108 FXHW60 PHFO 100630 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 830 PM HST MON JUN 9 2014 .SYNOPSIS... LOCALLY BREEZY TRADE WINDS WILL PREVAIL ACROSS THE MAIN HAWAIIAN ISLAND CHAIN DURING THE NEXT SEVERAL DAYS...WITH LOW CLOUDS AND PASSING TRADE SHOWERS FAVORING WINDWARD AND MAUKA AREAS...ESPECIALLY DURING NIGHTS AND MORNINGS. A SLIGHTLY DRIER AIR MASS MAY SPREAD ACROSS THE ALOHA STATE FROM FRIDAY THROUGH THE WEEKEND. && .DISCUSSION... THE TIGHT PRESSURE GRADIENT SOUTH OF A 1031 MB SURFACE HIGH CENTERED NEAR 39N 145W...OR ABOUT 1450 MILES NORTHEAST OF HONOLULU... CONTINUES TO MAINTAIN GUSTY TRADE WINDS ACROSS THE MAIN HAWAIIAN ISLANDS EARLY THIS EVENING. THIS HIGH IS MOVING TOWARD THE SOUTHWEST AT ALMOST 25 MPH. ALOFT...WATER VAPOR IMAGERY INDICATES A MID- TO UPPER-LEVEL LOW IS CENTERED NEAR 25.5N 155W...OR ABOUT 350 MILES NORTH NORTHEAST OF HONOLULU. THIS FEATURE HAS BEEN DRIFTING SLOWLY NORTHEASTWARD. THE COVERAGE OF LOW CLOUDS AND SHOWERS IS RATHER MEAGER ACROSS MOST AREAS OF THE ALOHA STATE AT SUNSET THIS EVENING BASED ON SATELLITE IMAGERY AND RADAR REFLECTIVITY DATA. THE EARLY AFTERNOON SOUNDINGS FROM LIHUE AND HILO SHOWED A SLIGHTLY BETTER DEFINED INVERSION BETWEEN 7 AND 8 THOUSAND FEET...COMPARED WITH THE PAST SEVERAL DAYS. THE PRECIPITABLE WATER /PW/ VALUES WERE ABOUT 1.3 INCHES AT LIHUE AND HILO. SATELLITE DERIVED PW IMAGERY DEPICTS THE LEADING EDGE OF AN AREA OF SLIGHTLY HIGHER LOW-LEVEL MOISTURE LESS THAN 100 MILES EAST OF HILO. THIS AREA OF SOMEWHAT ENHANCED MOISTURE WILL LIKELY MOVE INTO THE EASTERN HALF OF THE MAIN HAWAIIAN ISLAND CHAIN LATER TONIGHT. THE RELATIVELY CLOSE PROXIMITY OF THE MID- TO UPPER-LEVEL LOW NORTHEAST OF THE AREA MAY PROVIDE A SLIGHT INCREASE IN LOW CLOUDS AND TRADE SHOWERS OVER WINDWARD AND MAUKA AREAS OF THE BIG ISLAND AND PARTS OF MAUI COUNTY LATER TONIGHT. THE AREA OF SOMEWHAT ENHANCED MOISTURE MAY EVENTUALLY SPREAD ACROSS THE REMAINDER OF MAUI COUNTY AND OAHU...AND EVENTUALLY KAUAI...ON TUESDAY. THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE FORECAST SCENARIO THROUGH MID-WEEK. THE TIGHT PRESSURE GRADIENT SOUTH OF PERSISTENT HIGH PRESSURE LOCATED FAR NORTH AND NORTHEAST OF THE AREA WILL MAINTAIN BREEZY TRADE WINDS ACROSS MOST SECTIONS OF THE ALOHA STATE. THE LOW ALOFT WILL PERSIST NORTHEAST OF THE STATE ALSO...WHICH WILL LIKELY KEEP THE SUBSIDENCE INVERSION SLIGHTLY WEAKER AND SOMEWHAT MORE ELEVATED THAN NORMAL. THESE FORECAST ENVIRONMENTAL CONDITIONS COMBINED WITH NEAR TO SLIGHTLY ABOVE NORMAL PW VALUES WILL ALLOW TRADE SHOWERS TO REMAIN RELATIVELY ACTIVE ACROSS MOST WINDWARD AND MAUKA AREAS...ESPECIALLY DURING NIGHTS AND MORNINGS. SOME OF THESE SHOWERS WILL PUSH INTO LEEWARD AREAS OF SOME OF THE SMALLER ISLANDS DUE TO THE BREEZY LOW-LEVEL TRADE WIND FLOW...ESPECIALLY LATE AT NIGHT AND EARLY IN THE MORNING. A TYPICAL SUMMERTIME PATTERN IS EXPECTED TO PREVAIL ALONG SLOPES OF THE LEEWARD BIG ISLAND...WITH AFTERNOON / EARLY EVENING CLOUDS AND SHOWERS CLEARING OUT DURING THE LATE NIGHT AND MORNING HOURS. THE LATEST GUIDANCE FROM THE LONG-RANGE FORECAST MODELS CONTINUES TO SHOW HIGH PRESSURE FAR