ATL: HELENE - Post-Tropical

[brunota2003]

Buoy 41041 thus far:
Highest 1-minute Wind Speed
Time (EDT) 1-Minute Wind Speed WSPD 1-Minute Wind Direction WDIR
11:30 pm 27.2 kts ENE ( 60 deg true )

Pressure: 29.88 or 1011.8 millibars

So far, TD7 appears to have winds of at least 30 knots.

http://www.ndbc.noaa.gov/station_page.php?station=41041

[cheezyWXguy]

That doesn't make one season analogous to another. This season could then be claimed to be a lot like 2004 also because Bonnie took a similar track to both of those. Also, with the exception of the weak TS's earlier this year, the real active phase didnt take place this season until the beginning of August but I dont see anyone claiming a season parallel to that yet either. Theres a lot more going into it than just a track or two taking a similar direction. Its about the synoptic setup as a whole and how it evolves over time. Determining a season analog cannot be done with one or two storms just because they have similar tracks.

Of course I could also point out how the "A" storms both formed in May off the SE Coast or how the "C" storms in both years both formed between Bermuda and the Bahamas and moved to the North Atlantic. But aside from all of that, I guess they're not similar at all.

Yeah, they really aren't. 'A' storms that form in may are usually subtropical in origin and often form off the southeast coast, and the paths and intensities of the storms you mention are fairly common for early season tropical systems in general. Its just general climatology. Aside from that, the attempted comparison at hand is one between Ernesto and TD7 (a system thats only been numbered for a few hours now) and Dean and Felix (the two most recent cat5s in the atlantic and the only time IN HISTORY that 2 cat5s have made landfall in the same season, let alone a couple weeks from each other) just because they have/may make landfall in similar areas. Sorry, but thats a bit of a stretch to me.

[Nederlander]

Ernie's biggest issue, IMO, wasn't dry air, it was the llc continuously outrunning the mlc. He never could get a stacked shot to 200mb in the central/eastern Caribbean. Otherwise, I think he could have digested the small amount of midlevel dry air that he encountered. And if you believe the BAM suite, being too fast for your own good looks to be the fate for TD7 as well.. Things change daily though. Won't be paying too much attention to this for a while.

This may sound like a silly question, but what causes the speed of tropical waves coming off of Africa to vary as they develop in the open waters of the Atlantic? Also, what is the maximum speed a system can be moving and still attain a developing core without the lower and mid levels continuing to separate?

I may not be the best person to answer so I'll give you my knowledge and defer to a pro-met for further info or corrections. Basically the speed a system has is largely dictated by the general atmospheric flow in the troposphere. There are other steering mechanisms at work as well though. For instance high pressure ridges can dictate a lot with forward speed of systems. Tropical systems start tapping the brakes when they begin sensing a ridge in their path and head toward the path of least resistance, or in some cases completely stall out until something gives. As far as a baseline speed that makes it possible for a storm to stack, the best answer I can give is that it varies. Think of forward movement as a type of shear. If a developing system is trucking along at 10-12 kts, it'll be far easier to stack versus moving at 20 kts, assuming all other variables are equal. Faster moving systems can shear themselves apart sometimes.

[ROCK]

00Z CMC takes whats left of TD7 up thru the Yucatan channel.....strong wave.....also see 93L as just a wave also....


http://moe.met.fsu.edu/cgi-bin/cmctc2.c ... =Animation

[ROCK]

still see its fighting the SAL.....that anomaly to the SW is probably not helping either....needs to deepen and draw that sucker into it.....moving so fast though....should slow down as it gets closer to the islands

[Weatherfreak000]

CMC looks pretty interesting, track might be a tad North. Appears there is a conducive environment near the Eastern Caribbean that TD7 would take advantage of which appears to be validated by shear and dry air maps. At the end of the run it appears to be deepening again moving towards the WNW-NW into Cuba?

Interesting stuff. EURO might be helpful, perhaps the weakness is stronger on this run?

[fci]

for what its worth jb says forget about anything thru the 20th. he said that on bloomberg news. said td7 will fall apart. he does say he is warning his weatherbell clients the SE coast is at risk aug20th-sept5th. from what im not sure.

I think it would safe to say that every year, the SE Coast is at risk from August 20th-September 5th.

[Hurricane Alexis]

Still a TD.

