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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532. IKE
Quoting sporteguy03:


You missed August 23rd...


Yup...I'm a day off so far. That may end within minutes.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Dropsonde:
Maybe Frances is passe now. I'm waiting for "F" of 1999 to be mentioned (in a serious comparison, because I guess technically I mentioned it now!). It's inevitable somebody will bring that one up if this thing gets as big and strong as it is supposed to and the models continue to taunt the east coast.
I wonder if T.D.6 takes the same track as Floyd?...he he
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hmm it look like TD6/pre-TS Danielle is moving west now at 13.2N 35.3W I am very sure about this
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528. xcool
TD6 WNW motion 9K .JMO
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting IKE:
Heck...everybody else is puttin one up. Here's what TD6 looks like in track to me...maybe a little further east on the north end of the track vs. this one...

Even though people consider Bill more of a "fish storm" it made some big waves when it passed by!
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Quoting Hurricanes101:


actually its all the more reason not to automatically assume this will go harmlessly out to sea.
With tropical weather it's never a good idea to automatically assume something. In this science, there is no such thing as 100% certainty. There may be a handful who blather about a 100% hit, or a 100% fish...but 99%+ of us know it's best to watch. I just don't believe in wasting too much time dealing with models 384 hours out. Just look at today. 5 hours ago the NHC(and most models) said not much change for 12-24 hours. 5 hours later we see the convection exploding over the COC.
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Quoting IKE:
1301. IKE 6:09 AM CDT on August 14, 2010

Looks like a true Cape Verde system by this time next week. All of the models show it.

My prediction...

(1)There will be tons of "west"-casting going on.
(2)A few will say a track to Florida even though it's 4,000 miles away.
(3)Some will say..."aren't you forgetting the islands? They're first and foremost".
(4)Those that like to beat their chests will say...this is what I've been saying would happen. Even though their previous forecasts were wrong.
(5)Some will say....where are the downcasters and season-is-a-bust crowd at now?
.............................................

(1)Check.
(2)Check just about achieved.
(3)Never materialized....yet.
(4)Seen just a little of.
(5)Never materialized....yet.


You missed August 23rd...
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The recent convective burst with 06L should bring it up to TS Danielle. Those satellite estimates were before the new convective burst.
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351 plywoodstatenative "What is the range on the unmanned plane that NOAA has in its arsenal of weather recon?"

If you are talking about the Aerosonde, 3,000kilometres(1865miles).
However, NOAA has also used the GlobalHawk which has a range of 25,000kilometres(15,500miles); and more importantly a ceiling of 65,000feet, which oughtta allow ultra-long duration overflights.
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Quoting CybrTeddy:
Miami, see what the SAB has 06L at? 2.5. What's the TAFB? Still 3.0 or higher?
It went down to T2.5 but that's still qualifies for a 40mph TS. The T-numbers will likely increase at 0z since the system continues to organize.

IMO, we should have Danielle within the hour.
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Quoting DestinJeff:


Has anybody mentioned Frances in the past 30 minutes. It's in the bylaws.
Maybe Frances is passe now. I'm waiting for "F" of 1999 to be mentioned (in a serious comparison, because I guess technically I mentioned it now!). It's inevitable somebody will bring that one up if this thing gets as big and strong as it is supposed to and the models continue to taunt the east coast.
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Quoting DestinJeff:


[insert college humor here]


Re-ported for being too humorous!
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514. IKE
Heck...everybody else is puttin one up. Here's what TD6 looks like in track to me...maybe a little further east on the north end of the track vs. this one...EDIT...maybe a little further east on the whole track...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
511. xcool



Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting Hurricanes101:


MAJOR hurricane, nota hurricane, read again


Ah, yes. I am corrected.....still, nothing much to worry about for a few days at least. Probability high for a fish I suppose....
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Miami, see what the SAB has 06L at? 2.5. What's the TAFB? Still 3.0 or higher?
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The 18z position of TD6 almost exactly matches the 0z ECMWF position last night at 18 hours.
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ECMWF at 240hr has 06L at 932mb
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Quoting DestinJeff:


First "Aye!"

and now "We shall see" ???


How he's taking Levi's sentences!

First Storm's word and now that!

