT
LATM24 = 11.2N LONM24 = 20.3W
WNDCUR = 25KT RMAXWD = 60NM WNDM12 = 25KT
CENPRS = 1009MB OUTPRS = 1012MB OUTRAD = 180NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

just after 8 pm edt taz
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Quoting DM21Altestic:

Yeah, I'm on a BOAT! Everybody look at me, 'cuz I'm sailing on a boat!



lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115256
1853. IKE
Quoting ALCoastGambler:
My luck Ike, Model is wrong and it is 100mi. West


And I get 15 inches of rain.

I don't trust these systems...I guess that's why I keep up on them.
Member Since: Posts: Comments:
when dos this update next???


000
WHXX01 KWBC 131901
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1901 UTC THU AUG 13 2009

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (AL902009) 20090813 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090813 1800 090814 0600 090814 1800 090815 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 11.7N 23.3W 12.5N 26.1W 13.0N 29.7W 13.1N 33.5W
BAMD 11.7N 23.3W 12.0N 25.9W 12.0N 28.7W 11.8N 31.5W
BAMM 11.7N 23.3W 12.1N 25.9W 12.5N 29.0W 12.6N 32.2W
LBAR 11.7N 23.3W 11.9N 25.5W 12.2N 28.5W 12.5N 31.7W
SHIP 25KTS 29KTS 37KTS 48KTS
DSHP 25KTS 29KTS 37KTS 48KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090815 1800 090816 1800 090817 1800 090818 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 12.9N 38.0W 12.1N 46.9W 10.8N 54.5W 9.5N 60.1W
BAMD 11.9N 34.5W 12.4N 41.1W 13.2N 47.3W 14.4N 52.8W
BAMM 12.7N 35.9W 12.4N 43.7W 11.5N 49.5W 12.5N 52.5W
LBAR 12.7N 35.6W 13.2N 44.1W 13.2N 48.0W .0N .0W
SHIP 60KTS 79KTS 89KTS 98KTS
DSHP 60KTS 79KTS 89KTS 98KTS

...INITIAL CONDITIONS...
LATCUR = 11.7N LONCUR = 23.3W DIRCUR = 280DEG SPDCUR = 7KT
LATM12 = 11.5N LONM12 = 21.9W DIRM12 = 278DEG SPDM12 = 7KT
LATM24 = 11.2N LONM24 = 20.3W
WNDCUR = 25KT RMAXWD = 60NM WNDM12 = 25KT
CENPRS = 1009MB OUTPRS = 1012MB OUTRAD = 180NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

Member Since: May 21, 2006 Posts: 5091 Comments: 115256
1851. ssmate
Quoting 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...


Ike is Right!
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Quoting DM21Altestic:

Yeah, I'm on a BOAT! Everybody look at me, 'cuz I'm sailing on a boat!


I love that SNL skit!
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Quoting IKE:
My dock gets smashed again...

My luck Ike, Model is wrong and it is 100mi. West
Quoting farhaonhebrew:


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...




That's is my greeatest fear with this one. Has been over 70 years...since last cat 5.
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Quoting weatherfan92:


What is Dmax?


it's the same thing as a Hebert Box...
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What is Dmax?

Early in the morning when the ocean temperature is greater than the air temperature it causes a temperature gradient and warm air rises from the gulf(because it is less dense) causing an unstable atmosphere which in turn causes thunderstorms or in other words convection
Member Since: August 29, 2006 Posts: 22 Comments: 1352
in the long term models, isthis thing going into se fla or somewhere else. Sry but I can't see the models since I'm on my iPhone
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guys I think ex- TD2 will regenerate back into TD2 by tomorrow morning convection will increase during D-MAX and build up around the COC I mean look at it it is gaining convection and the bands from 90L pre-TD3
Member Since: June 13, 2009 Posts: 2 Comments: 12140
1842. KEEPEROFTHEGATE (Mod)
Quoting Drakoen:
90L is a very large circulation.
could even be too big that can effect dev as well
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1839. IKE
My dock gets smashed again...

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18z takes it to around the PCB area
Member Since: August 27, 2008 Posts: 0 Comments: 1497

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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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