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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Here is a poll.... how many blog reply posts will there be before Dr. Masters post another new blog... hmmm 3406 ! Na ,, kidding I dont want to calculate the votes. (Its like in the ER when we take bets on how high someone's alchohol level will come back!)... yes we do that!
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686. Skyepony (Mod)
Checking out which models are preforming best for 02L.. (in NM)

model ERROR Trend 24hr Error. 48hr 72hr Error Day 4 Error Day 5 Error
OFCL INCREASING 29.7 77.6 -1 -1 -1
KHRM INCREASING 68.9 161.8 -1 -1 -1
HWRF DECREASING 86.8 134.4 213.7 -1 -1
GFDL INCREASING 89.3 183.4 271 321.6 -1
BAMD CONSTANT 99.5 214.7 386.2 431 -1
LBAR DECREASING 104.1 273.3 603.1 794.7 -1
MM5E INCREASING 110.6 157.8 -1 -1 -1
MM5B INCREASING 121.4 201.2 257.8 -1 -1
BAMD CONSTANT 99.5 214.7 386.2 431 -1
CLP5 DECREASING 77.8 186.4 355.5 407.7 -1
CMC DECREASING 131.4 106.1 52 -1 -1
LGEM CONSTANT 93.4 215 354.8 420.3 -1
NGPS DECREASING 77.1 236 258.6 -1 -1
XTRP DECREASING 70.5 141 308.7 276.4 -1
Member Since: August 10, 2005 Posts: 179 Comments: 38321
685. srada
Quoting reedzone:
This run is not looking good for Long Island, NY.. It catches the trough but high pressure looks to build in and keep it from moving east.

12Z GFS 276 .. A stronger storm then the 06Z run.
Must remember that the 12Z and 00Z runs are more accurate then the 06Z and 18Z runs.



Whoa..thats heading straight for me! (Wilm, NC)
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683. JRRP

Member Since: August 16, 2007 Posts: 0 Comments: 5996
Quoting CaneWarning:
90L is red...just as expected.

Hmmpft, I said orange. oh well...
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Quoting wishcasterfromfsu:
i vote for red on the next TWO-however it will probably only be orange...

did anyone read that article about the insane number of jellyfish on the coast of the carolinas? maybe the jellyfish are like the ants in terms of forecasting possibilities ;)


Didn't read the article, but just took a waverunner out in Destin a couple of weeks ago and saw no less than 30 jellyfish around me at all times. Thank God, I didn't roll it messing around!

I know we always joke about the weird animal\insect behavior because some people tend to get overexcited about it on the blog, but there does seem to be at least some sort of coincidence...sometimes.
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90L is red...just as expected.
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000
ABNT20 KNHC 131732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 13 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION TWO...LOCATED ABOUT 885 MILES WEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE BROAD LOW PRESSURE
AREA AND TROPICAL WAVE CENTERED ABOUT 250 MILES SOUTH OF THE CAPE
VERDE ISLANDS ARE SLOWLY BECOMING BETTER ORGANIZED. A TROPICAL
DEPRESSION COULD FORM FROM THIS SYSTEM DURING THE NEXT COUPLE OF
DAYS AS IT MOVES WESTWARD AT 10 TO 15 MPH. THERE IS A HIGH
CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY EXTENDING FROM THE EASTERN CARIBBEAN SEA ACROSS
HISPANIOLA TO THE TURKS AND CAICOS ISLANDS ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. THERE ARE NO SIGNS OF ORGANIZATION
AND UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR SIGNIFICANT
DEVELOPMENT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN



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First Red Alert since 90L in May.
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Quoting futuremet:
Vorticy analysis




Futuremet-


Just a comment. You posted an Abolute Vorticity Chart, not a Relative Vorticity Chart. Obviously it still shows 90Ls vorticity well so from that standpoint it's ok.

However, Absolute vorticity includes the effect of latitude on vorticity (which is why the northern part of your chart is more red than near the Equator. Also, south of the equator the Absolute contribution due to latitude is opposite in sign.

