WTPA41 PHFO 020838 TCDCP1 TROPICAL STORM LANA DISCUSSION NUMBER 12 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP062009 1100 PM HST SAT AUG 01 2009 AT 800 PM HST...0600Z...THE LOW LEVEL CIRCULATION CENTER OF LANA WAS DUE SOUTH OF THE BIG ISLAND AND MOVING TO THE WEST AT A STEADY 16 KT. DEEP CONVECTION CONTINUES TO PULSE...WITH THUNDERSTORMS JUST NORTHEAST OF THE CYCLONE CENTER AT THIS TIME. CONFIDENCE IN THE CENTER POSITION IS GOOD AS IS THE CYCLONE MOVEMENT. JTWC...SAB AND HFO ALL CAME IN WITH FINAL T-NUMBERS OF 3.0. THE OFFICIAL INTENSITY THEREFORE REMAINS AT 45 KT. THE FORECAST TRACK FOLLOWS THE PREVIOUS TRACK WITH ONLY A SMALL SHIFT TO THE SOUTH. LANA LIES IN EASTERLY FLOW SOUTH OF A SUBTROPICAL HIGH AND RIDGE. THE LOW- AND MID-LEVEL RIDGE IS LOCATED NORTH OF HAWAII AND IS FORECAST TO BUILD WESTWARD OVER THE NEXT 120 HOURS...KEEPING LANA WELL WITHIN THE TRADE WIND BELT. THE FORECAST THEREFORE KEEPS LANA ON A WESTWARD TRACK CLOSE TO THE PREVIOUS TRACK AND JUST SOUTH OF MOST OF THE TIGHTLY GROUPED OBJECTIVE AIDES. AN UPPER-LEVEL LOW CENTERED SOUTHWEST OF KAUAI NEAR 18N 166W HAS BEEN STATIONARY FOR THE LAST 24 HOURS. SOUTHWEST WINDS ALOFT EAST OF THE LOW ARE RIDING UP OVER THE LOW- AND MID-LEVEL EASTERLIES RESULTING IN SUBSTANTIAL VERTICAL SHEARING. A CONSENSUS OF GLOBAL MODELS KEEP THE UPPER LOW NEAR ITS PRESENT POSITION OVER THE NEXT 24 TO 30 HOURS. THEY THEN WEAKEN AND LIFT THE UPPER LOW OUT TO THE NORTHWEST...RESULTING IN A SLACKENING OF THE SHEAR. THE PERSISTENT SHEAR SHOULD TAKE ITS TOLL ON LANA...FORCING IT TO SLOWLY SPIN DOWN THROUGH THE FORECAST PERIOD. THE INTENSITY FORECAST IS IN GOOD AGREEMENT WITH SHIPS AND ICON. FORECAST POSITIONS AND MAX WINDS INITIAL 02/0900Z 14.5N 156.7W 45 KT 12HR VT 02/1800Z 14.7N 159.0W 40 KT 24HR VT 03/0600Z 15.0N 162.0W 35 KT 36HR VT 03/1800Z 15.3N 164.9W 35 KT 48HR VT 04/0600Z 15.6N 167.6W 30 KT 72HR VT 05/0600Z 16.1N 173.1W 25 KT...DISSIPATING 96HR VT 06/0600Z 16.6N 178.3W 20 KT...REMNANT LOW 120HR VT 07/0600Z 17.1N 176.2E 20 KT...REMNANT LOW $$ FORECASTER CRAIG