Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans: Select a text product: Urgent Weather Message Marine Weather Statement/High Surf Advisory/Warning Special Marine Warning Narrow the Menu List Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special Hawaiian Islands Synoptic Discussion and Guidance 791 FXHW60 PHFO 220143 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 400 PM HST TUE MAY 21 2013 .SYNOPSIS... A WEAKENING LOW TO OUR NORTH AND A TROUGH JUST WEST OF KAUAI WILL KEEP WINDS LIGHT ACROSS THE STATE...LEADING TO OFFSHORE LAND BREEZES AT NIGHT AND ONSHORE SEA BREEZES DURING THE DAY. CLOUDS AND SHOWERS FOCUSED ACROSS INTERIOR SECTIONS OF THE ISLANDS EARLY EVENING WILL DIMINISH THIS EVENING...THEN ARE POSSIBLE AGAIN WEDNESDAY AFTERNOON. AS THE LOW MOVES WEST AND DISSIPATES...TRADE WINDS WILL RETURN BEGINNING THURSDAY AND STRENGTHEN THROUGH THE WEEKEND. && .DISCUSSION... WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL LOW OVER 600 MILES NORTH NORTHEAST OF THE STATE...WITH AN UPPER TROUGH EXTENDING ABOUT 200 MILES NORTHWEST OF KAUAI. AT THE SURFACE...LOW PRESSURE IS LOCATED LESS THAN 500 MILES NORTH OF KAUAI...WITH A TROUGH MOVING WELL WEST OF THE ISLAND. 00Z RAOB SHOW INVERSIONS HAVING STRENGTHENED OVER THE PAST 24 HOURS...BUT STILL REMAINING ELEVATED AROUND 8-9KFT. PRECIPITABLE WATERS ALSO RANGE FROM 1.1 INCHES AT LIHUE TO 1.5 INCHES AT HILO. EARLY AFTERNOON MIMIC TOTAL PRECIPITABLE WATER IMAGERY SHOWS HIGHER MOISTURE FROM OAHU EASTWARD...PART OF A CONVERGENCE BAND THAT EXTENDS FAR NORTHEAST OF THE STATE. WITH THE WEAK SURFACE FEATURES NEARBY...THE PRESSURE GRADIENT ACROSS THE ISLANDS REMAINS QUITE WEAK. THE PRESSURE DIFFERENCE BETWEEN BUOY 51101 TO THE NORTHWEST OF KAUAI AND BUOY 51003 TO THE SOUTH OF KAUAI HAS RISEN TO AROUND 1MB...WHICH IS STILL SLIGHTLY LESS THAN THE VALUES OBSERVED YESTERDAY. WIDESPREAD SEA BREEZES FORMED TODAY...AND LAND BREEZES ARE EXPECTED AGAIN TONIGHT. THIS TYPE OF CONVECTIVE PATTERN IS EXPECTED TO CONTINUE THROUGH WEDNESDAY...WITH AFTERNOON CLOUDS AND SHOWERS AND SOME CLEARING AT NIGHT. A BAND OF HIGH CLOUDS HAS FILLED IN OVER THE SMALLER ISLANDS EARLIER IN THE DAY AHEAD OF THE UPPER TROUGH...BUT ARE BEGINNING TO PULL AWAY TO THE EAST NORTHEAST. DESPITE OFFSHORE LAND BREEZES TONIGHT...WE MAY NOT SEE THE DEGREE OF CLEARING AS IN PAST NIGHTS AS MOISTURE AND CLOUDS FROM THE CONVERGENCE BAND EAST AND NORTHEAST OF THE STATE SPREAD WESTWARD. THE LOW NORTH OF THE STATE IS EXPECTED TO MOVE WESTWARD AND DISSIPATE...WITH THE SURFACE TROUGH MOVING FARTHER WEST OF KAUAI. THE GRADIENT REMAINS LIGHT THROUGH WEDNESDAY...WHICH WILL ALLOW FOR ANOTHER DAY OF ONSHORE SEA BREEZES AND AFTERNOON CLOUDS AND SHOWERS. THE ATMOSPHERE STABILIZED TODAY...WHICH LIMITED RAINFALL AMOUNTS ACROSS THE SMALLER ISLANDS...AND WILL STABILIZE FURTHER ON WEDNESDAY. HOWEVER...THE MOISTURE SPREADING WESTWARD MAY HELP TO ENHANCE SHOWERS DURING THE AFTERNOON. HIGH PRESSURE NORTHEAST OF THE STATE WILL REASSERT ITSELF ACROSS THE ISLANDS BY THURSDAY. AS THIS HIGH MOVES SOUTHWARD AND THE RIDGE REESTABLISHES ITSELF NORTH OF THE STATE...WE SHOULD SEE STRENGTHENING TRADE WINDS THROUGH THE WEEKEND. HOWEVER...AN UPPER LEVEL LOW DEVELOPING TO OUR NORTHEAST WILL HELP TO DESTABILIZE THE AIRMASS BY THE WEEKEND. WHILE THE LATEST MODEL RUNS SHOW THIS FEATURE CONFINED TO UPPER LEVELS...WITH TRADES PERSISTING AT THE SURFACE...IT WILL HELP TO ERODE THE TRADE WIND INVERSION AND ENHANCE TRADE WIND SHOWERS. THIS PATTERN IS EXPECTED TO LINGER INTO EARLY NEXT WEEK. && .AVIATION... VFR CONDITIONS PREVAIL AT MOST OF THE TAF SITES WITH SOME LOCAL MVFR IN THE VICINITY OF PHTO DUE TO VOLCANIC EMISSIONS. THESE CONDITIONS WILL LIKELY PERSIST THROUGH THE NIGHT. DAYTIME HEATING HAS CAUSED SOME MVFR CONDITIONS TO OCCUR MAINLY OVER THE BIG ISLAND DUE TO CLOUDS AND SHRA. CONDITIONS WILL LIKELY IMPROVE OVERNIGHT. && .MARINE... THE CURRENT SOUTH SWELL REMAINS ELEVATED...AND WAVEWATCH GUIDANCE SHOWS ADDITIONAL ENERGY AFFECTING THE AREA TONIGHT/WEDNESDAY. BASED ON CURRENT OBSERVATIONS AND A GRADUAL DOWNWARD TREND...WE WILL EXTEND THE HIGH SURF ADVISORY THROUGH WEDNESDAY. BEYOND WEDNESDAY...SURF WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE WEEK. A NEW LONGER-PERIOD WEST-NORTHWEST SWELL WILL CONTINUE TO BUILD TONIGHT AND PEAK WEDNESDAY INTO THURSDAY. WHILE THIS SWELL IS LARGER THAN NORMAL FOR THIS TIME OF YEAR...SURF IS EXPECTED TO REMAIN BELOW ADVISORY LEVELS 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 AREAS AROUND MAUI COUNTY AND THE BIG ISLAND. && .HFO WATCHES/WARNINGS/ADVISORIES... HIGH SURF ADVISORY UNTIL 6 PM HST WEDNESDAY FOR SOUTH FACING SHORES OF ALL ISLANDS. WIND ADVISORY UNTIL 6 AM HST WEDNESDAY FOR BIG ISLAND SUMMITS. && $$ PUBLIC/MARINE...BRAVENDER AVIATION...BURKE Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office This page is maintained voluntarily by the MKWC and the UHMET faculty, staff, and students. It was last modified on: Tue, Sep 21 2010 - 2314 UTC Send comments to: Ryan Lyman