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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2882. Engine2
They have added model data to this site

http://moe.met.fsu.edu/tcgengifs/
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Ike, the link for the 6Z nogap is not working
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Bouy at 15N 38W as of 5AM EDT




Member Since: September 23, 2005 Posts: 14 Comments: 10875
good morning ike.Had to laugh this morning at cw site,you notice the disclaimer he has at the bottom of his discussion?I guess thats a good way of covering yourself in a under achieving season so far.I will certainly not say anymore that something will develop but i would suppose the disturbed weather in the gulf will cause a lot more issues for the conus than anything Danielle will do, but unfortunately danielle will still get 10000 posts from the florida folks and probably less than 100 form the folks in bermuda lol.Ike have a blessed day.
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If you go here and then check the box for Trop PT. you can see how far south of the points She is moving... Link
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2874. breald
Quoting StormW:


Yes ma'am.


oh boy. Then Bermuda really needs to watch this. Hopefully it doesn't get too strong.
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2873. smuldy
Quoting homelesswanderer:


I was wondering about the trough. If what this says is true then the weakness will move farther out into the Atlantic with the SE ridge behind, to the west of it, or under the trough to the south?

THERE IS LESS CONFIDENCE ON THE EXTENDED PORTION OF THE FORECAST
FOR FRIDAY INTO THE WEEKEND. GUIDANCE OVERALL STILL DEVELOPS A
RIDGE OVER THE SOUTHEAST U.S. AND BUILDS IT INTO THE REGION. THE
23/00Z ECMWF AND 23/00Z GFS TAKE SOME ENERGY AT TAIL END OF EAST
COAST TROF OVER THE NORTHEAST GULF...AND RETROGRADE IT TO THE WEST
UNDER THE RIDGE IN THE FORM OF AN INVERTED TROF. THIS SCENARIO IS
DIFFERENT FROM THE SAME TIME 24 HOURS...BUT SIMILAR TO WHAT THE
GUIDANCE HAD BEEN SHOWING EARLIER IN THE WEEKEND. WILL KEEP THE
ON-GOING FORECAST MAINLY THE SAME AT THIS TIME...WITH JUST LOW END
CHANCE POPS TO ACCOUNT FOR SOME INCREASE IN MOISTURE WITH THE
SOUTHEAST FLOW OVER THE WEEKEND.

well i had started agreeing with general model guidance under the assumption that the weakness over fl picked up the storm in the midatlantic with the ridge behind it, then aw was posted suggesting it somehow skirts by that. anyone with help in how/why? if it misses that, a more sw track initially may actually matter to the long term track as a whole more than id thought 2 hours ago
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2870. IKE
6Z NOGAPS...Link...taking it to east of Bermuda with another trough coming off of the east coast of the USA....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
2869. breald
Quoting StormW:
Either way, it's south of the forecast points.


does south mean more west?
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This image is a couple of hours old, but I gotta say it doesn't look like any mere TS I've ever seen:

Click for larger image:
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2867. scott39
Quoting KEEPEROFTHEGATE:
06L/TS/D/CX
MARK
14.63n/39.23w

That is an obvious sharp left turn.
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2866. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Outlook
8:30 AM IST August 23 2010
==================================

A low pressure area has formed over west central Bay of Bengal off Andhra Pradesh coast
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It might be a bit further west than anticipated as well.
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2864. KEEPEROFTHEGATE (Mod)
06L/TS/D/CX
MARK
14.63n/39.23w

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Quoting StormW:


Morning Stef! How's that pretty Texas Lady this a.m.?


Days behind but catching up. :)
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Quoting Thundercloud01221991:


I think that is pretty close to where I hold the center although I am thinking 14.5 38.5

so either way though it is under the CDO and so intensification will happen today


Quoting wunderkidcayman:
not far off from where I see it StormW I am seeing it at 14.5N 38.5W



LOL did you steal the coords from me???
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not far off from where I see it StormW I am seeing it at 14.5N 38.5W
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Quoting StormW:
Either way, it's south of the forecast points.


way south and still moving westward so it will miss the next point way to the south
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2858. scott39
Quoting StormW:


Bending toward the W...WNW motion I'll post the link loop...you gotta look close and zoom in:
LINK

I see it thanks
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Quoting smuldy:
ya but will it be enough to build over that monster weakness over florida right now? and anyone have a map of current upper and mid level steering? at least over the CONUS?


I was wondering about the trough. If what this says is true then the weakness will move farther out into the Atlantic with the SE ridge behind, to the west of it, or under the trough to the south?

