Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 261334
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI DEC 26 2014

.SYNOPSIS...
LIGHT NORTHERLY WINDS AND COOL TEMPERATURES WILL PREVAIL THROUGH THE
WEEKEND. CLOUDS AND LIGHT SHOWERS WILL LINGER MAINLY OVER NORTH
THROUGH WEST SLOPES. MORE TYPICAL TRADE-WIND CONDITIONS WILL RETURN
GRADUALLY BY SUNDAY NIGHT AND MONDAY. A WEAK FRONT WILL MOVE
SOUTHEAST ACROSS THE STATE FROM MONDAY NIGHT OR TUESDAY INTO
WEDNESDAY.

&&

.DISCUSSION...
SURFACE OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS REPORTED
GENERALLY LIGHT WESTERLY TO NORTHWESTERLY WINDS. THE SUPPORTING
TROUGH ALOFT NOW DIRECTED MOST OF ITS ENERGY TO THE NORTHEAST...
AWAY FROM THE STATE. CLOUD COVER CONSISTED MOSTLY OF COLD-AIR CUMULI
BREAKING IN WAVES OVER THE ISLANDS FROM THE NORTHWEST. OVERALL...
THESE STABLE CLOUDS IN THE COOL POST-FRONTAL AIR MASS PRODUCED
LITTLE RAIN.

HOWEVER...BANDING IN THE CLOUD FIELD PRODUCED RAIN FROM OAHU TO MAUI
EARLIER IN THE NIGHT...AND UPLIFT ALONG NORTH SLOPES OF THE SMALLER
ISLANDS CONTINUED TO SQUEEZE OUT LIGHT RAIN. SATELLITE ESTIMATES OF
PRECIPITABLE WATER DETECTED PLUMES OF ENHANCED MOISTURE SHEARING OFF
FROM THE OCCLUSION TO THE NORTH OF THE STATE. GUIDANCE PREDICTED
THESE PLUMES TO MOVE SOUTH OVER THE ISLANDS AT TIMES THROUGH THE
WEEKEND...PROVIDING FUEL FOR PRECIPITATION IN THE OTHERWISE FAIRLY
DRY AIR MASS. POPS AND RELATED FIELDS HAVE BEEN INCREASED...MAINLY
FOR THIS MORNING...BUT ALSO THROUGH THE WEEKEND MORE GENERALLY.
DESPITE THE HIGHER POPS...ACCUMULATION SHOULD REMAIN LOW HOWEVER.

STRONG WINDS OVER HIGHER ELEVATIONS OF THE BIG ISLAND DROPPED OFF
BRIEFLY AROUND MIDNIGHT...BUT RECENTLY HAVE RISEN SIGNIFICANTLY
AGAIN...AND MAY NOT ABATE COMPLETELY UNTIL THE MID-LEVEL TROUGH
MOVES AWAY MORE DEFINITIVELY ON SATURDAY. FOR NOW...A WIND ADVISORY
IS IN EFFECT FOR THE SUMMITS ONCE MORE.

GUIDANCE PREDICTED SURFACE RIDGING TO THE NORTH TO EXPAND EASTWARD
SOMEWHAT MORE SLOWLY THAN USUALLY HAPPENS AFTER A FRONT HERE...SO
THAT LOCAL WINDS WILL TURN NORTHERLY...AND THEN NORTHEASTERLY...ONLY
GRADUALLY THROUGH THE WEEKEND. WIND DIRECTION MAY NOT RETURN TO
CLIMATOLOGY MUCH BEFORE SUNDAY NIGHT OR MONDAY MORNING. NORTHERLY
ADVECTION WILL KEEP TEMPERATURES ON THE LOW SIDE DURING THIS TIME.

BY MONDAY NIGHT...ANOTHER FRONT WILL APPROACH FROM THE NORTHWEST.
SOLUTIONS GENERALLY DEPICTED THIS FEATURE AS WEAKER...AND RECEIVING
LESS SUPPORT FROM ALOFT...THAN THE LAST FRONT. STILL...CONSENSUS DID
EXPECT THIS FEATURE TO HOLD TOGETHER LONG ENOUGH TO APPROACH THE BIG
ISLAND BY WEDNESDAY NIGHT. RAINFALL AND WINDS ACCOMPANYING THIS
FRONT LIKELY WILL BE QUITE MODEST.

BY LATE NEXT WEEK...GUIDANCE HINTED THAT A MUCH STRONGER MID-LEVEL
TROUGH WILL DIG SOUTH SHARPLY TOWARD THE ISLANDS...SUPPORTING THE
APPROACH OF A MUCH MORE SUBSTANTIAL FRONT CARRYING LARGE AMOUNTS OF
PRECIPITABLE WATER. IF CONSENSUS IS RIGHT...THEN NEXT FRIDAY INTO
SATURDAY MAY BE RATHER WET. THE 06Z GFS RUN DEPICTED SUBSTANTIAL
SHOWER DEVELOPMENT IN CONVERGENCE AHEAD OF THIS NEXT FRONT...
POSSIBLY ALONG THE REMNANTS OF THE ONE FROM EARLIER IN THE WEEK. IF
SO...THEN THE BIG ISLAND AND MAUI COUNTY MAY START TO RECEIVE
SIGNIFICANT RAINFALL AS EARLY AS THURSDAY NIGHT. THE FORECAST HAS
BEEN NUDGED IN THIS DIRECTION...BUT GENTLY...CONSIDERING SOLUTION
UNCERTAINTY THAT FAR OUT.

&&

.MARINE...
SURF HEIGHTS ALONG NORTH-FACING SHORES ARE EXPECTED TO REMAIN BELOW
ADVISORY LEVELS THROUGH THIS AFTERNOON. ANOTHER MODERATE NORTHWEST
SWELL SHOULD ARRIVE TONIGHT...PEAK ON SATURDAY...AND THEN DIMINISH A
LITTLE ON SUNDAY. A REINFORCING NORTHWEST SWELL WILL ARRIVE ON
MONDAY.

OVER THE COASTAL WATERS...WIND SPEEDS AND COMBINED SEAS ALSO ARE
EXPECTED TO REMAIN BELOW THE THRESHOLD FOR A SMALL CRAFT ADVISORY
THROUGH TODAY. THE PENDING MODERATE NORTHWEST SWELL MAY LIFT
COMBINED SEAS TO NEAR THE ADVISORY LEVEL BRIEFLY OVER EXPOSED
COASTAL WATERS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY UNTIL 6 PM HST THIS EVENING FOR BIG ISLAND SUMMITS.

&&

$$

RYSHKO




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