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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2985. centex
While interesting and not blaming those trying to figure 90L strength or path. Just remember no one knows how strong and where. Some may say they do know but they are only making a wild guess. People say chance like < 30% and some grab as most likely.
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2984. lennit
i agree. what people lest to forget is that if TD#2 becomes a vertical system that will affect steering for 90L
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Too far out to know exactly where it will go. So many things will change. Honestly take your pick with any ecoast state; florida getting the highest probability and NC in second.
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2980. lennit
exactly we have plenty of time to watch it do whatever it wants to do
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2979. lennit
ECMWF sees this shortwave as strong enough to erode ridge and recurve 90L
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This gives you a picture of the wide area Ike Affected...

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2976. lennit
with the strength of the mid layer ridge 90L will be hauling in a couple day around 15mph or so
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2975. centex
Quoting lennit:
what appears on most global models is that a shortwave will move off the east coast pulling 90L to the WNW or NW near day 4 to 5 then a ridge will build back in and he/she or whatever it is resumes a West to WNW track..
Totally agree, but trying to plot point is meaningless at this point.
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2974. lennit
what appears on most global models is that a shortwave will move off the east coast pulling 90L to the WNW or NW near day 4 to 5 then a ridge will build back in and he/she or whatever it is resumes a West to WNW track..
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2973. centex
Quoting lennit:
CMC DAY 10Link
I agree, within 1000 miles.
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2972. 7544
Quoting lennit:
CMC DAY 10Link


it sure does thanks havent seen that one yet
Member Since: May 6, 2007 Posts: 0 Comments: 6874
2971. lennit
CMC DAY 10Link
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What does the 00Z GFDL do with this system?
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2969. sctonya
Quoting TexasHurricane:
I see that TD2 may not be gone yet....back to orange.

Link


I guess the NHC finally found all of their crayons!!
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2968. centex
Don't be thinking CAT 3-5 and CONUS landfall. They are saying could or one option.. Fixing on today is wrong. Reading models several days out is like using your whiggie board. No one thinks accurate after 3 days. We need a downcaster on this system, Im proud to take this task on this system.
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Pretty weird to see all the models in such agreement WITHOUT reconnaissance data
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2966. 7544
Quoting lennit:
00z CMC 10 day has a major huricane hit directly on Fl Peninsula


link please
Member Since: May 6, 2007 Posts: 0 Comments: 6874
I see that TD2 may not be gone yet....back to orange.

Link
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2964. lennit
00z CMC 10 day has a major huricane hit directly on Fl Peninsula
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2963. Drakoen
00z models are in excellent agreement in targeting the northern islands or just north of there.
Member Since: October 28, 2006 Posts: 57 Comments: 30841
Quoting louisianaboy444:
I got 3 inches at my house Korithe

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Received 3 inches here in Prairieville as well.
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I got 3 inches at my house Korithe

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SHOWER AND THUNDERSTORM ACTIVITY HAS RECENTLY INCREASED IN
ASSOCIATION WITH THE REMNANT LOW OF FORMER TROPICAL DEPRESSION
TWO THERE IS A MEDIUM CHANCE...30 TO 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.
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2958. yamil20
Wow i supposed td2 is not done
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Quoting louisianaboy444:
and who can forget this december morning in South Louisiana...

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OMG! <3 <3 <3

Snow is soo nice. It's too bad that last year's snow was likely a once in 20 year event. :(
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and who can forget this december morning in South Louisiana...

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000
ABNT20 KNHC 140553
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT FRI AUG 14 2009

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

SHOWER AND THUNDERSTORM ACTIVITY HAS RECENTLY INCREASED IN
ASSOCIATION WITH THE REMNANT LOW OF FORMER TROPICAL DEPRESSION
TWO
...WHICH IS CURRENTLY LOCATED ABOUT 1375 MILES EAST OF THE
LESSER ANTILLES. WHILE UPPER-LEVEL CONDITIONS ARE ONLY MARGINALLY
FAVORABLE FOR DEVELOPMENT...SLOW REGENERATION OF THIS SYSTEM INTO A
TROPICAL CYCLONE IS POSSIBLE AS IT MOVES WESTWARD AT ABOUT 10 MPH
OVER THE NEXT COUPLE OF DAYS. THERE IS A MEDIUM CHANCE...30 TO 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.


SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED OVER THE PAST FEW
HOURS IN ASSOCIATION WITH A BROAD AREA OF LOW PRESSURE CENTERED
ABOUT 175 MILES SOUTH-SOUTHWEST OF THE SOUTHERN CAPE VERDE ISLANDS.
CONDITIONS APPEAR FAVORABLE FOR FURTHER DEVELOPMENT OF THIS
SYSTEM...AND A TROPICAL DEPRESSION COULD FORM DURING THE NEXT DAY
OR TWO 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.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
LARGE AREA OF CLOUDINESS AND SHOWERS OVER HISPANIOLA...THE TURKS
AND CAICOS ISLANDS...AND THE SOUTHEASTERN BAHAMAS. THIS ACTIVITY IS
EXPECTED TO SPREAD SLOWLY WEST OR WEST-NORTHWESTWARD DURING THE
NEXT COUPLE OF DAYS. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. 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 BRENNAN
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02L may regenerate and 90L basically has no change.
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Night all...will be back in the morning
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2951. IKE
Ex-Td2 making a comeback....already.
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2950. centex
Quoting Stormchaser2007:
-Upper level anticyclonic flow.