NORTH OF THE AREA WILL MAINTAIN A MODERATE TO LOCALLY BREEZY TRADE WIND WEATHER PATTERN THROUGH THE NEXT SEVEN DAYS...AND BEYOND. THE GUIDANCE ALSO SUGGESTS A DRIER AIR MASS WILL SPREAD FROM EAST TO WEST ACROSS THE ALOHA STATE FROM FRIDAY AND THROUGH THE WEEKEND. IN FACT...PW VALUES MAY DROP CLOSER TO ONE INCH. A LINGERING MID/UPPER LEVEL TROUGH ALSO APPEARS TO REMAIN IN RELATIVELY CLOSE PROXIMITY TO THE ISLANDS. AS A RESULT...THE TRADE WIND SUBSIDENCE INVERSION MAY REMAIN SOMEWHAT INHIBITED...SO SOME LOW CLOUDS AND LIMITED SHOWERS WILL CONTINUE TO BE POSSIBLE...MAINLY DURING NIGHT AND MORNINGS OVER WINDWARD AND MAUKA SECTIONS. HOWEVER...EXPECT MOST LEEWARD SECTIONS TO REMAIN RATHER DRY. && .AVIATION... MODERATE TRADES WINDS CONTINUE OVER THE ISLANDS. THE AREA OF INCREASED MOISTURE RIDING IN ON THE TRADES IS STARTING TO APPROACH THE BIG ISLAND. SHOWERS EMBEDDED IN THIS AREA ARE LIKELY TO BRING PERIODS OF MVFR CIGS/VIS TO THE WINDWARD AREAS OF THE BIG ISLAND... TONIGHT AND EARLY TUESDAY MORNING WITH MOISTURE SPREADING TO WINDWARD MAUI LATE TONIGHT. AN AIRMET FOR MOUNTAIN OBSCURATION CAN NOT BE RULED OUT LATER TONIGHT. ELSEWHERE ON THE SMALLER ISLANDS...BRIEF MVFR CONDITIONS ARE EXPECTED WITH PASSING SHOWERS BEING CARRIED BY THE TRADES...MAINLY FOR WINDWARD AREAS. OTHERWISE...VFR CONDITIONS ARE EXPECTED. AIRMET TANGO CONTINUES FOR MECHANICAL TURBULENCE TO THE LEE OF THE MOUNTAINS DUE TO THE MODERATE TRADES BLOWING OVER THE ISLANDS. && .MARINE... FRESH TO LOCALLY STRONG TRADE WINDS WILL PERSIST THROUGH THE REST OF THIS WEEK AND INTO THE WEEKEND. AS A RESULT...WINDS IN THE TYPICALLY WINDY WATERS ADJACENT TO THE ISLANDS IN MAUI AND HAWAII COUNTIES CONTINUE TO MEET SMALL CRAFT ADVISORY /SCA/ CRITERIA. THIS SCA CURRENTLY REMAINS IN EFFECT THROUGH WEDNESDAY AFTERNOON. THE FORECAST MODELS INDICATE THERE WILL LIKELY BE LITTLE SIGNIFICANT CHANGE IN TRADE WIND SPEEDS FOR THROUGH THIS WEEKEND...SO THE SCA WILL PROBABLY BE REQUIRED FOR THESE SAME WINDY WATERS FOR THE REST OF THIS WEEK. A RELATIVELY LONG-PERIOD SOUTH SOUTHWEST SWELL...WITH A SWELL HEIGHT OF 3 FEET AND A WAVE PERIOD OF 14 TO 15 SECONDS...IS GENERATING MODERATE-SIZED SURF ALONG MOST SOUTH FACING SHORES OF THE STATE EARLY THIS EVENING. THIS SOUTH SOUTHWEST SWELL IS EXPECTED TO BE REINFORCED FROM LATE TUESDAY INTO WEDNESDAY...WITH MODERATE-SIZED SURF CONTINUING ALONG SOUTH FACING SHORES. HOWEVER...WE DO NOT ANTICIPATE THAT A HIGH SURF ADVISORY WILL BE REQUIRED BASED ON THE LATEST GUIDANCE. AS THE SOUTH SWELL FADES TOWARD THE END OF THE WORK WEEK...EXPECT SURF HEIGHTS TO GRADUALLY DIMINISH ALONG SOUTH FACING THURSDAY AND FRIDAY...WITH SMALL SURF CONTINUING NEXT WEEKEND. ELSEWHERE...TYPICAL SHORT-PERIOD TRADE WIND WAVES COMBINED WITH A SMALL NORTHEAST SWELL WILL CONTINUE TO PRODUCE MODERATE-SIZED CHOPPY SURF ALONG EAST FACING BEACHES AND REEFS THROUGH THE END OF THIS WEEK. && .HFO WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY UNTIL 6 PM HST WEDNESDAY FOR MAALAEA BAY...THE WATERS SOUTH OF THE BIG ISLAND...AND THE PAILOLO AND ALENUIHAHA CHANNELS. && $$ DISCUSSION/MARINE...HOUSTON AVIATION...EATON