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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I have the center estimated at 14.4N/39W, just my guess!
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Not sure, but if I wanted to be certain about this track and the storm's intensity track given Bermuda as a very probably danger area, then I would send er up...
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Interesting. Looks like the center went under the deep convection. Eye seems to be forming.

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3079. smuldy
Quoting wayfaringstranger:
NHC is pretty reasonable so Im only guessing that they would send a recon aircraft today to see if Danielle has reached strength?
would they really fly into it before 50w?
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Storm,

Sorry if I did not respond soon after sending me that website regarding El Nino and La Nina seasons and hurricane landfall probabilities. I did reply to you on your tropical synopsis page from Friday.

Very interesting document and thanks for sending it.

On another note, I it is too early but what are your thoughts on the AOI that is about to exit Africa?
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Quoting wayfaringstranger:
NHC is pretty reasonable so Im only guessing that they would send a recon aircraft today to see if Danielle has reached strength?


Its too far east for Recon.
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3076. surfmom
Quoting GoofOff:
Mother Nature will behave as she damn well pleases.
smart man!!!
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Quoting kmanislander:
I'm out for now. Will come back later today. Have a great morning all.

PS. Center is left and South of the points :)



I agree with you, I am not seeing any circulation where sat estimates place it. A look at MIMIC suggest this also.
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3074. tkeith
Quoting kmanislander:


A strengthening storm can begin forming an eye, sometimes quite distinctly, before reaching actual hurricane strength.
Thanks
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3073. smuldy
Quoting scott39:
The center is that far N and E?
that is a forecast int and is 4 hours old now; kman suggested the center may have shifted as the storm organized
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NHC is pretty reasonable so Im only guessing that they would send a recon aircraft today to see if Danielle has reached strength?
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Quoting tkeith:
Does that mean it has reached Hurricane strength?


A strengthening storm can begin forming an eye, sometimes quite distinctly, before reaching actual hurricane strength.
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Quoting SLU:
Pre-Earl?



Looking good so far on that...
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3069. scott39
Quoting Stormchaser2007:
The center is that far N and E?
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3068. surfmom
Quoting SLU:


Looks like the horse has finally bolted.
Quoting StormW:


You betcha!

Yup - Barn door is wide OPEN
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3067. tkeith
Quoting kmanislander:
Danielle looks to be on the verge of popping out an eye in the next couple of hours so we won't have any trouble knowing where the center is.
Does that mean it has reached Hurricane strength?
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Quoting GoofOff:

Storm,
I have no training in that field. I am a retired mechanical engineer so I do enjoy studying charts and data. I really do appreciate all the information you give us. I am a native of Nebraska and have seen many tornadoes. I prefer hurricanes to them due to the advance notice. I moved to Florida over 10 years ago and live about a mile inland from the Atlantic about 45 miles north of West Palm Beach. Since I moved here we have taken three direct hits from hurricanes Francis, Jeanne and Wilma so I respect their power. My comments, on the very rare occasions I make one, are based upon what I can see from several different sources. I think the technology has made giant strides thanks to satellites. Needless to say, weather is a chain reaction over the entire earth and a change anywhere can affect the weather pattern everywhere. After the loop Jeanne made, I watch them very closely but don't get very concerned about my families' safety until about three days before the path is more clearly defined. I did have the pleasure of working on both the Gemini and Apollo projects for NASA subcontractors and am proud to have been involved in the technology that came from those projects. All things considered, Mother Nature will behave as she damn well pleases. Keep up the great work.


Uh uh. I like you. Lol. :)
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3064. SLU
Quoting StormW:


You betcha!


This is the type of action we've been expecting all season long.
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I'm out for now. Will come back later today. Have a great morning all.

PS. Center is left and South of the points :)
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Quoting SLU:
Microwave imagery suggests that the inner core is strengthening.



Judging by that microwave imagery, I'd think the center of Danielle is at 14.7 N 39.0 W.
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The last few screens of the MIMIC does suggest an eyewall feature being formed.
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3060. bird72


Looks like Danielle miss some forecast points.
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3057. SLU
Quoting Stormchaser2007:


Probably.



Looks like the horse has finally bolted.
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3056. hcubed
Quoting StormW:
I know I shouldn't, as I know everyone is entitled to their opinion on Doc's blog, but I have to ask...how many of you that come on here and just make blanket statements and like stirring the pot, REALLY know anything about tropical meteorology?


I come here to get the latest "between-the-bulletins" info. Anything that gets me a few extra hours to prepare.

I've learned who to pay attention to, and who to ignore.

And, several times, I've had to put on the hip waders just to get through the posts...

I'm slowly learning the "lingo", and how to read the charts, but I have nowhere near the expertise that you have. Thanks for putting up with us.
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i appreciate stormW and masters and people on here with a lot of know how because i cant depend on any tv weather available to me to really go into depth about things and i dont know enough about met to look at data online and translate it in any way. so its really kinda awesome i can come here and find out things three days before its on our local news.
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3054. lhwhelk
Quoting surfmom:


ME too!...but I think this is where forecasting isn't just hard science, but also an art & the talent to sense is a "gift"

This is why there is no Artificial Intelligence yet. Computers and all the data they provide are helpful, but they can only provide that data for human beings--in this case forecasters--to make sense of.
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Quoting SLU:
Pre-Earl?



Probably.

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3052. SLU
Pre-Earl?

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Danielle looks to be on the verge of popping out an eye in the next couple of hours so we won't have any trouble knowing where the center is.
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3050. GoofOff
Quoting StormW:
I know I shouldn't, as I know everyone is entitled to their opinion on Doc's blog, but I have to ask...how many of you that come on here and just make blanket statements and like stirring the pot, REALLY know anything about tropical meteorology?

