Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 210630
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST SAT DEC 20 2014

.SYNOPSIS...
LIGHT SOUTHEASTERLY WINDS WILL CONTINUE THROUGH SUNDAY AND ALLOWING
FOR LAND AND SEA BREEZES TO DEVELOP. EXPECT GENERALLY BENIGN WEATHER
CONDITIONS THROUGH SUNDAY WITH A FEW SHOWERS DEVELOPING IN THE
AFTERNOON AS SEA BREEZES PUSH INLAND. THEN A COLD FRONT APPROACHES
THE ISLANDS FROM THE NORTHWEST...BRINGING AN INCREASE IN SHOWERS
STARTING SUNDAY NIGHT. THERE IS POTENTIAL FOR HEAVY RAIN AND A FEW
THUNDERSTORMS ACROSS THE ALOHA STATE FROM MONDAY AFTERNOON THROUGH
TUESDAY. STRONG NORTHERLY WINDS WILL DEVELOP BEHIND THE FRONT BY MID
WEEK.

&&

.DISCUSSION...
AT 8 PM HST RADAR DATA WAS SHOWING A FEW SMALL SHOWERS MOVING ACROSS
WINDWARD AND MOUNTAIN AREAS. SFC WINDS ARE GENERALLY LIGHT...WITH
STILL SOME E FLOW PREVAILING OVER THE BIG ISLAND.

FOR THE REST OF TONIGHT...AN UPPER LEVEL RIDGE WILL REMAIN IN PLACE
OVER THE ALOHA STATE...WHICH WILL HELP KEEPING A RELATIVELY STABLE
AIRMASS ALOFT WITH SHOWER ACTIVITY REMAINING LOW. AT THE SFC...A
BROAD HIGH FAR ENE OF THE ISLANDS WILL CONTINUE TO MIGRATE E...WITH
GENERALLY LIGHT SE/S FLOW CONTINUING THROUGH SUN.

MEANWHILE...A DEEPENING TROUGH IS LOCATED FAR NW OF THE ISLAND CHAIN
AND GRADUALLY APPROACHING THE AREA. AN ASSOCIATED COLD FRONT IS
ABOUT 580 MILES NW OF KAUAI AND ALSO MOVING TOWARDS THE ISLANDS.
WITH THIS OVERALL SYNOPTIC SETUP...EXPECT ANOTHER DAY OF SEA BREEZES
DEVELOPING SUN AFTERNOON WITH CLOUDS AND SHOWERS AFFECTING SOME
LEEWARD AND INTERIOR AREAS. RAINFALL SHOULD REMAIN LIGHT.

THE UPPER LEVEL TROUGH AND ITS ASSOCIATED SFC COLD FRONT WILL
APPROACH THE W EDGE OF THE ALOHA STATE BY SUN NIGHT. SHOWER COVERAGE
WILL INCREASE AS THE LEADING EDGE OF THE FRONT REACHES THE
AREA...WITH POSSIBLY ENOUGH UPPER LVL SUPPORT FOR SOME DEEP
CONVECTION TO DEVELOP. A COLDER AIRMASS ALOFT WILL ARRIVE WITH THE
TROUGH...FURTHER DESTABILIZING THE ATMOSPHERE OVER THE ISLANDS.
LATEST MODEL ANALYSES SHOW 500 MB TEMPS DROPPING TO -12C TO -14C.
HOWEVER...THE LATEST TRENDS IN THE GLOBAL MODEL SOLUTIONS ARE
BECOMING LESS AGGRESSIVE IN TERMS OF OVERALL AVAILABLE MOISTURE FOR
SIGNIFICANT CONVECTION TO DEVELOP WITH THE FROPA. X-SEC ANALYSES
DEPICT A RATHER DRY SWATH ABOVE 700 MB. BUT THE TROUGH SHOULD
PROVIDE ENOUGH INSTABILITY TO ERODE LOW LVL INVERSIONS AND ALLOW FOR
SOME VERTICAL DEVELOPMENT OF SHOWERS AND ANY THUNDERSTORM CELLS THAT
MAY FORM.

