ATL: HELENE - Post-Tropical

[Gustywind]

000
WTNT32 KNHC 102337
TCPAT2

BULLETIN
TROPICAL DEPRESSION SEVEN INTERMEDIATE ADVISORY NUMBER 5A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
800 PM AST FRI AUG 10 2012

...TROPICAL DEPRESSION RACING WESTWARD...EXPECTED TO MOVE OVER THE
WINDWARD ISLANDS SATURDAY...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...13.8N 52.8W
ABOUT 450 MI...725 KM E OF BARBADOS
ABOUT 550 MI...890 KM E OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 24 MPH...39 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* GUADELOUPE AND MARTINIQUE
* DOMINICA
* ST. LUCIA
* BARBADOS
* ST. VINCENT AND THE GRENADINES
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE IN 24 TO 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM AST...0000 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN
WAS LOCATED NEAR LATITUDE 13.8 NORTH...LONGITUDE 52.8 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 24 MPH...39 KM/H...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH SUNDAY. ON THE
FORECAST TRACK...THE CENTER OF THE CYCLONE WILL BE NEAR THE
WINDWARD ISLANDS ON SATURDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS POSSIBLE OVER THE NEXT DAY OR SO...AND
THE DEPRESSION COULD BECOME A TROPICAL STORM BEFORE REACHING THE
ISLANDS.

NOAA BUOY 41040...LOCATED ABOUT 50 MILES...80 KM...NORTH-NORTHWEST
OF THE CENTER OF THE DEPRESSION...RECENTLY REPORTED A SUSTAINED
WIND OF 36 MPH...57 KM/H...AND A GUST OF 40 MPH...65 KM/H.

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


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA
SATURDAY AND SATURDAY NIGHT.

RAINFALL...TOTAL RAINFALL ACCUMULATIONS OF 1 TO 2 INCHES WITH
ISOLATED MAXIMUM AMOUNTS OF 3 INCHES ARE EXPECTED ACROSS PORTIONS
OF THE LESSER ANTILLES THROUGH SATURDAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 PM AST.

$$
FORECASTER BRENNAN

[Gustywind]

10/2345 UTC 13.7N 53.0W T1.5/1.5 07L
10/1745 UTC 13.8N 51.1W T1.5/1.5 07L

[ozonepete]

Thanks, Luis, for the RECON info. So we will find out a lot from the land obs before then. Hopefully they won't be significant! everyone take care there anyway, just in case.

[RL3AO]

moving west at 24mph and has upper level winds from the southwest...gee wonder why its struggling?

[ROCK]

I knew I would get some hits off that NOGAPS run....yeah goes over all the islands and remains intact....but once in the GOM it goes bonkers....only point I was making....

[RL3AO]

Guadeloupe sounding.



Look at the difference between the lower and middle level winds.

[ozonepete]

Guadeloupe sounding.

http://i44.photobucket.com/albums/f38/RL3AO/tffr.gif

Look at the difference between the lower and middle level winds.

There isn't much. 25 to 35 knots.

25 knots at 950mb near the surface, 25 knots at 700mb and 35 knots at about 640mb.

That's a 10 knot difference.

[RL3AO]

GFS at 24hr

700mb



300mb



Look at the difference in the Caribbean. 30+kt easterlies at 700mb and 10 to 15kt NE winds from 300mb. Too much shear. I'd be surprised if he can even make it near Jamaica without opening up or dissipating.

[RL3AO]

Guadeloupe sounding.

http://i44.photobucket.com/albums/f38/RL3AO/tffr.gif

Look at the difference between the lower and middle level winds.

There isn't much. 25 to 35 knots.

25 knots at 950mb near the surface, 25 knots at 700mb and 35 knots at about 640mb.

That's a 10 knot difference.

I should have said upper levels (300 and 400mb). Convection develops but gets sheared once it gets strong enough to get up to 400mb or higher.

[Kingarabian]

Consensus models shifted north because both the NOGAPS (worthless model) and UKMET take 7 north of the Caribbean toward the eastern Bahamas. That's unlikely, given the projected ridge (by GFS/Euro) building to its north. That ridge is forecast to extend form the Bahamas to Texas by next Wednesday. Throw those two models out and you have a track very much like Ernesto, except that this system may not survive the shear and dry air.

Why is the NOGAPS worthless lol?

I would love to explain... but I don't know where to start.

[ozonepete]

I should have said upper levels (300 and 400mb). Convection develops but gets sheared once it gets strong enough to get up to 400mb or higher.

