808
FXHW60 PHFO 062000
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
933 AM HST FRI NOV 6 2009
SYNOPSIS
HIGH PRESSURE TO THE NORTH WILL KEEP TRADE WINDS BLOWING INTO NEXT
WEEK. RAINFALL WILL BE GENERALLY SPARSE TODAY...BUT A SHOWER BAND
WILL SAG SOUTH OVER THE ISLANDS TONIGHT AND PROVIDE WINDWARD
SHOWERS OVER THE WEEKEND. HIGH CLOUDS WILL COVER HAWAIIAN SKIES OVER
MUCH OF THE WEEKEND AND INTO NEXT WEEK. TRADE SHOWERS WILL INCREASE
NEXT WEEK AS THE UPPER ATMOSPHERE BECOMES UNSTABLE.
DISCUSSION
RAINFALL OVERNIGHT WAS RELEGATED MAINLY TO WINDWARD AREAS OF MAUI
AND THE BIG ISLAND. A DECAYING BAND OF LOW CLOUDS EAST OF THE BIG
ISLAND IS PROVIDING THE MOISTURE FOR THESE SHOWERS. TWELVE HOUR
RAINFALL TOTALS FROM 5 PM TO 5 AM ON THE BIG ISLAND SHOW STEADY
RAIN FELL OVER THE FIRST HALF OF THE EVENING WITH RAIN TAPERING
OFF LATE AT NIGHT. TOTALS OVER THE TIME PERIOD RANGED FROM 0.16
INCHES TO 0.56 INCHES FOR WINDWARD GAGES. 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.
AT THE SURFACE...MODERATE TO FRESH TRADE WINDS ARE EXPECTED TO
CONTINUE NEXT WEEK AS HIGH PRESSURE REMAINS FAR NORTH OF THE
STATE WITH THE RIDGE REMAINING BETWEEN 30N AND 35N.
MID AND UPPER LEVEL CLOUD COVER WILL INCREASE FROM WEST TO EAST
BEGINNING SATURDAY AS CLOUDS FORMED BY A TROUGH 750 MILES WEST OF
KAUAI ARE ADVECTED OVER THE STATE. RIDGING ALOFT SOUTHEAST OF THE
STATE AND A TROUGH TO THE WEST WILL CREATE A CONVEYOR BELT ALLOWING
MID AND UPPER CLOUDS TO STREAM OVER THE ALOHA STATE. THE TROUGH
ALOFT IS EXPECTED TO PUSH EAST OVER THE NEXT FEW DAYS REACHING
KAUAI SUNDAY NIGHT. MODELS SHOW THE TROUGH WILL BRING SOME
INSTABILITY TO THE ATMOSPHERE SUNDAY NIGHT THOUGH
TUESDAY...ALLOWING FOR AN INCREASE IN COVERAGE AND INTENSITY OF
THE TRADE SHOWERS. AS THE UPPER TROUGH MOVES EAST...THE ENHANCED
UPPER CLOUD COVER WILL MOVE EAST OF THE STATE TUESDAY.
THE GLOBAL COMPUTER MODELS CONTINUE TO SHOW A STRONGER UPPER TROUGH
DIGGING TOWARD THE ISLANDS FROM THE NORTH WEDNESDAY AND THURSDAY.
THE MODELS HAVE BEEN INCONSISTENT IN THEIR FORECASTS FOR THIS
SYSTEM...BUT IT APPEARS A CONSENSUS IS BEING REACHED. THE GFS AND
ECMWF NOW BOTH SUGGEST THE TRADE WINDS WILL PERSIST THROUGH THE
PERIOD AS THE TROUGH ALOFT APPROACHES FROM THE NORTH DURING THE
SECOND HALF OF THE WEEK. THE MAIN IMPACT OF THE TROUGH WILL BE TO
DESTABILIZE THE ATMOSPHERE AND PRODUCE WET TRADE WIND WEATHER
TOWARD THE END OF NEXT WEEK. CONFIDENCE IN THIS LONG TERM FORECAST
REMAIN LOW WITH SMALL PERTURBATIONS IN THE MODELS CONTINUE TO
CAUSE LARGE CHANGES IN THE FORECAST SOLUTION.
MARINE
A SMALL CRAFT ADVISORY CONTINUES FOR SELECT AREAS. THE CURRENT
NORTH NORTHWEST SWELL WILL SLOWLY DIMINISH. THIS SWELL WILL BE
REINFORCED BY A NEW NORTH NORTHWEST SWELL ARRIVING TONIGHT...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 UNTIL NOON HST SATURDAY FOR KAUAI WINDWARD
WATERS-KAUAI LEEWARD WATERS-OAHU WINDWARD WATERS-KAIWI CHANNEL-
MAUI COUNTY WINDWARD WATERS-BIG ISLAND LEEWARD WATERS.
SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY FOR KAUAI NORTHWEST
WATERS-KAUAI CHANNEL-MAALAEA BAY-PAILOLO CHANNEL-ALENUIHAHA
CHANNEL-BIG ISLAND SOUTHEAST WATERS.
MORRISON
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