Tropical Depression Six and a new disturbance interact

By: Dr. Jeff Masters , 1:42 PM GMT on September 05, 2006

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Tropical Depression Six is not yet a tropical storm, as evidenced by the maximum winds of 25-30 knots (30-35 mph) seen on this morning's 4:33am EDT QuikSCAT pass (Figure 1). TD 6 has managed to consolidate the two circulation centers it was struggling with yesterday into one large circulation center. The storm's maximum winds are occurring in bands well removed from this broad center, and it will probably take another day before the winds tighten up around the center and the TD 6 can intensify into a tropical storm. Interfering with this process will be about 10-15 knots of shear and some dry air to the north.

The computer models all forecast that TD 6 will pass north of the Lesser Antilles Islands, although it is too far in the future to be confident of this forecast. A complicating factor is the development of a new disturbance about 800 miles to the east-southeast. This new disturbance, officially designated "Invest 91L" this morning by NHC, is close enough to alter both the strength and track of TD 6. Anytime two storms get within 13 arc-degrees of each other (900 miles), the two storms tend to rotate around a common center (the Fujiwhara effect). The computer models do make some allowances for this effect, but are not very good at handling it. For this reason, one should be suspicious of the track forecasts for TD 6 and 91L as long as they are so close. The intensities of both storms can also change as a result of the interaction, with both storms intensifying at a slower rate than they otherwise would, or one storm growing at the expense of the other. If the two storms approach within about 7 arc-degrees of each other (480 miles), this is considered the "zone of death" where one cyclone will surely destroy the other. The surviving storm will not be a "superstorm" that has the combined size and strength of the two storms, however.

The long-range GFS model forecast continues to show TD 6 becoming a powerful hurricane that threatens Bermuda, but recurves out to sea well east of the U.S. East Coast. Again, it is too early to be confident of this forecast, given the interactions that may occur with 91L and the inherent uncertainties in long-range hurricane track forecasts. The wind shear later this week is forecast to drop significantly, so if TD 6 manages to survive the next 36 hours, it is likely to become a hurricane.


Figure 1. QuikSCAT satellite winds from 4:33am EDT Tuesday September 5 2006. Wind speed and direction are coded according to the standard station model, and are color coded (in knots) according to the color scale at the upper right (10 knots = 11.5 mph). Black winds barbs occur where there is rain, and one cannot trust the wind speeds measured in those areas. Tropical storm force winds (35 knots) are colored red and need to have 3 long bars and one short bar attached to the end of the "barb"; there is one barb like this on the east side of TD 6, but it is pointing a different direction than the other barbs around it, and is surrounded by rain-contaminated (black) barbs. One should be suspicious of the accuracy of this lone tropical storm force wind barb.


Figure 2. Preliminary model tracks for Invest 91L, a well-organized tropical wave a few hundred miles west of the Cape Verde Islands.

Cape Verdes Islands tropical wave
A strong new tropical wave emerged from the coast of Africa Saturday and is a few hundred miles west-southwest of the Cape Verde Islands. The wave has a closed circulation, and visible satellite imagery from this morning shows an increase in thunderstorm activity on the west side. The wave is over warm water and is under a modest 10 knots of wind shear, and could be Tropical Depression Seven by Wednesday. Due to its more southerly starting position, this system is more likely to be a threat to land than TD 6.

Carolinas
North Carolina is still suffering flooding problems from Ernesto. Where Ernesto came ashore at Cape Fear, North Carolina, the North Cape Fear River is at 16.6 feet, and flood stage is only 10 feet. This is the second highest flood on this river; only Hurricane Floyd of 1999 caused a higher flood. With a strong cold front expected to move through tonight and stall offshore, North Carolina will receive another 1-2" of rain that will make flooded areas slow to recover. Once this cold front does stall over the warm Gulf Stream waters, we need to watch the area off the Carolina coast for possible tropical storm development.

Ioke
Ioke continues its slide into oblivion, and is now a mere tropical storm. Ioke is caught in a large trough of low pressure that is weakening it and recurving it out to sea. Ioke is not a threat to any land.

Next update
I'll have an update Wednesday morning, unless there's something interesting to report on this afternoon.

