TD 2 nearly dead; African disturbance 90L gathering strength
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
Reader Comments
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TTAA00 KNHC DDHHMM
BULLETIN
TROPICAL DEPRESSION TWO ADVISORY NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
1100 AM AST THU AUG 13 2009
...DEPRESSION REMAINS WEAK AND POORLY ORGANIZED...
AT 1100 AM AST...1500 UTC...THE CENTER OF TROPICAL DEPRESSION TWO
WAS LOCATED NEAR LATITUDE 14.0 NORTH...LONGITUDE 37.6 WEST OR ABOUT
885 MILES...1425 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.
THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 9 MPH...14 KM/HR.
THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT COUPLE OF
DAYS WITH A GRADUAL INCREASE IN FORWARD SPEED.
MAXIMUM SUSTAINED WINDS ARE NEAR 30 MPH...45 KM/HR...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT
48 HR. SATELLITE IMAGERY INDICATES THAT ONLY A FEW SHOWERS AND
THUNDERTSTORMS ARE ASSOCIATED WITH THE DEPRESSION...AND IF THIS
TREND CONTINUES THE SYSTEM COULD DECAY TO A REMNANT LOW PRESSURE
AREA LATER TODAY.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.
...SUMMARY OF 1100 AM AST INFORMATION...
LOCATION...14.0N 37.6W
MAXIMUM SUSTAINED WINDS...30 MPH
PRESENT MOVEMENT...WEST OR 270 DEGREES AT 9 MPH
MINIMUM CENTRAL PRESSURE...1008 MB
THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
500 PM AST.
$$
FORECASTER BEVEN
NNNN
It will surprise you all.
http://www.ssd.noaa.gov/PS/TROP/float2.html
I don't think it'll end up being a TD for 5 straight days.
It'll either dissipate in short order - perhaps regenerate later on - or it'll sort itself out.
Thanks Storm
000
WTNT42 KNHC 131433
TCDAT2
TROPICAL DEPRESSION TWO DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
1100 AM AST THU AUG 13 2009
TROPICAL DEPRESSION TWO CURRENTLY CONSISTS OF A SWIRL OF LOW CLOUDS
WITH ISOLATED SHOWERS AND THUNDERSTORMS...TOO FEW TO GET A DATA-T
NUMBER USING THE DVORAK TECHNIQUE. SSMI/DATA AT ABOUT 09Z
SUGGESTED 25 KT WINDS IN THE NORTHERN SEMICIRCLE...AND THAT IS USED
AS THE INITIAL INTENSITY. SSM/I AND AMSR-E PRECIPITABLE WATER
IMAGERY SUGGESTS THAT A TONGUE OF DRIER AIR HAS WRAPPED ALMOST ALL
THE WAY AROUND THE CIRCULATION...AND WATER VAPOR IMAGERY SHOWS
MID/UPPER-LEVEL DRY AIR IN THE VICINITY OF THE DEPRESSION. THESE
FACTORS...COMBINED WITH ABOUT 15 KT OF EASTERLY VERTICAL WIND
SHEAR...MAY BE PREVENTING THE SYSTEM FROM MAINTAINING ORGANIZED
CONVECTION.
THE INITIAL MOTION IS NOW 270/8. THERE IS LITTLE CHANGE TO THE
FORECAST PHILOSOPHY FROM THE PREVIOUS FORECAST. THE DEPRESSION IS
ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...WHICH SHOULD RESULT IN
A WESTWARD MOTION FOR THE NEXT COUPLE OF DAYS. AFTER THAT...THE
SYSTEM SHOULD GRADUALLY TURN WEST-NORTHWESTWARD TOWARD A WEAKNESS
IN THE RIDGE OVER THE WESTERN ATLANTIC. THE OVERALL GUIDANCE
ENVELOPE HAS SHIFTED SOUTHWARD SINCE THE LAST ADVISORY...SO THE NEW
FORECAST TRACK IS ALSO SHIFTED SOUTHWARD. IT SHOULD BE NOTED THAT
IF THE CYCLONE WEAKENS TO A TROPICAL WAVE...THE REMNANTS WOULD
LIKELY MOVE FARTHER SOUTH THAN CURRENTLY FORECAST...AS SHOWN BY THE
BAMM AND BAMS MODELS.
