WTPA41 PHFO 010256
TCDCP1

TROPICAL STORM LANA DISCUSSION NUMBER   7
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP062009
500 PM HST FRI JUL 31 2009

FOLLOWING AN EARLY MORNING BURST OF CONVECTION...VERTICAL WIND SHEAR
HAS BEEN AFFECTING LANA. VISIBLE IMAGES SINCE 1800 UTC HAVE REVEALED
THE LOW LEVEL CENTER THROUGH A VEIL OF THIN HIGH CLOUDS. DVORAK
INTENSITY ESTIMATES FOR 0000 UTC CAME IN AT 55 KT FROM CPHC...SAB
AND THE CIMSS ADT. THESE GENEROUS VALUES WERE THE RESULT OF DVORAK
CONSTRAINTS WITH RAW DT VALUES INDICATING LOWER WIND SPEEDS. 
RECENT IMAGES SHOW A NEW BURST OF DEEP CONVECTION DEVELOPING AROUND
THE NORTHERN QUADRANT OF THE CIRCULATION SO LANA CANNOT BE WRITTEN
OFF YET. THE INITIAL INTENSITY IS LOWERED TO 45 KT AS A BLEND OF
THE DVORAK CI AND DT VALUES. 
 
THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST REASONING FROM THE
PREVIOUS PACKAGE REGARDING TRACK. LANA CONTINUES TO MOVE WESTWARD TO
THE SOUTH OF A MID-LEVEL SUBTROPICAL RIDGE THAT IS FORECAST TO
BUILD WESTWARD OVER THE NEXT SEVERAL DAYS. THIS WILL KEEP THE
CYCLONE MOVING GENERALLY TOWARD THE WEST TO WEST-NORTHWEST THROUGH
THE FORECAST PERIOD.  DYNAMICAL OBJECTIVE AIDS HAVE A BIT MORE
SPREAD FOR THIS FORECAST CYCLE BUT STILL REMAIN RELATIVELY TIGHTLY
CLUSTERED.  THE FORECAST TRACK REMAINS CLOSE TO THE PREVIOUS
FORECAST AND CLOSE TO THE CONSENSUS THROUGH 36 HOURS. BEYOND THAT
TIME THE FORECAST IS SOUTH OF THE CONSENSUS SINCE LANA IS EXPECTED
TO MOVE WITH THE LOW LEVEL EASTERLY FLOW AS A WEAKENING SYSTEM.
MOST OF THE DYNAMICAL AIDS REFLECT A PATH A BIT FARTHER TO THE
NORTH...APPARENTLY HOLDING ON TO A STRONGER AND DEEPER CYCLONE.
 
ALTHOUGH SST VALUES ARE MORE THAN ADEQUATE AT AROUND 27C...VERTICAL
WIND SHEAR FROM UPPER LEVEL SOUTHWESTERLIES WILL BE THE LIMITING
FACTOR ON INTENSITY.  THE INITIAL INTENSITY WILL BE HELD AT 45 KT
THROUGH TONIGHT IN DEFERENCE TO NORMAL DIURNAL TENDENCY. STEADY
WEAKENING IS FORECAST FROM 24 HOURS AND BEYOND DUE TO THE EFFECTS
OF INCREASING VERTICAL SHEAR ALONG LANA/S PROJECTED TRACK. THE
FORECAST IS FOR LANA TO BE A REMNANT LOW BY 96 HOURS AND POTENTIALLY
SOONER.
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0300Z 14.1N 149.2W    45 KT
 12HR VT     01/1200Z 14.4N 151.4W    45 KT
 24HR VT     02/0000Z 15.0N 154.3W    35 KT
 36HR VT     02/1200Z 15.5N 157.1W    30 KT
 48HR VT     03/0000Z 15.8N 159.9W    25 KT
 72HR VT     04/0000Z 16.7N 165.3W    20 KT...DISSIPATING
 96HR VT     05/0000Z 17.3N 170.9W    20 KT...REMNANT LOW
120HR VT     06/0000Z 17.8N 176.3W    20 KT...REMNANT LOW
 
$$
FORECASTER KODAMA