931
FXHW60 PHFO 060805 AAA
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1005 PM HST THU NOV 5 2009
UPDATE
A RECENT SCATTEROMETER PASS SHOWED WINDS ABOVE 25 KT IN SOME AREAS
OF THE COASTAL WATERS. WE HAVE UPDATED THE WIND FORECASTS AND ISSUED
A SMALL CRAFT ADVISORY FOR THE WINDIER AREAS.
SYNOPSIS
HIGH PRESSURE TO THE NORTH WILL KEEP TRADE WINDS BLOWING THROUGH
EARLY NEXT WEEK. A WEAK SHOWER BAND WILL KEEP THE WINDWARD SIDE OF
THE BIG ISLAND CLOUDY AND WET TONIGHT BEFORE DISSIPATING TOMORROW.
ANOTHER SHOWER BAND WILL SAG SOUTH OVER THE ISLANDS FRIDAY NIGHT AND
KEEP WINDWARD AREAS A BIT WET THROUGH EARLY NEXT WEEK. THE WEATHER
MAY TURN UNSETTLED BY THE MIDDLE OF NEXT WEEK AS A TROUGH ALOFT DIGS
SOUTH TOWARD THE ISLANDS.
DISCUSSION
A COUPLE OF HIGHS MOVING EASTWARD TO THE NORTH OF THE ISLANDS WILL
MAINTAIN TRADE WINDS THROUGH EARLY NEXT WEEK. AN EAST TO WEST BAND
OF SHOWERY LOW CLOUDS...THE REMNANT OF AN OLD FRONT...IS OVER THE
BIG ISLAND NOW. THIS BAND WILL BRING SHOWERS TO THE HILO SIDE OF THE
BIG ISLAND TONIGHT BEFORE DISSIPATING TOMORROW. ANOTHER CLOUD BAND
ABOUT 120 MILES NORTH OF THE ISLANDS WILL MOVE SOUTH ABOUT 5 MPH AND
SPREAD OVER THE ISLANDS FRIDAY NIGHT. RIDGING ALOFT WILL KEEP THE
ATMOSPHERE RATHER STABLE. THIS STABILITY WILL PREVENT HEAVY RAINFALL
AND WILL KEEP THE SHOWERS TOO SHALLOW TO REACH MOST LEEWARD AREAS.
THE GLOBAL COMPUTER MODELS CONTINUE TO SHOW A TROUGH ALOFT DIGGING
TOWARD THE ISLANDS FROM THE NORTH AROUND THE MIDDLE OF NEXT WEEK.
THE MODELS HAVE BEEN UNUSUALLY INCONSISTENT IN THEIR FORECASTS FOR
THIS SYSTEM...BUT IT APPEARS THE MODELS MAY NOW BE SETTLING DOWN.
THE GFS AND ECMWF...WHICH HAD BEEN FAR APART...ARE NOW BOTH
SUGGESTING THAT TRADE WINDS WILL PERSIST OVER THE ISLANDS THROUGH
WEDNESDAY. AS THE TROUGH ALOFT APPROACHES IT WILL INDUCE A SURFACE
TROUGH IN THE EASTERLY LOW LEVEL FLOW. BOTH THE GFS AND ECMWF NOW
FORECAST THE TROUGH TO FORM EAST OF THE ISLANDS AND SHOW A WEAKER
TROUGH THAN EARLIER MODEL RUNS SUGGESTED. THE SURFACE TROUGH WILL
MOVE WEST OVER THE ISLANDS LATE NEXT WEEK. SOUTHEAST WINDS ON THE
EAST SIDE OF THE SURFACE TROUGH MAY BRING LOTS OF LOW LEVEL MOISTURE
OVER THE ISLANDS WHILE THE TROUGH ALOFT WILL MAKE THE ATMOSPHERE
UNSTABLE. THIS COMBINATION OF MOISTURE AND INSTABILITY WOULD BRING
THE POSSIBILITY FOR WIDESPREAD HEAVY RAIN. THERE IS STILL A GREAT
DEAL OF UNCERTAINTY IN THE FORECAST BEYOND EARLY NEXT WEEK.
MARINE
THE CURRENT NORTH NORTHWEST SWELL WILL SLOWLY DIMINISH. THIS SWELL
WILL BE REINFORCED BY A NEW NORTH NORTHWEST SWELL ARRIVING FRIDAY
NIGHT...BUT SURF WILL REMAIN BELOW THE ADVISORY THRESHOLD. THE NORTH
NORTHWEST SWELL WILL GET ANOTHER BOOST ON SUNDAY.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY FOR KAUAI NORTHWEST WATERS...THE KAUAI
CHANNEL...THE PAILOLO CHANNEL...MAALAEA BAY...THE ALENUIHAHA
CHANNEL...AND THE BIG ISLAND SOUTHEAST WATERS THROUGH SATURDAY NIGHT.
DONALDSON
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