000 FXHW60 PHFO 211411 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 400 AM HST TUE MAY 21 2013 .SYNOPSIS... A LAND AND SEA BREEZE WEATHER PATTERN WILL PERSIST OVER THE ISLANDS THROUGH WEDNESDAY AS AN AREA OF LOW PRESSURE STAYS SEVERAL HUNDRED MILES NORTH OF THE STATE. LINGERING MOISTURE ASSOCIATED WITH THE LOW PRESSURE WILL BRING SLIGHTLY HIGHER CHANCES OF RAIN TO THE EASTERN PORTION OF THE STATE TODAY. TRADE WINDS WILL REBUILD OVER THE ISLANDS BY THURSDAY AS THE AREA OF LOW PRESSURE DRIFTS AWAY AND DISSIPATES WHILE A SURFACE HIGH PRESSURE MOVES TO FAR NORTHEAST OF THE STATE. && .DISCUSSION... AN AREA OF SURFACE LOW PRESSURE PERSISTS IN THE ISLAND VICINITY THIS MORNING...KEEP WINDS LIGHT OVER THE ISLANDS. LAND BREEZES HAVE DEVELOPED OVERNIGHT RESULTING IN A DECREASE IN SHOWERS OVER THE ISLANDS. MOISTURE FROM A DISSIPATING FRONT AS WELL AS LOW LEVEL CONVERGENCE BANDS LINGERS OVER THE EASTERN PORTION OF THE MAIN HAWAIIAN ISLANDS. THE MOISTURE...COUPLED A SLIGHTLY UNSTABLE AIR MASS...AS DEPICTED BY EARLY MORNING HILO SOUNDING...HAS ALLOWED SOME DEEPER CONVECTION TO DEVELOP IN THE MAUI COUNTY AND BIG ISLAND VICINITY SINCE LAST NIGHT. THERE IS ALSO A BATCH OF LOW CLOUDS AFFECTING KAUAI...THOUGH EARLY MORNING LIHUE SOUNDING INDICATES THE AIR MASS IS MORE STABLE AND DRIER COMPARED TO HILO/S. STRONG WINDS ASSOCIATED WITH THE UPPER LEVEL LOW PRESSURE SYSTEM CONTINUE TO AFFECT THE SUMMITS OF THE BIG ISLAND EARLY THIS MORNING. THE WINDS WILL PROBABLY LAST THROUGH THIS EVENING...THEREFORE A WIND ADVISORY REMAINS IN EFFECT FOR THAT AREA. EXPECT A REPEAT OF YESTERDAY WEATHER OVER THE ISLANDS TODAY AS THE STATE/S WEATHER IS STILL PRETTY MUCH UNDER THE INFLUENCE OF THE NEARBY LOW PRESSURE...WITH HIGHEST THREAT OF RAIN AS WELL AS POSSIBLY LOCALLY HEAVY SHOWERS OVER THE EASTERN ISLANDS. THE REST OF THE ISLANDS MAY SEE A CHANCE OF RAIN...ESPECIALLY DURING THE AFTERNOON AND EVENING WITH THE CONVECTIVE CLOUDS UNDER DAY TIME HEATING. THE AREA OF SURFACE LOW PRESSURE WILL SLOWLY WEAKEN AND DRIFT AWAY FROM THE ISLANDS IN THE NEXT COUPLE OF DAYS...AS THE ASSOCIATED UPPER LEVEL CUT-OFF LOW LIFTS NORTH. WINDS WILL REMAIN LIGHT ENOUGH OVER THE ISLANDS WEDNESDAY SUCH THAT THE PRESENT CONVECTIVE WEATHER SCENARIO WILL CONTINUE. LINGERING MOISTURE ASSOCIATED WITH LOW LEVEL CONVERGENCE AND THE OLD FRONTAL BOUNDARY IS ALSO EXPECTED TO HOVER NEARLY THE EASTERN ISLANDS WHILE SLOWLY DISSIPATE. THEREFORE...A SLIGHTLY HIGHER CHANCE OF RAIN IS EXPECTED OVER MAUI COUNTY AND THE BIG ISLAND WEDNESDAY FORECAST CHARTS INDICATE A SURFACE HIGH PRESSURE WILL MOVE TO FAR NORTHEAST OF THE STATE BY THURSDAY. AS THE SURFACE LOW PRESSURE SYSTEM DRIFTS AWAY AND DISSIPATES...TRADE WINDS WILL SLOWLY REBUILD OVER THE ISLANDS. TRADE WIND WEATHER WILL RETURN TO THE STATE BY THEN AS WELL. MOREOVER...THE SURFACE PRESSURE GRADIENT ACROSS THE ISLANDS IS EXPECTED TO TIGHTEN BY THE WEEKEND. TRADE WINDS WILL STRENGTHEN AND BECOME LOCALLY BREEZY. PASSING LOW CLOUDS AND SHOWERS WILL AFFECT MAINLY WINDWARD AND MAUKA AREAS...AND MAY EVEN REACH THE LEE AREAS OF THE SMALLER ISLANDS AT TIMES. FORECAST CHARTS DO HINT THE DEVELOPMENT OF A WEAK UPPER FEATURE NEAR THE WESTERN ISLANDS. THIS FEATURE MAY ENHANCE THE TRADE SHOWERS AT TIMES. && .AVIATION... VFR CONDITIONS CONTINUE FOR ALL TAF SITES THIS MORNING...WITH LOW CLOUDS LINGERING IN THE ISLAND VICINITY. THERE ARE SOME DEEPER CONVECTION PRESENT IN THE SURROUNDING COASTAL WATERS WITH TOPS TO AT LEAST 10K FEET...BRINGING LOCALIZED MVFR CEILING AND SHRA. EXPECT MOSTLY VFR CONDITIONS TO PREVAIL FOR ALL THE TAF SITES TODAY...THROUGH WITH MOISTURE LINGERING OVER THE STATE...ESPECIALLY OVER THE EASTERN ISLANDS...MORE BRIEF MVFR CEILING AND SHRA CONDITIONS MAY DEVELOP DURING THE AFTERNOON AND EVENING OVER THE ISLANDS. && .MARINE... THE HIGH SURF ADVISORY FOR SOUTH FACING SHORES CONTINUES THROUGH THIS EVENING AS A LARGE SOUTH SWELL PERSISTS. ELEVATED SURF FOR SOUTH FACING SHORES WILL LAST AT LEAST THROUGH WEDNESDAY. AN OUT OF SEASON... MODERATE...WEST-NORTHWEST SWELL IS EXPECTED TO ARRIVE TONIGHT AND PEAK WEDNESDAY INTO THURSDAY...BRINGING NEAR ADVISORY LEVEL SURF FOR NORTH AND WEST FACING SHORES. TRADE WINDS ARE EXPECTED TO BE STRONG ENOUGH BY THE WEEKEND FOR SMALL CRAFT WIND CONDITIONS TO DEVELOP OVER THE WINDIER MAUI COUNTY AND BIG ISLAND COASTAL WATERS. && .HFO WATCHES/WARNINGS/ADVISORIES... HIGH SURF ADVISORY UNTIL 600 PM HST THIS EVENING FOR SOUTH SHORES OF ALL ISLANDS. WIND ADVISORY IN EFFECT FOR BIG ISLAND SUMMITS UNTIL 6 PM HST THIS EVENING. && $$ HUI