Jeff Masters

Cape May Harbor (clamboynj)
Tropical depression Ernesto leaves downed trees ,broken branches and sunken vessels in its' wake...
Cape May Harbor
Belhaven, NC - Ernesto 2006 (FlounderBandit)
Water Street, looking west. Abandoned sailboat.
Belhaven, NC - Ernesto 2006

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269. Patrap
7:11 PM GMT on September 05, 2006
.Florence large Cape Verde TRopical Storm with a wnw @13motion..Florence should bring a signifcant forcast challenge out past 72hrs..as she has the potential to reach Hurricane strength by then.
Member Since: July 3, 2005 Posts: 420 Comments: 127543
268. Eastcoast
5:30 PM GMT on September 05, 2006
Hurricane threat east coast Sept 11-14,Florence a little further west on GFS 4

Any one remeber Gloria ? Looks just like
it.

More here Maps and tracks
267. CosmicEvents
4:08 PM GMT on September 05, 2006
DCDeer....anything more than 1 year is known as years. It's been 2 years.
Member Since: August 3, 2005 Posts: 10 Comments: 5526
266. IKE
4:02 PM GMT on September 05, 2006
FOLKS....DR. M HAS A NEW BLOG!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
265. ricderr
4:01 PM GMT on September 05, 2006
been tough to be posting on here for "years" cosmic....and i still think your blamket statement is ludicrous...but..enjoy your day
Member Since: June 27, 2006 Posts: 670 Comments: 21389
264. ricderr
3:58 PM GMT on September 05, 2006
statistics and history mean absolutly squat!


guess you're right....so then...we should pay no special mind to the tropics in oct and sept....there should be no "hurricane season"...models...based on statistics such as movements...because hey..they all boil down to a statistical equation..should not be looked at or even run...
personally...i think climatology is poo - pooed a bit much on this blog..but i still love ya
Member Since: June 27, 2006 Posts: 670 Comments: 21389
263. CosmicEvents
3:58 PM GMT on September 05, 2006
Nebula...I don't think that most people here want to experience a cat5 up close and personal. Anyone that's been through a cat2 or 3 would(or should) no better than to want to experience a cat5. I would agree with those that say you're nuts if you want to experience a cat5.
.
.
RcDeer....I've been posting here for years dear. I just don't post that often. And I hardly ever post on this blog. There's only one forecaster I follow on WUBA and he's got his own blog. I post more on this blog when a major storm is nearing land and we get scared newcomers looking for assistance.
Member Since: August 3, 2005 Posts: 10 Comments: 5526
262. DestinRick
3:58 PM GMT on September 05, 2006
Ahhhh...Blue Oyster Cult...one of the great philosophical bands of all time!
261. tropicallydepressed
3:57 PM GMT on September 05, 2006
The NHC official forecast say the "storm" is going to move due west for the next 24hours. Why then, does their cone show a NW/WNW movement.

On a side note, I can only listen to Echoes after eating a handfull of magic mushrooms.
Member Since: August 11, 2006 Posts: 0 Comments: 131
260. CycloneOz
3:57 PM GMT on September 05, 2006
"History shows again and again how nature points out the folly of man."

-Blue Oyster Cult
Member Since: August 26, 2006 Posts: 10 Comments: 3617
259. Barkeep1967
3:56 PM GMT on September 05, 2006
statistics and history mean absolutly squat!

Look at your statement again and tell me who the fool is.

Also you have now proven you have taken zero formal met classes. the intro classes all focus heavily on statistics and history. Of course you are here on an amateur blog. You probably know far more than any professor or professional forcaster.
Member Since: June 26, 2006 Posts: 0 Comments: 207
258. nebula420
3:55 PM GMT on September 05, 2006
cosmic, believe me when I say I don't want to have to do another three year cleanup like I did after Andrew, but I'm not going to feign incredulty over wanting to experience one, preferably a safe distance from land. Just so you know, I live in Homestead, Fl. My family lives in Perrine and they just had their insurance sold by citizens to so other insurance company that just double their windstorm from $4000 to $8000. They want the cash now. My parents didn't have the money so they were dropped---in the middle of hurricane season. Insurance companies are scams as they are only fair weather friendly. ALLSTATE (Who I have and my parents had before they were dumped to citizens and then again)---the middle finger people.
257. CycloneOz
3:54 PM GMT on September 05, 2006
BRAND NEW INFRARED ANIMATION FOR TODAY!!!

FLORENCE - GOES IR ANIMATION

Here's the latest GOES infrared animation that plays from 9/3/2006 2045Z - 9/5/2006 1415Z
Member Since: August 26, 2006 Posts: 10 Comments: 3617
256. DestinRick
3:53 PM GMT on September 05, 2006
Cosmic writes, "Nature being nature, they'll go where they go on their own and there's nothing we can do about it."