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Quoting leftovers:
they need to send instructions to us drak how to get rid of it completely. still having problems it crashes easily. or how about this give adminstration a 24 hr ban for not doing their job


Mine crashes easily too. I just have to use my laptop mostly now.
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Code red and Caribbean code yellow:
000
ABNT20 KNHC 131732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 13 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION TWO...LOCATED ABOUT 885 MILES WEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE BROAD LOW PRESSURE
AREA AND TROPICAL WAVE CENTERED ABOUT 250 MILES SOUTH OF THE CAPE
VERDE ISLANDS ARE SLOWLY BECOMING BETTER ORGANIZED. A TROPICAL
DEPRESSION COULD FORM FROM THIS SYSTEM DURING THE NEXT COUPLE OF
DAYS AS IT MOVES WESTWARD AT 10 TO 15 MPH. THERE IS A HIGH
CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY EXTENDING FROM THE EASTERN CARIBBEAN SEA ACROSS
HISPANIOLA TO THE TURKS AND CAICOS ISLANDS ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. THERE ARE NO SIGNS OF ORGANIZATION
AND UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR SIGNIFICANT
DEVELOPMENT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN

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Quoting TStormSC:

I thought it was turtle activity to watch out for.


haha forgot about the turtles lmao.
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Quoting wishcasterfromfsu:
i vote for red on the next TWO-however it will probably only be orange...

did anyone read that article about the insane number of jellyfish on the coast of the carolinas? maybe the jellyfish are like the ants in terms of forecasting possibilities ;)


Interesting - couple that with an mysterious explosion in the starfish populations in the waters of New England....
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yes TD2 will hop on the metrorail and end up in Hialeah before being ate up by a mammoth python in the everglades
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B
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I think the one near Hispanola needs to be orange at 2.
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90L IS RED!!!

000
ABNT20 KNHC 131732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 13 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION TWO...LOCATED ABOUT 885 MILES WEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE BROAD LOW PRESSURE
AREA AND TROPICAL WAVE CENTERED ABOUT 250 MILES SOUTH OF THE CAPE
VERDE ISLANDS ARE SLOWLY BECOMING BETTER ORGANIZED. A TROPICAL
DEPRESSION COULD FORM FROM THIS SYSTEM DURING THE NEXT COUPLE OF
DAYS AS IT MOVES WESTWARD AT 10 TO 15 MPH. THERE IS A HIGH
CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY EXTENDING FROM THE EASTERN CARIBBEAN SEA ACROSS
HISPANIOLA TO THE TURKS AND CAICOS ISLANDS ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. THERE ARE NO SIGNS OF ORGANIZATION
AND UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR SIGNIFICANT
DEVELOPMENT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Member Since: Posts: Comments:
Quoting btwntx08:
its a tie 6 red aND orange so if u please 1 voter is allow to vote
a.orange
b.red
votee quickly 1 voter only thanks


B
Member Since: Posts: Comments:
000
ABNT20 KNHC 131732
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT THU AUG 13 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
DEPRESSION TWO...LOCATED ABOUT 885 MILES WEST OF THE SOUTHERNMOST
CAPE VERDE ISLANDS.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE BROAD LOW PRESSURE
AREA AND TROPICAL WAVE CENTERED ABOUT 250 MILES SOUTH OF THE CAPE
VERDE ISLANDS ARE SLOWLY BECOMING BETTER ORGANIZED. A TROPICAL
DEPRESSION COULD FORM FROM THIS SYSTEM DURING THE NEXT COUPLE OF
DAYS AS IT MOVES WESTWARD AT 10 TO 15 MPH. THERE IS A HIGH
CHANCE...GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY EXTENDING FROM THE EASTERN CARIBBEAN SEA ACROSS
HISPANIOLA TO THE TURKS AND CAICOS ISLANDS ARE ASSOCIATED WITH A
WESTWARD-MOVING TROPICAL WAVE. THERE ARE NO SIGNS OF ORGANIZATION
AND UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE FOR SIGNIFICANT
DEVELOPMENT. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN

Member Since: August 10, 2009 Posts: 0 Comments: 64
Orange.
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Quoting btwntx08:
its a tie 6 red aND orange so if u please 1 voter is allow to vote
a.orange
b.red
votee quickly 1 voter only thanks
Red at 2
Member Since: Posts: Comments:
Quoting btwntx08:
its a tie 6 red aND orange so if u please 1 voter is allow to vote
a.orange
b.red
votee quickly 1 voter only thanks


OrANGE
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Quoting 954FtLCane:
I can see TD2 is definitely pointing towards Hialeah... there is no doubt
ROFLMAO, or maybe little havana.
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I'll vote A at 2pm
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Quoting wishcasterfromfsu:
did anyone read that article about the insane number of jellyfish on the coast of the carolinas? maybe the jellyfish are like the ants in terms of forecasting possibilities ;)

I thought it was turtle activity to watch out for. :)
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Quoting bdimainman:
Anybody else think a depression is trying to form here


Link
maybe, ill give it a 30% chance because it is acquiring some 850 MB vorticity, nut the convection is very disorganized:
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BBBBBBBBBBBBBBBB
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I can see TD2 is definitely pointing towards Hialeah... there is no doubt
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Looks like 90L could just miss Florida in the last minute and move to the north like Floyd.
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Quoting bdimainman:
Anybody else think a depression is trying to form here


Link
maybe Looks like that headed right for South Florida
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i vote for red on the next TWO-however it will probably only be orange...

did anyone read that article about the insane number of jellyfish on the coast of the carolinas? maybe the jellyfish are like the ants in terms of forecasting possibilities ;)
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Quoting PimpCane:


Actually, I don't think you can even say for sure that we'll have a substantial tropical cyclone in three days. We could, but I don't see it being a slam-dunk either. Just because it's in better surroundings than TD2 doesn't mean it has a free pass to rapid development. Be alert to the possibility, sure, but there's a lot of people out here making foolhardy predictions about island and even U.S. landfalls when the bloody thing's around the Cape Verde islands and not even a depression yet.



Yes, you're right.
Amen, and absoutely agree with you ;)
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i vote B
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647. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5996
646. 7544
no dry air in the way for the 65 west wave

Link
Member Since: May 6, 2007 Posts: 0 Comments: 6862
Quoting 954FtLCane:
B... Im in FL I can still vote... I vote for B


funny..
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Anybody else think a depression is trying to form here


Link
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Quoting TreasureCoastFl:


Amen.
Absolutely


Actually, I don't think you can even say for sure that we'll have a substantial tropical cyclone in three days. We could, but I don't see it being a slam-dunk either. Just because it's in better surroundings than TD2 doesn't mean it has a free pass to rapid development. Be alert to the possibility, sure, but there's a lot of people out here making foolhardy predictions about island and even U.S. landfalls when the bloody thing's around the Cape Verde islands and not even a depression yet.

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Quoting 954FtLCane:
B... Im in FL I can still vote... I vote for B
LOL - gotta love those chads
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The TWO will be up in around 10 minutes.
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Vorticy analysis

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Quoting OSUWXGUY:
Drak-

I'm probably spending too much time analyzing a models output...

As you discussed, there is a weak initial trough, followed by a stronger second trough over the Eastern US as 90L is forecast to approach.

By looking at the Northern Pacific section of the GFS, it appears the source region for the jet streak that digs the second, stronger trough is in the Central Pacific. Obviously still a long way aways, but we'll probably have to watch this in coming runs.

Link


Hopefully it'll turn and just be one for the fish.
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Quoting OSUWXGUY:
Drak-

I'm probably spending too much time analyzing a models output...

As you discussed, there is a weak initial trough, followed by a stronger second trough over the Eastern US as 90L is forecast to approach.

By looking at the Northern Pacific section of the GFS, it appears the source region for the jet streak that digs the second, stronger trough is in the Central Pacific. Obviously still a long way aways, but we'll probably have to watch this in coming runs.

Link



Yes we will have to watch it
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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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