ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM ERIKA DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT FRI AUG 15 2003 THE INITIAL MOTION ESTIMATE IS 270/21...ALTHOUGH THE MOTION OVER THE PAST SIX HOURS HAS BEEN A LITTLE FASTER. THE GUIDANCE MODELS INDICATE A WEST TO WEST-SOUTHWESTWARD MOTION FOR THE NEXT 48 HOURS WITH THE FORWARD SPEED DECREASING TO ABOUT 10 KNOTS. THIS TRACK BRINGS THE CENTER TO THE COAST IN 36 HOURS AND INLAND IN 48 HOURS. IT IS NOT EASY TO SEE WHY THE FORWARD SPEED SHOULD DECREASE SO MUCH AS THE GFS MODEL SHOWS THE STORM EMBEDDED WESTWARD DEEP LAYER MEAN FLOW TO THE SOUTH OF AN ANTICYCLONE FOR THE NEXT 72 HOURS. PERHAPS A RIDGE IS PUSHING SOUTHWARD AHEAD OF THE STORM OR THE ANTICYCLONE MAY BE FORECAST TO WEAKEN. IN ANY CASE...ALL OF THE MAJOR GLOBAL MODELS SHOW THIS SLOWING DOWN AND SO DOES THE OFFICIAL FORECAST. THE OFFICIAL FORECAST TRACK IS SLIGHTLY SOUTH OF THE PREVIOUS ADVISORY. A RECONNAISSANCE PLANE FOUND 50 KT AT A LOCATION 60 N MI NORTHWEST OF THE CENTER AT 850 MB FLIGHT LEVEL AND 1008 MB CENTRAL PRESSURE. THE INITIAL WIND SPEED IS KEPT AT 40 KNOTS BASED ON THIS DATA. THE CONVECTIVE ORGANIZATION LOOKS PRETTY GOOD ON INFRARED IMAGERY WITH A BANDING FEATURE AROUND THE NORTH SEMICIRCLE AND ANOTHER STARTING TO EXTEND TOWARD THE SOUTHWEST. THE CENTER IS VERY NEAR BUOY 42001 AT THIS TIME. THE GLOBAL MODELS FORECAST MODEST STRENGTHENING BUT NOT TO HURRICANE FORCE BEFORE LANDFALL...BUT THE SHIPS MODEL DOES AND ALSO SHOWS THAT THERE IS A CHANCE OF RAPID DEEPENING. SO A FORECAST OF 65 KT BEFORE LANDFALL STILL WORKS. MY ONLY QUESTION IS WHETHER TO PUT UP A HURRICANE WARNING OR A TROPICAL STORM WARNING THIS MORNING. THE CONSERVATIVE APPROACH IS A TROPICAL STORM WARNING AND THE PATH OF LEAST REGRET IS A HURRICANE WARNING. LETS GO WITH TROPICAL STORM WARNING...TO BE UPGRADED LATER IF THE FORECAST STRENGTHENING IS OBSERVED TO BEGIN. FORECASTER LAWRENCE FORECAST POSITIONS AND MAX WINDS INITIAL 15/0900Z 26.3N 89.4W 40 KT 12HR VT 15/1800Z 26.2N 92.2W 45 KT 24HR VT 16/0600Z 26.0N 95.5W 55 KT 36HR VT 16/1800Z 25.8N 98.4W 65 KT 48HR VT 17/0600Z 25.4N 99.8W 30 KT...INLAND DISSIPATING 72HR VT 18/0600Z 26.5N 102.5W 20 KT...INLAND DISSIPATING 96HR VT 19/0600Z...INLAND DISSIPATED NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:57 UTC