| National Hurricane Center 000 WTNT41 KNHC 260847 TCDAT1 TROPICAL STORM ALEX DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010 500 AM EDT SAT JUN 26 2010 AN AIR FORCE RESERVE HURRICANE HUNTER INVESTIGATING TROPICAL DEPRESSION ONE REPORTED 925 MB FLIGHT-LEVEL WINDS OF 46 KT ABOUT 90 NM EAST OF THE CENTER...WHICH SUGGEST SURFACE WINDS OF NEAR 35 KT. THE STEPPED FREQUENCY MICROWAVE RADIOMETER ON THE AIRCRAFT SHOWED A LARGE AREA OF WINDS NEAR 35 KT THAT DID NOT APPEAR TO BE RAIN- CONTAMINATED. BASED ON THIS...THE DEPRESSION IS UPGRADED TO TROPICAL STORM ALEX WITH AN INITIAL INTENSITY OF 35 KT. THE AIRCRAFT DATA SUGGESTS THAT THE CIRCULATION OF ALEX REMAINS BROAD...AND THAT THE RECENTLY REPORTED CENTRAL PRESSURE OF 1004 MB MAY HAVE BEEN MEASURED IN A MESOSCALE LOW PRESSURE AREA. IT SHOULD BE NOTED THAT THE AIRCRAFT REPORTED SFMR WINDS IN EXCESS OF 40 KT WHICH APPEAR SUSPECT DUE TO RAIN CONTAMINATION. THE INITIAL MOTION REMAINS UNCERTAIN...WITH THE BEST ESTIMATE OF 285/7. FOR THE NEXT 24 TO 48 HOURS ALEX IS EXPECTED TO MOVE WEST-NORTHWESTWARD OR NORTHWESTWARD TO THE SOUTH OF A LOW/MID-LEVEL RIDGE CENTERED OVER THE EASTERN UNITED STATES. AFTER THAT...THE LARGE-SCALE MODELS FORECAST THE RIDGE TO WEAKEN AS A DEEP-LAYER TROUGH MOVES INTO THE EASTERN U. S. THERE REMAINS A SIGNIFICANT SPREAD IN THE MODEL GUIDANCE ON HOW THIS EVOLUTION WILL AFFECT ALEX. THE GFS...GFS ENSEMBLE MEAN...AND THE GFDL SHOW ENOUGH OF A BREAK IN THE RIDGE TO STEER ALEX NORTHWARD TOWARD THE NORTHWESTERN GULF COAST. THE ECMWF...NOGAPS...AND UKMET SHOW THE RIDGE REMAINING STRONG ENOUGH TO STEER ALEX GENERALLY WESTWARD INTO NORTHEASTERN MEXICO. THE HWRF AND THE CANADIAN MODELS ARE BETWEEN THESE EXTREMES. OVERALL...THE GUIDANCE ENVELOPE HAS SHIFTED WESTWARD SINCE THE LAST ADVISORY...SO THE NEW FORECAST TRACK WILL BE NUDGED WESTWARD AS WELL. HOWEVER...THE NEW TRACK IS STILL A LITTLE TO THE RIGHT OF THE CENTER OF THE GUIDANCE ENVELOPE AND THE VARIOUS CONSENSUS MODELS. IT IS IN BEST OVERALL AGREEMENT WITH THE HWRF. THE LARGE-SCALE MODELS FORECAST ALEX TO BE NEAR OR UNDER A LARGE UPPER-LEVEL ANTICYCLONE THROUGH THE FORECAST PERIOD...WHICH SHOULD CAUSE AN ENVIRONMENT OF LIGHT VERTICAL WIND SHEAR. AS A RESULT... ALEX IS FORECAST TO INTENSIFY AS LONG AS IT REMAINS OVER WATER. THE NEW INTENSITY FORECAST CALLS FOR A 50 KT INTENSITY AS THE CENTER REACHES THE COAST OF BELIZE OR THE YUCATAN PENINSULA... FOLLOWED BY WEAKENING OVER LAND. THE GFDL...SHIPS...AND LGEM MODELS FORECAST ALEX TO BE A HURRICANE OVER THE GULF OF MEXICO. THE INTENSITY FORECAST WILL NOT YET DO THAT...BUT WILL CALL FOR MORE STRENGTHENING OVER THE GULF THAN THE PREVIOUS FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0900Z 16.9N 84.9W 35 KT 12HR VT 26/1800Z 17.4N 86.3W 45 KT 24HR VT 27/0600Z 18.4N 88.0W 50 KT 36HR VT 27/1800Z 19.4N 89.5W 35 KT...INLAND 48HR VT 28/0600Z 20.5N 90.5W 30 KT...OVER WATER 72HR VT 29/0600Z 22.5N 92.5W 35 KT 96HR VT 30/0600Z 24.0N 94.0W 45 KT 120HR VT 01/0600Z 24.5N 95.5W 60 KT $$ FORECASTER BEVEN |