Tropical Depression Four whips the Cape Verde Islands

By: Dr. Jeff Masters , 12:49 PM GMT on August 22, 2006

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Tropical Depression Four is making what is likely to be its closest pass to any land areas during its life--a brush of the Cape Verde Islands off the coast of Africa. The storm should get no closer than about 100 miles from the islands today, and its outer rain bands could bring 2-4 inches of rain and winds gusts to 50 mph to these islands today. The only station that reports hourly observations in these islands is Sal, which has seen the winds increase to a steady 17 mph so far this morning. Winds measured from the QuikSCAT satellite in a 4am EDT pass this morning were about 35 mph in the islands.

TD Four is a favorable environment for intensification, and should be Tropical Storm Debby later today. Wind shear is a low 5-10 knots. There is a large area of dry air and Saharan dust to the wave's north, but this is far enough away that it shouldn't inhibit intensification over the next day or two. The GFDL intensifies the storm up to a strong Category 1 hurricane by Saturday, and the official NHC forecast is close behind.

Unless you live in the Cape Verde Islands, this storm is unlikely to affect you. As we can see from the plot of historical storm tracks of August tropical depressions that formed near the location of the current storm (Figure 1), none of these storms that have started out as far north as this storm have affected any land areas other than the Cape Verde Islands. The GFS and GFDL models have the storm recurving northwards well east of Bermuda early next week, as a trough of low pressure picks up the storm. However, it is too early to have high confidence in this forecast. The UKMET, NOGAPS, and Canadian models all predict that this trough of low pressure will miss TD 4, which will continue on a more westerly path and possibly threaten Bermuda. The models have not done a great job with the track of this storm, which was 70 miles further south than the models predicted it would be last night.


Figure 1. Historical tracks of August tropical depressions that tracked near the current position of TD 4.

Elsewhere in the tropical Atlantic
An area of thunderstorms in the western Caribbean west of Jamaica is drifting northwestwards towards the Yucatan Channel and Gulf of Mexico. Wind shear is a high 20 knots over this area, and upper level winds are not favorable for development. The shear is expected to drop over the Gulf by Thursday, so we'll have to keep an eye on this system later this week. None of the computer models develop anything in the Gulf or Caribbean this week, though. The long-range GFS model is no longer predicting any new tropical storms forming anywhere in the Atlantic in the next 10 days.

I'll have an update on this system when it becomes Debby.
Jeff Masters

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1102. rwdobson
9:07 PM GMT on August 22, 2006
actually, if you read the NHC discussion, posted twice on this blog, the NHC is still agreeing with the turn to the north.

the nhc's thoughts are out in public, for anyone to see...
Member Since: June 12, 2002 Posts: 0 Comments: 1574
1101. Patrap
9:03 PM GMT on August 22, 2006
..sees TD4 ingesting bad fuel mix..like DRy Air from the N...
Member Since: July 3, 2005 Posts: 414 Comments: 125418
1100. Patrap
9:02 PM GMT on August 22, 2006
..TD..a swirl offa The Azores in 6 days...dying like a Flat creme soda on a Biloxi Beach in August,..but..97 L ..robust..heading to better environs...in 72..
Member Since: July 3, 2005 Posts: 414 Comments: 125418
1099. StormJunkie
9:01 PM GMT on August 22, 2006
New blog up ya'll
Member Since: August 17, 2005 Posts: 26 Comments: 15472
1098. StLucieHurricane
9:00 PM GMT on August 22, 2006
I heard from other blogs that the NHC is disagreeing with the turn to the north, and the models?
Anyone else heard this?
1097. CoastalMs
9:00 PM GMT on August 22, 2006
Thanks to whomever posts the satellite images and NWS discussions. I come here often to check on the current situation and like being able to see what's going on without having to follow a bunch of links.
1096. WPBHurricane05
8:57 PM GMT on August 22, 2006
check this out
seems the winds with 97L are near 30-35knts in some spots
Member Since: July 31, 2006 Posts: 56 Comments: 8112
1094. NWAtlanticCyclone
8:55 PM GMT on August 22, 2006
I think the depression looks better this morning with the convection increasing to the northeast and northwest of the circulation. Convection has intensified recently and is gaining strength and a tropical storm is likely within 12 hours. 97L is looking very good now and I could expect a TD within a day if this increase in organization continues to occur. 97L looks to be located inside a very unstable and a low latitude also favors it for development. This location will keep the invest from higher shear and African dust/ dry air.
1091. HCW
8:49 PM GMT on August 22, 2006
If the Atlantic doesn't hurry up and heat up I may have to start tracking Pacific cyclones.

