ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION SERGIO DISCUSSION NUMBER 26 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP212006 700 PM PST SUN NOV 19 2006 DEEP CONVECTION COMES AND GOES IN SPORADIC DISORGANIZED BURSTS...BUT RECENTLY THESE BURSTS HAVE BEEN OCCURRING MAINLY WELL TO THE EAST OF THE CENTER. THERE IS STILL A WELL-DEFINED...MOSTLY EXPOSED... SWIRL OF LOW CLOUDS ASSOCIATED WITH SERGIO. GIVEN THAT DEEP CONVECTION HAS NOT PERSISTED NEAR THE CENTER OVER THE PAST SEVERAL HOURS IT IS ASSUMED THE CYCLONE HAS SPUN DOWN TO BELOW TROPICAL STORM INTENSITY. THE SYSTEM IS LIKELY TO REMAIN IN AN ENVIRONMENT OF STRONG WEST-SOUTHWESTERLY SHEAR OVER THE NEXT DAY OR TWO. OUTPUT FROM THE OPERATIONAL SHIPS MODEL SHOWS 30-35 KT OF 850-200 MB VERTICAL SHEAR AFFECTING SERGIO OVER THE NEXT 24 HOURS OR SO. THIS IS PROBABLY AN OVERESTIMATE OF THE SHEAR THAT WILL DIRECTLY IMPACT THE SYSTEM...SINCE IT IS AN AVERAGE OVER A LARGE AREA THAT INCLUDES EVEN STRONGER UPPER-LEVEL WINDS TO THE NORTH OF SERGIO. HOWEVER EVEN THE EXPERIMENTAL SHIPS OUTPUT...WHICH IS BASED ON THE SHEAR AVERAGED OVER A SMALLER AREA OVER THE TROPICAL CYCLONE...SHOWS MORE THAN 25 KT OF SHEAR DURING THE NEXT 36 HOURS. THIS ATMOSPHERIC ENVIRONMENT SHOULD RESULT IN CONTINUED WEAKENING...AND SERGIO COULD DISSIPATE SOONER THAN ANTICIPATED BY THE OFFICIAL FORECAST. THE SYSTEM HAS BEEN MOVING SLOWLY WEST-SOUTHWESTWARD IN RESPONSE TO THE FLOW SOUTH OF A WEAK LOW- TO MID-LEVEL HIGH PRESSURE AREA. THIS HIGH IS FORECAST TO SHIFT EASTWARD AND THE WEAKENING TROPICAL CYCLONE OR ITS REMNANT IS PREDICTED TO TURN TO THE WEST AND WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS. THIS IS SIMILAR TO THE PREVIOUS OFFICIAL TRACK FORECAST....BUT NOT AS FAST AS INDICATED BY THE MEDIUM TO SHALLOW BAM GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 20/0300Z 15.0N 106.4W 30 KT 12HR VT 20/1200Z 14.9N 106.8W 30 KT 24HR VT 21/0000Z 15.0N 107.7W 25 KT 36HR VT 21/1200Z 15.3N 108.8W 25 KT...DISSIPATING 48HR VT 22/0000Z 15.6N 110.0W 20 KT...REMNANT LOW 72HR VT 23/0000Z...DISSIPATED $$ FORECASTER PASCH NNNN
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Page last modified: Monday, 20-Nov-2006 02:35:04 UTC