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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This blog might crash tomorrow with all the talk.....its gonna be wild.
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2730. xcool
off forecast poinst wnw move.Central Atlantic - Rainbow Loop .6.45
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Quoting errantlythought:


I would suggest checking the sheer maps, those aren't cirrus, but are feathering of the upper levels of the CDO. I believe that would mean that the anticyclone much talked about in previous hours is approaching alignment with the CDO, as this is evidence of outflow sheer.

Atmo or StormW, I believe that's your expertises though. Just my obs.


Feathery clouds at the top of a CDO is technically called cirrus clouds. The anticyclonic center of cirrus outflow is currently west of the low-level center right now because of the easterly shear.
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2728. xcool
nice
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Quoting Stormchaser2007:
Those upper-level cirrus clouds usually mean the intense convection has peaked or will be peaking soon.



I would suggest checking the sheer maps, those aren't cirrus, but are feathering of the upper levels of the CDO. I believe that would mean that the anticyclone much talked about in previous hours is approaching alignment with the CDO, as this is evidence of outflow sheer.

Atmo or StormW, I believe that's your expertises though. Just my obs.
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Leo,

This shortwave infrared loop may help you in seeing the low-level spin easier.

http://www.ssd.noaa.gov/goes/flt/t1/flash-ir2.html

Ignore the blue-colored clouds, those are the high cloud tops that distract you from seeing where the low-level center is. The black clouds are the low-level clouds, and looking carefully during the animation, you can see a swirl moving west and west-northwest into the east edge of the blue clouds. That swirl is the surface center of Danielle.
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2723. xcool
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Quoting leo305:


I'm not just looking at the fact that's the strongest convection, I'm looking at the possibility that, that is where the strongest spin is located on infared

http://www.ssd.noaa.gov/goes/flt/t1/loop-ft.html

if you look at the northern side of the convection you can see the spin clearly, that's what I see, could it be wrong? Sure, but if it is then it's one very disorganized system, and there is no way that it is stacked, if it's stacked that's where the center should be imo


I hate to tell you this, its probably tilted westward with height so any spin well-embedded in the deep-convectin is possibly a mid-level spin west of the surface spin.

I do agree with you that she's fightin' the shear, and fightin' hard like a true champion. Even if its not perfectly vertically stacked, a system fighting this hard in shear can gradually strengthen in the shear.
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2721. leo305
also look at the banding it's developing..
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Quoting NCHurricane2009:


I don't think its under the deepest convection, but I don't think its as far east as ADT puts it either (see post 2712). I think its under the northeast side of the convective blob, not right at the edge of the convective blob like ADT has it.


Your estimate seems pretty plausible.
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2719. leo305
Quoting hunkerdown:
you have got it wrong, see how the eastern side is somewhat flattened, that is from the shear. don't be fooled by the strongest convection must have the COC centered within, there are more variables involved.


I'm not just looking at the fact that's the strongest convection, I'm looking at the possibility that, that is where the strongest spin is located on infared

http://www.ssd.noaa.gov/goes/flt/t1/loop-ft.html

if you look at the northern side of the convection you can see the spin clearly, that's what I see, could it be wrong? Sure, but if it is then it's one very disorganized system, and there is no way that it is stacked, if it's stacked that's where the center should be imo
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Oh well. Not really worth arguing over.

Anyways, this wave will likely be our next invest.

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2717. xcool
CoopNTexas .yeah i hope so.she bad bad girl.
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Quoting Stormchaser2007:


I highly doubt that the circulation is directly under the deep convection. Its more than likely stuck in the right quadrant due to the 20 knots of easterly shear.

As Korithe was saying, if the center was in the deep convection we'd be seeing more outflow on the eastern side.


I don't think its under the deepest convection, but I don't think its as far east as ADT puts it either (see post 2712). I think its under the northeast side of the convective blob, not right at the edge of the convective blob like ADT has it.
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Hey cooleo....Does "bear" watching. Hope models & EURO is right with Danielle...she looks like she's gonna be mad...like catching her husband cheating.

Keep her away from CONUS
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Quoting leo305:
around 14.1N 38.8 W

the heaviest convection is wrapped around it, and the CDO like feature that it has developed is spinning around that area the strongest, so either it has a MONSTER MID LEVEL LOW or that's where the center is.

Because even though there is easterly shear, it's still breathing on the east side.. showing how strong the thing is becoming how it's literally fighting the shear
you have got it wrong, see how the eastern side is somewhat flattened, that is from the shear. don't be fooled by the strongest convection must have the COC centered within, there are more variables involved.
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Those upper-level cirrus clouds usually mean the intense convection has peaked or will be peaking soon.

