Heavy Rain in Hawaii, June 6, 2003

HAWAIIAN ISLANDS SYNOPTIC DISCUSSION AND GUIDANCE
NATIONAL WEATHER SERVICE HONOLULU HI
205 PM HST FRI JUN 6 2003

SUMMARY...THE UPPER LEVEL TROUGH THAT HAS BEEN NEAR HAWAII THE PAST
FEW DAYS WILL SLOWLY WEAKEN AND MOVE AWAY FROM THE AREA. THIS WILL
ALLOW HIGH PRESSURE TO BEGIN BUILDING NORTH OF THE ISLANDS ON
MONDAY...USHERING IN A RETURN TO LESS MUGGY TRADE WIND WEATHER.

DISCUSSION...BASED ON RECENT REPORTS OF SOME 8 FOOT SETS ON THE
SOUTH SHORE...WILL ISSUE AN UPDATE FOR HIGH SURF ADVISORY ON SOUTH
SHORES. PREVIOUS DISCUSSION FOLLOWS.

THE UPPER TROUGH IS STILL EVIDENT ON WATER VAPOR IMAGERY JUST TO OUR
WEST...THOUGH THE VORT MAX WHICH HELPED TO ENHANCE YESTERDAYS
CONVECTION IS NOW MOVING AWAY FROM US. THE 12Z SOUNDINGS ARE STILL
MOIST AND UNSTABLE...THOUGH SLIGHTLY LESS SO THAN 24 HOURS AGO. WITH
SLIGHTLY LESS INSTABILITY AND NO OBVIOUS SYNOPTIC SCALE
TRIGGERS...DEEP CONVECTION SHOULD NOT BE AS VIGOROUS AS YESTERDAY.
HOWEVER...SATELLITE IMAGERY SHOWS THAT ISLAND SKIES ARE STILL
RELATIVELY CLEAR THIS MORNING...SO PLENTY OF INSOLATION AVAILABLE
FOR LOW LEVEL HEATING. DESPITE LIGHT EASTERLY FLOW ACROSS THE
REGION...SURFACE OBSERVATIONS INDICATE THAT SEA BREEZES HAVE ALREADY
STARTED IN SOME PLACES AND THESE WILL PROVIDE MESOSCALE FORCING FOR
AFTERNOON CONVECTION OVER THE ISLANDS. CURRENT FORECAST INCLUDING
THE RISK OF HEAVY RAINFALL LOOKS ON TRACK. WILL TAKE A LOOK AT
TODAYS TRENDS IN ORDER TO DECIDE IF WE CAN CONFIDENTLY REMOVE LOCAL
HEAVY RAIN THREAT FOR SATURDAY AFTERNOON FOR THE NEXT SCHEDULED
PACKAGE.

MODELS CONTINUE TO INDICATE RISING PRESSURES NORTH OF THE ISLANDS
STARTING ON SUNDAY...AND HIGH PRESSURE BECOMING MORE FIRMLY
ESTABLISHED FROM MONDAY ONWARD. THE LONG-AWAITED RETURN OF THE
TRADES WILL OCCUR AS THE PRESSURE GRADIENT TIGHTENS. 850 MB THETA-E
VALUES DROPPING BELOW NORMAL SUGGESTS THAT THESE MAY END UP BEING
RATHER DRY TRADES WITH ONLY LIGHT RAINFALL IN WINDWARD AND MAUKA
SECTIONS.

R BALLARD

.HFO...HIGH SURF ADVISORY FOR SOUTH SHORES.