ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NORMA DISCUSSION NUMBER 13 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 PM PDT SUN SEP 25 2005 THE LOW LEVEL CENTER REMAINS PARTIALLY OBSCURED BY CIRRUS AND STILL APPEARS TO BE LOCATED NORTHEAST OF THE DEEPEST CONVECTION... WHICH HAS LESSENED DURING THE PAST FEW HOURS. THERE IS ONE REMAINING CONVECTIVE BURST WITH TOPS COLDER THAN -70C. DVORAK INTENSITY ESTIMATES AT 00Z WERE 35-45 KT... AND THE ADVISORY INTENSITY IS ADJUSTED DOWNWARD TO 40 KT. EASTERLY SHEAR ON THE SOUTH SIDE OF AN UPPER LEVEL ANTICYCLONE CONTINUES TO PREVENT THE SYSTEM FROM ORGANIZING. EVEN THOUGH NORMA MIGHT GAIN ENOUGH LATITUDE IN A DAY OR TWO TO WHERE THE SHEAR IS A LITTLE WEAKER... OCEAN TEMPERATURES WILL ONLY GET COOLER ALONG THE WAY. GRADUAL WEAKENING APPEARS LIKELY TO CONTINUE AS FORECAST BY THE SHIPS AND GFDL GUIDANCE. THE NEW OFFICIAL FORECAST ANTICIPATES AN EVEN FASTER PACE OF DECLINE THAN THE PREVIOUS ADVISORY. THE ESTIMATED INITIAL MOTION IS 310/7... STILL NORTHWESTWARD BUT WITH A SLIGHTLY MORE WESTERLY COMPONENT THAN EARLIER TODAY. THE CURRENT STEERING IS PROVIDED BY FLOW AROUND THE SOUTHWESTERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER TEXAS. THIS RIDGE IS FORECAST BY THE DYNAMICAL MODELS TO BUILD WESTWARD IN A COUPLE OF DAYS AS A LOW CURRENTLY OFFSHORE CALIFORNIA MOVES INLAND. AS A RESULT... A WEAKENING NORMA SHOULD BE FORCED TO THEN TURN WESTWARD... ESPECIALLY SINCE IT WILL LIKELY BE WEAKER AND STEERED INCREASINGLY BY THE LOW LEVEL TRADE WIND FLOW. THE NEW OFFICIAL TRACK FORECAST IS ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE SINCE THE MODELS MIGHT HAVE A SLIGHT EAST BIAS FOR A SYSTEM UNDER EASTERLY SHEAR. THIS TRACK IS ALSO A BIT SOUTH OF AND SLOWER THAN THE PREVIOUS ONE LATE IN THE FORECAST PERIOD... LEANING MORE TOWARD THE GFDL AND GFS THAN THE NOGAPS... SINCE THE LATTER DEPICTS WHAT APPEARS TO BE TOO STRONG OF A CIRCULATION FOR WHAT IS EXPECTED TO BE A DEPRESSION AND EVENTUAL REMNANT LOW. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 18.7N 113.0W 40 KT 12HR VT 26/1200Z 19.4N 113.9W 40 KT 24HR VT 27/0000Z 20.3N 114.9W 35 KT 36HR VT 27/1200Z 21.0N 116.0W 30 KT 48HR VT 28/0000Z 21.1N 117.0W 25 KT...DISSIPATING 72HR VT 29/0000Z 21.0N 118.5W 20 KT...REMNANT LOW 96HR VT 30/0000Z 20.5N 120.5W 20 KT...REMNANT LOW 120HR VT 01/0000Z 20.0N 123.0W 20 KT...REMNANT LOW $$ NNNN
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Page last modified: Monday, 26-Sep-2005 02:55:24 UTC