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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Quoting DestinJeff:


I can make it to Da Funyak Springs on a gallon of gas. No need to worry.


A gallon will get me to Youngstown, should be plenty. The house there will be empty as my mother-in-law will have already evacuated to North Dakota or Maine. lol
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Quoting washingtonian115:
This reminds me of the Gustav,and Hanna situation.Due to Gustavs size and outflow Hanna was sheard.
By the looks of it Danieele already won the battle I still don't think rapid intensification will occur though conditions aren't ideal
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1330. hydrus
Quoting will45:


all the old people are in the Carolinas

With the very oldest existing in Florida....Grothar for example is act....Oh...Hi Gro
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Quoting 1992Andrew:
Hey I feel like wishcasting. Something about living in Miami and driving through its traffic... on a sunday.

What are the chances this thing misses the second trof? I could use a day or two off from school and work.
be careful what u wish for, i was without electricity for 5 weeks post ivan 2004, living like they did back in the 50s here no fun!
Member Since: April 29, 2007 Posts: 0 Comments: 7931
Quoting StormChaser81:


That's a cool avatar. I love Alex Grey paintings.
Psychedelic paintings are definitely far more interesting than hurricanes.
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Intensity guidance starting to increase again.
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Quoting Huracaneer:
Wow, hadn't looked at Danielle in a while, nice blowup. Kind of scary since I been watching National Geographic specials on Katrina. Always remember the day after she blew up in the Gulf and became a Cat 5. Still gives a sick feeling because I knew at that time that it was going to be real bad for somebody.


Ahh yes very good programming, although some of those home videos have been making me a bit queasy because the people are fumbling with the cameras so much. Some of those people are also complete idiots for staying in their houses knowing that it was going to flood, and sure enough it did.
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1324. aquak9
ya'll aren't gonna let this go, are ya.

ok I thought my screen name and my email addy had to be the same. WaterDog and every version of it was already taken many many years ago on AOL. Comcast, yahoo, gmail, everything. Aquak9 was the best I could come up with.

Now I answer my phone as Aqua. I morphed from a semi-intelligent human to a weather-obsessed wet dog.
Member Since: August 13, 2005 Posts: 168 Comments: 26066
1323. Patrap
Computer Models Used to Forecast Hurricanes


The behavior of the atmosphere is governed by physical laws which can be expressed as mathematical equations. These equations represent how atmospheric quantities such as temperature, wind speed and direction, humidity, etc., will change from their initial current values (at the present time). If we can solve these equations, we will have a forecast. We can do this by sub-dividing the atmosphere into a 3-D grid of points and solving these equations at each point. These models have three main sources of error:

1) Initialization. We have an imperfect description of what the atmosphere is doing right now, due to lack of data (particularly over the oceans). When the model starts, is has an incorrect picture of the initial state of the atmosphere, so will always generate a forecast that is imperfect.

2) Resolution. Models are run on 3-D grids that cover the entire globe. Each grid point represents of piece of atmosphere perhaps 40 km on a side. Thus, processes smaller than that (such as thunderstorms) are not handled well, and must be "parameterized". This means we make up parameters (fudge factors) that do a good job giving the right forecast most of the time. Obviously, the fudge factors aren't going to work for all situations.

3) Basic understanding. Our basic understanding of the physics governing the atmosphere is imperfect, so the equations we're using aren't quite right.

Types of hurricane forecasting models
The best hurricane forecasting models we have are "global" models, that solve the mathematical equations governing the behavior of the atmosphere at every point on the globe. Models that solve these equations are called "dynamical" models. The four best hurricane forecast models--GFDL, GFS, UKMET, and NOGAPS--are all global dynamical models. These models take several hours to run on the world's most advanced supercomputers. There are also dynamical models that cover just a portion of the globe. These are less useful, unless the hurricane happens to start out inside the domain the model covers and stay there. Hurricanes moving from outside the model domain into the model domain are not well handled. An example of this kind of model is the NAM model covering North America and the surrounding waters, run by the National Weather Service (NWS). Another type of hurricane model is a statistical model. These models do not try to solve mathematical equations on a grid. The advantage of these statistical models is that they are fast to run and can provide output in a few minutes. There are also hybrid statistical/dynamical models, and simple trajectory models.

A summary of the top six models:
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1322. srada
You know it makes me wonder if most of the models are saying that Danielle will recurve out to sea, then why did the NHC state in their discussions about the uncertainity of Danielle catching the trough..there are other variables in track predictions that have to be taken in consideration and even with the consenscous of the models in agreement with recurving, the NHC isnt buying the scenario as 100%..why state the supposedly 10% chance of this not recurving? .......
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1321. Grothar

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Quoting aquak9:
ryuujin- if ya hadn't been reading here for a long time, ya might not realize who, how folks are. We're stuck with each other, and just trying to make the best of it.

I've been locked in this room now for over five years....

Very true. Reminds me of the song "Stuck In The Middle With You", sang by "Steelers Wheel". Link below for your listening pleasure.
Link

Danielle is singing, "Trough of Low Pressure to the left of me and a Blocking High" to the North, here I am, stuck in the middle with you"!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
GOMEX





Member Since: August 15, 2008 Posts: 0 Comments: 2133
Quoting 1992Andrew:
Hey I feel like wishcasting. Something about living in Miami and driving through its traffic... on a sunday.

