377 FXHW60 PHFO 171400 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 400 AM HST SUN FEB 17 2013 .SYNOPSIS... VERY STRONG AND GUSTY TRADE WINDS WILL CONTINUE ACROSS THE MAIN HAWAIIAN ISLANDS THROUGH EARLY NEXT WEEK AS HIGH PRESSURE BUILDS FAR NORTH OF THE AREA. LOW CLOUDS AND SHOWERS TRANSPORTED BY THE TRADES WILL CONTINUE ACROSS WINDWARD AND MAUKA AREAS...WITH THE STRONG TRADES CARRYING A FEW SHOWERS OVER TO LEEWARD SECTIONS OF SOME OF THE SMALLER ISLANDS. EXPECT A SLIGHTLY WETTER TRADE WIND WEATHER PATTERN EARLY NEXT WEEK. && .DISCUSSION... THE VERY TIGHT PRESSURE GRADIENT SOUTH OF TWIN 1035 MB SURFACE HIGHS...ONE NEAR 38N 145W AND ANOTHER NEAR 39N 159W...CONTINUE TO PRODUCE STRONG AND GUSTY LOW-LEVEL TRADE WINDS ACROSS THE MAIN HAWAIIAN ISLANDS EARLY THIS MORNING. ALOFT...MIDDLE AND UPPER LEVEL TROUGH ARE IN THE VICINITY OF THE EASTERN END OF THE ISLAND CHAIN. THIS IS CAUSING THE ATMOSPHERE ACROSS THE EASTERN ISLANDS TO BE SLIGHTLY UNSTABLE. ALSO...A WEAKENING UPPER-LEVEL RIDGE IS EVIDENT NEAR KAUAI AND OAHU. LOW-LEVEL MOISTURE REMAINS RATHER LIMITED OVER THE WESTERN ISLANDS...WITH SLIGHTLY GREATER PRECIPITABLE WATER VALUES NEAR THE BIG ISLAND. THE PRESENCE OF THE TROUGHING ALOFT NEAR THE EASTERN ISLANDS IS ENHANCING THE LOW CLOUDS AND SHOWERS CARRIED BY THE TRADES. THESE SHOWERS ARE MAINLY AFFECTING WINDWARD AND MAUKA AREAS OF THE STATE...BUT A FEW OF THE SHOWERS MAY SPREAD TO LEEWARD SECTIONS OF THE SMALLER ISLANDS DUE TO THE ROBUST TRADES...ESPECIALLY THIS MORNING. THE FORECAST MODELS INDICATE STRONG HIGH PRESSURE WILL REMAIN FAR NORTH OF THE ISLAND CHAIN THROUGH TONIGHT. THIS WILL KEEP SUSTAINED WIND SPEEDS AND/OR PEAK WIND GUSTS NEAR THE WIND ADVISORY CRITERIA ACROSS MOST OF THE ALOHA STATE...EXCEPT THE BIG ISLAND SUMMITS...AT LEAST THROUGH TONIGHT. SINCE THE MODELS SUGGEST THE HIGH PRESSURE MAY BUILD EARLY NEXT WEEK...THE PRESSURE GRADIENT OVER THE STATE MAY BECOME EVEN TIGHTER. IF SO...THIS WOULD RESULT IN THE STRONG GUSTY TRADES CONTINUING THROUGH EARLY NEXT WEEK...AND THE WIND ADVISORY MAY NEED TO BE CONTINUED FOR PORTIONS OF THE STATE ON MONDAY ALSO. MEANWHILE...THE UPPER-LEVEL RIDGE OVER THE WESTERN ISLANDS IS EXPECTED TO CONTINUE TO WEAKEN TODAY. AT THE SAME TIME...THE RELATIVELY UNSTABLE AIR MASS IS FORECAST TO REMAIN NEAR THE EASTERN ISLANDS. THIS WILL ALLOW FOR ENHANCEMENT OF THE LOW CLOUDS AND SHOWERS CARRIED BY THE TRADES TO CONTINUE FROM TODAY INTO EARLY NEXT WEEK. AS A RESULT...EXPECT LOW CLOUDS AND SHOWERS TO CONTINUE FAVORING WINDWARD AND MAUKA AREAS. THE STRONG TRADES WILL ALSO CONTINUE TO CARRY SOME OF THESE SHOWERS OVER TO LEEWARD AREAS OF THE SMALLER ISLANDS...ESPECIALLY NIGHTS AND MORNINGS. LOOKING BEYOND MID-WEEK...THE MODELS SUGGEST A TRADE WIND WEATHER PATTERN WILL CONTINUE THROUGH THE END OF THE NEW WORK WEEK. THE FORECAST GUIDANCE SUGGESTS THE TRADES WILL REMAIN STRONG AND GUSTY ALSO. IN ADDITION...THE RELATIVELY WET TRADE WIND WEATHER PATTERN MAY CONTINUE ACROSS MOST WINDWARD AND MAUKA AREAS OF THE STATE. IF SO...LEEWARD AREAS OF THE SMALLER ISLANDS MIGHT CONTINUE TO RECEIVE BRIEF PASSING SHOWERS CARRIED OVER BY THE STRONG TRADES. && .MARINE... A GALE