Tropical Depression Six arrives

By: Dr. Jeff Masters , 5:14 PM GMT on August 22, 2010

Tropical Storm Tropical Depression Six is here, but it will not be a threat to land for at least the next five days. Tropical Depression Six is a classic "Cape Verdes"-type storm common during the peak part of hurricane season. Cape Verdes-type storms are so named because they form from tropical waves that come off the coast of Africa and pass near the Cape Verdes Islands just west of Africa. Cape Verdes hurricanes are the largest and most dangerous types of hurricane in the Atlantic, since they spend a long time over water have and have of opportunity to reach full maturity. Tropical Depression Six has a ways to go before it becomes a hurricane, as the storm is embedded in a strong easterly flow of wind courtesy of the African Monsoon that is generating a moderately high 15 - 20 knots of wind shear. There is also a tropical disturbance to the northeast of TD 6 that is sucking away some moisture and is interfering with the storm's circulation. Sea Surface Temperatures (SSTs) are a warm 28┬░C, and the storm is embedded in a moist environment, so wind shear is the primary inhibiting factor for development. The strong east winds imparting the shear are keeping any heavy thunderstorms from developing on the east side of the center of circulation, which is exposed to view in satellite imagery (Figure 1.)


Figure 1. Afternoon satellite image of Tropical Depression Six.

Forecast for Tropical Depression Six
A ridge of high pressure will force Tropical Depression Six to the west-northwest for the next five days, and the system should increase its forward speed from its current 10 mph to 15 mph by Monday night. A powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Tropical Depression Six more to the northwest late this week, and the storm should pass well to the northeast of the Lesser Antilles Islands. It remains to be seen, however, it this trough will be strong enough to fully recurve Tropical Depression Six out to sea. The GFS predicts that Tropical Depression Six may pass close to Bermuda about eight days from now, and it is also possible that Tropical Depression Six could eventually hit the U.S. East Coast 9 - 15 days from now. However, we have no skill in making these sort of ultra-long range forecasts, and the long-range fate of TD 6 is uncertain.

Elsewhere in the tropics
The ECMWF and NOGAPS models are predicting formation of a tropical depression off the coast of Africa 3 - 4 days from now.

Jeff Masters

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781. IKE
Quoting scott39:
Sounds like dry air and wind shear may keep this at bay after day 3. Weak system will go more W. IMO


Two words I hate now....

(1)Fish.
(2)West.
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Quoting IKE:
WITH THE EXCEPTION OF THE GFDL...THE INTENSITY GUIDANCE HAS
CONTINUED TO SCALE BACK ON THE INTENSIFICATION OF THE CYCLONE.
SLOW STRENGTHENING IS ANTICIPATED FOR MUCH OF THE FORECAST PERIOD
SINCE VERTICAL SHEAR IS CURRENTLY NOT IDEAL...AND SOME DRY AIR
APPEARS TO SURROUND THE SYSTEM. THE STATISTICAL GUIDANCE SEEMS TO
SUGGEST THAT THE VERTICAL SHEAR COULD INCREASE AGAIN AFTER DAY
3...AND THE LGEM DOES NOT EVEN STRENGTHEN THE CYCLONE TO A HURRICANE
DURING THE FORECAST PERIOD. FOR NOW...THE OFFICIAL INTENSITY
FORECAST IS LEFT UNCHANGED OUT OF RESPECT FOR CONTINUITY.


Interesting.
Sounds like dry air and wind shear may keep this at bay after day 3. Weak system will go more W. IMO
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776. IKE
Quoting DestinJeff:


you got to give respect to get respect, Continuity.

maybe setting the stage for a weaker storm missing the trough.


Please don't let that happen.
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Quoting MoltenIce:
THIS is a fish, and a big one too.

...and hello Danielle!
That is one cool looking fish!
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Quoting floridiancanuck:
I haven't posted anything yet this season but reading the comments here is totally a guilty pleasure of mine. Y'all get so passionate during storm season.

On that note, I have a question. I read a lot of heated discussions on here about the computer models and it seemed that for this current storm in the making people were making predictions based on the models right off the bat, when we were looking at a disorganized blob of thunder storms emerging off Africa. Do forcasting sciences really give any weight to computer models this early? Also, is there any rule of thumb to guage when computer models are reliabe vs when they aren't? Thanks, and happy tracking! =)


72hrs

Modified: And NHC is very good, and getting better by the year, out to 72hrs.

For that, just look at how narrow the cone now is compared to 5 years ago at that time.

The cone is 67% chance based on the past 5 years of forecasting.
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773. IKE
Quoting FLdewey:
Bermuda is NOT a fish. We should all be concerned about such an important tax haven.

