000 WTPZ43 KNHC 071430 TCDEP3 TROPICAL STORM LOWELL DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP132008 800 AM PDT SUN SEP 07 2008 FIRST LIGHT VISIBLE IMAGES SHOW THAT THE CENTER OF LOWELL REMAINS ON THE NORTHEASTERN EDGE OF THE DEEP CONVECTION. SATELLITE INTENSITY ESTIMATES ARE 2.5 FROM SAB...35 KT...AND 3.0 FROM TAFB...45 KT. I'M GOING TO SPLIT THE DIFFERENCE AND USE 40 KT AS AN INITIAL INTENSITY. NORTHEASTERLY WIND SHEAR CURRENTLY AFFECTING LOWELL IS FORECAST TO GRADUALLY WEAKEN BY THE GLOBAL MODELS OVER THE NEXT COUPLE OF DAYS. IN ADDITION...SSTS SHOULD BE WARM ENOUGH FOR SOME INCREASE IN STRENGTH FOR AT LEAST TWO OR THREE DAYS...SO IT IS A LITTLE SURPRISING THAN NEITHER THE GFDL NOR THE HWRF SHOW MUCH DEVELOPMENT WITH LOWELL. THE OFFICIAL FORECAST IS A LITTLE LOWER THAN THE PREVIOUS ONE...BUT IS STILL HIGHER THAN THE INTENSITY MODEL CONSENSUS. THE BEST ESTIMATE OF INITIAL MOTION IS 300/11. LOWELL IS EXPECTED TO REMAIN SOUTH OF A SUBTROPICAL RIDGE EXTENDING WESTWARD FROM MEXICO FOR THE NEXT FEW DAYS. THEREAFTER...A TROUGH DIVING DOWN FROM THE NORTHWEST IS EXPECTED TO ERODE THE RIDGE...CAUSING A TURN TOWARD THE NORTH AND EVENTUALLY NORTHEAST. MODELS AREN'T IN VERY GOOD AGREEMENT ON WHEN THIS TURN WILL OCCUR. THE GFS/UK ARE MUCH FARTHER TO THE SOUTH WITH THE STORM INITIALLY...AND CONSEQUENTLY TURN THE STORM LATER THAN OTHER GUIDANCE. THE ECMWF/GFDL SHOW A MOTION MORE TOWARD THE NORTHWEST IN THE SHORT-TERM AND POSITION LOWELL FAR ENOUGH TO THE NORTH TO BE AFFECTED BY THE TROUGH IN LESS THAN 2 DAYS. THE OFFICIAL FORECAST IS SHIFTED TO THE RIGHT BUT IS STILL WEST AND SLOWER THAN THE DYNAMICAL MODEL CONSENSUS. THERE IS CONSIDERABLE UNCERTAINTY IN THE LONG-RANGE FORECAST WITH LOWELL. FORECAST POSITIONS AND MAX WINDS INITIAL 07/1500Z 17.2N 108.1W 40 KT 12HR VT 08/0000Z 17.9N 109.5W 45 KT 24HR VT 08/1200Z 18.7N 111.2W 50 KT 36HR VT 09/0000Z 19.3N 112.6W 55 KT 48HR VT 09/1200Z 20.0N 113.5W 55 KT 72HR VT 10/1200Z 21.0N 114.5W 55 KT 96HR VT 11/1200Z 22.0N 114.0W 45 KT 120HR VT 12/1200Z 23.0N 113.0W 35 KT $$ FORECASTER BLAKE