Tropical Depression Six arrives

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

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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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We have some kind of light show in Houma tonight. No thunder yet, but lightening everywhere.
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Quoting StormW:
Here, this will give you the best view on steering flow

LINK


The ridge looks like it would block all northerly movement. How long will it take for that little spill of a trough to start eroding the ridge or is the trough on its way out?
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1924. beell
Quoting weatherguy03:


Can I get a third trough??? Woot!


Two is all we need, 03!
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1919. will45
StormW the one you showed she dont curve until about 60W?
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Quoting AstroHurricane001:
This is very long-term, but 18z GFS shows a possible cat. 3 hurricane in the Gulf.



It clearly shows a big area of red colors of FL.

Clearly!

lol!
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Quoting ShenValleyFlyFish:
Been a good name for it!


Thats a good one, have to remember that lol
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1915. beell
Quoting aquak9:


THANK YOU BEELL!! I said second trough about two hours ago and got rasberried!!


Sorry about the raz, aqua. At some point, a jump to a higher steering level might indeed make some sense. 500mb is close for a strong TS/CAT 1 and the second trough could be a factor, fer sure.

GFS showing a pretty strong northward push behind (south of) Danielle in the lower levels. Hard to find on the sats. May account for some of the northward movement today.

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1914. aquak9
Quoting weatherguy03:


Can I get a third trough??? Woot!


Third trough, fourth trough, heck I'll go buy a dozen of'm at the Dollar Store. Conus Threat? I'll be at the beach tossin' troughs out there like frisbees.
Member Since: August 13, 2005 Posts: 178 Comments: 26677
daniellle starting to ventilate now, won't be long before it becomes a hurricane imo. I said by 12 noon tomorrow, might even be earlier!
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Quoting ShenValleyFlyFish:
Been a good name for it!

thats a good one, have to remember that lol
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Blog hole?
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This is very long-term, but 18z GFS shows a possible cat. 3 hurricane in the Gulf.

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Quoting MiamiHurricanes09:
Vorticity?
Been a good name for it!
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Quoting all4hurricanes:
I think wish-casters will move on from Francis to this storm, except I think there is a definite possibility of this type of track


Now I see that is 55's Diana, but at first I was unsure of the storm/year.
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Quoting aquak9:


THANK YOU BEELL!! I said second trough about two hours ago and got rasberried!!


Can I get a third trough??? Woot!
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Quoting StormW:
STATISTICAL



DYNAMIC

very tightly clustered for now..
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1897. xcool
11pm 45k by nhc ,jmo
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting ShenValleyFlyFish:
Sounds like a cat I once knew.
Vorticity?
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1895. aquak9
gigglesnort-

Bord, we're just about to push him over the edge
Member Since: August 13, 2005 Posts: 178 Comments: 26677
1894. pottery
Quoting KEEPEROFTHEGATE:
ring around the moon rain or snow by noon

Scratch the Snow. Unless I am badly mistaken.
And replace Noon with Midnight!
And it Shall come to Pass.
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1893. will45
Quoting StormW:


Will, unless she's at 45kts or above right now, she is still being steered at this level:



ty StormW tooooooooooo many circles for me
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Quoting Bordonaro:


Most computer models after 72 hrs could not find there way out of an open paper bag :O)
Sounds like a cat I once knew.
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Well, I called the TS at 4 today. So now at 10 I'll call for 50-60 MPH winds at 11. She's very symetrical. A beauty queen.
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1887. aquak9
Quoting beell:
A couple of good days of intensification ahead for Danielle. Then some shear over the northern half of the storm as she encounters the ULL currently at 28N 44W as it passes by to the NW on a slow trip to the SW or WSW (?). A bend to the west may indeed occur as Danielle weakens enough to fall back under a lower level steering regime. But she just might be strong enough to follow the first trough out-or at least keep a track more north of WNW. If not she should be far enough north to turn in front of the second trough. It would be foolish to count out Bermuda at this point.


THANK YOU BEELL!! I said second trough about two hours ago and got rasberried!!
Member Since: August 13, 2005 Posts: 178 Comments: 26677
Tropical Storm Danielle on NASA at 9:50 pm Eastern and four hours ahead of the forecast track.

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Quoting MrstormX:
If Frank is a 60MPH storm, what do you think Danielle is?


50 mph.
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Tropical Storm Danielle will probably be at 50 mph at 11PM

Hurricane tomorrow seems plausible
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Quoting Bordonaro:


Most computer models after 72 hrs could not find there way out of an open paper bag :O)


Thanks Bordonaro...grocery shopping!
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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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