But doggone if lots of folks here don't forget that on a daily basis. No matter what the computers predict (and they're only as good as the info fed into them) or what the NHC, TWC, CNN, FBI, CIA, NAACP, etc. or anyone here predicts, it's pretty much guessing. Mother Nature plays by her own rules...and she's not showing them to any of us...at least she hasn't yet.
255. Rick54
3:52 PM GMT on September 05, 2006
you have no idea what happened in the thousands of years before we were keeping track.

statistics and history mean absolutly squat!

Yes it may be true until one does and then it becomes part of the history.
254. CycloneOz
3:51 PM GMT on September 05, 2006
That's a great link, Barkeep.

I'll go out on a limb and say that it stays at sea and becomes a fishstorm.
Member Since: August 26, 2006 Posts: 10 Comments: 3617
253. IKE
3:50 PM GMT on September 05, 2006
They'll always be wishcasters on here....just sift thru the posts and move on...or run on...like a flock of seagulls.........

Flo is an odd looking creature........
Member Since: June 9, 2005 Posts: 23 Comments: 37858
252. Thaale
3:49 PM GMT on September 05, 2006
"OK....I guess it's time for you wishcasters out there to start calling for a major hurricane hitting the US. I'll never understand why there are people like this. What's wrong with following and looking at a strong storm that stays out with the fishes? Geez....you'd think seeing the bodies floating in the waters last year would at least have given us a 1 year break from these dodo's."

We got the bubble-headed-bleach-blonde who comes on at five
She can tell you bout the plane crash with a gleam in her eye
It's interesting when people die-
Give us dirty laundry
Member Since: October 19, 2005 Posts: 0 Comments: 308
249. Dr. Jeff Masters , Director of Meteorology (Admin)
3:48 PM GMT on September 05, 2006
There's a new blog, mostly I changed the name TD 6 to Florence.

Jeff Masters
248. DestinRick
3:48 PM GMT on September 05, 2006
bocadave...I'm with you, brother! Shoot Flo and all of her siblings wayyyyyy out to sea!
247. nebula420
3:47 PM GMT on September 05, 2006
Look, lets face it, most on this board would love to experience a cat. 5 hurricane up close and personal. I do. My friends say I'm nuts. They all went through Andrew. I acme home one month late from Korea. I got to deal with the crap after the storm. They are probably right, but it's us nuts that make the world go round, certainly not the meek and the too intelligent for their own good. We all love the power of mother nature. That is why we spend so much time here. Of course, the best of both worlds is to experience a cat 5 and receive no damage. Maybe I'll go skydiving.
246. SavannahStorm
3:47 PM GMT on September 05, 2006
There are wishcasters on both sides, those wishing it'll hit the East Coast as a major hurricane, and those wishing it to be a fish storm. It goes both ways.
Member Since: September 22, 2005 Posts: 18 Comments: 2313
245. CosmicEvents
3:47 PM GMT on September 05, 2006
nebula...I'm here because I'm an interested observer. I live in hurricane alley and I like the added information to be found here. It can assist me in keeping my family and possessions safe. I do have an interest in tropical cyclones but I don't wish that any come near me, or towards anyone else. Nature being nature, they'll go where they go on their own and there's nothing we can do about it.
Member Since: August 3, 2005 Posts: 10 Comments: 5526
244. Randrewl
3:47 PM GMT on September 05, 2006
ricderr...Heavy, heavy rain here right now.
Member Since: June 8, 2006 Posts: 114 Comments: 31557
242. FLCrackerGirl
3:46 PM GMT on September 05, 2006
EYE, To View Older Blog Entries:
Click on Dr. Masters Title & Scroll Down,
Most Recent Entries There.

For Older Blogs:
Look to The Right Of This Entry----->
Click On Month or Complete Archive.
Member Since: August 12, 2004 Posts: 47 Comments: 597
241. pseabury
3:46 PM GMT on September 05, 2006
Only buoy close is 41041
Member Since: May 28, 2005 Posts: 0 Comments: 3
240. ricderr
3:45 PM GMT on September 05, 2006
oh my......gloom and doom wishcasters we are....ok..raise of hands.....who among us and change the course of a storm?.....who among us regs has not had some to major life upheavals from storms?...so then..someone..who has never commented here before...who has no idea who on here...watches..for what various reasons..is gonna "forecast" that we...as a whole...are doom and gloom...pretty much shows you what a time they are
Member Since: June 27, 2006 Posts: 670 Comments: 21389
239. ClearH2OFla
3:45 PM GMT on September 05, 2006
h23 can you email me the latest im at work ty
238. eye
3:44 PM GMT on September 05, 2006
Thanks Cracker!!!!!!!!
Member Since: August 21, 2006 Posts: 0 Comments: 147
237. Barkeep1967
3:44 PM GMT on September 05, 2006
Well before the wishcasting circus kicks into full gear. I will yet again refer you all to 150+ years of history.

