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#49700 (Received by flhurricane at: 5:03 AM 03.Oct.2005) TCDAT5 TROPICAL STORM STAN DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT MON OCT 03 2005 THE CENTER OF STAN EMERGED OFF THE NORTHWESTERN COAST OF THE YUCATAN PENINSULA AT ABOUT 0430Z. SHORTLY THEREAFTER AN AIR FORCE HURRICANE HUNTER PLANE FLEW INTO THE CENTER AND MEASURED A CENTRAL PRESSURE OF 1003 MB... THEN 1002 MB ON A MORE RECENT PENETRATION. MAXIMUM 850 MB FLIGHT LEVEL WINDS WERE 43 KT TO THE NORTHEAST OF THE CENTER... IN THE BAND OF CONVECTION EMANATING OFFSHORE FROM THE NORTHERN COAST OF THE PENINSULA. THIS CONVECTION APPEARS TO BE DEEP ENOUGH TO MIX THE FLIGHT LEVEL WINDS DOWN TO THE SURFACE USING THE 80 PERCENT REDUCTION...WHICH CORRESPONDS TO ABOUT 35 KT AT THE SURFACE. ADDITIONALLY...CONVECTION HAS BEGUN BURSTING NEAR THE CIRCULATION CENTER...AND TROPICAL STORM FORCE WINDS SHOULD SOON BE OCCURRING THERE. THE ADVISORY INTENSITY IS SET TO 35 KT... MAKING STAN A TROPICAL STORM ONCE AGAIN. THE AIRCRAFT LOCATED THE CENTER OF CIRCULATION A BIT TO THE SOUTH OF THE PREVIOUS ADVISORY POSITION... AND THE ESTIMATED INITIAL MOTION IS NOW WESTWARD... 270/9. A MID LEVEL RIDGE EXTENDING FROM TEXAS TO THE CAROLINAS SHOULD CONTINUE TO STEER STAN TOWARD THE WEST DURING THE NEXT COUPLE OF DAYS... WITH AN EVENTUAL SLIGHT BEND SOUTH OF WEST AND A SLOWING OF THE FORWARD SPEED. MOST OF THE MODELS INDICATE THAT ENOUGH RIDGING WILL PERSIST TO TAKE STAN ALL THE WAY ACROSS THE BAY OF CAMPECHE. HOWEVER... IT IS POSSIBLE THAT SOME COMPLICATING FACTORS... INCLUDING INTERACTION WITH HIGH TERRAIN AS STAN APPROACHES THE COAST... A DEVELOPING DISTURBANCE IN THE GULF OF TEHUANTEPEC... AND LOW PRESSURE FORECAST TO DEVELOP OVER THE EASTERN GULF OF MEXICO... COULD CAUSE A SLOWER MOTION THAN INDICATED IN THE OFFICIAL FORECAST. THE NEW FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY EXCEPT FOR A SOUTHWARD ADJUSTMENT DUE TO THE INITIAL POSITION. STAN IS NOW OVER THE VERY WARM WATERS OF THE SOUTHWESTERN GULF OF MEXICO... AND IS BENEATH A LARGE UPPER LEVEL ANTICYCLONE AS DEPICTED IN GOES WATER VAPOR IMAGERY. THE COMBINATION OF THESE FACTORS WILL LIKELY LEAD TO STRENGTHENING. AN UPPER LEVEL SHORTWAVE TROUGH CURRENTLY OVER THE APPALACHIANS IS FORECAST BY THE DYNAMICAL MODELS TO DIVE INTO THE EASTERN GULF OF MEXICO WITHIN 48 HOURS AND ERODE THE UPPER LEVEL RIDGE...BUT THE SHEAR WILL PROBABLY NOT INCREASE IN TIME TO WEAKEN STAN BEFORE FINAL LANDFALL. ACCORDINGLY THE SHIPS GUIDANCE DIAGNOSES WEAK SHEAR AND FORECASTS A 65 KT HURRICANE APPROACHING THE GULF COAST OF MEXICO IN ABOUT 48 HOURS. THE OFFICIAL FORECAST IS SIMILAR TO SHIPS AND THE PREVIOUS ADVISORY. THE NEW FORECAST REQUIRES A HURRICANE WATCH FOR PORTIONS OF THE GULF COAST OF MEXICO. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 03/0900Z 20.5N 91.5W 35 KT 12HR VT 03/1800Z 20.5N 92.9W 40 KT 24HR VT 04/0600Z 20.4N 94.2W 50 KT 36HR VT 04/1800Z 20.2N 95.2W 60 KT 48HR VT 05/0600Z 20.0N 96.3W 70 KT 72HR VT 06/0600Z 19.5N 97.5W 30 KT...INLAND 96HR VT 07/0600Z...DISSIPATED |