ATL HANNA: Extratropical - Discussion

[BigA]

Once again it looks like the LLC is being pulled eastward toward the deep convection....similar thing happened last night.

[x-y-no]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
301 PM EDT SAT AUG 30 2008

.DISCUSSION...

WED-SAT...HANNA FCST TO SLOWLY PUSH ACROSS THE BAHAMAS WED/THU...
AND BEYOND THEN IT`S REALLY ANYONE`S GUESS. LATEST 12Z GFS STALLS
HANNA BEFORE IT REACHES THE BAHAMAS AND TURNS IT SHARPLY NW TOWARD
THE CAROLINAS. CYCLONE SHOULD STILL BE EXPERIENCING SOME SHEAR
WED... BUT BEYOND THEN...WE`RE REALLY THROWING DARTS AS TO WHAT
KIND OF SHAPE HANNA WILL BE IN. EVENTUALLY THE CYCLONE SHOULD LIFT
NORTHWARD SOMEWHERE NEARBY AS MID LEVEL TROUGH ERODES THE WRN
PORTION OF THE STRONG ERN CONUS- WRN ATLC RIDGE. WILL KEEP GENERAL
STATUS QUO THRU THU...FOLLOWING OFFICIAL NHC/HPC FORECAST WHICH
BRINGS HANNA UP THE FL WEST COAST. SUFFICE IT TO SAY...CONFIDENCE
IN THE FCST FOR LATE NEXT WEEK IS LOW.

up the west coast????

That apparently was the thinking mid-day anyway ... This from the HPC long-term discussion:

EWD T.S.HANNA FORECAST TO BECOME A HURCN AND THEN WEAKEN TO STRONG
TS WITH MUCH INTENSITY FORECAST SPREAD. ALL GUIDANCE TAKES THIS
NWD AND THEN WWD WITH HURCN MODEL GUIDANCE THEN BECOMING MORE
ERRATIC AT DAY 5 WED-THU. GLOBAL DYNAMICAL MODELS HAVE BEEN MUCH
MORE CONSISTENT AND IN FAIRLY GOOD AGREEMENT ON ITS SW TRACK INTO
THE BAHAMAS BY DAY 5. ITS FUTURE DEPENDS MUCH UPON HOW MUCH
RIDGING BUILDS IN NORTH OF THE SYSTEM ACROSS THE MID ATLC STATES
AND ADJACENT ATLC AS THE RIDGING REPLACES AN EXITING MID LEVEL LOW
OFF THE MARITIMES.
CMC/GFS AND ECMWF AND ITS ENS MEAN HOLD ONTO THE RIDGE AND MOVE
HANNA AROUND ITS WEST PERIPHERY. BIGGEST QUESTION IS WHERE WILL
HANNA BE AS THE MID LEVEL EVOLVES. 00Z/06Z GFS/NOGAPS AND GFS ENS
MEAN GAIN THE HIGHEST LATITUDE IN THE BAHAMAS WITH HANNA ALLOWING
FOR A FUTURE DAYS 6 AND 7 TRACK MUCH MORE EWD TAKING HANNA INTO
THE SOUTHEAST COAST DAYS 6/7 AS DOES DGEX. CMC AND ECMWF START OUT
FROM DAY 5 AT LOWER LATITUDES AND MAKE THE NW AND N TURN ALONG THE
WEST COAST OF FL OR ERN GLFMEX. UKMET GOES THE FARTHEST SOUTH WITH
THIS SYSTEM ON THE SOUTH SIDE OF CUBA BY DAY 5. PREVIOUS YEARS THE
UKMET WAS ONE OF THE BETTER MODELS IN THE CARRIBEAN AND WRN ATLC
IF ONE ADJUSTED ITS LATITUDE SEVERAL DEGREES NWD. MAKING THIS
ADJUSTMENT WOULD PUT IT INTO THE ECMWF/CMC CAMP. BEGINNING FROM
THE TPC DAY 5 POSITION WHICH IS IN THE MIDDLE OF THE GROUPING..HPC
PREFERENCE WOULD BE AN ECMWF ENS MEAN AND PROGS HAVE BEEN ADJUSTED
FOR THIS FOR DAYS 6 AND 7 FRI/SAT. THIS IS WITHIN THE SPREAD
ENVELOPE ON THE WEST SIDE TAKING HANNA FROM THE FL STRAITS FRI
ALONG THE WEST FL COAST TO NEAR APALACHEE BAY SAT. THIS SOLUTION
IS ALSO SLOWER THAN ALL OP MODELS BUT IN LATITUDINAL AGREEMENT OF
BOTH GFS AND ECMWF ENS MEANS. SEE TPC
FORCASTS/ADVISORIES/DISCUSSION OF HANNA.

