Heavy Rain in Hawaii, May 3 to 5, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST FRI MAY 3 2013

.SYNOPSIS...
A WEAKENING COLD FRONT IS APPROACHING KAUAI FROM THE NORTHWEST...AND
SHOULD MOVE ACROSS THE ISLAND CHAIN THROUGH THE WEEKEND. THE FRONT
WILL EVENTUALLY DISSIPATE NEAR THE BIG ISLAND ON MONDAY. PREVAILING
LIGHT WINDS WILL ALLOW FOR SEA BREEZES TO BRING LOW CLOUDS AND
SHOWERS ACROSS INTERIOR AND MOUNTAIN AREAS...ALONG WITH VOLCANIC
HAZE OVER MUCH OF THE SMALLER ISLANDS DURING THE NEXT SEVERAL DAYS.
NORTHERLY WINDS BEHIND THE FRONT WILL BE LIGHT...ALLOWING LOCAL SEA
BREEZES AND LAND BREEZES TO CONTINUE INTO EARLY NEXT WEEK.

&&

.DISCUSSION...
AN AMPLIFYING UPPER LVL TROUGH/LOW COMPLEX FAR NW OF THE MAIN
HAWAIIAN ISLANDS IS PUSHING A SFC COLD FRONT TOWARD THE AREA. THE
LEADING EDGE OF THE FRONT IS LOCATED ABOUT 130 MILES NW OF
KAUAI...AND IS GRADUALLY NEARING THE W EDGE OF THE ISLAND CHAIN.

ABUNDANT MOISTURE AHEAD OF THE FRONT WILL CONTINUE TO FEED EVENING
SHOWERS ACROSS KAUAI COUNTY AND OAHU...AND TO A LESSER EXTENT OVER
THE E HALF OF THE ISLAND CHAIN. EXPECT THE CURRENT LIGHT AND
VARIABLE WIND REGIME TO CONTINUE DURING THE WEEKEND...WHICH WILL
ALLOW FOR SEA BREEZES TO DEVELOP AND BRING PERIODS OF LOW CLOUDS
AND RAIN OVER LEEWARD AND INTERIOR AREAS.

A SHORTWAVE IS ALSO MOVING ALONG THE BASE OF THE UPPER LVL TROUGH
AND IS HELPING IN PUSHING THE FRONT E/SE AND TOWARD THE STATE...BUT
THE BEST DYNAMICS FOR CONVECTIVE SUPPORT ARE EXPECTED TO REMAIN N OF
THE AREA. LATEST SATELLITE IMAGERY AND MODEL DATA SHOW THAT THE
FRONT IS GRADUALLY WEAKENING AND MOVING SLOWER. GFS AND ECMWF SHOW
FAIR CONSENSUS REGARDING THE OVERALL SOLUTION FOR THE
FRONT...ALTHOUGH GFS IS DEPICTING A SLIGHTLY FASTER FROPA ACROSS
THE ISLAND CHAIN DURING THE WEEKEND. AN OUTLIER SOLUTION IS SHOWN BY
THE NAVGEM...WHICH STALLS THE DECAYING FRONT NEAR KAUAI. THE
OFFICIAL FORECAST WILL CONTINUE TO FOLLOW THE GFS/ECMWF CONSENSUS
SINCE THERE IS NO COMPELLING EVIDENCE TO DEVIATE FROM THAT SCENARIO
ATTM.

THE AIR MASS OVER THE AREA WILL BECOME INCREASINGLY UNSTABLE AS THE
UPPER LVL SWINGS BY N OF THE ISLANDS THROUGH THE WEEKEND. LATEST
FORECAST SOUNDINGS AND MODEL X-SEC ANALYSIS SHOW WEAKENING
INVERSIONS ACROSS THE ISLANDS. THIS WILL COMBINE WITH A PREVAILING
LIGHT GRADIENT ASSOCIATED TO THE FROPA TO FEED LOCALIZED AFTERNOON
SEA BREEZES AND NIGHTTIME LAND BREEZES EACH DAY.

WINDS WILL LIKELY TURN TO A MORE N/NE FLOW BEHIND THE FROPA BY EARLY
NEXT WEEK...BUT SHOULD REMAIN LIGHT ENOUGH FOR SEA BREEZES TO
DEVELOP ON MON AND TUE...THEN ANOTHER FRONT APPROACHES THE AREA BY
MIDWEEK. THIS WILL ENSURE THAT A RETURN TO A TRADE WIND WEATHER
PATTERN IS NOT EXPECTED UNTIL THE LATER PART OF NEXT WEEK.

&&

.AVIATION...
VFR WILL HOLD OVER MOST OF THE STATE THIS EVENING AND IN THE
OVERNIGHT PERIOD...THOUGH TEMPORARY MVFR CONDITIONS ARE POSSIBLE
OVER THE BIG ISLAND...PHKO AND PHTO...AS COLLAPSING LOW CLOUDS FROM
DAYTIME HEATING SLOWLY DISSIPATE. LANAI MAY ALSO SEE BRIEF MVFR THIS
EVENING.

&&

.MARINE...
A COUPLE OF SMALL NW AND S/SW SWELLS WILL BRING A MODEST SURF
ALONG EXPOSED SHORES OF THE ISLANDS INTO THE MIDDLE OF NEXT WEEK.
WITH SMALL SWELLS AND LIGHT WINDS IN THE FORECAST...NO SMALL CRAFT
ADVISORY CONDITIONS OR SURF HIGHLIGHTS ARE EXPECTED THROUGH THE
FORECAST PERIOD.

&&

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

&&

DISCUSSION/MARINE...REYNES
AVIATION...KINEL