| Current Conditions | ||
| Temp |  | -0.0 C |
| RH | | 60 % |
| Wind | | WSW 19 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 807 FXHW60 PHFO 201337 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 335 AM HST MON MAY 20 2013 .SYNOPSIS... A WEAK SURFACE FRONT WILL SLOWLY MOVE ACROSS THE EASTERN PORTIONS OF THE ISLAND CHAIN TODAY. SEA BREEZES WILL BRING AFTERNOON AND EARLY EVENING SHOWERS DURING THE NEXT COUPLE OF DAYS. THERE IS A CHANCE OF LOCALLY HEAVY RAIN THIS AFTERNOON...MAINLY OVER MOUNTAIN AREAS. HIGH PRESSURE BEGINS BUILDING NORTHEAST OF THE ISLANDS BY MIDWEEK WITH TRADES EXPECTED TO GRADUALLY RETURN DURING THE SECOND HALF OF THE WEEK. && .DISCUSSION... LATEST SFC ANALYSES SHOWS A FRONTAL BOUNDARY OVER THE CENTRAL PORTIONS OF THE ISLAND CHAIN AND VERY SLOWLY PUSHING SE...AND WILL LIKELY MERGE WITH THE REMNANTS OF A FORMER SFC TROUGH LINGERING BETWEEN THE BIG ISLAND AND MAUI. ALSO...WATER VAPOR IMAGERY AND MODEL DATA DEPICT AN UPPER LVL TROUGH/LOW COMPLEX LINGERING N OF MAUI. WITH THIS SYNOPTIC SCENARIO IN PLACE...EXPECT PARTLY TO MOSTLY CLOUDY CONDITIONS TODAY WITH SHOWERS AFFECTING MOST OF INTERIOR AND MAUKA AREAS OF THE ISLANDS. SHOWERS WILL ALSO SPREAD INTO LEEWARD LOCATIONS AT TIMES. SOME LOCALIZED HEAVY SHOWERS ARE AGAIN POSSIBLE TODAY...ESPECIALLY OVER THE MOUNTAIN RANGES...MAINLY IN THE AFTERNOON HOURS. THE AIRMASS ACROSS THE AREA REMAINS MOIST AND UNSTABLE DUE TO THE COMBINATION OF THE AFOREMENTIONED SYNOPTIC FEATURES. 12Z SOUNDING DATA STILL SHOWS PWAT VALUES AROUND ONE AND A HALF INCHES ACROSS THE AREA. THE ABUNDANT MOISTURE WILL REMAIN AVAILABLE FOR ADDITIONAL SHOWER ACTIVITY THROUGH THE NEXT COUPLE OF DAYS. LATEST MODEL GUIDANCE SHOW THE WEAKENING SFC BOUNDARY LINGERING NEAR THE E HALF OF THE MAIN HAWAIIAN ISLANDS THROUGH MIDWEEK. EXPECT DAYTIME SEA BREEZES AND NIGHTTIME LAND BREEZES TO DEVELOP EACH DAY. SKIES WILL REMAIN PARTLY TO MOSTLY CLOUDY WITH SHOWERS FAVORING INTERIOR AND MOUNTAIN AREAS DURING THE AFTERNOON/EARLY EVENING HOURS...AND PARTLY CLEARING DURING THE OVERNIGHT HOURS. ONLY EXCEPTION MIGHT BE KAUAI WHERE A MORE ROBUST N/NE FLOW BEHIND THE FROPA COULD FOCUS RAIN OVER N AND E FACING SLOPES. THE GLOBAL MODELS SHOW GOOD CONSENSUS REGARDING A RETURN OF THE TRADES BY LATE THU-EARLY FRI WITH SHOWERS FOCUSING OVER WINDWARD AND MAUKA AREAS. && .AVIATION... UNSTABLE ATMOSPHERIC CONDITIONS ASSOCIATED WITH MIDDLE AND UPPER LEVEL TROUGHS...A DIFFUSE FRONTAL BOUNDARY AND ENHANCED LOW-LEVEL MOISTURE WILL BRING ISOL MVFR CONDITIONS DUE TO LOW CEILINGS AND REDUCED VISIBILITIES IN LOW CLD AND SHRA...ESPECIALLY ALONG THE NORTH FACING SLOPES AND HIGHER TERRAIN OF PARTS OF MAUI COUNTY THIS MORNING. ELSEWHERE...A SURFACE TROUGH OVER THE EASTERN END OF THE ISLAND CHAIN CONTINUES TO BE THE FOCUS FOR LOW CLOUDS WITH EMBEDDED SCATTERED SHRA AND ISOLATED +SHRA NEAR THE BIG ISLAND. THEREFORE... EXPECT TEMPO MVFR CEILINGS AND VISIBILITIES...WITH POSSIBLE BRIEF PERIODS OF IFR...ACROSS PARTS OF THE BIG ISLAND AND ADJACENT COASTAL WATERS...THROUGH THIS AFTERNOON. LATER TODAY...THE FORECAST MODEL GUIDANCE SHOWS AN AFTERNOON CONVECTIVE PATTERN WITH LOCAL SEA BREEZE CIRCULATIONS MAY DEVELOP ACROSS THE SMALLER ISLANDS...INCLUDING KAUAI AND OAHU. THE FRONTAL BOUNDARY MAY ALSO BE A TRIGGER MECHANISM FOR ENHANCED CLOUDS AND SHOWERS..,ESPECIALLY OVER MAUI COUNTY. THEREFORE...EXTENSIVE CLOUDS AND ISOLATED +SHRA MAY PRODUCE TEMPO MVFR CEILINGS AND VISIBILITIES...AND POSSIBLY ISOLATED IFR CONDITIONS...ACROSS PARTS OF THE WESTERN AND CENTRAL ISLANDS THIS AFTERNOON. THERE ARE CURRENTLY NO AIRMETS IN PLACE...BUT THERE MAY BE A NEED FOR A MTN OBSCURATION AIRMET IF CONDITIONS DETERIORATE OVER SOME OF THE HIGHER TERRAIN ON THE ISLAND CHAIN LATER TODAY. && .MARINE... WINDS AND SEAS ACROSS THE COASTAL WATERS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH THE REST OF THE WEEK. SURF ALONG THE SOUTH SHORES WILL REMAIN AT ADVISORY LEVELS UNTIL THIS EVENING...THEN REMAINING ELEVATED THROUGH THE REST OF THE WEEK. && .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. && $$ DISCUSSION/MARINE...REYNES AVIATION...HOUSTON Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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