Heavy Rain in Hawaii, November 14 to 15, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1018 AM HST FRI NOV 14 2014

.SYNOPSIS...
AN UPPER TROUGH WILL BRING PASSING CLOUDS AND SHOWERS... WITH A
SLIGHT CHANCE OF THUNDERSTORMS THROUGH TONIGHT. VARIABLE WINDS TODAY
WILL SHIFT OUT OF THE SOUTH TONIGHT AS A FRONT APPROACHES FROM THE
NORTHWEST. THIS FRONT WILL REACH KAUAI SATURDAY AND MOVE SOUTHEAST
OVER THE ISLANDS THROUGH SUNDAY. A HIGH MOVING EAST BEHIND THE
FRONT WILL PRODUCE LOCALLY BREEZY TRADE WINDS MONDAY AND THROUGH
NEXT WEEK.

&&

.DISCUSSION...
LIGHT WINDS PREVAIL ACROSS THE STATE TODAY EVERYWHERE EXCEPT THE
BIG ISLAND SUMMITS. A WEAK COLD FRONT APPROACHING FROM THE
NORTHWEST IS ABOUT 375 MILES NW OF KAUAI THIS MORNING AND MOVING
20 MPH TOWARD THE ISLANDS. WINDS WILL INCREASE OUT OF THE SW
TONIGHT AS THE FRONT APPROACHES. MID AND HIGH CLOUDS ASSOCIATED
WITH AN UPPER LEVEL TROUGH ARE OBSCURING SKIES OVER OAHU THIS
MORNING AND WILL COVER MAUI COUNTY SKIES IN THE LATE MORNING AND
AFTERNOON. THE TROUGH IS RESPONSIBLE FOR THE STRONG WINDS ALONG
THE BIG ISLAND SUMMITS... AND IS COOLING TEMPERATURES ALOFT
BRINGING SOME SLIGHT INSTABILITY TO THE STATE. THE OVERNIGHT LIHUE
SOUNDING SHOWS COOLING IN THE MID- LAYERS WITH A 500 MB TEMP OF -9
CELSIUS. MODEL GUIDANCE SHOWS TEMPS DECREASING A BIT MORE THIS
AFTERNOON WITH 500 MB TEMPS BETWEEN -9 AND -10 C ACROSS THE STATE
THROUGH TONIGHT.

PREFRONTAL MOISTURE CONVERGENCE BROUGHT SOME LOCALLY HEAVY SHOWERS
TO THE BIG ISLAND OVERNIGHT BUT THAT BAND OF MOISTURE IS NOW
MOVING AWAY TO THE NE. SURFACE FORCING THIS AFTERNOON FROM EITHER
PREFRONTAL CONVERGENCE OR SEA BREEZE CONVERGENCE WILL BE ENOUGH TO
SET OFF PASSING SHOWERS WITH A SLIGHT CHANCE OF THUNDERSTORMS
ACROSS THE STATE. AS THE SW WINDS INCREASE TONIGHT... THE CHANCE OF
BANDING SHOWERS INCREASES WITH THE STRONGER FLOW SO SIMILAR PASSING
SHOWERS AND THUNDERSTORMS REMAIN POSSIBLE TONIGHT. HEATING ALONG
THE UPPER BIG ISLAND SLOPES MAY SET OFF ISOLATED THUNDERSTORMS
THIS AFTERNOON AS WELL.

THE UPPER TROUGH AXIS WILL SWING BY THE ISLANDS LATE TONIGHT AND
TEMPS ALOFT WILL WARM BRINGING MORE STABILITY TO THE ATMOSPHERE
AND ENDING ANY THUNDERSTORM THREAT BY SATURDAY MORNING. AN UPPER
RIDGE WILL TAKE THE TROUGH/S PLACE AND A STABLE ATMOSPHERE LOOKS TO
REMAIN THROUGH NEXT WEEK.