Shame on you Miami! Shame on you!
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Quoting nola70119:
NHC downcasting TD6. 1 in 5 chance of becoming a hurricane in the next 5 days.

.THE DEPRESSION
CURRENTLY HAS A 1 IN 5 CHANCE OF REACHING MAJOR HURRICANE STATUS AT
SOME POINT OVER THE NEXT FIVE DAYS.


MAJOR hurricane, not a hurricane, read again
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Looks like a broad circulation over S. Florida.

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Quoting Cotillion:


Be fairly unlikely to reach Category 5 at that latitude outside the GoM anyway. Off the top of my head, I suspect Dog of 1950 would be the closest. Measurements of wind speeds were not entirely spot on back then, either.


Yeah.


Not sure about the accuracy of measurements either, but it hold the record for the longest continuous duration of a Cat 5 in the Atlantic, plus it's max wind speeds were measured at 185 mph so I think it probably was a 5, at least in the lower latitudes recorded of it being a 5.

I also remember a blog post by Dr. M posting a graphic depicting the changes in the amount of Cat 4/5 hurricanes in certain areas if Climate Change were to keep happening in the next 10 years. I'll have to find it because it showed more Cat4/5's out in the middle of the Atlantic and less in the Caribbean and Gulf. Although I don't want to bring any GW discussion to the blog lol.
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Quoting nola70119:
NHC downcasting TD6. 1 in 5 chance of becoming a hurricane in the next 5 days.

.THE DEPRESSION
CURRENTLY HAS A 1 IN 5 CHANCE OF REACHING MAJOR HURRICANE STATUS AT
SOME POINT OVER THE NEXT FIVE DAYS.


That says major hurricane...
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Quoting DestinJeff:


First "Aye!"

and now "We shall see" ???
Wait, who says "we shall see"? LOL!
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The shear has certainly relaxed over the past several hours. Look at any image from earlier in the day, and you'll notice long anvils streaming southwestward from every cumulonimbus. Far fewer of those are evident now.

Certainly looks like a TS to me...
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NHC downcasting TD6. 1 in 5 chance of becoming a hurricane in the next 5 days.

.THE DEPRESSION
CURRENTLY HAS A 1 IN 5 CHANCE OF REACHING MAJOR HURRICANE STATUS AT
SOME POINT OVER THE NEXT FIVE DAYS.
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Quoting CosmicEvents:

That's proved to be a mere speed bump for the 384 hour crowd.


actually its all the more reason not to automatically assume this will go harmlessly out to sea.
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Quoting Seflhurricane:
everyone from Florida and along the eastern seaboard needs to watch TD 6 in the coming days, we could potentially have a major hurricane nearby, hopefully it recurves out to sea


If by nearby you mean over 1000 miles away, then yeah.
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488. IKE
1301. IKE 6:09 AM CDT on August 14, 2010

Looks like a true Cape Verde system by this time next week. All of the models show it.

My prediction...

(1)There will be tons of "west"-casting going on.
(2)A few will say a track to Florida even though it's 4,000 miles away.
(3)Some will say..."aren't you forgetting the islands? They're first and foremost".
(4)Those that like to beat their chests will say...this is what I've been saying would happen. Even though their previous forecasts were wrong.
(5)Some will say....where are the downcasters and season-is-a-bust crowd at now?
.............................................

(1)Check.
(2)Check just about achieved.
(3)Never materialized....yet.
(4)Seen just a little of.
(5)Never materialized....yet.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting tkeith:
From Doc MHowever, we have no skill in making these sort of ultra-long range forecasts,


That's proved to be a mere speed bump for the 384 hour crowd.
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Quoting DestinJeff:


NO! POOF FOR YOU!

COME BACK, ONE YEAR!


lol, maybe the best episode ever
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SAB 22/1745 UTC 12.7N 34.6W T2.5/2.5 06L

Judging by the increased very deep convection we will probably have Danielle at 5.
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i see this being a bigger threat to the east coast of the US than anything the models continue to shift west in the 120 hrs, even though things chance it is looking likely that the ridge will quickly build west and not alow it to recurve
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Quoting hydrus:
The CMC has some interesting high pressure scenarios...Link
"poof!"....oh thats me...:)
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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.