Harcoreweather.com
Link
Member Since: August 10, 2002 Posts: 0 Comments: 1346
1089. mrpuertorico
8:49 PM GMT on August 22, 2006
so whats the haps with 97l just doing a check in and it looks like the bamm has it going right over my apartment
Member Since: July 10, 2006 Posts: 0 Comments: 833
1088. hurricane23
8:48 PM GMT on August 22, 2006
Looks like models are now in good agreement the TD 4 will make that sharp turn in response to the weakening ridge.

CLICK ON THUMBNAIL
Free Image Hosting at www.ImageShack.us
Member Since: May 14, 2006 Posts: 8 Comments: 13594
1087. robinvtx
8:48 PM GMT on August 22, 2006
i think whoever is doing what gets the picture. gosh sometimes you people just go on and on and on. amazing.
1083. Cavin Rawlins
8:44 PM GMT on August 22, 2006
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1082. Oreodog
8:43 PM GMT on August 22, 2006
HadesGod: Where are you --- "JST"??
1081. rwdobson
8:43 PM GMT on August 22, 2006
This is a forecast from the Deparment of Redundancy Department...we expect the full 5:00 advisory and discussion will be posted at least 5 more times on this blog by at least 4 different people....
Member Since: June 12, 2002 Posts: 0 Comments: 1574
1078. hurricane23
8:43 PM GMT on August 22, 2006
Stop what?My pc was running slow.Again my bad.
Member Since: May 14, 2006 Posts: 8 Comments: 13594
1077. katrina2005
8:43 PM GMT on August 22, 2006
looks like alll the convection is on the soutside of the storm
1076. HadesGodWyvern (Mod)
8:42 PM GMT on August 22, 2006
LOL Head-on commercial
Member Since: May 24, 2006 Posts: 48 Comments: 43639
1075. Oreodog
8:42 PM GMT on August 22, 2006
The WU echo chamber
1074. Cavin Rawlins
8:42 PM GMT on August 22, 2006
Ileana is now a Hurricane (65knots/75mph)
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1073. rwdobson
8:42 PM GMT on August 22, 2006
taz, it means exactly what it says. look at the track on a map, then shift it to the right.
Member Since: June 12, 2002 Posts: 0 Comments: 1574
1072. HadesGodWyvern (Mod)
8:41 PM GMT on August 22, 2006
just can't make it to storm status.. one day past still stuck at 30 knots.. hmm
Member Since: May 24, 2006 Posts: 48 Comments: 43639
1071. amazinwxman
8:41 PM GMT on August 22, 2006
Back to the Atlantic how is TD 4 looking? I was just reading on another site's blog it wad sickly looking and looked like it would be dead by end of day or later tonight is that true?
1068. Tazmanian
8:40 PM GMT on August 22, 2006
SHIFTED SLIGHTLY
TO THE RIGHT OF THE PREVIOUS TRACK


now what dos that mean
Member Since: May 21, 2006 Posts: 5089 Comments: 114024
1066. hurricane23
8:40 PM GMT on August 22, 2006
My bad guys posted the 5:00 twice...
Member Since: May 14, 2006 Posts: 8 Comments: 13594
1065. HadesGodWyvern (Mod)
8:39 PM GMT on August 22, 2006
LOL and it gets posted twice
Member Since: May 24, 2006 Posts: 48 Comments: 43639
1064. rwdobson
8:38 PM GMT on August 22, 2006
and extra redundant to post it twice! This has been a bulletin from the Department of Redundancy Department.
Member Since: June 12, 2002 Posts: 0 Comments: 1574
1062. HadesGodWyvern (Mod)
8:38 PM GMT on August 22, 2006
hmm hurricane got dropped out of the advisory, but still a severe tropical storm is forecasted..
Member Since: May 24, 2006 Posts: 48 Comments: 43639
1061. hurricane23
8:37 PM GMT on August 22, 2006
BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006
500 PM AST TUE AUG 22 2006

...DEPRESSION CONTINUES MOVING WEST-NORTHWESTWARD AWAY FROM THE CAPE
VERDE ISLANDS...