GLOBAL MODELS ARE SHOWING BETTER AGREEMENT IN TERMS OF TIMING AND
OVERALL SCENARIO...WITH BOTH GFS AND ECMWF SOLUTIONS DEPICTING A
FROPA THROUGH THE ISLAND CHAIN AND A CUTOFF LOW DEVELOPING NE OF THE
STATE MON THROUGH TUE. SO FAR IT SEEMS THE HIGHEST IMPACTS
WEATHERWISE ARE EXPECTED OVER KAUAI COUNTY AND OAHU...WHERE THE
HIGHEST POPS AND CHANCES FOR LOCALIZED HEAVY RAINFALL COVERAGE
RESIDE. THERE IS ALSO A SLIGHT CHANCE OF THUNDERSTORMS FROM MON
AFTERNOON TO TUE NIGHT.

STRONG NNE WINDS WILL ARRIVE IN THE WAKE OF THE FROPA BY MID
WEEK...THEN GRADUALLY RELAX THROUGH THE SECOND HALF OF THE WEEK.
WIND WILL FINALLY VEER TO A MORE TYPICAL NE FLOW NEXT WEEKEND AS
HIGH PRESSURE BUILDS NW OF THE ALOHA STATE.

&&

.AVIATION...
LIGHT WINDS WILL ALLOW LAND BREEZES TO CLEAR SKIES OVER THE SMALLER
ISLANDS TONIGHT THROUGH SUNDAY MORNING...WITH PREVAILING VFR.
MEANWHILE...WEAKENING BUT PERSISTENT TRADE WINDS NEAR THE BIG
ISLAND WILL CARRY A FEW SHRA OVER WINDWARD COASTS...SLOPES AND
ADJACENT WATERS...RESULTING IN ISOL MVFR CIG/VIS. LIGHT WINDS AND A
STABLE ISLAND ATMOSPHERE CONTINUING THROUGH SUNDAY WILL LEAD TO
AREAS OF INTERIOR CLOUDINESS BY SUNDAY AFTERNOON...WITH ISOL MVFR
CIG POSSIBLE OVER ALL ISLANDS. A FRONT ARRIVING FROM THE NW LATE IN
THE DAY WILL BRING INCREASING N TO NE WINDS AND MVFR VIS/CIG IN
SHRA...AFFECTING KAUAI INITIALLY TOMORROW EVENING.

&&

.MARINE...
A LONG PERIOD NORTHWEST SWELL GENERATED BY A LARGE AND POWERFUL LOW
PRESSURE SYSTEM IS EXPECTED TO BRING WARNING LEVEL SURF TO THE
ISLANDS ON SUNDAY. THIS SWELL WILL REMAIN IN PLACE THROUGH MONDAY
BEFORE GRADUALLY DIMINISHING. A HIGH SURF WARNING STARTS AT 4 AM
SUNDAY FOR NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS...
AND LATE SUNDAY MORNING FOR WEST FACING SHORES OF THE BIG ISLAND.

A HIGH SURF ADVISORY ALSO REMAINS IN EFFECT FOR EAST FACING SHORES
OF THE BIG ISLAND THROUGH SUNDAY.

THIS INCREASING SWELL WILL ALSO GENERATE SMALL CRAFT ADVISORY
CONDITIONS STARTING SUNDAY EARLY MORNING OVER MOST COASTAL WATERS
DUE TO HAZARDOUS SEAS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF WARNING FROM 4 AM HST SUNDAY TO 6 AM HST TUESDAY FOR NORTH
AND WEST FACING SHORES OF NIIHAU KAUAI OAHU AND MOLOKAI AND FOR
NORTH FACING SHORES OF MAUI.

HIGH SURF WARNING FROM 10 AM HST SUNDAY TO 6 AM HST TUESDAY FOR WEST
FACING SHORES OF THE BIG ISLAND.

HIGH SURF ADVISORY UNTIL 6 PM HST SUNDAY FOR EAST FACING SHORES OF
THE BIG ISLAND.

SMALL CRAFT ADVISORY FROM 4 AM SUNDAY TO 6 AM HST TUESDAY FOR ALL
HAWAIIAN WATERS EXCEPT MAALAEA BAY.

&&

$$

DISCUSSION/MARINE...REYNES
AVIATION...BIRCHARD





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