THERE IS LESS CONFIDENCE ON THE EXTENDED PORTION OF THE FORECAST
FOR FRIDAY INTO THE WEEKEND. GUIDANCE OVERALL STILL DEVELOPS A
RIDGE OVER THE SOUTHEAST U.S. AND BUILDS IT INTO THE REGION. THE
23/00Z ECMWF AND 23/00Z GFS TAKE SOME ENERGY AT TAIL END OF EAST
COAST TROF OVER THE NORTHEAST GULF...AND RETROGRADE IT TO THE WEST
UNDER THE RIDGE IN THE FORM OF AN INVERTED TROF. THIS SCENARIO IS
DIFFERENT FROM THE SAME TIME 24 HOURS...BUT SIMILAR TO WHAT THE
GUIDANCE HAD BEEN SHOWING EARLIER IN THE WEEKEND. WILL KEEP THE
ON-GOING FORECAST MAINLY THE SAME AT THIS TIME...WITH JUST LOW END
CHANCE POPS TO ACCOUNT FOR SOME INCREASE IN MOISTURE WITH THE
SOUTHEAST FLOW OVER THE WEEKEND.

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Quoting StormW:
I hold the center at 14.8N;38.6W


I think that is pretty close to where I hold the center although I am thinking 14.5 38.5

so either way though it is under the CDO and so intensification will happen today
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2853. smuldy
Quoting KEEPEROFTHEGATE:
the high is back building in storm
ya but will it be enough to build through that monster weakness over florida right now? and anyone have a map of current upper and mid level steering? at least over the CONUS?
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Quoting StormW:
I hold the center at 14.8N;38.6W


K I was in the right neighborhood. :) Morning Storm.
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2851. KEEPEROFTHEGATE (Mod)
2849 west
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2850. KEEPEROFTHEGATE (Mod)
the high is back building in storm
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2849. scott39
Quoting StormW:
I hold the center at 14.8N;38.6W
what direction?
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2848. KEEPEROFTHEGATE (Mod)
morning bloggers
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2847. smuldy
Quoting scott39:
Im confused about the first trough because accuweather says bypass--stall--and then second one picks it up.
idk about AW, the models had the one over FL now picking it up in the central at hence the track way east of bermuda; if there is a split off georgia that travels ne and becomes a noreaster that could create a seperate low ahead of the trough in florida and that low could be too far north for D to feel, maybe that is what they mean, but i honestly dont know; i was fighting the models until i saw how low that weakness was, if someone wants to convince me that D will miss that I love being contrarion so I'll take a listen
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2845. KEEPEROFTHEGATE (Mod)
UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 23 AUG 2010 Time : 083000 UTC
Lat : 14:44:59 N Lon : 36:59:49 W


CI# /Pressure/ Vmax
3.4 / 995.2mb/ 53.0kt


Final T# Adj T# Raw T#
3.4 3.4 3.4

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -37.4C Cloud Region Temp : -44.2C

Scene Type : SHEAR (0.04^ TO DG)

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

****************************************************
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Send some of that cooler air to the Texas Gulf Coast,,,,We are baking! Heat Index of 107 forecasted again this afternoon......Kids back in school,,so no fun for football practice...
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2843. KEEPEROFTHEGATE (Mod)
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I'm probably days behind, again, but they added ECMWF op and ensemble to this site. Link
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2841. KEEPEROFTHEGATE (Mod)
x
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Danielle looks to be a classic fish storm...great. The models have been predicting its future path quite well over the past couple of days. Hopefully, the weakness left behind by Danielle, combined with stronger troughs to the north as the fall season approaches will influence the paths of any other Cape Verde storms and keep them out to sea also.

Late-season storms which form in the Caribbean may be another story, but that's something to worry about later, from late September through about mid-November.
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2839. scott39
Quoting smuldy:
the GIANT weakness over florida in the image i just posted; only way anything else happens is if an outflow from D buids a stronger ridge to its north but with a trough that deep-idk, usually thats an october feature not august but models seem to have been right
Im confused about the first trough because accuweather says bypass--stall--and then second one picks it up.
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2838. smuldy
about the steering & trough though it should be pointed out that StormW was right, the early models showed that trough but no strong ridge to its west, which is why they were deemed unbelievable, that is one monster ridge to its west in real life
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59F.. 88% humidity.. light rain, west winds at 10mph.
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2836. surfmom
Quoting spathy:
Good Mornin Surf:0)
Yes waking up to rain tapping on the window.
Such a great way to start the day.

Spathy : )
I'm soooooo REFRESHED
- lol
the caffeine even has kick this AM
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2835. surfmom
GOMEX/SWFL - Surf Report - AURASURF
Troughy WX sticks around and there will be a knee to possibly thigh high wave late Monday into Tuesday as the kids go back to school. By next weekend a solid swell from a tropical cyclone will hit the EC. Before you go and book your hotel keep in mind it looks like a devil wind with 15knt onshores by Sunday. Keep an eye on it.

I always enjoy comparing the surf perspective w/the WU "weatherboys" view
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2833. smuldy
Quoting scott39:
If the first trough is expected to bypass Danielle, what is going to make her turn more N?
the GIANT weakness over florida in the image i just posted; only way anything else happens is if an outflow from D buids a stronger ridge to its north but with a trough that deep-idk, usually thats an october feature not august but models seem to have been right
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2832. scott39
Quoting DestinJeff:
Not a mammal, but a....
I will not say the F word!
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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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