000 WTPA41 PHFO 302031 TCDCP1 TROPICAL STORM LANA DISCUSSION NUMBER 2 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP062009 ISSUED BY NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1100 AM HST THU JUL 30 2009 VISIBLE SATELLITE IMAGERY INDICATES THAT THE CLOUD PATTERN ASSOCIATED WITH THE DEPRESSION HAS CONTINUED TO IMPROVE IN ORGANIZATION WITH A PROMINENT CONVECTIVE BAND COILING AROUND THE LOW-LEVEL CENTER. T-NUMBERS FROM TAFB AND SAB...AS WELL AS THE ADT FROM UW-CIMSS...HAVE ALL INCREASED TO 2.5 ON THE DVORAK SCALE. THE SYSTEM IS THEREFORE BEING UPGRADED TO TROPICAL STORM LANA. FURTHER STRENGTHENING IS ANTICIPATED DUE TO WARM OCEAN WATERS AND LOW SHEAR. IN FACT...THE SHIPS RI INDEX IS INDICATING A 50% CHANCE OF RAPID INTENSIFICATION WITHIN THE NEXT 24 HOURS. THE OFFICIAL FORECAST DOES NOT SHOW SUCH QUICK STRENGTHENING BUT IS AT THE UPPER END OF THE INTENSITY GUIDANCE AND BRINGS LANA CLOSE TO HURRICANE STRENGTH IN 36 HOURS. SOUTHWESTERLY TO WEST- SOUTHWESTERLY SHEAR IS EXPECTED TO INCREASE DRAMATICALLY BY 72 HOURS AND SHOULD LEAD TO WEAKENING AT THAT TIME. THEREAFTER...THE SHEAR IS NOT FORECAST TO ABATE...AND LANA IS EXPECTED TO BE A TROPICAL DEPRESSION...OR POSSIBLY A REMNANT LOW...BY DAY 5. THE INITIAL MOTION IS 280/16. LANA IS BEING STEERED QUICKLY WESTWARD BY A MID-LEVEL RIDGE LOCATED TO ITS NORTH...AND THIS RIDGE IS EXPECTED TO REMAIN IN PLACE AND KEEP LANA ON A GENERAL WESTWARD COURSE SOUTH OF THE HAWAIIAN ISLANDS. THE DYNAMICAL MODELS...WITH THE EXCEPTION OF THE UKMET...ARE TIGHTLY-CLUSTERED AND HAVE SHIFTED A LITTLE TO THE SOUTH. THE OFFICIAL FORECAST IS THEREFORE NUDGED SOUTHWARD TOWARDS THE MODEL CONSENSUS. EVEN THOUGH THE CYCLONE FORMED IN THE EASTERN PACIFIC BASIN...IT HAS BECOME A TROPICAL STORM IN THE AREA OF RESPONSIBILITY OF THE CENTRAL PACIFIC HURRICANE CENTER AND IS THEREFORE GIVEN THE CORRESPONDING NAME FROM THE CENTRAL PACIFIC NAME LIST. FORECAST POSITIONS AND MAX WINDS INITIAL 30/2100Z 12.3N 141.4W 35 KT 12HR VT 31/0600Z 12.5N 143.7W 45 KT 24HR VT 31/1800Z 12.9N 146.7W 55 KT 36HR VT 01/0600Z 13.2N 149.7W 60 KT 48HR VT 01/1800Z 13.4N 152.5W 60 KT 72HR VT 02/1800Z 14.0N 158.0W 50 KT 96HR VT 03/1800Z 14.5N 163.5W 35 KT 120HR VT 04/1800Z 15.0N 168.5W 25 KT $$ FORECASTER BERG