069
FXHW60 PHFO 031912
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
912 AM HST TUE NOV 3 2009
SYNOPSIS
MODERATE TO LOCALLY FRESH TRADE WINDS WILL FOCUS SHOWERS ON KAUAI
AND OAHU TODAY...AND INTO TONIGHT...BEFORE SHOWERS DIMINISH ON
WEDNESDAY. A COLD FRONT IS NO LONGER EXPECTED TO CROSS THE ISLAND
CHAIN...BUT TRADE WINDS WILL INCREASE INTO TONIGHT AS HIGH PRESSURE
WELL TO THE NORTHWEST SLOWLY BUILDS SOUTHEAST. TRADE WINDS WILL EASE
ON THURSDAY AND FRIDAY...AND VEER TO THE SOUTHEAST OVER THE
WEEKEND.
DISCUSSION
SOME SIGNIFICANT CHANGES TO THE FORECAST AND FORECAST REASONING THIS
MORNING...AS THE ADVERTISED FRONT/SHEAR LINE PASSAGE IS NO LONGER
ANTICIPATED. ALTHOUGH CLOUDS AND SHOWERS HAVE INCREASED AND ARE
RATHER ACTIVE OVER KAUAI AND OAHU THIS MORNING...THE ADVERTISED
CHANGED IN AIR MASS IS NO LONGER EXPECTED...AND WINDS ARE NOT
EXPECTED TO INCREASE AS MUCH AS EARLIER FORECAST. HAVE MADE CHANGES
TO MANY OF THE FORECAST ELEMENTS AND UPDATED CORRESPONDING FORECASTS
TO ACCOUNT FOR THESE CHANGES.
THE CHANGE IN FORECAST REASONING IS DUE TO THE DEVELOPMENT OF A MID
AND UPPER-LEVEL CUT-OFF LOW JUST N OF KAUAI...WHICH IS CLEARLY
EVIDENT ON WATER VAPOR IMAGERY THIS MORNING. THIS LOW IS NOW
FORECAST TO MOVE W OVER THE NEXT COUPLE OF DAYS...INVOKING A SURFACE
TROUGH ALONG THE STALLED SURFACE FRONT/SHEAR LINE CURRENTLY TO THE
NW OF KAUAI. STRONG N/NE WINDS EXIST JUST TO THE N AND W OF THIS
BOUNDARY...WITH BUOYS TO THE NW OF KAUAI INDICATING SUSTAINED WINDS
OF 30 KT+...AND FULLY DEVELOPED SEAS NEAR 18 FEET.
AS THIS TROUGH SHARPENS JUST W OF KAUAI TODAY AND TONIGHT...THE
TRADE WINDS WILL INCREASE OVER KAUAI AND OAHU...AND THE ASSOCIATED
TIGHTENED SURFACE GRADIENT WILL SUPPORT LOW-LEVEL CONVERGENCE...AND
SHOWER DEVELOPMENT...IN THE SAME GENERAL AREA. HOWEVER...AS THE LOW
ALOFT TRACKS W OVER THE NEXT SEVERAL DAYS...IT/S INDUCED SURFACE
TROUGH WILL FOLLOW SUIT...AND TRADE WINDS WILL MODERATE ON
WEDNESDAY. TRADE SHOWERS WILL REMAIN ESPECIALLY ACTIVE OVER KAUAI
AND OAHU INTO TONIGHT...BUT WILL DECREASE ON WEDNESDAY. WITH AN
UPPER RIDGE FORECAST TO DEVELOP OVER THE ISLANDS LATER WEDNESDAY...
AND INTO THE WEEKEND...A RATHER DRY TRADE WIND PATTERN IS EXPECTED.
THE STRONG SURFACE HIGH TO THE NW WILL WEAKEN WHILE REMAINING
STATIONARY INTO WEDNESDAY NIGHT...AND WILL THEN BUILD E WELL N OF
THE ISLANDS. THIS WILL SUPPORT A MODERATE TRADE WIND FLOW OVER THE
ISLANDS INTO THE WEEKEND. THE HIGH WILL CONTINUE TO TRACK E OVER THE
WEEKEND...AND WINDS OVER THE ISLANDS WILL VEER TO THE SE. THE
SURFACE RIDGE MAY MOVE OVER THE ISLANDS ON MONDAY AND TUESDAY IN
ADVANCE OF AN APPROACHING FRONT.
MARINE
THE OAHU SURF FORECAST /SRFHFO/ CONTAINS A DETAILED LOOK AT EXPECTED
SWELL CONDITIONS OVER THE NEXT COUPLE OF DAYS...AND CAN BE LOOSELY
APPLIED TO THE OTHER ISLANDS. A SMALL CRAFT ADVISORY /SCA/ IS
CURRENTLY IN EFFECT FOR MOST WATERS AROUND KAUAI AND OAHU...AS
COMBINED SEAS ARE AT OR ABOVE 10 FEET...WITH SEAS RANGING FROM 17 TO
20 FEET AT BUOYS 51001/51101 200 NM TO THE NW OF KAUAI.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY FOR KAUAI NORTHWEST WATERS-KAUAI WINDWARD
WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-OAHU WINDWARD WATERS.
BIRCHARD
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