LOL!
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Quoting washingtonian115:
Good the blog is beack on track.Now we finally hve our 5th named storm.The chances of this hitting bermuda have increased.
Fourth.
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Quoting hydrus:
Or storms...The waves are lined up...Link
Reminds me of 2008.A follow the leader type situation?.I think so.
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761. IKE
WITH THE EXCEPTION OF THE GFDL...THE INTENSITY GUIDANCE HAS
CONTINUED TO SCALE BACK ON THE INTENSIFICATION OF THE CYCLONE.
SLOW STRENGTHENING IS ANTICIPATED FOR MUCH OF THE FORECAST PERIOD
SINCE VERTICAL SHEAR IS CURRENTLY NOT IDEAL...AND SOME DRY AIR
APPEARS TO SURROUND THE SYSTEM. THE STATISTICAL GUIDANCE SEEMS TO
SUGGEST THAT THE VERTICAL SHEAR COULD INCREASE AGAIN AFTER DAY
3...AND THE LGEM DOES NOT EVEN STRENGTHEN THE CYCLONE TO A HURRICANE
DURING THE FORECAST PERIOD. FOR NOW...THE OFFICIAL INTENSITY
FORECAST IS LEFT UNCHANGED OUT OF RESPECT FOR CONTINUITY.


Interesting.
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Is there any reason that the waves that hit the caribbean moving too fast are doing more in the Pacific than they are in the Atlantic Basin?
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i dont have as much faith in it re-curving as much as everyone wants it to/ thought. As i did earlier this weekend. my 2 cents.
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Backing off on Strength again in the discussion. My feeling is 60mph tropical strom at best. Shear is abudant in the Atlantic this year and therefore it has been a SLOWER than average hurricane season. Sorry you overpaid experts
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bye bye 3-1-0

it is now 4-1-0


ah NHC notes a turn toward the WNW on satellite, interesting
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000
WTNT41 KNHC 222044
TCDAT1
TROPICAL STORM DANIELLE DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062010
500 PM AST SUN AUG 22 2010

GIVEN THE NORTHWARD MOVEMENT OF THE CENTER OF DANIELLE THROUGH MUCH
OF THE DAY...THE ESTIMATED INITIAL MOTION IS 310/10. HOWEVER...
RECENT SATELLITE IMAGES SUGGEST THAT THE CENTER IS TURNING BACK
TOWARD THE WEST-NORTHWEST
...AND THIS MOTION IS EXPECTED TO CONTINUE
FOR THE NEXT 72 HOURS AS THE SYSTEM IS STEERED BY THE SUBTROPICAL
RIDGE TO ITS NORTH. A BREAK IN THE RIDGE BY DAY 3 COULD ALLOW THE
CYCLONE TO TURN TOWARD THE NORTHWEST...BUT DANIELLE IS EXPECTED TO
SLOW DOWN AS IT APPROACHES A NEW RIDGE TO ITS NORTH ON DAY 5.
THE
NEW OFFICIAL FORECAST IS A LITTLE NORTH OF THE PREVIOUS FORECAST
DURING THE FIRST 72 HOURS TO ACCOUNT FOR THE INITIAL POSITION...BUT
IT CONVERGES BACK WITH THE PREVIOUS FORECAST ON DAYS 4 AND 5. THERE
HAS BEEN NO SIGNIFICANT SHIFT IN THE MODEL GUIDANCE SINCE THE LAST
ADVISORY...AND THE MULTI-MODEL CONSENSUS TVCN IS EXTREMELY CLOSE TO
OFCI.


$$
FORECASTER BERG
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That puts us at 4-1-0.

Average date for the 4th named storm is Aug. 24th. We are slightly ahead of schedule.
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Good the blog is beack on track.Now we finally hve our 5th named storm.The chances of this hitting bermuda have increased.
Member Since: Posts: Comments:
I haven't posted anything yet this season but reading the comments here is totally a guilty pleasure of mine. Y'all get so passionate during storm season.

On that note, I have a question. I read a lot of heated discussions on here about the computer models and it seemed that for this current storm in the making people were making predictions based on the models right off the bat, when we were looking at a disorganized blob of thunder storms emerging off Africa. Do forcasting sciences really give any weight to computer models this early? Also, is there any rule of thumb to guage when computer models are reliabe vs when they aren't? Thanks, and happy tracking! =)
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Quoting washingtonian115:
Yes a ridge is expected to build back in.But I think Danielle will find a weakness in the ridge.However the same cannot be said for the storm that will be followig it.
Or storms...The waves are lined up...Link
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Quoting IKE:
At 11am EDST....was at....

12.7N and 34.1W

At 5pm EDST....is at.....

13.4N and 35.1W

Moved .7N and 1.0W.


+ one for staying on topic, LOL
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northwest movement now?
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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