8:00 PM EDT Sun Aug 26

Location: 24.1°N 82.6°W

Moving: WNW at 15 mph

Min pressure: 991 mb

Max sustained: 65 mph

 

TROPICAL STORM ISAAC DISCUSSION NUMBER  23

NWS NATIONAL HUR

RICANE CENTER MIAMI FL       AL092012

500 PM EDT SUN AUG 26 2012

 

ALTHOUGH SATELLITE AND RADAR IMAGES HAVE SUGGESTED THAT THE TROPICAL CYCLONE WAS BECOMING A LITTLE BETTER ORGANIZED…AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING ISAAC THIS AFTERNOON HAVE FOUND THAT THERE HAS BEEN NO STRENGTHENING OF THE STORM.

FLIGHT-LEVEL AND SFMR-OBSERVED WINDS SUPPORT AN INTENSITY OF 50 KT.

THERE IS STILL A WELL-ESTABLISHED UPPER-LEVEL OUTFLOW PATTERN OVER

THE SYSTEM…AND VERTICAL SHEAR SHOULD REMAIN FAIRLY LIGHT FOR THE

NEXT COUPLE OF DAYS.  INTENSIFICATION STILL SEEMS LIKELY AS ISAAC

MOVES OVER THE EASTERN GULF

…AND POSSIBLY OVER THE HIGHER HEAT

CONTENT OF THE LOOP CURRENT.  THE OFFICIAL INTENSITY FOREAST IS

CLOSE TO THE LATEST LGEM GUIDANCE…AND NOT MUCH DIFFERENT FROM THE

PREVIOUS NHC FORECAST.

 

ISAAC HAS MOVED A LITTLE TO THE LEFT OF PREVIOUS PROJECTIONS AND

CENTER FIXES YIELD A 6- TO 12-HOUR AVERAGED MOTION OF 295/15.   THE

TRACK FORECAST CONTINUES TO BE CHALLENGING.  THE DYNAMICAL MODELS

SHOW THE TROPICAL STORM/HURRICANE GRADUALLY TURNING TO THE RIGHT

AND HEADING FOR A BREAK IN THE SUBTROPICAL RIDGE.  HOWEVER…THERE

ARE SUBSTANTIAL DIFFERENCES AMONG THE MOST RELIABLE MODELS AS TO

WHERE ISAAC MIGHT CROSS THE NORTHERN GULF COAST.  THE U.K. MET.

OFFICE AND ECMWF MODELS ARE ABOUT 300 N MI TO THE EAST OF THE GFS

AT LANDFALL.  IT SHOULD BE NOTED THAT NEARLY ALL OF THE GFS ENSMEBLE

MEMBERS ARE EAST OF THE GFS CONTROL TRACK.  BECAUSE OF THE WIDE

MODEL SPREAD…THERE CONTINUES TO BE GREATER THAN USUAL TRACK

FORECAST UNCERTAINTY.

 

THROUGHOUT THE PERIOD…IT IS IMPORTANT NOT TO FOCUS ON THE EXACT

FORECAST TRACK DUE TO FORECAST UNCERTAINTIES AND THE FACT THAT

SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER.

 

THE OFFICIAL FORECAST TRACK AND WIND RADII NECESSITATE THE ISSUANCE

OF A HURRICANE WARNING FOR THE NORTHERN GULF COAST AT THIS TIME.

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  26/2100Z 24.2N  82.3W   50 KT  60 MPH

12H  27/0600Z 25.1N  83.9W   55 KT  65 MPH

24H  27/1800Z 26.3N  85.9W   60 KT  70 MPH

36H  28/0600Z 27.7N  87.6W   70 KT  80 MPH

48H  28/1800Z 28.9N  88.5W   80 KT  90 MPH

72H  29/1800Z 30.7N  89.5W   85 KT 100 MPH…INLAND

96H  30/1800Z 32.5N  90.0W   30 KT  35 MPH…INLAND

120H  31/1800Z 34.5N  90.0W   20 KT  25 MPH…INLAND