AL, 07, 2012081006, , BEST, 0, 136N, 463W, 30, 1008, TD,

[meriland23]

Funny that NHC keeps it as a TS without a curve round 75w like most models suggest. Is this anticipated shear not looking to be as much of a threat as it did? If it gets to 17N 80W+...iono.. if it gets pushed by then, would Florida and the keys be in trouble? Otherwise it is all the GOM and who knows where it wants to end up there. It would have to go ENE just to avoid florida completely if it ends up inside of the coordinates.

[meriland23]

for what its worth jb says forget about anything thru the 20th. he said that on bloomberg news. said td7 will fall apart. he does say he is warning his weatherbell clients the SE coast is at risk aug20th-sept5th. from what im not sure.

I think it would safe to say that every year, the SE Coast is at risk from August 20th-September 5th.

'Forget' about anything thru the 20th? Well that is quite the balsy statement. Does he have conversations with mother nature? Do they make plans? You can't put a specific date of when a specific part of the country is at risk. What about Charlie? Connie? There are quite a few that happened before the 20th of August.

[Weatherfreak000]

He's a forecaster it's all about the ballsy decisions. I don't really know what to believe when I see his predictions but it can be entertaining.

TD 7 blossoming convection overnight. Diurnal maxima anyone? I expect to see a healthier storm tomorrow. This one may still be Gordon first yet.

[christchurchguy]

Vis image


Uploaded with ImageShack.us

[Nimbus]

We are getting to the longitude that Ernesto started to intensify and break away from the ITCZ. The TUTT to the north has been providing light shear but that will diminish as TD7 approaches Guadalupe. The NHC track looks about right for a TD/TS, who knows exactly if/when it decides to spin up.

The current track is just far enough north passing close to Jamaica that the models will probably split on Mexico/gulf solutions for a while. Climo shows that storms that track north of Merida coming off the Yucatan historically tend to hook north and storms that exit the west coast of the Yucatan further south into the BOC usually continue west into Mexico.

[wxman57]

http://tropic.ssec.wisc.edu/real-time/windmain.php?&basin=atlantic&sat=wg8&prod=sht&zoom=&time=

Apologize to the admin for the confusion.


Taking a look at shear tendency profile shear is not an issue for either invest. It appears shear may not be sure a problem for TD7 for the short term. Man it's just coming in way too fast...given how negative features are present throughout the forecast period maybe it can outrun them.

That map shows shear 20-30 kts in Seven's path and increasing by 5-10 kts in the past 24 hrs. Shear definitely will be a problem at multiple levels, as well as dry air. Conditions in its path look as hostile or more so than for Ernesto.

[Gustywind]

000
WTNT32 KNHC 100840
TCPAT2

BULLETIN
TROPICAL DEPRESSION SEVEN ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
500 AM AST FRI AUG 10 2012

...TROPICAL DEPRESSION MOVING RAPIDLY WESTWARD...NO CHANGE IN
STRENGTH...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...13.6N 47.2W
ABOUT 930 MI...1495 KM E OF THE WINDWARD ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 20 MPH...32 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTERESTS IN THE WINDWARD ISLANDS SHOULD MONITOR THE PROGRESS OF
THIS SYSTEM. TROPICAL STORM WATCHES COULD BE REQUIRED LATER TODAY.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 AM AST...0900 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN
WAS LOCATED NEAR LATITUDE 13.6 NORTH...LONGITUDE 47.2 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 20 MPH...32 KM/H...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 48 HOURS.
ON THE FORECAST TRACK...THE DEPRESSION WILL APPROACH THE WINDWARD
ISLANDS SATURDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND THE DEPRESSION COULD BECOME A TROPICAL STORM LATER TODAY.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB...29.80 INCHES.

[Gustywind]

10/0545 UTC 13.7N 46.2W T1.5/1.5 07L
09/2345 UTC 13.7N 44.3W T1.5/1.5 07L

[Sanibel]

Looks like shear bait at that weakness.


Maybe it will burst closer to the islands.

[KWT]

That map shows shear 20-30 kts in Seven's path and increasing by 5-10 kts in the past 24 hrs. Shear definitely will be a problem at multiple levels, as well as dry air. Conditions in its path look as hostile or more so than for Ernesto.

Downright brutal is what I'd call it, its why I've been calling for it to die in the E.Caribbean for the last few days. That being said if it does survive it probably will find better conditions further west.

Track should eventually allow it into the NW Caribbean or the S.Gulf and I wouldn't be shocked if it re-forms there even if it does decay away.

[tolakram]

latest

[Aric Dunn]

Still hanging in there. Needs to slow down if its going to strengthen.