But at 400mb the wind is 5 knots and at 300mb it's 10 knots. So there's no shear at all at 400mb and around 300mb we expect winds to go light as you look for an anticyclone to start showing its presence. ??

[ozonepete]

Yes there is shear thru the entire layer. See later posts.

[RL3AO]

I should have said upper levels (300 and 400mb). Convection develops but gets sheared once it gets strong enough to get up to 400mb or higher.

But at 400mb the wind is 5 knots and at 300mb it's 10 knots. So there's no shear at all at 400mb and around 300mb we expect winds to go light as you look for an anticyclone to start showing its presence. ??

If the winds are 30kt at 700mb and 5kt at 400mb thats shear.

[brunota2003]

I should have said upper levels (300 and 400mb). Convection develops but gets sheared once it gets strong enough to get up to 400mb or higher.

But at 400mb the wind is 5 knots and at 300mb it's 10 knots. So there's no shear at all at 400mb and around 300mb we expect winds to go light as you look for an anticyclone to start showing its presence. ??

Down around the 700 to 600 millibar range, winds are 25 to 35 knots...up at 400 mb it is around 5 knots...that is a pretty big difference for something that needs to stay vertically stacked!

Within a 24 hour period, something at the 600 mb level is going to go 840 nautical miles, at 400 mb it is only going to go 120 nm.

[ozonepete]

Hey RLA30 so sorry! I completely misread your sounding. Yeah sure there's shear there. I often misread the mid and upper levels because I try to convert them to feet in my head. I need to take a break. Sorry my friend.

[cycloneye]

BULLETIN
TROPICAL DEPRESSION SEVEN ADVISORY NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
1100 PM AST FRI AUG 10 2012

...TROPICAL DEPRESSION HEADING FOR THE WINDWARD ISLANDS ON
SATURDAY...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.9N 54.1W
ABOUT 365 MI...590 KM E OF BARBADOS
ABOUT 465 MI...750 KM E OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 24 MPH...39 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* GUADELOUPE AND MARTINIQUE
* DOMINICA
* ST. LUCIA
* BARBADOS
* ST. VINCENT AND THE GRENADINES

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE IN 24 TO 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM AST...0300 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN
WAS LOCATED NEAR LATITUDE 13.9 NORTH...LONGITUDE 54.1 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 24 MPH...39 KM/H...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH SUNDAY. ON THE
FORECAST TRACK THE DEPRESSION IS EXPECTED TO APPROACH THE WINDWARD
ISLANDS ON SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS POSSIBLE OVER THE NEXT DAY OR SO...AND
THE DEPRESSION COULD BECOME A TROPICAL STORM BEFORE REACHING THE
WINDWARD ISLANDS.

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


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA
SATURDAY AND SATURDAY NIGHT.

RAINFALL...TOTAL RAINFALL ACCUMULATIONS OF 1 TO 2 INCHES WITH
ISOLATED MAXIMUM AMOUNTS OF 3 INCHES ARE EXPECTED ACROSS PORTIONS
OF THE LESSER ANTILLES THROUGH SATURDAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...200 AM AST.
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BRENNAN

WTNT42 KNHC 110233
TCDAT2

TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
1100 PM AST FRI AUG 10 2012

WHILE THERE HAS BEEN SOME INCREASE IN DEEP CONVECTION NEAR THE
CENTER OVER THE PAST FEW HOURS...THE OVERALL CLOUD PATTERN REMAINS
RATHER SHAPELESS WITH LITTLE EVIDENCE OF BANDING. SATELLITE
ESTIMATES ARE STILL T1.5 FROM TAFB AND SAB...AND THE INITIAL
INTENSITY OF 30 KT IS BASED ON A 1-MINUTE WIND OBSERVATION AT NOAA
BUOY 41040 OF 31 KNOTS AT 2246Z. THE ENVIRONMENT IS CURRENTLY
MARGINAL FOR INTENSIFICATION...AND THE SHIPS MODEL SHOWS THE SHEAR
INCREASING ABOVE 20 KT IN THE NEXT DAY OR SO AS AN UPPER-LEVEL
TROUGH AMPLIFIES TO THE NORTHWEST OF THE CYCLONE. THE NEW NHC
FORECAST SHOWS THE DEPRESSION BECOMING A TROPICAL STORM IN 12 HOURS
WITH LITTLE CHANGE AFTER THAT TIME UNTIL DISSIPATION IN 72 HOURS.
THIS SCENARIO IS SUPPORTED BY THE GFS AND ECMWF GLOBAL MODELS...
WHICH CONTINUE TO SHOW THE CYCLONE DEGENERATING INTO A TROUGH OVER
THE EASTERN OR CENTRAL CARIBBEAN SEA IN 2 TO 3 DAYS.

