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