WARNING REMAINS IN EFFECT FOR THE WINDIER WATERS ADJACENT TO THE ISLANDS OF MAUI COUNTY AND THE BIG ISLAND DUE TO THE LOCALIZED AFFECTS THE ISLAND TERRAIN HAS IN ACCELERATING THE ALREADY STRONG LOW-LEVEL TRADE WIND FLOW. A SMALL CRAFT ADVISORY /SCA/ ALSO REMAINS IN EFFECT FOR THE REMAINING HAWAIIAN WATERS DUE TO THE COMBINATION OF THESE STRONG TRADE WINDS...INCREASED SHORT-PERIOD TRADE WIND GENERATED WAVES AND A LONG-PERIOD NORTHWEST SWELL. THE GALE WARNING AND SCA ARE IN EFFECT THROUGH WEDNESDAY. THE NEW WEST NORTHWEST SWELL ARRIVED AT NATIONAL DATA BUOY CENTER BUOY 51101...WHICH IS LOCATED NORTHWEST OF KAUAI. HOWEVER...BASED ON THE WAVE WATCH III MODEL GUIDANCE...THE SWELL HEIGHT APPEARS TO BE ABOUT 2 FEET BELOW THE GUIDANCE. WE EXPECT THIS SWELL WILL CONTINUE TO BUILD THIS MORNING BEFORE PEAKING LATER TODAY. THE SURF PRODUCED BY THIS SWELL IS EXPECTED TO REACH HEIGHTS ABOVE THE HIGH SURF ADVISORY THRESHOLDS ALONG MOST NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS...BEFORE SLOWLY SUBSIDING FROM LATE TONIGHT THROUGH MONDAY. THEREFORE...A HIGH SURF ADVISORY REMAINS IN EFFECT THROUGH MONDAY AFTERNOON FOR EXPOSED NORTH AND WEST FACING SHORES OF THE SMALLER ISLANDS DUE TO THIS SWELL. A HIGH SURF ADVISORY IS ALSO IN EFFECT STARTING LATER THIS MORNING AND CONTINUING THROUGH TONIGHT FOR WEST FACING SHORES OF THE BIG ISLAND. OTHERWISE...ONLY A MODEST NORTHWEST SWELL IS EXPECTED FROM LATE WEDNESDAY NIGHT INTO FRIDAY. ELSEWHERE...THE STRONG TRADE WINDS HAVE GENERATED ELEVATED CHOPPY SURF ALONG EAST FACING SHORES. AS A RESULT...A HIGH SURF ADVISORY REMAINS IN EFFECT THROUGH WEDNESDAY AFTERNOON FOR EAST FACING SHORES OF MOST ISLANDS. THIS HIGH SURF ADVISORY WILL LIKELY BE EXTENDED BEYOND WEDNESDAY DUE TO THE STRONG TRADES...WHICH ARE EXPECTED TO CONTINUE NEXT WEEK. && .AVIATION... STRENGTHENING TRADE WINDS CONTINUE AIRMET TANGO FOR TEMPO MODERATE ISOL SEVERE LOW LEVEL TURBULENCE DOWNWIND OF MOUNTAINS ON ALL ISLANDS. SUSTAINED SURFACE WINDS HAVE BEEN BETWEEN 25 AND 30 KT OVERNIGHT. WITH WINDS EXPECTED TO INCREASE AGAIN DURING THE DAY TODAY...AN AIRMET WILL LIKELY BE NEEDED FOR SURFACE WINDS. STRONG WINDS WILL CONTINUE FOR THE NEXT SEVERAL DAYS. OVERALL VFR CONDITIONS ARE EXPECTED WITH BRIEF MVFR CIGS AND VIS POSSIBLE FOR WINDWARD AREAS DUE TO CLOUDS AND SHOWERS BEING CARRIED IN ON THE TRADES. && .HFO WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY THROUGH 600 AM HST MONDAY FOR THE ENTIRE STATE OF HAWAII...EXCEPT THE BIG ISLAND SUMMITS. HIGH SURF ADVISORY THROUGH 600 PM HST WEDNESDAY FOR EAST FACING SHORES OF KAUAI...OAHU...MOLOKAI...MAUI AND THE BIG ISLAND. HIGH SURF ADVISORY THROUGH 600 PM HST MONDAY FOR NORTH AND WEST FACING SHORES OF NIIHAU...KAUAI...OAHU AND MOLOKAI...AND FOR NORTH FACING SHORES OF MAUI. HIGH SURF ADVISORY FROM 600 AM THIS MORNING THROUGH 600 AM HST MONDAY FOR WEST FACING SHORES OF THE BIG ISLAND. GALE WARNING UNTIL 600 PM HST WEDNESDAY FOR MAALAEA BAY...THE WATERS SOUTH OF THE BIG ISLAND...AND THE PAILOLO AND ALENUIHAHA CHANNELS. SMALL CRAFT ADVISORY UNTIL 600 PM HST WEDNESDAY FOR ALL REMAINING HAWAIIAN WATERS. && $$ DISCUSSION/MARINE...HOUSTON AVIATION...M BALLARD