Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 270600
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM 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 TUESDAY INTO WEDNESDAY. A STRONGER
FRONT MAY BRING HEAVIER RAINFALL LATE IN THE WEEK.

&&

.DISCUSSION...
SURFACE OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS STILL REPORTED
GENERALLY LIGHT WESTERLY WINDS...THOUGH WITH MORE OF A NORTHERLY
COMPONENT NOW. THE FRONT THAT HAD PASSED OVER THE STATE EARLIER THIS
WEEK WAS LOCATED SOLIDLY TO THE NORTH THROUGH EAST...AND CONTINUED
TO MOVE AWAY. THE LARGE MID-LEVEL TROUGH THAT HAD PROVIDED SUPPORT
FOR THE FRONT ALSO DIRECTED MOST OF ITS ENERGY TO THE NORTHEAST...
THOUGH SHORT WAVES ROTATING AROUND THE WEST EDGE OF THE LARGER
TROUGH ACCELERATED WINDS OVER THE BIG ISLAND SUMMITS...AND PRODUCED
LOCAL UPLIFT OVER THE OTHERWISE MOSTLY STABLE COLD-AIR CUMULI
SURROUNDING THE ISLANDS. SURFACE WINDS ALSO PUSHED CLOUD COVER
ASHORE ALONG NORTHERLY SLOPES...SQUEEZING OUT A LITTLE RAIN.
ELSEWHERE...THE RELATIVELY DRY AIR MASS AND LOW INVERSION SUPPRESSED
PRECIPITATION...THOUGH CLOUD COVER WAS COMPARABLE TO CLIMATOLOGY IN
AREAL EXTENT. NORTHERLY ADVECTION KEPT TEMPERATURES ON THE LOW SIDE.
BROADLY SPEAKING...THIS SCENARIO SHOULD REMAIN IN PLACE WELL INTO
THE WEEKEND.

GUIDANCE PREDICTED SURFACE RIDGING TO THE NORTH TO EXPAND EASTWARD
SOMEWHAT MORE SLOWLY THAN USUALLY HAPPENS AFTER A FRONTAL PASSAGE
HERE...SO THAT LOCAL WINDS WILL TURN NORTHEASTERLY ONLY GRADUALLY
THROUGH THE WEEKEND. WIND DIRECTION MAY NOT RETURN TO CLIMATOLOGY
MUCH BEFORE SUNDAY NIGHT OR MONDAY MORNING.

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 FRONT TO HOLD TOGETHER LONG ENOUGH TO APPROACH THE
ALENUIHAHA CHANNEL 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 MORE SUBSTANTIAL FRONT CARRYING LARGE AMOUNTS OF
PRECIPITABLE WATER. IF CONSENSUS IS RIGHT...THEN NEXT THURSDAY
NIGHT INTO SATURDAY MAY BE RATHER WET. SEVERAL RUNS EVEN DEPICTED
SUBSTANTIAL SHOWER DEVELOPMENT IN CONVERGENCE AHEAD OF THIS NEXT
FRONT...POSSIBLY ALONG THE REMNANTS OF THE ONE FROM EARLIER IN THE
WEEK. ON THE OTHER HAND...RECENT SOLUTIONS DISAGREED MORE VISIBLY...
ESPECIALLY WITH RESPECT TO BEHAVIOR OF SUBSIDIARY SHORT WAVES WITHIN
THE SUPPORTING MID-LEVEL TROUGH. TIMING OF THIS FRONT...AND ITS
POTENTIAL FOR PRODUCING RAIN...MAY BE DIFFICULT TO PIN DOWN UNTIL
THESE DIFFERENCES RESOLVE...OR LATE NEXT WEEK DRAWS CLOSE.

&&

.MARINE...
SURF HEIGHTS ALONG NORTH-FACING SHORES ARE EXPECTED TO REMAIN BELOW
ADVISORY LEVELS THROUGH TUESDAY. A MODERATE NORTHWEST SWELL WILL
ARRIVE TONIGHT...PEAK SATURDAY AFTERNOON...AND DIMINISH SUNDAY. A
SHORT-PERIOD NORTH SWELL WILL ARRIVE SUNDAY...AND DECREASE INTO
TUESDAY. A NORTHWEST SWELL IS EXPECTED TO BUILD SURF TO NEAR
ADVISORY LEVELS FROM TUESDAY THROUGH THURSDAY.

OVER THE COASTAL WATERS...WIND SPEEDS AND COMBINED SEAS ARE EXPECTED
TO REMAIN BELOW THE THRESHOLD FOR A SMALL CRAFT ADVISORY.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 6 PM HST SATURDAY FOR BIG ISLAND SUMMITS.

&&

$$

RYSHKO




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