700 AM PST SUN NOV 03 2013 THE AREA OF DEEP CONVECTION THAT DEVELOPED OVERNIGHT IN ASSOCIATION WITH SONIA HAS EXPANDED THIS MORNING. EARLY MORNING VISIBLE SATELLITE IMAGES SUGGEST THAT THE CENTER IS LOCATED JUST BENEATH THE SOUTHEAST PORTION OF THE LARGE CONVECTIVE MASS. BASED ON THE SLIGHTLY IMPROVED ORGANIZATION AND DVORAK T-NUMBERS OF 2.5 AND 3.0 FROM SAB AND TAFB...RESPECTIVELY...THE INITIAL WIND SPEED IS INCREASED TO 40 KT. THE RECENT STRENGTHENING APPEARS TO BE THE RESULT OF DECREASING SHEAR AS SONIA MOVED BENEATH AN UPPER-LEVEL RIDGE AXIS OVERNIGHT. THIS RELAXATION IN SHEAR IS EXPECTED TO BE SHORT-LIVED AS SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF A MID- TO UPPER-LEVEL TROUGH WILL CAUSE A SUBSTANTIAL INCREASE IN SHEAR TONIGHT....AND NO SIGNIFICANT ADDITIONAL STRENGTHENING IS EXPECTED. SOME WEAKENING IS POSSIBLE AROUND THE TIME SONIA REACHES THE COAST AS THE SHEAR IS EXPECTED TO CAUSE THE LOW- AND MID-LEVEL CENTERS TO DECOUPLE. SONIA IS FORECAST TO DISSIPATE SHORTLY AFTER LANDFALL OVER THE MOUNTAINS OF WESTERN MEXICO. THE INITIAL MOTION IS STILL NORTHWARD OR 005 DEGREES AT 7 KT. SONIA SHOULD TURN NORTH-NORTHEASTWARD VERY SOON AS DEEP LAYER SOUTHWESTERLY FLOW STRENGTHENS AHEAD OF A MID-LATITUDE TROUGH MOVING INTO THE SOUTHWESTERN UNITED STATES AND NORTHERN MEXICO. SONIA SHOULD BEGIN TO ACCELERATE LATER TODAY AND MAKE LANDFALL ALONG THE COAST OF MAINLAND MEXICO MONDAY MORNING. THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND NO SIGNIFICANT CHANGES WERE REQUIRED FROM THE PREVIOUS NHC ADVISORY. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 19.9N 109.8W 40 KT 45 MPH 12H 04/0000Z 21.6N 109.1W 40 KT 45 MPH 24H 04/1200Z 23.7N 107.6W 35 KT 40 MPH 36H 05/0000Z 25.9N 106.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/1200Z...DISSIPATED $$ FORECASTER BROWN MC
Posted on: Sun, 03 Nov 2013 14:46:18 +0000
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