AT 500 PM AST...2100Z...THE CENTER OF TROPICAL DEPRESSION FOUR WAS
LOCATED NEAR LATITUDE 14.5 NORTH...LONGITUDE 27.5 WEST OR ABOUT 210
MILES...335 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.

THE DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. THE DEPRESSION COULD BECOME A TROPICAL STORM LATER TONIGHT
OR TOMORROW.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

REPEATING THE 500 PM AST POSITION...14.5 N...27.5 W. MOVEMENT
TOWARD...WEST-NORTHWEST NEAR 18 MPH. MAXIMUM SUSTAINED WINDS...35
MPH. MINIMUM CENTRAL PRESSURE...1005 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.

$$
FORECASTER FRANKLIN

TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006
500 PM EDT TUE AUG 22 2006

DESPITE SOME INCREASE OF CONVECTION NEAR THE CENTER THIS
AFTERNOON...THERE IS LIMITED BANDING AND DVORAK INTENSITY ESTIMATES
FROM TAFB AND SAB REMAIN AT 30 KT. CONSEQUENTLY THE SYSTEM WILL NOT
BE UPGRADED AT THIS TIME. HOWEVER...WITH CONVECTION ON THE INCREASE
THE CLASSIFICATIONS SHOULD SUPPORT TROPICAL STORM STRENGTH VERY
SOON. WHILE THE OUTFLOW PATTERN HAS BEEN IMPROVING TODAY AND THE
SHEAR IS FAIRLY LOW...THE CYCLONE WILL BE MOVING OVER SLIGHTLY
COOLER WATERS AND A MORE STABLE BOUNDARY LAYER FLOW...SO I AM
ANTICIPATING ONLY SLOW DEVELOPMENT OVER THE NEXT COUPLE OF DAYS.
AFTER THAT...WATERS WARM BUT SOME OF THE GLOBAL MODELS SUGGEST AN
INCREASE IN SOUTHERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL LOW IN
THE CENTRAL ATLANTIC. BOTH THE SHIPS AND GFDL MODELS HAVE BACKED
OFF SLIGHTLY WITH THEIR INTENSITY FORECASTS AND THE OFFICIAL
FORECAST IS ALSO NUDGED DOWN.

THE INITIAL MOTION IS 300/16...OR ABOUT 15 DEGREES TO THE RIGHT OF
THIS TIME YESTERDAY. RECENT MICROWAVE PASSES SUGGEST A BETTER
CO-LOCATION OF THE MID AND LOW-LEVEL CENTERS. THERE HAS BEEN
SIGNIFICANT CONVERGENCE IN HOW THE GLOBAL MODELS HANDLE THE
DEPRESSION...WITH THE 12Z RUNS OF THE UKMET AND ECMWF NOW
MAINTAINING THE SYSTEM AND SHIFTING THEIR TRACKS TO THE RIGHT.
THEY ARE NOW IN GOOD AGREEMENT WITH THE GFS AND ALSO WITH THE GFDL
THROUGH ABOUT 72 HOURS. THERE HAS BEEN LITTLE CHANGE TO THE
SYNOPTIC SITUATION...WITH ALL THE GUIDANCE INDICATING AN EASTWARD
SHIFT OF THE SUBTROPICAL RIDGE AND TROUGHING DEVELOPING OVER THE
CENTRAL ATLANTIC. THE OFFICIAL FORECAST HAS BEEN SHIFTED SLIGHTLY
TO THE RIGHT OF THE PREVIOUS TRACK AND IS IN BEST AGREEMENT WITH
THE GFS AND ECMWF.


