Flhurricane.com - Central Florida Hurricane Center - Tracking Storms since 1995Hurricanes Without the Hype! Since 1995
The Atlantic is quiet
|
Show Selection: |
| #535921 (Received by flhurricane at: 4:53 PM 21.Aug.2012) TCDAT4 TROPICAL STORM ISAAC DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012 500 PM AST TUE AUG 21 2012 AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION REPORTED 44-KT FLIGHT-LEVEL WINDS AT 1000 FT TO THE NORTHEAST OF THE CENTER...AS WELL AS BIAS-CORRECTED SFMR SURFACE WINDS ESTIMATES OF 35 KT. THE MINIMUM CENTRAL PRESSURE WAS NEAR 1005 MB. BASED ON THESE DATA...THE DEPRESSION IS UPGRADED TO TROPICAL STORM ISAAC. DESPITE THE UPGRADE...THE CYCLONE REMAINS SOMEWHAT DISORGANIZED...WITH THE LOW-LEVEL CENTER PARTLY EXPOSED TO THE NORTH OF THE MAIN CONVECTIVE MASS. THE LOW-LEVEL CENTER HAS NUDGED NORTHWARD DURING THE AFTERNOON...BUT THE LONGER TERM MOTION IS 275/15. ISAAC REMAINS SOUTH OF A DEEP-LAYER SUBTROPICAL RIDGE THAT IS FORECAST TO REMAIN INTACT FOR THE NEXT 72 HR...WHICH SHOULD KEEP THE CYCLONE MOVING GENERALLY WESTWARD AS SHOWN BY THE TIGHTLY CLUSTERED TRACK MODEL GUIDANCE. AFTER THAT...THE GLOBAL MODELS CONTINUE TO FORECAST A SHORTWAVE TROUGH TO DIG SOUTHWARD OVER THE SOUTHEASTERN U.S. AND THE GULF OF MEXICO...WHICH IS EXPECTED TO WEAKEN THE RIDGE ACROSS FLORIDA AND THE BAHAMAS. THIS SHOULD ALLOW THE CYCLONE TO TURN WEST- NORTHWESTWARD AND SLOW DOWN OVER THE NORTH-CENTRAL CARIBBEAN SEA AND THE GREATER ANTILLES. THE GUIDANCE HAS BECOME LESS CONSISTENT SINCE THE PREVIOUS ADVISORY. WHILE THE CENTER OF THE GUIDANCE ENVELOPE HAS CHANGED LITTLE...THE ECMWF HAS SHIFTED WELL TO THE LEFT OF ITS PREVIOUS FORECAST AND NOW CALLS FOR A WESTWARD MOTION AFTER ISAAC PASSES HISPANIOLA. THE GFS ENSEMBLES HAVE ALSO SHIFTED WESTWARD...ALTHOUGH THE ENSEMBLE MEAN STILL LIES NEAR THE FORECAST TRACK. THE NEW TRACK IS NUDGED A LITTLE TO THE NORTH OF THE PREVIOUS TRACK BEFORE 72 HR...AND THEN IS NUDGED A LITTLE TO THE RIGHT THEREAFTER. THE TRACK FORECAST AFTER 72 HR LIES NEAR THE LEFT EDGE OF THE GUIDANCE ENVELOPE...WITH ONLY THE ECMWF WELL TO THE LEFT OF THE CURRENT FORECAST. USERS ARE CAUTIONED THAT FIVE-DAY TRACK ERRORS AVERAGE ABOUT 225 N MI. ISAAC CONTINUES TO EXPERIENCE SOME LIGHT NORTHEASTERLY VERTICAL WIND SHEAR...AND IT MAY NOT YET HAVE FULLY MIXED OUT THE DRY AIR THAT HAS BEEN AFFECTING IT. THE SHEAR IS FORECAST TO DIMINISH IN 12-24 HR...WHICH SHOULD ALLOW SOME STRENGTHENING. THAT BEING SAID...THE GFDL AND HWRF MODELS HAVE BACKED OFF ON THEIR FORECASTS OF INTENSIFICATION...AND THE SHIPS AND LGEM MODELS ARE ALSO LESS BULLISH. BASED ON THIS...THE NEW INTENSITY FORECAST SHOWS A LITTLE LESS STRENGTHENING THAN THE PREVIOUS ADVISORY. THE INTENSITY FORECAST AFTER 72 HR HAS AGAIN BEEN REDUCED DUE TO THE FORECAST TRACK SHOWING INCREASED LAND INTERACTION WITH HISPANIOLA AND CUBA. FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 15.4N 53.9W 35 KT 40 MPH 12H 22/0600Z 15.6N 56.4W 40 KT 45 MPH 24H 22/1800Z 15.9N 59.8W 45 KT 50 MPH 36H 23/0600Z 16.3N 63.1W 50 KT 60 MPH 48H 23/1800Z 16.6N 66.3W 65 KT 75 MPH 72H 24/1800Z 17.0N 71.0W 75 KT 85 MPH 96H 25/1800Z 19.5N 75.0W 75 KT 85 MPH 120H 26/1800Z 21.5N 78.0W 65 KT 75 MPH...INLAND $$ FORECASTER BEVEN |