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Quoting leo305:
14.1N 38.8W

is where I believe the center is


Your fix puts the center in the center of the convective burst. I am fixing the center between where you are and ADT is, like at 14.5 N 36.3 W.
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2711. xcool
CoopNTexas HEY.YEP
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2710. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #9
TROPICAL STORM MINDULLE (T1005)
15:00 PM JST August 23 2010
===============================

SUBJECT: Category One Typhoon In South China Sea

At 6:00 AM UTC, Tropical Storm Mindulle (994 hPa) located at 16.2N 109.9E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The storm is reported as moving west northwest at 11 knots

Dvorak Intensity: T2.5

Gale Force Winds
=================
150 NM from the center

Forecast and Intensity
=======================
24 HRS: 18.2N 106.5E - 45 knots (CAT 1/Tropical Storm)
48 HRS: 19.5N 104.1E - 40 knots (CAT 1/Tropical Storm)
72 HRS: 20.5N 102.0E - 30 knots (Tropical Depression)
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2709. leo305
around 14.1N 38.8 W

the heaviest convection is wrapped around it, and the CDO like feature that it has developed is spinning around that area the strongest, so either it has a MONSTER MID LEVEL LOW or that's where the center is.

Because even though there is easterly shear, it's still breathing on the east side.. showing how strong the thing is becoming how it's literally fighting the shear
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Not putting much stock in EURO GOM solutions...It's been on again off again with that for a few days now. Seems EURO has done better this year when something does develop.
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Quoting hunkerdown:
thats not what I was saying...I don't believe the position they have "earl" in, I don't think he will be that far west at that time, if he actually materializes.


Ah, okay. Sorry for the misunderstanding.
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Quoting NCHurricane2009:


Is this ADT center estimate updated frequently? If Danielle is centered there right now, she surely is weaker than she looks now. Some of us got tricked by Bonnie, thinking the center was closer to its circular burst of convection than in reality. Could this be pulling another Bonnie at this moment?


I highly doubt that the circulation is directly under the deep convection. Its more than likely stuck in the right quadrant due to the 20 knots of easterly shear.

As Korithe was saying, if the center was in the deep convection we'd be seeing more outflow on the eastern side.
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Quoting KoritheMan:


Not... necessarily a good thing.

Here's an excerpt on the history of 1979's Hurricane Frederic:

Frederic originated as a tropical wave which moved off the west coast of Africa late on August 27, 1979, and became a tropical depression at 0600 (GMT) on August 29. Moving westward with a steady forward speed of 18 knots, it strengthened into Tropical Storm Frederic at 1200 (GMT) on August 30 and was further upgraded to a hurricane at 0600 (GMT) on September 1, while centered approximately 650 miles (1045 km) east of Barbados.[1]

Although conditions were initially very favorable for significant intensification, Frederic began to experience the outflow of Hurricane David (which had greatly intensified in the same area just days before). Subsequently, Frederic began a weakening trend early on September 2, when it weakened back to tropical storm status: this weakening trend would continue for several days as the storm followed in David's wake. Frederic passed over Puerto Rico and approached the Dominican Republic, then suddenly turned northwest during the afternoon of September 5 (just as David had done before): it passed just west of Santo Domingo on September 6. Further weakening caused Frederic to drop below tropical storm strength later on the 6th just north of Haiti.[1]
thats not what I was saying...I don't believe the position they have "earl" in, I don't think he will be that far west at that time, if he actually materializes.
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TropicalStormDanielle's heading has turned northward from 3.6degrees west of WestNorthWest to 9.2degrees west of due North.
- Date - - - Time - - - - - Location - - Windspeed - Pressure
22Aug - 06amGMT - 11.7n33.0w - - 30knots . . . . 1007mb - NHC-ATCF *was11.8n*
22Aug - 09amGMT - 12.1n33.4w - - 35mph . . . . . 1007mb - NHC.Adv.3
22Aug - 12pmGMT - 12.2n33.9w - - 30knots . . . . 1007mb - NHC-ATCF
22Aug - 03pmGMT - 12.7n34.1w - - 35mph . . . . . 1007mb - NHC.Adv.4
22Aug - 06pmGMT - 13.2n34.6w - - 30knots . . . . 1007mb - NHC-ATCF
*before NHC reevaluated&altered TD6's path*
22Aug - 09pmGMT - 13.4n35.1w - - 40mph . . . . . 1005mb - NHC.Adv.5
23Aug - 12amGMT - 14.0n35.3w - - 40knots . . . . 1003mb - NHC-ATCF
23Aug - 03amGMT - 14.2n35.9w - - 50mph . . . . . 1000mb - NHC.Adv.6
23Aug - 06amGMT - 14.8n36.0w - - 45knots . . . . 1000mb - NHC-ATCF
40knots=~46mph _ _ _ ~43.5knots=50mph _ _ _ 45knots=~51.8mph
NHC rounds windspeeds to the nearest 5mph or to the nearest 5knots