THE DEPRESSION CONTINUES TO MOVE RAPIDLY WESTWARD WITH AN INITIAL
MOTION OF 275/21. THIS MOTION IS EXPECTED TO CONTINUE THROUGH
DISSIPATION AS THE TROPICAL CYCLONE IS STEERED BY THE ATLANTIC
SUBTROPICAL RIDGE TO THE NORTH. THE NEW NHC FORECAST IS AN UPDATE
OF THE PREVIOUS ONE AND IS CLOSE TO A CONSENSUS OF THE GFS AND
ECMWF MODELS.

GIVEN THE CONTINUING UNCERTAINTY AS TO WHETHER THE DEPRESSION WILL
BECOME A TROPICAL STORM...TROPICAL STORM WATCHES CONTINUE FOR PART
OF THE LESSER ANTILLES...EVEN THOUGH TROPICAL STORM CONDITIONS
WOULD REACH THOSE LOCATIONS WITHIN THE NEXT 24 TO 36 HOURS.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 13.9N 54.1W 30 KT 35 MPH
12H 11/1200Z 14.1N 57.0W 35 KT 40 MPH
24H 12/0000Z 14.3N 60.8W 35 KT 40 MPH
36H 12/1200Z 14.6N 64.7W 35 KT 40 MPH
48H 13/0000Z 14.8N 68.7W 35 KT 40 MPH
72H 14/0000Z...DISSIPATED

$$
FORECASTER BRENNAN

[ozonepete]

The one thing it does show well is that the shear isn't coming from strong upper level winds. It is coming from the very fast speed of the TC itself at lower and low to mid levels.

[RL3AO]

Anyone know what the pattern difference was for Dean/Felix and this year? Both had very strong ridging causing the due west path but obviously Dean and Felix didn't have the shear problem. Was it just the fact that the easterlies wern't as strong in 2007?

[AJC3]

Anyone know what the pattern difference was for Dean/Felix and this year? Both had very strong ridging causing the due west path but obviously Dean and Felix didn't have the shear problem. Was it just the fact that the easterlies wern't as strong in 2007?

Seems to be the most reasonable scenario. If you reconstruct 850 and 250 MB winds/anomalies from that year, you'd get your answer for sure.

[Gustywind]

BULLETIN
TROPICAL DEPRESSION SEVEN ADVISORY NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
1100 PM AST FRI AUG 10 2012

...TROPICAL DEPRESSION HEADING FOR THE WINDWARD ISLANDS ON
SATURDAY...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.9N 54.1W
ABOUT 365 MI...590 KM E OF BARBADOS
ABOUT 465 MI...750 KM E OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 24 MPH...39 KM/H
MINIMUM CENTRAL PRESSURE...1009 MB...29.80 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* GUADELOUPE AND MARTINIQUE
* DOMINICA
* ST. LUCIA
* BARBADOS
* ST. VINCENT AND THE GRENADINES
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...IN THIS CASE IN 24 TO 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM AST...0300 UTC...THE CENTER OF TROPICAL DEPRESSION SEVEN
WAS LOCATED NEAR LATITUDE 13.9 NORTH...LONGITUDE 54.1 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST NEAR 24 MPH...39 KM/H...AND
THIS GENERAL MOTION IS EXPECTED TO CONTINUE THROUGH SUNDAY. ON THE
FORECAST TRACK THE DEPRESSION IS EXPECTED TO APPROACH THE WINDWARD
ISLANDS ON SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS POSSIBLE OVER THE NEXT DAY OR SO...AND
THE DEPRESSION COULD BECOME A TROPICAL STORM BEFORE REACHING THE
WINDWARD ISLANDS.

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


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA
SATURDAY AND SATURDAY NIGHT.

RAINFALL...TOTAL RAINFALL ACCUMULATIONS OF 1 TO 2 INCHES WITH
ISOLATED MAXIMUM AMOUNTS OF 3 INCHES ARE EXPECTED ACROSS PORTIONS
OF THE LESSER ANTILLES THROUGH SATURDAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...200 AM AST.
NEXT COMPLETE ADVISORY...500 AM AST.

$$
FORECASTER BRENNAN