FORECAST POSITIONS AND MAX WINDS

INITIAL 22/2100Z 14.5N 27.5W 30 KT
12HR VT 23/0600Z 15.7N 29.7W 35 KT
24HR VT 23/1800Z 17.2N 32.4W 40 KT
36HR VT 24/0600Z 18.8N 35.2W 40 KT
48HR VT 24/1800Z 20.1N 38.0W 45 KT
72HR VT 25/1800Z 23.0N 44.0W 50 KT
96HR VT 26/1800Z 27.0N 49.0W 55 KT
120HR VT 27/1800Z 30.0N 53.0W 60 KT

$$
FORECASTER FRANKLIN

Member Since: May 14, 2006 Posts: 8 Comments: 13594
1059. Tazmanian
8:36 PM GMT on August 22, 2006


pary that this 97L dos not go in to the gulf if it dos this will not be good news
Member Since: May 21, 2006 Posts: 5089 Comments: 114024
1057. hurricane23
8:36 PM GMT on August 22, 2006
BULLETIN
TROPICAL DEPRESSION FOUR ADVISORY NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006
500 PM AST TUE AUG 22 2006

...DEPRESSION CONTINUES MOVING WEST-NORTHWESTWARD AWAY FROM THE CAPE
VERDE ISLANDS...

AT 500 PM AST...2100Z...THE CENTER OF TROPICAL DEPRESSION FOUR WAS
LOCATED NEAR LATITUDE 14.5 NORTH...LONGITUDE 27.5 WEST OR ABOUT 210
MILES...335 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.

THE DEPRESSION IS MOVING TOWARD THE WEST-NORTHWEST NEAR 18 MPH...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. THE DEPRESSION COULD BECOME A TROPICAL STORM LATER TONIGHT
OR TOMORROW.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

REPEATING THE 500 PM AST POSITION...14.5 N...27.5 W. MOVEMENT
TOWARD...WEST-NORTHWEST NEAR 18 MPH. MAXIMUM SUSTAINED WINDS...35
MPH. MINIMUM CENTRAL PRESSURE...1005 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.

$$
FORECASTER FRANKLIN

TROPICAL DEPRESSION FOUR DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL042006
500 PM EDT TUE AUG 22 2006

DESPITE SOME INCREASE OF CONVECTION NEAR THE CENTER THIS
AFTERNOON...THERE IS LIMITED BANDING AND DVORAK INTENSITY ESTIMATES
FROM TAFB AND SAB REMAIN AT 30 KT. CONSEQUENTLY THE SYSTEM WILL NOT
BE UPGRADED AT THIS TIME. HOWEVER...WITH CONVECTION ON THE INCREASE
THE CLASSIFICATIONS SHOULD SUPPORT TROPICAL STORM STRENGTH VERY
SOON. WHILE THE OUTFLOW PATTERN HAS BEEN IMPROVING TODAY AND THE
SHEAR IS FAIRLY LOW...THE CYCLONE WILL BE MOVING OVER SLIGHTLY
COOLER WATERS AND A MORE STABLE BOUNDARY LAYER FLOW...SO I AM
ANTICIPATING ONLY SLOW DEVELOPMENT OVER THE NEXT COUPLE OF DAYS.
AFTER THAT...WATERS WARM BUT SOME OF THE GLOBAL MODELS SUGGEST AN
INCREASE IN SOUTHERLY SHEAR ASSOCIATED WITH AN UPPER-LEVEL LOW IN
THE CENTRAL ATLANTIC. BOTH THE SHIPS AND GFDL MODELS HAVE BACKED
OFF SLIGHTLY WITH THEIR INTENSITY FORECASTS AND THE OFFICIAL
FORECAST IS ALSO NUDGED DOWN.