[OuterBanker]

Thanks John. Until your post I had never seen the anagram in carp

I think we all need a lighter moment right now.

[fci]

WOW, is this going to be a giant circulation. Was it the EURO that was predicting the massive size of Hanna. Amazing!!

Yup, and it's going to be knocking at my door in the not too distant future

You "should" be facing a pretty well sheared, disorganized system when it passes a little bit north of you.

[Evil Jeremy]

WNW at the end of the run, all of SFL in the cone:

http://www.wunderground.com/tropical/tr ... ml#a_topad

[jlauderdal]

WNW at the end of the run, all of SFL in the cone:

http://www.wunderground.com/tropical/tr ... ml#a_topad

well that wsw idea didnt last long at nhc, lets hope that northerly shear builds in ajc3 has been talking about because if it doesnt, watch out, ortt mentioned the high building overhead and at least giving the system a chance take up alot of real estate which should allow for intensification , all interests from key west up to NC better pay alot closer attention to this than cat 4 gus

[Evil Jeremy]

18z GFS, which starts in a half hour, should be interesting.

[gatorcane]

big shift in the cone to the north.....

[fci]

Well, let's be glad that the "extrap" is not what guides us.

If it did, then the center would be 7.5 miles from me on Saturday the 6th.

So, the "latest" NHC track seems to show the start of the turn to the NW which would allow her to bypass us here in SE Fl. Unlike yesterday at this time where the turn was SW and would allow her to bypass us to the south.

What are the odds that it changes 24 hours from now??????

[Trader Ron]

big shift in the cone to the north.....

Yep. Now the big question, does Hanna miss Florida ?

[HURAKAN]

VERY IMPORTANT:

5 PM Discussion.

"With all of that said...there is very low confidence in the track forecast"

[Bocadude85]

Well, let's be glad that the "extrap" is not what guides us.

If it did, then the center would be 7.5 miles from me on Saturday the 6th.

So, the "latest" NHC track seems to show the start of the turn to the NW which would allow her to bypass us here in SE Fl. Unlike yesterday at this time where the turn was SW and would allow her to bypass us to the south.

What are the odds that it changes 24 hours from now??????

hmm lets see it has missed us to the south and now to the north lol only option left is to hit us

[sfwx]

The forecast doesn't show much strengthening. Also the discussion of a sub tropical system is interesting.


000
WTNT43 KNHC 302048
TCDAT3
TROPICAL STORM HANNA DISCUSSION NUMBER 11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008
500 PM EDT SAT AUG 30 2008

THE CLOUD PATTERN OF HANNA HAS CHANGED QUITE A BIT DURING THE DAY
TODAY. THE TROPICAL STORM HAS BECOME INVOLVED WITH THE UPPER-LEVEL
LOW THAT WAS LOCATED TO ITS WEST...AND HANNA NOW HAS SOME
RESEMBLANCE OF A SUB-TROPICAL CYCLONE. EVEN THOUGH THE CENTER IS
LOCATED WELL SOUTHWEST OF THE THUNDERSTORM ACTIVITY...BANDING OVER
THE NORTHEASTERN SEMICIRCLE STILL YIELD INTENSITY ESTIMATES OF T3.0
OR 45 KT FROM BOTH AGENCIES.

HANNA HAS BEEN MOVING BETWEEN THE WEST AND WEST-NORTHWEST AT
ABOUT 7 KT TODAY. A SIMILAR MOTION IS FORECAST BY THE NUMERICAL
MODEL GUIDANCE FOR THE NEXT 24-36 HOURS...SO VERY LITTLE CHANGE WAS
NEEDED TO THE PREVIOUS FORECAST DURING THAT TIME. THEREAFTER...THE
MODEL SPREAD HAS BECOME EXTREMELY LARGE AS A STRONG HIGH PRESSURE
RIDGE BUILDS OVER THE EASTERN UNITED STATES. THE TRACK GUIDANCE NOW
PREDICTS A SLOW AND ERRATIC MOTION OF HANNA DURING THE 48 TO ABOUT
96 HOUR TIME FRAME. THE GFDL AND HWRF BOTH PREDICT HANNA TO MAKE A
CYCLONIC LOOP NEAR THE SOUTHEASTERN BAHAMAS. MEANWHILE...THE ECMWF
AND UKMET SHOW A SOUTHWESTWARD MOTION...WITH THE LATTER MODEL
FORECASTING HANNA TO BE OVER EASTERN CUBA. BEYOND 96 HOURS...
NEARLY ALL OF THE GUIDANCE...EXCEPT THE UKMET...NOW FORECAST A
WEST-NORTHWESTWARD OR NORTHWESTWARD MOTION TO RESUME AS THE RIDGE
OVER THE EASTERN UNITED STATES WEAKENS. WITH ALL OF THAT SAID...
THERE IS VERY LOW CONFIDENCE IN THE TRACK FORECAST. THE NEW TRACK
SLOWS DOWN THE STORM CONSIDERABLY...AND NOW PREDICTS A SLOW
WEST-NORTHWESTWARD MOTION LATE IN THE PERIOD. THE NHC TRACK IS A
LITTLE SOUTH OF THE CONSENSUS...ESPECIALLY AT DAY 5...BUT IS IN
GENERAL AGREEMENT WITH THE 12Z ECMWF.