What are the chances this thing misses the second trof? I could use a day or two off from school and work.


Well, its seems to me its quiet unlikely that it'll go to Florida even if it misses the trough. The trough's definetly going to bend the track NW, and it seems right now that even if it bent back to the WNW, it would be at a far north latitude enough already that it would miss Florida.
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Wow, hadn't looked at Danielle in a while, nice blowup. Kind of scary since I been watching National Geographic specials on Katrina. Always remember the day after she blew up in the Gulf and became a Cat 5. Still gives a sick feeling because I knew at that time that it was going to be real bad for somebody.
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Quoting 1992Andrew:
Hey I feel like wishcasting. Something about living in Miami and driving through its traffic... on a sunday.

What are the chances this thing misses the second trof? I could use a day or two off from school and work.


Spoken like someone who's never been through a big one. It's never just a few days, and living in the South without ac for weeks is not fun. School/work are paradise compared to that.
Member Since: July 29, 2005 Posts: 21 Comments: 794
1314. Grothar
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I beleive Tropical Storm Danielle is at 50 mph.

The National Hurricane Center will likely make it 45 mph though.
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1311. xcool


flip-flopping.
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting doorman79:
Yea, there are a few out there, was just trying to give the link ;)


That's a cool avatar. I love Alex Grey paintings.
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Quoting snowboy:


Cat 1 by morning!


In your dreams!
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1306. Grothar
Hey PcolaDan, thought you moved out of the country. How you been? Back now that the tropics are active? See how you are!!!
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Hey I feel like wishcasting. Something about living in Miami and driving through its traffic... on a sunday.

What are the chances this thing misses the second trof? I could use a day or two off from school and work.
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1303. xcool



Danielle .50k.move to wnw 9mph jmojmojmo
Member Since: September 26, 2009 Posts: 2 Comments: 15684
1302. aquak9
ryuujin- if ya hadn't been reading here for a long time, ya might not realize who, how folks are. We're stuck with each other, and just trying to make the best of it.

I've been locked in this room now for over five years....
Member Since: August 13, 2005 Posts: 168 Comments: 26066
1301. snowboy
Quoting CybrTeddy:
Impressive convection.


Cat 1 by morning!
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Member Since: August 15, 2008 Posts: 0 Comments: 2133
1298. KEEPEROFTHEGATE (Mod)
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1297. Ryuujin
Quoting PcolaDan:


Yes, I knew you were new. Yet you jump on a remark Ike made without a thought that it might be sarcastic humor. Those of us who know him realized right away it was a joke. Sarcasm in here is rampant, as is other humor (see Dewey and Jeff). Being arrogant in here will get you ignored pretty fast in here.


Hahahhaha. Okay. Okay. Defend IKE all you wish bro. My remark, even if made in error, was an in earnest questioning to why people agree with one model when it suits their needs but do-not when it doesn't. That's it. It also hits home to the question I've raised over and over again about the known cold bias GFS has and the potential non-effect it may have on Danielle.
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Quoting FLPandhandleJG:


Seeing some outflow developing on the east side, indicative of decreasing shear.
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Quoting tropics21:
are you a newbie to weather if not You should know Danielle is fighting the susytm above her, not blowing up into a hurricane immediately
This reminds me of the Gustav,and Hanna situation.Due to Gustavs size and outflow Hanna was sheard.
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Quoting smuldy:
not every system that forms off of florida is xxtd5. I might be wrong but I believe td5's energy is inte3racting with the low level trough to produce the noreaster the gfs shows in the latest runs, and what is in florida is a new remnant of an entirely different trough split.


You're right, I believe XTD5 met its end when it was absorbed by a stalled front in NW Mississippi on August 18.
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I know its old.. but pretty impressive TS we got brewing probably getting stronger..
Member Since: August 15, 2008 Posts: 0 Comments: 2133
1288. Ryuujin
Quoting smuldy:
well said. until model consensus has a recurve within 48 hours it is reasonable to question the turn being a foregone conclusion.


Thanks. It seems like no one else has read any of my posts, so it doesn't matter. They all seem to follow one crowd, like ducks in a row.

I thought this blog was a place for intelligent, thoughtful discussions for tropical formation and development.
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Quoting Ryuujin:


I am new here, I've stated that repeatedly, just as I've stated my questions to the blog repeatedly. It's simply obvious that some people either aren't comfortable debating them, or cannot find them.


Yes, I knew you were new. Yet you jump on a remark Ike made without a thought that it might be sarcastic humor. Those of us who know him realized right away it was a joke. Sarcasm in here is rampant, as is other humor (see Dewey and Jeff). Being arrogant in here will get you ignored pretty fast in here.
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Quoting JupiterFL:


KOG yes, that is how I always read it. Never new what the 9 was for exactly. Oh well, if you can't figure mine out then email me and I will walk you through it.
Let me guess, you live in Jupiter Florida?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting 7544:
daniele wants to be the first buzsaw of the season and just might do it


2nd* Buzzsaw of the season.
Member Since: July 8, 2005 Posts: 259 Comments: 24185
Where is STORM W?
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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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