THE INITIAL MOTION IS 300/16...OR ABOUT 15 DEGREES TO THE RIGHT OF
THIS TIME YESTERDAY. RECENT MICROWAVE PASSES SUGGEST A BETTER
CO-LOCATION OF THE MID AND LOW-LEVEL CENTERS. THERE HAS BEEN
SIGNIFICANT CONVERGENCE IN HOW THE GLOBAL MODELS HANDLE THE
DEPRESSION...WITH THE 12Z RUNS OF THE UKMET AND ECMWF NOW
MAINTAINING THE SYSTEM AND SHIFTING THEIR TRACKS TO THE RIGHT.
THEY ARE NOW IN GOOD AGREEMENT WITH THE GFS AND ALSO WITH THE GFDL
THROUGH ABOUT 72 HOURS. THERE HAS BEEN LITTLE CHANGE TO THE
SYNOPTIC SITUATION...WITH ALL THE GUIDANCE INDICATING AN EASTWARD
SHIFT OF THE SUBTROPICAL RIDGE AND TROUGHING DEVELOPING OVER THE
CENTRAL ATLANTIC. THE OFFICIAL FORECAST HAS BEEN SHIFTED SLIGHTLY
TO THE RIGHT OF THE PREVIOUS TRACK AND IS IN BEST AGREEMENT WITH
THE GFS AND ECMWF.


FORECAST POSITIONS AND MAX WINDS

INITIAL 22/2100Z 14.5N 27.5W 30 KT
12HR VT 23/0600Z 15.7N 29.7W 35 KT
24HR VT 23/1800Z 17.2N 32.4W 40 KT
36HR VT 24/0600Z 18.8N 35.2W 40 KT
48HR VT 24/1800Z 20.1N 38.0W 45 KT
72HR VT 25/1800Z 23.0N 44.0W 50 KT
96HR VT 26/1800Z 27.0N 49.0W 55 KT
120HR VT 27/1800Z 30.0N 53.0W 60 KT

$$
FORECASTER FRANKLIN
Member Since: May 14, 2006 Posts: 8 Comments: 13594
1056. Cavin Rawlins
8:35 PM GMT on August 22, 2006
Ileana Estimated Expected Intensity at 5:00pmEDT

Curved Band Pattern/Cloud Pattern
0.3 Spiral - DT 1.5

Shear Pattern
None - 0.00

CDO
-CDO Central Feature

1 degrees latitude- DT 2

-CDO Banding Features

1 degree - DT 0.75

Eye Feature/Pattern
None - DT 0.00

Further Considerations (environmental factors)
The storm has a very strong and well define CDO, contributing to a higher T-Number than officially stated.

Notes
The stormís eye is not visible anymore.

Ileana T Number is 1.5+2+0.75=4.25

4.25 is 81.5mph, 986mbar MCP/Category One Hurricane

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1055. WPBHurricane05
8:34 PM GMT on August 22, 2006
well as of 5PM it doesnt look like we have TSDebby
Member Since: July 31, 2006 Posts: 56 Comments: 8112
1054. Joshfsu123
8:31 PM GMT on August 22, 2006
97L is not a TD yet and it hasn't shown great signs of becoming one. It does look to have rotation at the surface but thunderstorms haven't been firing up, partly due to the African Dust that is in the northern part of it's circulation.

If it can develop strong thunderstorms around the center, it would possibly develop but it probably won't be classified for a couple days yet.

Also, it needs to start gaining some ground as it is current apart of the ITCZ and it has South America in it's sites, being around 10.5 degrees north.

But yes, this system is the one to watch as TD4 will not be a threat to anyone but the fish in the central Atlantic, unless it stays weaker than expected.
Member Since: July 6, 2005 Posts: 5 Comments: 578
1053. MisipiGrl
8:30 PM GMT on August 22, 2006
Hi, Lyon. I'm also in Long Beach. I've done the Goula commute and...never again! :)

(I failed the meteorology section of science in college. I just come here to read and maybe, just maybe...learn something!)
Member Since: August 27, 2005 Posts: 0 Comments: 101
1052. HCW
8:29 PM GMT on August 22, 2006
I don't see this cooler water that everyone is talking about. Looks normal to above average both near the surface and deep down. The water is alot warmer off the central gulfcoast than it was last season .I guess this may because of the lack of winter and drought that we have had since Katrina . James


Hardcoreweather.comLink
Member Since: August 10, 2002 Posts: 0 Comments: 1346

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.