000 WTPZ45 KNHC 061445 TCDEP5 TROPICAL STORM NORBERT DISCUSSION NUMBER 11 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152008 800 AM PDT MON OCT 06 2008 DVORAK INTENSITY ESTIMATES FROM 1200 UTC SUPPORT AN INITIAL INTENSITY OF 55 KT FOR THIS ADVISORY BUT THE LAST FEW SATELLITE IMAGES SUGGEST THAT THE CYCLONE IS BECOMING BETTER ORGANIZED. NORBERT IS EXPECTED TO BE WITHIN A FAVORABLE ENVIRONMENT FOR STRENGTHENING AND THE OFFICIAL FORECAST CALLS FOR THE CYCLONE TO BECOME A HURRICANE DURING THE NEXT 12-24 HOURS. THE HWRF MODEL REMAINS SOMEWHAT OF AN OUTLIER AND SHOWS NORBERT REACHING MAJOR HURRICANE STRENGTH. THE OFFICIAL FORECAST IS MORE CONSERVATIVE AND IS IN BEST AGREEMENT WITH THE GFDL SOLUTION. BY DAYS 4 AND 5...NORBERT IS FORECAST TO BE APPROACHING COOLER WATERS AND A MORE STABLE AIR MASS. THEREFORE...SOME WEAKENING IS SHOWN AT THE EXTENDED TIME RANGES. HOWEVER...THE ULTIMATE ENVIRONMENT IN WHICH NORBERT WILL BE LOCATED AT DAYS 4 AND 5 IS STRONGLY DEPENDENT ON THE TRACK FORECAST...AND NORBERT COULD ENCOUNTER LESS FAVORABLE CONDITIONS SOONER OR LATER THAN SHOWN HERE. NORBERT CONTINUES TO BE STEERED BY A MID-LEVEL RIDGE TO THE NORTH AND IS MOVING WESTWARD OR 280/7. THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 2 DAYS AS THE RIDGE REMAINS TO THE NORTH OF THE CYCLONE. THEREAFTER...A LARGE TROUGH IS FORECAST TO DIG SOUTHWARD ALONG THE WEST COAST OF THE UNITED STATES WHICH SHOULD RESULT IN A NORTHWARD TURN IN 3-4 DAYS. THERE ARE STILL SOME DIFFERENCES AMONG THE VARIOUS TRACK MODELS BEYOND 72 HOURS WITH THE GFS MODEL NEVER GETTING NORBERT FAR ENOUGH NORTH TO RESPOND TO THE AFOREMENTIONED TROUGH AND THE ECMWF SHOWING THE TROUGH BYPASSING NORBERT AND LEAVING IT BEHIND. WHILE THESE SOLUTIONS CANNOT BE COMPLETELY IGNORED...THE OFFICIAL FORECAST FOLLOWS THE REMAINING TRACK MODELS BY SHOWING A NORTHWARD AND NORTH-NORTHEASTWARD TURN AT DAYS 4 AND 5...RESPECTIVELY. HOWEVER...THE FORWARD SPEED SHOWN IN THE OFFICIAL FORECAST IS SLOWER THAN FORECAST BY THOSE MODELS. THIS RESULTS IN ONLY A SMALL SOUTHWARD SHIFT TO THE PREVIOUS OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INITIAL 06/1500Z 14.3N 104.7W 55 KT 12HR VT 07/0000Z 14.5N 105.6W 65 KT 24HR VT 07/1200Z 14.9N 106.9W 70 KT 36HR VT 08/0000Z 15.4N 108.2W 75 KT 48HR VT 08/1200Z 16.2N 109.6W 80 KT 72HR VT 09/1200Z 18.0N 112.0W 80 KT 96HR VT 10/1200Z 20.5N 113.0W 75 KT 120HR VT 11/1200Z 23.5N 112.5W 60 KT $$ FORECASTER RHOME