Storm,
I have no training in that field. I am a retired mechanical engineer so I do enjoy studying charts and data. I really do appreciate all the information you give us. I am a native of Nebraska and have seen many tornadoes. I prefer hurricanes to them due to the advance notice. I moved to Florida over 10 years ago and live about a mile inland from the Atlantic about 45 miles north of West Palm Beach. Since I moved here we have taken three direct hits from hurricanes Francis, Jeanne and Wilma so I respect their power. My comments, on the very rare occasions I make one, are based upon what I can see from several different sources. I think the technology has made giant strides thanks to satellites. Needless to say, weather is a chain reaction over the entire earth and a change anywhere can affect the weather pattern everywhere. After the loop Jeanne made, I watch them very closely but don't get very concerned about my families' safety until about three days before the path is more clearly defined. I did have the pleasure of working on both the Gemini and Apollo projects for NASA subcontractors and am proud to have been involved in the technology that came from those projects. All things considered, Mother Nature will behave as she damn well pleases. Keep up the great work.
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Morning Storm! How are you?
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3048. CapnJak
Quoting surfmom:


well spoken - sometimes I have to wipe the testosterone off the screen
though I'm sure a Hot Flash or two have happened through the years
Generally speaking though -- the women are better students w/far less aggression, since most of us have raised kids we're savvy at side-stepping tantrums and pre-school behaviors - IMHO

Well said lol.
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Quoting kmanislander:


There are numerous instances where a building high has blocked the path of a system and even caused it to reverse course. Remember Andrew ?.

It was a weak and almost dissipated system headed out to sea and the next thing everyone knew it stopped in its tracks, intensified, made a turn due West and the rest is history.

Ivan did the same. It was on a track to pass over Jamaica, came to a dead stop 30 miles S of the island when it ran up underneath a high building to the West over Florida and then made a turn due West and passed about 25 miles S of Grand Cayman.

It is important to note though that it is not just the position of a high but also where other atmospheric features may be at the time. For instance, a building high / ULL combination would create a different steering regime than just having a strong ridge dominating.

The overriding point however is simple. Even strong hurricanes can head off in odd directions when least expected.



I didn't know about Andrew and Ivan. Although I do remember someone saying he wished that Andrew was headed away from Miami like they thought at one time. But you are correct that they can make unexpected moves in track and intensity.
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.
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Quoting Stormchaser2007:
Pretty darn tight consensus.





Add climatology to that and hell its damn near a slam dunk!!! Of course never say never I guess.
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Quoting Neapolitan:


No, that's not what he was saying. He was basically suggesting that folks who don't know a whit about tropical weather should maybe sit back and quietly learn rather than constantly flood the forum with their non-scientific and biased points of view. To put it succinctly: an opinion or a wish is not a forecast.


and that's fine. But who gets to decide who is qualified enough to post? I paid for my membership here, I'm not allowed to post? I never post forecasts, just ask questions mostly. But if Dr. Masters wanted to limit participation, I'm sure he would.
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This whole model thing is like a double standard. It's one thing to criticize the model's data when its 100+ hrs out and it doesnt quite fit your idea but then the same folks who are critical of the data turn around and present model data like it's the holy grail at 100+ hrs to prove their own synopsis?


I'm starting to wonder who has more spin - some of these statements that I am reading or Danielle?
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Hi. I have a question, but in PGI34L, what does PGI stand for? Also I found a site http://www.nrlmry.navy.mil/predict-bin/tc_home2.cgi and looked in the archive, but there's no 01L.PGI01L, 02L, 03L, ..., 15L.PGI15L. Can somebody explain why?
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Quoting Stormchaser2007:
Pretty darn tight consensus.



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Quoting BobinTampa:


no, not at all. I'm on your side on this one. StormW's post was basically saying "you guys don't know as much as me so shut up and listen."

I was responding to that.


No, that's not what he was saying. He was basically suggesting that folks who don't know a whit about tropical weather should maybe sit back and quietly learn rather than constantly flood the forum with their non-scientific and biased points of view. To put it succinctly: an opinion or a wish is not a forecast.
Member Since: November 8, 2009 Posts: 4 Comments: 13555
Quoting StormW:


I don't know Stef...I blew that one.


Huh? You didn't blow that one. My locals, now they blew it big-time! And didn't admit it until after the fact. UGH! Which is another reason I'm glad there are other places to go for information than just the "Official" channels. No, what you did was save my ass. :)
Just asked if that is what happened to Ike because thats what the track looked like.
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3037. SLU
Microwave imagery suggests that the inner core is strengthening.

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3036. surfmom
Hey Pottery -- just thinking of you!! I suspect Missy Danielle will bring waves to your shores - the thinking here in FL is it'll be a blustery windy mess on the Ecoast -
Hope you have a very SPECIAL & Happy B-day Link
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Quoting homelesswanderer:


Is that what happened with Ike?



There are numerous instances where a building high has blocked the path of a system and even caused it to reverse course. Remember Andrew ?.

It was a weak and almost dissipated system headed out to sea and the next thing everyone knew it stopped in its tracks, intensified, made a turn due West and the rest is history.

Ivan did the same. It was on a track to pass over Jamaica, came to a dead stop 30 miles S of the island when it ran up underneath a high building to the West over Florida and then made a turn due West and passed about 25 miles S of Grand Cayman.

It is important to note though that it is not just the position of a high but also where other atmospheric features may be at the time. For instance, a building high / ULL combination would create a different steering regime than just having a strong ridge dominating.

The overriding point however is simple. Even strong hurricanes can head off in odd directions when least expected.

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3008 and 3022

SURFIE - well said, well said. I poked my head in for a quick look this morning, but think I will back out and let the morning feeding frenzy wear a few folks out.

Back later in the day for the next discussion.
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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.