THE SHIPS MODEL CONTINUES TO FORECAST MODERATE TO OCCASIONALLY
STRONG SHEAR OVER THE SYSTEM DURING THE FORECAST PERIOD...AND THUS
THE SHIPS AND LGEM MODELS SHOW LITTLE OR NO STRENGTHENING. ON THE
OTHER HAND...THE HWRF AND GFDN SHOW SIGNIFICANT STRENGTHENING...
WITH THE HWRF MAKING THE SYSTEM A HURRICANE BY 120 HR. BASED ON
THE FORECAST SHEAR AND CURRENT TRENDS...THE INTENSITY FORECAST NOW
CALLS FOR LITTLE CHANGE IN STRENGTH DURING THE FORECAST PERIOD IN
BEST AGREEMENT WITH THE LGEM MODEL. THERE IS A DISTINCT
POSSIBILITY THE CYCLONE COULD WEAKEN TO A REMNANT LOW OR TROPICAL
WAVE DURING THE FORECAST PERIOD...AS FORECAST BY ALL THE GLOBAL
MODELS EXCEPT THE NOGAPS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 13/1500Z 14.0N 37.6W 25 KT
12HR VT 14/0000Z 14.0N 39.1W 25 KT
24HR VT 14/1200Z 14.2N 41.3W 25 KT
36HR VT 15/0000Z 14.4N 43.9W 25 KT
48HR VT 15/1200Z 14.8N 46.6W 25 KT
72HR VT 16/1200Z 16.0N 52.5W 25 KT
96HR VT 17/1200Z 18.5N 59.5W 25 KT
120HR VT 18/1200Z 22.0N 66.0W 25 KT
$$
FORECASTER BEVEN
I see at least you are watching it - thanks Storm!!!!
Tropical Disturbance Summary (1200z 13AUG)
=========================================
At 21:00 PM JST, Tropical Depression, Former Maka (1010 hPa) located at 14.0N 179.0E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The depression is reported as moving west at 10 knots
At 21:00 PM JST, Tropical Depression, Former Etau (998 hPa) located at 34.0N 152.0E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The depression is reported as almost stationary
http://www.daughtersoftiresias.org/buoygraph/product/pressure_change_large.jpg
You can see it has a broad circulation.
Here is the link to the latest models: Link
Good Update Storm...
Are you serious?
I would watch yourself... eventually talk like that might get you banned
Jason
Here's my analysis of the situation.
TD2 is only going have a brief summary, I'm unimpressed but it still has a shot if it can take advantage of the conditions in front of it.
Now 90L concerns me. 90L is MASSIVE and will take atleast 24 hours for it to continue to become better organized because of its massive size, to bring together its convection and there on forth steady intensification to possibility Hurricane status as it gets close to the Islands. It's a long ways out, so we have a lot of time to track it.
That wave entering the Bahamas is starting to flare up again, eh? Any models developing it?
90L looks like it might turn out to be like one of the many other Cape Verde storms. Certainly one to watch.
5 years ago today I was making my final preparations for Charley. What a day that was!
5 Years ago today I was doing the same. Fortunately, Charley was a non-event in Tampa. Too bad it wasn't the same further south.
Link
apology for repost, just got lost in the transition to new blog
Just an observation and something that may need to be monitored a little more closely. Watching quite a few satelite images and loops for the last few hours. AOI just to the east of the SE Bahamas is showing more signs of circulation and much more convection quickly.
Probably a mid level entity at present, but it bears watching since it is close to any significant populated land mass. The area aprox. 21-23 north & 68-69 west moving WNW
Thanks for the update. I'll keep checking on on the GOM.
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