For the general user, this may of interest - from NCEP:

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1000 AM EDT WED AUG 22 2012

VALID 12Z SUN AUG 26 2012 - 12Z WED AUG 29 2012

...HURCN ISAAC MAY IMPACT FL DURING THE D5-D7 TIME PERIOD...

THE MAJOR THREAT DURING THE MEDIUM RANGE TIME FRAME WILL BE WITH
HURCN ISAAC WHICH IS CURRENTLY CHURNING THE WATERS NEARBY THE
LESSER ANTILLES. THE LATEST NHC TRACK SUGGESTS THIS TROPICAL
SYSTEM WILL BE LOCATED JUST EAST OF CUBA BY 25/1200Z WITH A
GENERAL SHIFT TOWARD THE NORTHWEST CARRYING IT NEAR THE FL KEYS BY
27/1200Z. FCST MODELS SUGGEST A WEAKNESS IN THE MID-LEVEL RIDGE
AXIS SHOULD EVENTUALLY LIFT ISAAC TOWARD THE SERN U.S. BY MID-NEXT
WEEK. UNFORTUNATELY...THE CURRENT 06Z/00Z MODEL SUITE HAS A
VARIETY OF SOLNS PRESENTED THEREBY COMPLICATING MATTERS FOR
INTERESTED PARTIES ACRS THE SERN U.S. THE CURRENT TRACK INDICATED
BY THE NHC GENERALLY FOLLOWS THE 00Z GFS/GEFS MEAN THRU D5 WITH
HPC CONTINUING ITS GENERALLY MOTION TOWARD THE NNW INTO CNTRL GA
BY THE END OF THE PERIOD. OF COURSE...PLEASE VISIT THE LATEST
TRACK OF HURCN ISAAC ON THE NHC WEBSITE AT www.NHC.NOAA.GOV.

ACRS THE REMAINDER OF THE CONUS...THE MID/UPPER PATTERN WILL
GRADUALLY BECOME MORE HIGH AMPLITUDE IN NATURE BY EARLY NEXT WEEK.
A MEAN NEG ANOMALY SHOULD BE FEATURED JUST TO THE WEST OF BRITISH
COLUMBIA WITH THIS AXIS OF HGT FALLS GRADUALLY SPREADING SERD
TOWARD VANCOUVER ISLAND/COASTAL PAC NW BY 27/1200Z. CONSIDERING
TELECONNECTIONS UTILIZING THIS NEG ANOMALY CENTER...A BROAD AXIS
OF MID-LEVEL RIDGING IS SUGGESTED OVER THE MIDDLE OF THE CONUS
WITH A GENERAL MAX ACRS THE NRN/CNTRL PLAINS. IN THIS OMEGA BLOCK
SIGNATURE...AN ELONGATED TROF AXIS WILL BE IN PLACE ALONG THE ERN
THIRD OF THE U.S. THIS FEATURE IN PARTICULAR WILL PLAY A CRUCIAL
ROLE IN HOW MUCH LATITUDE ISAAC WILL GAIN THROUGHOUT THE MEDIUM
RANGE PERIOD.

LOOKING AT THE DETERMINISTIC/ENS GUIDANCE AS A WHOLE...THE IDEA OF
THIS HIGH-AMPLITUDE PATTERN IS CONVEYED ACRS THE BOARD.
HOWEVER...THE TIMING/STRENGTH OF THE NRN STREAM TROF MOVING THRU
THE TN/OH VALLEYS AND ERN U.S. DOES VARY WHICH HAS IMPLICATIONS OF
THE EVENTUAL PATH OF ISAAC. CURRENTLY...THE 00Z ECMWF/ECMWF ENS
MEAN MAINTAIN A STRONG ENOUGH 500-MB RIDGE TO KEEP THE SYSTEM
SOUTH OF 30N. HOWEVER...THE REMAINING GUIDANCE...ESPECIALLY THE
GFS WHICH HAS MAINTAINED ITS SOLN THE PAST 4 RUNS...INSIST ON
ISAAC BEING DRAWN NWRD. OVERALL...HPC FAVORED A SOLN COMPRISING
THE 00Z GFS/GEFS MEAN WITH SOME COMPLIMENTS FROM THE 00Z UKMET
EARLY ON GIVEN ITS FAVORABLE HANDLING OF THE NRN STREAM.