GIVEN ALL THE UNCERTAINTIES IN THE TRACK FORECAST...THE INTENSITY
FORECAST SEEMS JUST AS DIFFICULT. THE DYNAMICAL MODELS AND SHIPS
GUIDANCE SUGGEST THAT WEST TO NORTHWESTERLY SHEAR WILL CONTINUE
DURING THE NEXT 24-36 HOURS...FOLLOWED BY AN INCREASE IN NORTHERLY
SHEAR. GIVEN THE UNCERTAINTIES AS TO HOW HANNA WILL RESPOND TO THE
SHEAR...THE INTENSITY FORECAST ALLOWS FOR SOME STRENGTHENING IN THE
SHORT-TERM...BUT LEVELS OFF THE INTENSITY BETWEEN 36-96 HOURS.
THERE ARE SOME INDICATIONS THAT THE UPPER-LEVEL ENVIRONMENT COULD
BECOME MORE CONDUCIVE VERY LATE IN THE PERIOD...SO SLIGHT
STRENGTHENING IS INDICATE AT DAY 5. THE NHC FORECAST REMAINS BELOW
ALL OF THE RELIABLE INTENSITY GUIDANCE.

THE 12-FT SEA RADII WERE ADJUSTED OUTWARD OVER THE NORTHWESTERN
SEMICIRCLE BASED ON REPORTS FROM NOAA BUOY 41046.

FORECAST POSITIONS AND MAX WINDS

INITIAL 30/2100Z 22.4N 67.2W 45 KT
12HR VT 31/0600Z 22.8N 68.6W 45 KT
24HR VT 31/1800Z 23.3N 70.2W 50 KT
36HR VT 01/0600Z 23.5N 71.4W 55 KT
48HR VT 01/1800Z 23.5N 72.1W 55 KT
72HR VT 02/1800Z 23.5N 72.8W 55 KT
96HR VT 03/1800Z 24.0N 74.0W 55 KT
120HR VT 04/1800Z 25.0N 76.5W 60 KT

$$
FORECASTER BROWN

[KWT]

This really looks like Philleppe right in 05, ironically Rita was powering up in the gulf as well, so hardly surprised this has happened, I seriously doubt Hanna does anything major and may well go subtropical, who knows!

[Blown Away]

VERY IMPORTANT:

5 PM Discussion.

"With all of that said...there is very low confidence in the track forecast"

The NHC is putting their "low" confidence in the EURO which moves Hanna into E Central FL going NW then NNW up into Georgia. The EURO has been good w/ Hanna so maybe we should continue to follow the Euro. It's all about timing, I think yesterday Hanna was moving through the Keys on Thursday up the W coast of FL on Friday. Now Hanna doesn't make it to the FL EC until Friday and is making that same turn up into FL EC. IMO, If Hanna's track speeds up she goes S, if the track slows down even more maybe misses SFL to the E. Rate now it's coming at me and maybe that's the place to be 5 days out.

[HURAKAN]

AccuWeather sticks to their forecast.

[lbvbl]

I'm surprised they made such a dramatic shift. There is now no SW dip. What happens at the end? Does it continue NW and miss FL altogether, or does it go W or WNW and hit FL?

[Blown Away]

I'm surprised they made such a dramatic shift. There is now no SW dip. What happens at the end? Does it continue NW and miss FL altogether, or does it go W or WNW and hit FL?

The NHC was following the ECMWF model and that goes into FL somewhere between WPB and Cap Canaveral, then NW to NNW through the State into Georgia.

[tolakram]

[HURAKAN]

Convection developing over center.