000
WTPA41 PHFO 311438
TCDCP1
TROPICAL STORM LANA DISCUSSION NUMBER   5
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP062009
ISSUED BY NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
500 AM HST FRI JUL 31 2009
 
THE INTENSIFICATION TREND OBSERVED YESTERDAY HAS REVERSED AND
THE CLOUD PATTERN HAS DETERIORATED INSTEAD. IT APPEARS THAT SOME
SOUTHERLY SHEAR INDUCED BY A LARGE UPPER-LEVEL TROUGH JUST WEST OF
THE HAWAIIAN ISLANDS HAS BEGUN TO AFFECT THE CYCLONE. LANA CONSISTS
OF TWO CONVECTIVE AREAS SURROUNDING THE CENTER AND NOW HAS LESS
DEFINED OUTFLOW.  DVORAK T-NUMBERS HAVE DECREASED AND THE INITIAL
INTENSITY HAS BEEN LOWERED TO 45 KNOTS. LANA STILL HAS THE
OPPORTUNITY TO STRENGTHEN SOME BEFORE THE SHEAR INCREASES FURTHER
IN ABOUT 24 TO 36 HOURS. THEREAFTER...A GRADUAL WEAKENING IS
INDICATED. MOST OF CURRENT INTENSITY GUIDANCE DOES NOT SHOW ANY
SIGNIFICANT STRENGTHENING EITHER...AND WEAKENS THE CYCLONE LATER IN
THE FORECAST PERIOD.

LANA IS FULLY EMBEDDED WITHIN THE TROPICAL TRADE WINDS AND IS MOVING
TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT 17 KNOTS. THE CURRENT
WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE HAWAIIAN ISLANDS IS
FORECAST TO BE REPLACED BY A STRONGER RIDGE. THIS PATTERN EVOLUTION
SHOULD KEEP LANA ON A WEST-NORTHWEST TRACK WITH A SMALL DECREASE IN
FORWARD SPEED THROUGH FIVE DAYS. THIS WILL KEEP THE CYCLONE
WELL SOUTH OF THE HAWAIIAN ISLANDS.  THE OFFICIAL FORECAST IS IN THE
MIDDLE OF THE TIGHTLY CLUSTERED GUIDANCE ENVELOPE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/1500Z 13.6N 146.3W    45 KT
 12HR VT     01/0000Z 14.0N 148.7W    50 KT
 24HR VT     01/1200Z 14.5N 151.5W    50 KT
 36HR VT     02/0000Z 15.0N 154.5W    45 KT
 48HR VT     02/1200Z 15.5N 157.0W    40 KT
 72HR VT     03/1200Z 16.5N 162.5W    35 KT
 96HR VT     04/1200Z 17.0N 168.0W    30 KT
120HR VT     05/1200Z 17.5N 174.0W    25 KT...REMNANT LOW
 
$$
FORECASTER AVILA