Heavy Rain in Hawaii, May 23 to 26, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
801 PM HST FRI MAY 23 2014

.SYNOPSIS...
LIGHT WINDS AND HUMID CONDITIONS WILL PREVAIL STATE-WIDE THROUGH
SUNDAY...WHILE UNSETTLED WEATHER IS IN STORE FOR MAINLY THE WESTERN
PORTION OF THE ISLAND CHAIN. THE THREAT OF HEAVY SHOWERS AND
THUNDERSTORMS NEAR KAUAI TONIGHT WILL SPREAD TO OAHU SATURDAY AND
SUNDAY AS AN UPPER LEVEL LOW DROPS DOWN NEAR THE ISLANDS. INSTABILITY
WILL LINGER INTO THE MEMORIAL DAY HOLIDAY AS TRADE WINDS RETURN.
DRIER...LESS HUMID WEATHER IS ON TAP FOR NEXT WEEK.

&&

.DISCUSSION...
HEAVY SHOWERS AND EMBEDDED THUNDERSTORMS WILL CONTINUE NEAR KAUAI
THIS EVENING AS A WEAK SURFACE TROUGH LINGERS JUST WEST OF THE
GARDEN ISLE. AN UNSEASONABLE STRONG UPPER LEVEL TROUGH APPROACHING
FROM THE NW IS TRIGGERING THE THUNDERSTORMS...AND ENHANCED
MOISTURE NEAR THE SURFACE IS FUELING THE CLOUDS AND SHOWERS.

SATURDAY AND SUNDAY...SOUTHEAST FLOW ACROSS THE STATE WILL BRING
WARM...MUGGY CONDITIONS WITH SEA BREEZES FORMING IN THE AFTERNOON...
AND LAND BREEZES SETTING UP AT NIGHT. THE MAJORITY OF INSTABILITY
WILL REMAIN OVER THE WESTERN HALF OF THE STATE AND THE CHANCE FOR
HEAVIEST SHOWERS WILL REMAIN GREATEST OVER KAUAI...AND TO A LESSER
EXTENT OAHU AND MOLOKAI. THE REST OF MAUI COUNTY AND THE BIG
ISLAND WILL REMAIN MOSTLY DRY WITH ONLY A FEW POP-UP SHOWERS.

THE UPPER TROUGH WILL REACH KAUAI SATURDAY AFTERNOON BRINGING 500
MB TEMPS NEAR -12C OVER THE WESTERN ISLANDS. ADD IN DAYTIME HEATING
AND ENHANCED LOW LEVEL MOISTURE AND THIS MIX GIVES A RECIPE FOR
THUNDERSTORMS... FREQUENT LIGHTNING AND THE POSSIBILITY OF FUNNEL
CLOUDS AND WATERSPOUTS.

HIGH PRESSURE FAR NORTH OF THE ISLANDS WILL KICK THE SURFACE RIDGE
BACK TO THE NORTH MONDAY BRINGING ISLANDS TRADE WINDS BACK TO THE
STATE. THE UPPER TROUGH WILL LINGER OVER HAWAII AS IT WEAKENS NEXT
WEEK...ALLOWING FOR WET TRADE WINDS WEATHER AND AFTERNOON SHOWERS
OVER THE LEEWARD BIG ISLAND.

&&

.AVIATION...
SHOWERS...SOME HEAVY...REMAIN POSSIBLE OVERNIGHT AND TOMORROW OVER
KAUAI AND ADJACENT WATERS. PERIODS OF MVFR AND ISOLATED IFR
CONDITIONS HAVE PROMPTED A MOUNTAIN OBSCURATION AIRMET FOR KAUAI
THAT WILL LIKELY CONTINUE THROUGH SATURDAY. THUNDERSTORMS REMAIN A
POSSIBILITY OVER AS WELL...WITH THE THUNDERSTORM THREAT EXPANDING TO
OAHU SATURDAY.

OVERNIGHT...EXPECT PASSING SHOWERS...WHICH COULD BRING BRIEF MVFR
CONDITIONS TO OAHU. A MOUNTAIN OBSCURATION AIRMET MAY BE NEEDED
FOR OAHU SATURDAY AFTERNOON AS DAYTIME HEATING COMBINED WITH THE
UNSTABLE AIRMASS WILL BRING SHOWERS AND POSSIBLE THUNDERSTORMS TO
OAHU.

THE REMAINDER OF THE MAIN ISLANDS ARE EXPECTED TO REMAIN DRIER WITH
VFR CONDITIONS PREVAILING. ISOLATED MVFR CONDITIONS ARE POSSIBLE IN
PASSING SHOWERS.

&&

.MARINE...
MONDAY OR TUESDAY...THE HIGH TO THE NORTH SHOULD BE STRONG ENOUGH
FOR SMALL CRAFT ADVISORY /SCA/ WINDS THROUGH THE WINDIER AREAS
AROUND MAUI COUNTY AND THE BIG ISLAND. SCA WINDS BECOME
INCREASINGLY LIKELY BY MID WEEK AS THE HIGH STRENGTHENS FURTHER.

ANOTHER SSW SWELL WILL PRODUCE SETS AROUND THE ADVISORY LEVEL THIS
WEEKEND...WITH SOUTH SHORE SURF FADING BACK TO SUMMER BACKGROUND
LEVELS BY MID WEEK. A SMALL BUT STRONG LOW EAST OF JAPAN MAY SEND A
LONG PERIOD SMALL WNW SWELL OUR WAY LATE MONDAY AND TUESDAY. SEE
THE RECENTLY ISSUED COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST
FOR OAHU...SRDHFO...FOR MORE DETAILS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

MORRISON...DISCUSSION/MARINE
M BALLARD...AVIATION