-NO SAL

-Gradually organizing LLC that may be closed.

-Growing convection

I really dont see how you could downcast this.

How can you downcast a slow developing system, when it's not even TD?
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000
ABNT20 KNHC 140553
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT FRI AUG 14 2009

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

SHOWER AND THUNDERSTORM ACTIVITY HAS RECENTLY INCREASED IN
ASSOCIATION WITH THE REMNANT LOW OF FORMER TROPICAL DEPRESSION
TWO...WHICH IS CURRENTLY LOCATED ABOUT 1375 MILES EAST OF THE
LESSER ANTILLES. WHILE UPPER-LEVEL CONDITIONS ARE ONLY MARGINALLY
FAVORABLE FOR DEVELOPMENT...SLOW REGENERATION OF THIS SYSTEM INTO A
TROPICAL CYCLONE IS POSSIBLE AS IT MOVES WESTWARD AT ABOUT 10 MPH
OVER THE NEXT COUPLE OF DAYS. THERE IS A MEDIUM CHANCE...30 TO 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED OVER THE PAST FEW
HOURS IN ASSOCIATION WITH A BROAD AREA OF LOW PRESSURE CENTERED
ABOUT 175 MILES SOUTH-SOUTHWEST OF THE SOUTHERN CAPE VERDE ISLANDS.
CONDITIONS APPEAR FAVORABLE FOR FURTHER DEVELOPMENT OF THIS
SYSTEM...AND A TROPICAL DEPRESSION COULD FORM DURING THE NEXT DAY
OR TWO 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.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
LARGE AREA OF CLOUDINESS AND SHOWERS OVER HISPANIOLA...THE TURKS
AND CAICOS ISLANDS...AND THE SOUTHEASTERN BAHAMAS. THIS ACTIVITY IS
EXPECTED TO SPREAD SLOWLY WEST OR WEST-NORTHWESTWARD DURING THE
NEXT COUPLE OF DAYS. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. 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 BRENNAN
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Quoting IKE:
Models are zeroing in on the northern islands.


00z

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Who's anxious for the 2AM EDT TWO?
Member Since: Posts: Comments:
000
ABNT20 KNHC 140553
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT FRI AUG 14 2009

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

SHOWER AND THUNDERSTORM ACTIVITY HAS RECENTLY INCREASED IN
ASSOCIATION WITH THE REMNANT LOW OF FORMER TROPICAL DEPRESSION
TWO...WHICH IS CURRENTLY LOCATED ABOUT 1375 MILES EAST OF THE
LESSER ANTILLES. WHILE UPPER-LEVEL CONDITIONS ARE ONLY MARGINALLY
FAVORABLE FOR DEVELOPMENT...SLOW REGENERATION OF THIS SYSTEM INTO A
TROPICAL CYCLONE IS POSSIBLE AS IT MOVES WESTWARD AT ABOUT 10 MPH
OVER THE NEXT COUPLE OF DAYS. THERE IS A MEDIUM CHANCE...30 TO 50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED OVER THE PAST FEW
HOURS IN ASSOCIATION WITH A BROAD AREA OF LOW PRESSURE CENTERED
ABOUT 175 MILES SOUTH-SOUTHWEST OF THE SOUTHERN CAPE VERDE ISLANDS.
CONDITIONS APPEAR FAVORABLE FOR FURTHER DEVELOPMENT OF THIS
SYSTEM...AND A TROPICAL DEPRESSION COULD FORM DURING THE NEXT DAY
OR TWO 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.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
LARGE AREA OF CLOUDINESS AND SHOWERS OVER HISPANIOLA...THE TURKS
AND CAICOS ISLANDS...AND THE SOUTHEASTERN BAHAMAS. THIS ACTIVITY IS
EXPECTED TO SPREAD SLOWLY WEST OR WEST-NORTHWESTWARD DURING THE
NEXT COUPLE OF DAYS. UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM. 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 BRENNAN

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The TWO isn't out yet, but the 2am discussion is.
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Quoting extreme236:


NHC's latest surface map has a closed low.


I havent been here for a while. Thanks.
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Crowley isn't *that* small. I think Delcambre has you beat. lol
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2941. IKE
Models are zeroing in on the northern islands.
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Im tired...come on TWO come out so I can sleep.
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Can someone post me a link as to where I can find the SAB and TAFB dvorak classifications when they come out? And what time is this usually around? Thanks.
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Quoting Stormchaser2007:
-Upper level anticyclonic flow.

-NO SAL

-Gradually organizing LLC that may be closed.

-Growing convection

I really dont see how you could downcast this.



NHC's latest surface map has a closed low.
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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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