Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 211330
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST FRI NOV 21 2014

.SYNOPSIS...
MODERATE TRADE WINDS WILL DIMINISH INTO THE WEEKEND. MOST SHOWERS
WILL BE LIMITED TO WINDWARD SLOPES...ESPECIALLY OVER THE BIG ISLAND.
A FRONT WILL BRING MODEST RAIN AND STRONGER...NORTHERLY WINDS TO
MOST OF THE STATE FROM SUNDAY NIGHT INTO TUESDAY. THE WINDS THEN
WILL WEAKEN AND BECOME NORTHEASTERLY AGAIN AS THE COOL AND DRY AIR
MASS MOISTENS GRADUALLY INTO FRIDAY.

&&

.DISCUSSION...
OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS STILL REPORTED
MODERATE TO LOCALLY STRONG TRADE WINDS BLOWING...AND A TIMELY
SATELLITE SCATTEROMETER PASS SUPPORTED A SMALL CRAFT ADVISORY AROUND
MAUI AND HAWAII COUNTIES. THE FAIRLY SOLID RIDGE PREVAILING ALOFT TO
THE NORTHWEST THROUGH NORTH EXPANDED OVER THE STATE OVERNIGHT...
LOWERING AND STRENGTHENING THE INVERSION. TOGETHER WITH LAND
BREEZES...THIS DEVELOPMENT LARGELY KEPT OFFSHORE THE MODERATELY
ACTIVE SHOWERS VISIBLE JUST OFFSHORE...ESPECIALLY TO THE SOUTHEAST
OF THE BIG ISLAND. FURTHER NORTH...CLOUD COVER UPWIND SHIFTED TO A
CLEARLY MORE STABLE FORM...AND SATELLITE ESTIMATES OF PRECIPITABLE
WATER SHOWED SOLIDLY BELOW-AVERAGE PRECIPITABLE WATER IN THE AIR
MASS ABOUT TO MOVE ACROSS THE STATE.

THUS...POPS HAVE BEEN REDUCED FOR ALL AREAS DURING THE FIRST
PERIOD. UNDER THESE CONDITIONS...AFTERNOON CONVECTION WILL BE HARD
PRESSED TO PRODUCE ANY THUNDER TODAY...SO NO MENTION HAS BEEN ADDED.
HOWEVER...THE MAINLY STABLE CLOUD COVER SHOULD BE AT LEAST AS
WIDESPREAD AS FORECAST EARLIER.

BY SATURDAY...GUIDANCE STILL LARGELY AGREED THAT A DEEPENING
LONG-WAVE TROUGH ALOFT WILL DISPLACE THE MID-LEVEL RIDGE TOWARD THE
NORTHEAST...SUPPORTING THE APPROACH AT THE SURFACE OF THE FRONT
CURRENTLY CROSSING 30N NEAR 170W. AS THE SURFACE RIDGE RETREATS TO
THE SOUTHEAST AHEAD OF THE FRONT...THE TRADE WINDS WILL DIMINISH
LOCALLY...BECOMING SOUTHEASTERLY IN PLACES BY SUNDAY.

THE FRONT ITSELF SHOULD REACH KAUAI BY SUNDAY NIGHT...BUT RECENT
SOLUTIONS PREDICTED THE SUPPORTING MID-LEVEL TROUGH TO FOCUS MAINLY
TO THE EAST OF THE STATE. THUS...MOST DEVELOPMENT ALONG THE FRONT
SHOULD REMAIN NORTHEAST OF THE ISLANDS...LEAVING ONLY A FAIRLY
SHALLOW BOUNDARY TO MOVE DOWN THE STATE FROM SUNDAY NIGHT INTO
TUESDAY. SOME RAIN WILL ACCOMPANY THE FRONT...MAINLY OVER THE
SMALLER ISLANDS. THE BIG ISLAND MORE LIKELY WILL EXPERIENCE A LESS
ORGANIZED INCREASE IN SHOWERS FROM THE FRONTAL REMNANTS MOVING
ASHORE ON TUESDAY AND WEDNESDAY. MODERATE TO STRONG NORTHERLY WINDS
IN THE COOLER AND DRIER AIR MASS BEHIND THE FRONT MAY BE MORE
SIGNIFICANT THAN THE FRONT ITSELF.

FROM WEDNESDAY INTO THE LATTER HALF OF THE WEEK...THE SUBTROPICAL
RIDGE WILL REESTABLISH ITSELF NORTH OF THE STATE GRADUALLY...
RETURNING THE WINDS TO A MORE FAMILIAR NORTHEASTERLY DIRECTION...
THOUGH WIND SPEEDS WILL DROP OFF SIGNIFICANTLY UNTIL THE RIDGE
SHIFTS FAR ENOUGH NORTH. THE COOL AND DRY AIR MASS WILL MODIFY IN
PLACE...ALLOWING WINDWARD SHOWERS TO INCREASE WITH TIME AGAIN.

&&

.MARINE...
WIND SPEEDS ARE EXPECTED TO REMAIN ABOVE THE THRESHOLD FOR A SMALL
CRAFT ADVISORY /SCA/ AROUND MAUI AND HAWAII COUNTIES INTO TONIGHT.
AFTER A BRIEF LULL..SPEEDS LIKELY WILL INCREASE BEHIND THE FRONT
FROM SUNDAY INTO MONDAY...PROBABLY REQUIRING AN SCA AGAIN AROUND
MUCH OF THE STATE.

NORTHWEST SWELLS WILL CONTINUE TO PRODUCE MODEST SURF THROUGH
SATURDAY NIGHT. A SLIGHTLY LARGER SWELL IS EXPECTED TO ARRIVE BY
SUNDAY...POSSIBLY BUILDING SURF TO NEAR THE ADVISORY LEVEL ALONG
NORTH-FACING AND WEST-FACING SHORES OF THE SMALLER ISLANDS THROUGH
MONDAY. THIS SWELL ALSO MAY CONTRIBUTE TO THE NEED FOR AN SCA OVER
THE COASTAL WATERS.

SURF FROM TRADE-WIND WAVES ALONG EAST-FACING SHORES SHOULD DECLINE
AS THE TRADE WINDS DIMINISH.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY UNTIL MIDNIGHT HST TONIGHT FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.

&&

$$

RYSHKO




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