NORTH WINDS WILL SEEP OVER KAUAI SATURDAY MORNING AS THE WEAKENING
FRONT MOVES PAST THE GARDEN ISLE TO THE SE. SW WINDS AND PASSING
SHOWERS WILL PREVAIL AHEAD OF THE FRONT WITH BOUTS OF SUNSHINE
MIXED IN. BOTH THE GFS AND ECMWF PLACE A LINGERING BAND OF WEAK
MOISTURE CONVERGENCE OVER MAUI COUNTY SATURDAY AFTERNOON AND POPS
HAVE BEEN INCREASED TO REFLECT THIS POSSIBILITY. NORTHERLY FLOW
REACHES OAHU SATURDAY NIGHT AND MAUI COUNTY SUNDAY MORNING.
ISOLATED SHOWERS ARE POSSIBLE SATURDAY NIGHT...FAVORING NORTH
SLOPES FOR KAUAI AND OAHU.

THE WEAK OR DISSIPATED FRONT WILL PUSH SOUTH OF THE ISLANDS SUNDAY
AND WINDS WILL QUICKLY INCREASE AND SHIFT TO MODERATE TRADE WINDS
SUNDAY AND SUNDAY NIGHT. HIGH PRESSURE WILL REMAIN N OF THE ISLANDS
NEXT WEEK PROVIDING MODERATE TO FRESH TRADE WINDS. LIMITED SHOWERS
WILL FOCUS OVER THE NORMAL WINDWARD AND MOUNTAIN AREAS WITH DRY
CONDITIONS FOR LEEWARD AREAS. LONG RANGE... AND HIGHLY VARIABLE
FORECASTS FOR LATE NEXT WEEK SHOW ANOTHER FRONT APPROACHING THE
ISLANDS FROM THE NW.

&&

.AVIATION...
A BROAD MID TO UPPER LEVEL TROUGH IS SLOWLY MOVING OVER THE ISLANDS.
THICK HIGH CLOUDS BETWEEN FL200 AND FL300 ARE CURRENTLY BETWEEN
OAHU AND MOLOKAI...AND WILL CONTINUE TO MOVE EAST. THE UNSTABLE AND MOIST
ATMOSPHERE HAS THE POTENTIAL FOR ISOL THUNDERSTORMS THIS AFTERNOON
THROUGH TONIGHT OVER ALL ISLANDS. THUNDERSTORMS WILL LIKELY CARRY
MVFR TO IFR CONDITIONS WITH CB TOPS ABOVE FL350.

OTHERWISE...BACKGROUND FLOW IS PREDOMINATELY LIGHT SOUTH TO
SOUTH WESTERLIES WITH ISOLATED TO SCATTERED SHOWERS. THIS WILL ALLOW
FOR SEA BREEZES TO DEVELOP THIS AFTERNOON. CURRENTLY...THERE ARE NO
AIRMETS IN EFFECT. HOWEVER...IF CONDITIONS WARRANT...THEY WILL BE
ISSUED AS NEEDED.

&&

.MARINE...
A NORTHWEST SWELL IS RUNNING THROUGH THE ISLANDS BRINGING ADVISORY
LEVEL SURF TO EXPOSED NORTH AND WEST FACING SHORES OF THE SMALLER
ISLANDS. THE WAIMEA BAY BUOY IS SHOWING 8 FEET 13 SECONDS WHICH IS
RIGHT IN LINE WITH THE WAVE WATCH 3 MODEL. SURF WILL SLOWLY DIMINISH
TODAY AND LOOKS TO DROP BELOW ADVISORY LEVELS THIS EVENING. SURF
WILL REMAIN ELEVATED OVER THE WEEKEND WITH AN AVERAGE SWELL OF 6
FEET 12 SECONDS. A NORTH SWELL ENTERING HAWAIIAN WATERS MONDAY
LOOKS TO BUMP SURF BACK INTO ADVISORY LEVELS.

WINDS WILL REMAIN BELOW SCA LEVELS THROUGH MONDAY AFTERNOON. INCREASING
TRADE WINDS MAY REACH SCA CRITERIA IN THE WINDY AREAS AROUND MAUI AND
THE BIG ISLAND STARTING MONDAY EVENING.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 PM HST THIS EVENING FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU
KOOLAU-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-WINDWARD
HALEAKALA.

WIND ADVISORY UNTIL 6 AM HST SATURDAY FOR BIG ISLAND SUMMITS.

&&

MORRISON/EATON