Link

NOtice not a single storm has ever made it to the US mainland fromn where flo is located. I am just going to go out on a limb and say thats not going to change.

Could it? sure
Odds are very slim however.
Member Since: June 26, 2006 Posts: 0 Comments: 207
236. FLCrackerGirl
3:44 PM GMT on September 05, 2006
Hurricane79's site:flhurricane.com
Member Since: August 12, 2004 Posts: 47 Comments: 597
235. Zaphod
3:43 PM GMT on September 05, 2006
CNN online isn't worth the paper it's printed on!

To me, the problem with the models isn't the fact that they are error prone and are sometimes greatly affected by relatively small changes in initial conditions, but that the model runs do not (and probably currently cannot) provide a "cone of error" for the predicted track based on the quality of measurements and sensitivity to initial conditions. A probability-weighted prediction would better allow a weighted-sum combined track, with an aggregate probability cone to match. I believe that not only should we "ignore the line", but that we should improve the models to better indicate their sensitivity to initial conditions and expected errors.
Zap
Member Since: October 5, 2005 Posts: 15 Comments: 3239
234. eye
3:43 PM GMT on September 05, 2006
how do i view past blogs for Masters?
Member Since: August 21, 2006 Posts: 0 Comments: 147
231. bocadave
3:42 PM GMT on September 05, 2006
not your typical floridian here then- i want them to stay as far away as possible!
230. billybadbird
3:42 PM GMT on September 05, 2006
zap - 27, lol. i aint no bad bird that's just my name.
Member Since: June 13, 2006 Posts: 1 Comments: 256
229. nebula420
3:41 PM GMT on September 05, 2006
Cosmic, why are you here. For me it's curiosity killed the cat.
228. eye
3:41 PM GMT on September 05, 2006
COULD SOMEONE POST THE LINK TO HURRICANE79'S SITE, THANAKS A BUNCH!!!!
Member Since: August 21, 2006 Posts: 0 Comments: 147
226. nebula420
3:40 PM GMT on September 05, 2006
I'm not sure I'd past six hours, gulf, unless the NHC is presented with cut and dry scenarios.
225. eye
3:40 PM GMT on September 05, 2006
Cosmic, i dont understanding it, i have been calling for Flo to be a fishwoman for days now....people in FL are the worse at it, wishcasting the system on them. Maybe something in the water?
Member Since: August 21, 2006 Posts: 0 Comments: 147
224. CosmicEvents
3:38 PM GMT on September 05, 2006
OK....I guess it's time for you wishcasters out there to start calling for a major hurricane hitting the US. I'll never understand why there are people like this. What's wrong with following and looking at a strong storm that stays out with the fishes? Geez....you'd think seeing the bodies floating in the waters last year would at least have given us a 1 year break from these dodo's.
Member Since: August 3, 2005 Posts: 10 Comments: 5526
223. eye
3:38 PM GMT on September 05, 2006
Gulf, it has been renamed, "The Cone of Doom"
Member Since: August 21, 2006 Posts: 0 Comments: 147
222. nebula420
3:38 PM GMT on September 05, 2006
Good man Ike! Check out how Echoes builds (like a tropical storm) and then crescendos towards the end not unlike landfall. Imagination run amok.
220. eye
3:37 PM GMT on September 05, 2006
is that yet another wave even further S coming off Africa?
Member Since: August 21, 2006 Posts: 0 Comments: 147
219. IKE
3:36 PM GMT on September 05, 2006
Posted By: nebula420 at 10:33 AM CDT on September 05, 2006.
Ike, great song..... gag....That 70's show mocked it! Try listening to echoes by Pink Floyd. Now that's a song worthy of hurricanes.


Hey...I LUV Pink Floyd...come to think of it...let me look.........I've got the ECHOES CD in my CD player right now...along with 1 of 4 CD's from the Zeppelin box set.....

Another Brick In The Wall.......
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.