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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2632. mbjjm
Position Estimate from UW - CIMSS satellite 1 hour ago Lat : 14:21:53 N Lon : 36:19:29 W

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2631. smuldy
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Quoting JLPR2:
Well I'm not taking a guess at where the center is.
But I'll say this:
close to the center of convection = bad, and to the SW of the forecast points
to the NE side of the convection following the NHC's track = good and disorganized storm.

I don't know why the first one looks more possible with the amount of images we got available.

We should have a better idea at morning.


Well, it's always frustratingly difficult to accurately pinpoint a center location in storms with structures like Danielle. IR imagery only serves to worsen the problem. I could be way off in my estimate.
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Quoting jason2010xxxx:
the sun is coming up soon we see the center soon in two hours from now.


Cool, will be watching... should be interesting!
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Quoting txsweetpea:
Anyone know the most recent coordinates of Daniellw?


14.2°N 35.9°W as per the 11:00 PM EDT advisory from the National Hurricane Center.
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2625. JLPR2
Well I'm not taking a guess at where the center is.
But I'll say this:
close to the center of convection = bad, and to the SW of the forecast points
to the NE side of the convection following the NHC's track = good and disorganized storm.

I don't know why the first one looks more possible with the amount of images we got available.

We should have a better idea at morning.
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2624. smuldy
Quoting xcool:
jmo she at 40w move wnw .anyway.
looks to me at 37w and 14.6n moving quickly wnw having gained 3w for last .6n
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Quoting TORMENTOSO83:

which model?
he is talking about the GFS ensembles which are not "models" per se. They are show all possible tracks based on the input of all possible atmospheric conditions.
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Anyone know the most recent coordinates of Daniellw?
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2621. xcool


00z ECMWF 48hrs
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting nwFLstormstalker:
COC is in center of convection. why is their such doubt about it....


Because outflow is still restricted (but gradually improving) to the east, implying easterly shear?
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2619. mbjjm
It is moving wnw based on the forecast interpolation loop

Interpolation
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COC is in center of convection. why is their such doubt about it....
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2617. xcool


00z ECMWF
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting Walshy:



I see two lines hitting land. I see several near Bermuda and if its a hurricane then it will affect them.

which model?
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2615. JLPR2
Quoting KoritheMan:


Or some recent microwave passes. :(


That's even better!
Jeez when you need em they miss or aren't updated. T_T
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2614. xcool
jmo she at 40w move wnw .anyway.
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting jason2010xxxx:
ARE THE T.STORM IN THE CENTER NOW.
no, the center is NOT centered under the deepest convection, it is on the eastern periphery.
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Quoting JLPR2:


Then Yikes!
Something is spinning in that blob, and if the MLC and LLC are stacked then... ah...
I dont know LOL! I need some visible images. XD


Or some recent microwave passes. :(
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2609. xcool
used Infrared Channel 2 Loop .JLPR2
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2608. xcool
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2607. will45
Quoting xcool:
she move at wnw .bull nw


just saying what NHC says
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Quoting will45:
NW at 11 kts
that is the 11:00 PM number...
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2605. JLPR2
Quoting KoritheMan:


Nope:

850 mb:



500 mb:



Vertical decoupling is not evident. Just a slight elongation of the 500 mb center.

Animation of shortwave infrared satellite imagery also supports this, showing the northeastern periphery of the convection.


Then Yikes!
Something is spinning in that blob, and if the MLC and LLC are stacked then... ah...
I dont know LOL! I need some visible images. XD
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2604. xcool
she move at wnw .bull nw
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2602. will45
NW at 11 kts
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2601. mbjjm
Danielle moving wnw around 13mph
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2600. will45
Quoting Hurricanes101:
2585. will45 5:46 AM GMT on August 23, 2010

On Frank yes, on Danielle now

the TWO has just come out


it just showed up on mine
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2599. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting JLPR2:
I'm really confused, Danielle looks way off track, but then again that may be the mid level circulation, and if so Danielle is doing horrible but if the LLC is under the blob then...
yikes! XD



Nope:

850 mb:



500 mb:



Vertical decoupling is not evident. Just a slight elongation of the 500 mb center.

Animation of shortwave infrared satellite imagery also supports this, showing the center along northeastern periphery of the convection.
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Quoting xcool:
txsweetpea .Everything is up in the sky right now.

Yea ...I know that just trying to make conversation.
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2595. mbjjm
Based on the Tropical Cyclone Intensity Estimate Danielle still 50mph





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2585. will45 5:46 AM GMT on August 23, 2010

On Frank yes, on Danielle now

the TWO has just come out
Member Since: March 10, 2010 Posts: 1 Comments: 7233
2593. Gearsts
WOW is moving west of the track by alot
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Quoting will45:


2:00 AM
nope, only id there is a watch or warning...only thing yo get at 2am is the TWO.
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2591. leo305
Quoting stormtopz:


maybe when it gets an eye though





hurricane's don't need an eye to become a hurricane!
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2590. xcool
txsweetpea .Everything is up in the sky right now.
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting mbjjm:
Seasonally meaning storms in its current position this time of the year are usually fishes.
again, it has nothing to do with season or position, it has to do with the atmospheric conditions in place at the specific times (ridge, trough, weakness, etc.)
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Quoting BreadandCircuses:
I think this could be a hurricane right now


maybe when it gets an eye though



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the LLC and MLC are perfectly stacked right now, they are just not center in the convection yet, some slight easterly shear is causing that
Member Since: March 10, 2010 Posts: 1 Comments: 7233
Xcool- see I thought you were being serious- dont do that!
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2585. will45
Quoting mbjjm:


Next Nhc update 5am


2:00 AM
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Quoting neonlazer:
These storms going through central LA are creating more lightning than I have seen all year combined! It's been flashing nicely outside for well over an hour...these just don't run out of electrical powa!


UNLIMITED POWAAAAAAAAAAH!
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2583. leo305
Quoting JLPR2:
I'm really confused, Danielle looks way off track, but then again that may be the mid level circulation, and if so Danielle is doing horrible but if the LLC is under the blob then...
yikes! XD



I doubt it's the MLC it's spinning too fast for that.. but it's possible
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2582. mbjjm
Quoting will45:


we will say what NHC says in a few minutes


Next Nhc update 5am
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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.

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