WTPA41 PHFO 312057 TCDCP1 TROPICAL STORM LANA DISCUSSION NUMBER 6 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP062009 1100 AM HST FRI JUL 31 2009 AFTER ORGANIZATION DETERIORATED EARLY LAST NIGHT...A BURST OF CENTRAL CONVECTION AFTER 1200 UTC HELPED REINVIGORATE LANA. DVORAK ESTIMATES FROM CPHC AND SAB CAME IN AT T3.5...OR 55 KT AND AN AMSU INTENSITY ESTIMATE AT 1437 UTC ALSO INDICATED 55 KT. BASED ON THIS CONSENSUS...THE INITIAL INTENSITY WILL BE RAISED TO 55 KT. THE 37 GHZ SSMI PASS FROM 1610 UTC HELPED LOCATE THE SYSTEM CENTER JUST EAST OF THE DEEP CONVECTION CENTROID. INFRARED AND VISIBLE SATELLITE IMAGES SHOW LANA/S OUTFLOW IS BEING RESTRICTED TO THE WEST AND SOUTHWEST. THIS INDICATES UPPER SOUTHWESTERLIES...AND INCREASED VERTICAL SHEAR...ARE STARTING TO AFFECT THE CYCLONE. LANA IS MOVING WESTWARD TO THE SOUTH OF A SUBTROPICAL RIDGE THAT WILL BUILD WESTWARD OVER THE NEXT SEVERAL DAYS. THIS WILL KEEP THE CYCLONE TRACK GENERALLY TOWARD THE WEST TO WEST-NORTHWEST THROUGH THE FORECAST PERIOD AND WELL SOUTH OF THE HAWAIIAN ISLANDS. THE DYNAMICAL OBJECTIVE AIDS ARE TIGHTLY PACKED AND CONSISTENT WITH THE PREVIOUS PACKAGE. THUS...THE CURRENT FORECAST FOLLOWS THE PREVIOUS FORECAST AND IS CLOSE TO THE DYNAMICAL MODEL CONSENSUS...ESPECIALLY THROUGH 72 HOURS. IN TERMS OF INTENSITY...LANA MAY HAVE REACHED ITS PEAK. WHILE SST VALUES ARE MORE THAN ADEQUATE...UPPER LEVEL SOUTHWESTERLIES ARE EXPECTED TO INCREASE ALONG THE CYCLONE/S PROJECTED TRACK SO VERTICAL SHEAR WILL TAKE ITS TOLL...ESPECIALLY FROM 24 TO 36 HOURS ONWARD. THE FORECAST FOLLOWS THE TREND OF THE ICON AND IVCN WITH SLOW WEAKENING FROM 24 THROUGH 48 HOURS FOLLOWED BY A MORE RAPID WEAKENING TO A REMNANT LOW BY 120 HOURS. IF VERTICAL WIND SHEAR TAKES HOLD EARLIER...THE WEAKENING TREND WILL ALSO OCCUR EARLIER. FORECAST POSITIONS AND MAX WINDS INITIAL 31/2100Z 13.7N 147.7W 55 KT 12HR VT 01/0600Z 14.1N 150.0W 55 KT 24HR VT 01/1800Z 14.7N 152.9W 50 KT 36HR VT 02/0600Z 15.2N 155.7W 45 KT 48HR VT 02/1800Z 15.7N 158.3W 45 KT 72HR VT 03/1800Z 16.5N 163.8W 35 KT 96HR VT 04/1800Z 17.1N 169.5W 25 KT...DISSIPATING 120HR VT 05/1800Z 17.6N 175.6W 20 KT...REMNANT LOW $$ FORECASTER KODAMA