ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION EIGHTEEN-E DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP182006 200 AM PDT FRI OCT 27 2006 IF THE DEPRESSION STILL HAS A WELL-DEFINED SURFACE CIRCULATION CENTER...YOU WOULD NEVER KNOW IT FROM THE QUIKSCAT AMBIGUITIES AT 0144Z. THIS PASS SHOWED A LOT OF LIGHT WINDS...A SHARP NORTH-SOUTH TROUGH AXIS...AND PRECIOUS LITTLE ELSE. AN SSMIS MICROWAVE PASS AT 0305Z SHOWED ALMOST NO STRUCTURE IN THE LOW CLOUD LINES. HOWEVER... THERE DOES APPEAR TO BE ROTATION ALOFT AROUND THE LIMITED DEEP CONVECTION...SO IF THE CONVECTION SHOULD INCREASE A SURFACE CIRCULATION COULD BECOME BETTER DEFINED AGAIN. THE INITIAL INTENSITY OF THE CYCLONE REMAINS SUB-ROSA...AND IS LOWERED TO 25 KT IN ACCORD WITH THE QUIKSCAT DATA. THE INITIAL MOTION IS HARD TO GAUGE. WHILE THERE ARE HINTS THAT WHATEVER SURFACE CENTER EXISTS MAY BE LAGGING BEHIND THE DEEP CONVECTION...I'LL GO WITH CONTINUITY AND THE ROTATION ALOFT FOR AN INITIAL MOTION ESTIMATE OF 265/8. THE LATEST RUNS OF THE GLOBAL MODELS CONTINUE TO INDICATE THAT MID-LEVEL RIDGING WILL BUILD TO THE NORTH AND NORTHWEST OF THE DEPRESSION...WHICH WOULD TAKE THE SYSTEM ON A TRACK A LITTLE SOUTH OF WEST. THE OFFICIAL FORECAST IS ADJUSTED JUST A LITTLE SOUTH OF THE PREVIOUS TRACK...AND IS IN GOOD AGREEMENT WITH THE GFDL AND MEDIUM BAM GUIDANCE. WITH LIMITED CONVECTION AND POOR DEFINITION OF THE WIND FIELD...THE DEPRESSION IS BECOMING A CANDIDATE FOR EARLY DISSIPATION. HOWEVER...BOTH THE SHIPS AND GFDL GUIDANCE SUGGEST MODEST STRENGTHENING OVER THE NEXT COUPLE OF DAYS AND THE OFFICIAL FORECAST...FOR NOW...WILL INDICATE THE SAME. FACTORS FAVORING THIS SCENARIO INCLUDE LIGHT SHEAR AND VERY WARM WATERS. ON THE OTHER HAND...THE UPPER-LEVEL OUTFLOW IS NOT WELL ESTABLISHED AND THE ENVIRONMENT IS A LITTLE DRY...AND IF THESE FACTORS KEEP A LID ON THE CONVECTION OVER THE NEXT DAY OR SO THEN THE DEPRESSION COULD DISSIPATE. FORECAST POSITIONS AND MAX WINDS INITIAL 27/0900Z 16.6N 106.4W 25 KT 12HR VT 27/1800Z 16.4N 107.7W 30 KT 24HR VT 28/0600Z 16.0N 109.5W 35 KT 36HR VT 28/1800Z 15.7N 111.5W 45 KT 48HR VT 29/0600Z 15.5N 113.6W 45 KT 72HR VT 30/0600Z 15.5N 117.5W 45 KT 96HR VT 31/0600Z 15.5N 121.5W 40 KT 120HR VT 01/0600Z 15.5N 125.5W 40 KT $$ FORECASTER FRANKLIN NNNN
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Page last modified: Friday, 27-Oct-2006 08:35:03 UTC