261
FXHW60 PHFO 061330
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI NOV 6 2009
SYNOPSIS
HIGH PRESSURE TO THE NORTH WILL KEEP TRADE WINDS BLOWING THROUGH
EARLY NEXT WEEK. RAINFALL WILL BE GENERALLY SPARSE TODAY...BUT A
SHOWER BAND WILL SAG SOUTH OVER THE ISLANDS TONIGHT AND KEEP
WINDWARD AREAS A BIT WET THROUGH EARLY NEXT WEEK. THE WEATHER MAY
TURN UNSETTLED BY THE END 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 THE MIDDLE OF 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 CONTINUE TO PRODUCE A FEW
SHOWERS OVER THE HILO SIDE OF THE BIG ISLAND BEFORE DISSIPATING
LATER TODAY. ANOTHER CLOUD BAND ABOUT 100 MILES NORTH OF THE ISLANDS
WILL MOVE SOUTH ABOUT 5 MPH AND SPREAD OVER THE ISLANDS TONIGHT.
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 TRADE-WIND 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 TROUGH IS LIKELY TO BE BROAD AND
WEAK ENOUGH SO THAT SURFACE WINDS OVER THE ISLANDS WILL REMAIN
EASTERLY AS THE TROUGH MOVES WEST OVER THE ISLANDS. IT NOW LOOKS
LIKE THE MAIN IMPACT THE TROUGH WILL HAVE WILL BE TO DESTABILIZE THE
ATMOSPHERE AND PRODUCE RATHER WET TRADE-WIND WEATHER TOWARD THE END
OF NEXT WEEK. THERE IS STILL A GREAT DEAL OF UNCERTAINTY IN THE
FORECAST BEYOND EARLY NEXT WEEK.
MARINE
A SCATTEROMETER LAST EVENING PASS SHOWED WINDS ABOVE 25 KT IN SOME
AREAS OF THE COASTAL WATERS. A SMALL CRAFT ADVISORY CONTINUES FOR
THE WINDIER AREAS. 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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