| Current Conditions | ||
| Temp |  | 0.1 C |
| RH | | 33 % |
| Wind | | W 27 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 219 FXHW60 PHFO 210631 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 830 PM HST MON MAY 20 2013 .SYNOPSIS... A LAND AND SEA BREEZE WEATHER PATTERN WILL PERSIST OVER THE ISLANDS THROUGH WEDNESDAY AS AN UNSEASONABLY STRONG AREA OF LOW PRESSURE STAYS SEVERAL HUNDRED MILES NORTH OF THE STATE. A BAND OF MOISTURE ASSOCIATED WITH THE LOW WILL BRING SLIGHTLY HIGHER CHANCES OF RAIN OVER THE EASTERN END OF THE STATE THROUGH TUESDAY...WITH SHOWERS DEVELOPING MAINLY IN THE AFTERNOON AND EVENING HOURS. 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. WET TRADE WIND WEATHER IS POSSIBLE THIS WEEKEND AS AIR MASS IN THE ISLAND VICINITY MAY BECOME MORE UNSTABLE. && .DISCUSSION... A LIGHT WIND WITH LAND AND SEA BREEZE CONVECTIVE WEATHER PATTERN CONTINUES OVER THE ISLANDS AS A RELATIVELY RARE...MID-MAY CUTOFF LOW STAYS ABOUT 400 MILES NORTH OF THE STATE. THERE ARE MORE CLOUDS AFFECTING MAUI COUNTY AS WELL AS THE BIG ISLAND THIS EVENING...AS MOISTURE FROM A DISSIPATING FRONTAL BAND AND LOW LEVEL CONVERGENCE LINGERS OVER THE EASTERN PORTION OF THE MAIN HAWAIIAN ISLANDS. AS THE AIR MASS IS ONLY MARGINALLY STABLE...THE DEEP MOISTURE MAY ALLOW LOCALLY HEAVY RAIN TO DEVELOP IN THE NEXT FEW HOURS OVER THE EASTERN ISLANDS. SHOWER ACTIVITIES SHOULD DECREASE OVER THOSE ISLANDS AS THE NIGHT PROGRESSES WHILE SUBSIDING LAND BREEZES DEVELOP. KAUAI AND OAHU HAVE LESS SHOWERS THUS FAR AS THE AIR MASS IS SLIGHTLY DRIER OVER THE WESTERN END OF THE ISLAND CHAIN AND WILL SEE MAINLY FAIR WEATHER. STRONG WINDS ASSOCIATED WITH THE UPPER LEVEL SYSTEM CONTINUE TO AFFECT THE SUMMITS OF THE BIG ISLAND THIS EVENING. BELIEVE THE WINDS WILL PERSIST THROUGH TUESDAY...THEREFORE A WIND ADVISORY REMAINS IN EFFECT FOR THAT AREA. SIMILAR WEATHER SCENARIO WILL REPEAT THROUGH WEDNESDAY...AS THE CUTOFF LOW WILL SLOWLY DRIFT AWAY AND GRADUALLY FILL. THE BAND OF DEEP MOISTURE ASSOCIATED WITH LOW LEVEL CONVERGENCE AS WELL AS THE OLD FRONTAL BOUNDARY IS ALSO EXPECTED TO LINGER NEAR THE EASTERN ISLANDS WHILE SLOWLY DISSIPATE. EXPECT A SLIGHTLY HIGHER CHANCE FOR RAIN TO AFFECT MAUI COUNTY AS WELL AS THE BIG ISLAND IN THE NEXT COUPLE OF DAYS. SINCE THE CONVECTIVE WEATHER PATTERN WILL PREVAIL OVER THE ISLANDS...SHOWER ACTIVITIES MAY BE ENHANCED DURING THE AFTERNOON AND EVENING HOURS UNDER DAY TIME HEATING. FORECAST CHARTS STILL INDICATE A SURFACE HIGH PRESSURE WILL MOVE TO FAR NORTHEAST OF THE STATE LATER HALF OF THE WEEK. AS THE LOW PRESSURE SYSTEM DRIFTS AWAY AND DISSIPATES...TRADE WINDS WILL SLOWLY REBUILD OVER THE ISLANDS. MORE TYPICAL TRADE WIND WEATHER TO RETURN TO THE STATE BY THURSDAY. IN FACT...THE SURFACE PRESSURE GRADIENT IS EXPECTED TO TIGHTEN IN THE ISLAND VICINITY 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 ALSO HINT A WEAK UPPER FEATURE MAY DEVELOP NEAR THE ISLANDS...AND MAY PROVIDE SOME ENHANCEMENTS TO THE TRADE WIND SHOWERS. && .AVIATION... LINGERING MOISTURE WILL CONTINUE TO AFFECT MAUI COUNTY AS WELL THE BIG ISLAND...WITH MUCH OF THE SHOWERS AFFECTING KAHOOLAWE...EAST MAUI AS SOUTHEAST BIG ISLAND ACCORDING TO RADAR DATA. THERE IS A PROBLEM WITH THE WEATHER SERVICE DATA DELIVERY SYSTEM THUS LATEST METARS ARE NOT AVAILABLE IN OUR SYSTEM AT TIME. ON THE OTHER HAND...OLD OBSERVATIONS OF THE TAF SITES ACROSS THE EASTERN ISLANDS REPORTED MAINLY VFR CONDITIONS. AFTERNOON CONVECTION AFFECTED THE REST OF THE ISLANDS EARLIER THIS AFTERNOON WILL SLOWLY CLEAR AS THE NIGHT PROGRESSES. EXPECT MAINLY VFR CONDITIONS FOR ALL TAF SITES THROUGH EARLY TUESDAY...THOUGH MAUI COUNTY AND BIG ISLAND SITES MAY SEE BRIEF MVFR CEILING AND SHRA CONDITIONS. && .MARINE... THE HIGH SURF ADVISORY FOR SOUTH FACING SHORES CONTINUES THROUGH TUESDAY AS A LARGE SOUTH SWELL PERSISTS. ELEVATED SURF FOR SOUTH FACING SHORES WILL LAST AT LEAST TO WEDNESDAY. AN OUT OF SEASON... MODERATE...WEST-NORTHWEST SWELL IS EXPECTED TO ARRIVE TUESDAY NIGHT 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 TUESDAY FOR SOUTH SHORES OF ALL ISLANDS. WIND ADVISORY IN EFFECT FOR BIG ISLAND SUMMITS UNTIL 6 PM HST TUESDAY. && $$ HUI Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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