000 WTPZ45 KNHC 060852 TCDEP5 TROPICAL STORM NORBERT DISCUSSION NUMBER 10 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP152008 200 AM PDT MON OCT 06 2008 THE CLOUD PATTERN ASSOCIATED WITH NORBERT HAS CONTINUED TO GRADUALLY IMPROVE. THE LATEST MICROWAVE IMAGERY AND AN 0121 UTC QUIKSCAT PASS SUGGEST THAT THE CENTER OF NORBERT IS LOCATED A LITTLE TO THE SOUTH AND EAST OF THE PREVIOUS ESTIMATES...BUT WELL WITHIN THE AREA OF DEEP CONVECTION. THE INITIAL INTENSITY REMAINS 55 KT...BASED ON DVORAK T3.5 OR 55 KT FROM BOTH TAFB AND SAB. NORBERT CONTINUES TO MOVE WESTWARD OR 270/6. NORBERT IS FORECAST TO MOVE ON A WEST TO WEST-NORTHWESTWARD MOTION TO THE SOUTH OF A NARROW MID-LEVEL RIDGE DURING THE NEXT FEW DAYS. THEREAFTER...A TROUGH IS FORECAST TO DIG SOUTHWARD ALONG THE WEST COAST OF THE UNITED STATES WHICH SHOULD ALLOW THE CYCLONE TO TURN NORTHWARD IN ABOUT 96 HOURS. THE OVERALL TRACK GUIDANCE ENVELOPE HAS CHANGED LITTLE...BUT SOME OF THE INDIVIDUAL MODELS HAVE BEEN SHOWING SOME RUN TO RUN INCONSISTENCIES. THE GFDL WHICH WAS ALONG THE EASTERN EDGE OF THE GUIDANCE HAS MADE A SIGNIFICANT SHIFT WESTWARD BACK TOWARD THE MIDDLE OF THE PACK. THERE ALSO CONTINUES TO BE A LARGE SPREAD IN THE GUIDANCE ON THE PREDICTED FORWARD SPEED OF NORBERT. THE ECMWF AND GFS ARE MUCH SLOWER THAN THE NOGAPS...UKMET...AND HWRF WHICH ALL BRING THE CYCLONE INTO THE BAJA PENINSULA WITHIN 5 DAYS. GIVEN THE LARGE SPREAD OF THE GUIDANCE...ESPECIALLY AT THE LONG RANGE...THE NEW OFFICIAL FORECAST REMAINS NEAR THE MODEL CONSENSUS AND THE PREVIOUS NHC TRACK. CONDITIONS APPEAR FAVORABLE FOR GRADUAL STRENGTHENING DURING THE NEXT FEW DAYS...AND NORBERT IS EXPECTED TO BECOME A HURRICANE. THE OFFICIAL FORECAST IS A LITTLE HIGHER THAN THE SHIPS GUIDANCE...BUT IS LOWER THAN THE VERY AGGRESSIVE HWRF MODEL. BY 96 HOURS...NORBERT IS EXPECTED TO BE NEARING COOLER WATERS AND BEYOND THAT TIME... SOUTHWESTERLY SHEAR IS FORECAST TO INCREASE. THEREFORE...WEAKENING IS PREDICTED AT DAYS 4-5...BUT THE OFFICIAL FORECAST DOES NOT SHOW AS MUCH WEAKENING AS INDICATED BY THE SHIPS AND LGEM GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 06/0900Z 14.1N 103.9W 55 KT 12HR VT 06/1800Z 14.3N 104.8W 65 KT 24HR VT 07/0600Z 14.6N 105.9W 70 KT 36HR VT 07/1800Z 15.1N 107.2W 75 KT 48HR VT 08/0600Z 15.8N 108.5W 80 KT 72HR VT 09/0600Z 17.7N 111.0W 80 KT 96HR VT 10/0600Z 20.0N 112.5W 75 KT 120HR VT 11/0600Z 23.0N 112.5W 60 KT $$ FORECASTER BROWN