Copy&paste 13.2n34.6w-13.4n35.1w, 13.4n35.1w-14.0n35.3w, 14.0n35.3w-14.2n35.9w, 14.2n35.9w-14.8n36.0w, hex, bda, sid into the GreatCircleMapper for a look at the last 12hours.
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Quoting BreadandCircuses:
It looks to me like that is the center of circulation, look how all the colder cloudtops are almost completely wrapped around it



The circulation is on the eastern edge of the convection. Its been said many times.

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Quoting BreadandCircuses:
It looks to me like that is the center of circulation, look how all the colder cloudtops are almost completely wrapped around it

you are not taking the shear into account...
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Quoting Stormchaser2007:


Thats the ADT center estimate.


Is this ADT center estimate updated frequently? If Danielle is centered there right now, she surely is weaker than she looks now. Some of us got tricked by Bonnie, thinking the center was closer to its circular burst of convection than in reality. Could this be pulling another Bonnie at this moment?
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2698. leo305
14.1N 38.8W

is where I believe the center is
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Quoting xcool:
hunkerdown .maybe 3 storms soon.
for some reason I am not buying the GOMEX storm...way too often this year the models show something in the GOMEX when there is nothing there.
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Quoting hunkerdown:
seems that has "Earl" too close to Danielle, unless he is hauling butt...


Not... necessarily a good thing.

Here's an excerpt on the history of 1979's Hurricane Frederic:

Frederic originated as a tropical wave which moved off the west coast of Africa late on August 27, 1979, and became a tropical depression at 0600 (GMT) on August 29. Moving westward with a steady forward speed of 18 knots, it strengthened into Tropical Storm Frederic at 1200 (GMT) on August 30 and was further upgraded to a hurricane at 0600 (GMT) on September 1, while centered approximately 650 miles (1045 km) east of Barbados.[1]

Although conditions were initially very favorable for significant intensification, Frederic began to experience the outflow of Hurricane David (which had greatly intensified in the same area just days before). Subsequently, Frederic began a weakening trend early on September 2, when it weakened back to tropical storm status: this weakening trend would continue for several days as the storm followed in David's wake. Frederic passed over Puerto Rico and approached the Dominican Republic, then suddenly turned northwest during the afternoon of September 5 (just as David had done before): it passed just west of Santo Domingo on September 6. Further weakening caused Frederic to drop below tropical storm strength later on the 6th just north of Haiti.[1]
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2694. xcool


TD OR TS GOM
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2693. xcool
keep an eye on.. gom this week
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2692. xcool
hunkerdown .maybe 3 storms soon.
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Quoting xcool:


gom lower
seems that has "Earl" too close to Danielle, unless he is hauling butt...
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Quoting NCHurricane2009:


Is that blue square the current center fix of Danielle RIGHT NOW or as of 11 PM? I thought its further west than that now.


Thats the ADT center estimate.
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2688. JLPR2
Quoting KoritheMan:


Not necessarily. In some cases a mature hurricane's upper-level outflow can pump additional heat into the ridge, thereby strengthening it.

But you're correct: an alternate scenario would be for Danielle to leave behind a weakness in the subtropical ridge.

But the synoptic scale pattern over North America does not favor such a ridiculous and unrealistically deep trough, as depicted by the GFS. Enough to recurve Danielle? Probably. But to recurve the other area? Doubtful.


Ah nice, thank you for clearing that up.
--------------------------
I'm off to bed, will be interesting to see to what I wake up to. :)
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Quoting NCHurricane2009:


Is that blue square the current center fix of Danielle RIGHT NOW or as of 11 PM? I thought its further west than that now.
thats at 1:45 am eastern...you may have thought it was further west cause people kept saying the center was centered under the deepest convection, which based on CIMSS is incorrect.
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2686. xcool


gom lower
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Quoting NCHurricane2009:


I saw the convection trying to spin with the low-level circulation, and I agree its still chocked on its east side. I do think this'll be a hurricane eventually, but not by 5 AM. Give it some more time, perhaps as early as tomorrow afternoon, this could be a hurricane.



Is Danielle ever going to accelerate faster to the west over the next day or two?


She should accelerate, for sure. And I do think a due W motion is possible over the next day or so, based on water vapor imagery. But she should still recurve.
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2684. awp5141
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2683. xcool


better image
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Quoting Stormchaser2007:


Is that blue square the current center fix of Danielle RIGHT NOW or as of 11 PM? I thought its further west than that now.
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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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