| Current Conditions | ||
| Temp |  | 0.3 C |
| RH | | 9 % |
| Wind | | W 45 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 200 FXHW60 PHFO 070633 RRA AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 830 PM HST THU MAR 6 2014 .SYNOPSIS... LIGHT WINDS WILL BECOME SOUTHWEST AND STRENGTHEN INTO FRIDAY AS SHOWERS INCREASE AHEAD OF A FRONT APPROACHING FROM THE NORTHWEST. THE FRONT ITSELF WILL BRING HEAVIER RAIN AND NORTHERLY WINDS FROM FRIDAY INTO SATURDAY. TRADE WINDS WILL RETURN AFTER THE FRONT PASSES...FOCUSING SHOWERS ONTO WINDWARD SLOPES INTO MID-WEEK. MORE TYPICAL TRADE-WIND WEATHER WILL RETURN GRADUALLY BY THE END OF THE WEEK. && .DISCUSSION... WINDS AROUND THE MAIN HAWAIIAN ISLANDS REMAINED VARIABLE...AND ON THE LIGHT SIDE...BUT A GREATER PROPORTION OF OBSERVATIONS REPORTED SOUTHWEST FLOW. SPEEDS INCREASED MODESTLY AS WELL. ALTHOUGH LAND BREEZES LIKELY WILL DEVELOP TO SOME DEGREE OVERNIGHT...SOUTHWEST WINDS WILL PREVAIL...ESPECIALLY OVER THE WEST END OF THE STATE. THE AIR MASS CONTINUED TO MOISTEN FROM THE SOUTHEAST...AND THE INVERSION BOTH ROSE AND GREW WEAKER. UNSURPRISINGLY...SHOWERS WERE MORE ACTIVE THAN THEY WERE 24 HOURS AGO...SOME ORGANIZING INTO BANDS OR STREETS ROUGHLY PARALLEL TO THE PREVAILING SOUTHWEST FLOW. ACCUMULATION THUS FAR HAD NOT POSED SERIOUS PROBLEMS...BUT EARLIER MODEL PREDICTIONS OF LOCALLY HEAVY RAIN FROM LATE TONIGHT INTO SATURDAY CERTAINLY APPEARED BETTER GROUNDED. ALOFT...EXTREMELY BROAD TROUGHING PREVAILED OVER MOST OF THE CENTRAL NORTH PACIFIC OCEAN JUST NORTH OF THE ISLANDS...THOUGH THE DEEPER LOW REMAINED MUCH FURTHER TO THE NORTH. GUIDANCE AGREED REASONABLY WELL THAT THE TROUGH WILL SHARPEN MODESTLY INTO FRIDAY AS A MASSIVE RIDGE BUILDS OVER THE WEST COAST OF NORTH AMERICA. THE SHARPER TROUGH WILL PROVIDE INCREASED SUPPORT FOR THE FRONT APPROACHING THE ISLANDS FROM THE NORTHWEST AT THE SURFACE. THIS SUPPORT WILL FOCUS A BIT TOO FAR TO THE NORTHEAST TO BE OPTIMAL FOR THE STATE...BUT STILL SHOULD BE MORE THAN ENOUGH TO ENHANCE RAINFALL LOCALLY. SIMILARLY... STABILITY PROBABLY WILL NOT FALL LOW ENOUGH TO SUPPORT THUNDERSTORM DEVELOPMENT HERE. SOUTHWEST WINDS WILL INCREASE AHEAD OF THE FRONT INTO FRIDAY...AND PRE-FRONTAL SHOWERS ARE EXPECTED TO CONTINUE DOING LIKEWISE. HEAVIER RAIN WILL ACCOMPANY THE FRONT ITSELF AS IT MOVES ACROSS THE STATE FROM FRIDAY INTO SATURDAY...BUT THE RAGGED LEADING EDGE OF THIS FEATURE PROBABLY WILL MAKE THE TRANSITION RATHER GRADUAL. FROM AN EULERIAN PERSPECTIVE...IT MAY JUST SEEM THAT SHOWERS BECOME MORE FREQUENT AND HEAVIER WITH TIME. ON THE OTHER HAND...THE BACK EDGE OF THE BAND WAS BETTER DEFINED...LIKELY REPRESENTING A MORE NOTICEABLE CHANGE TO A COOLER AND DRIER AIR MASS WHEN IT ARRIVES. NORTHERLY WINDS FOLLOWING THE FRONT WILL BECOME NORTHEASTERLY FAIRLY SOON... CARRYING ANY LINGERING MOISTURE ONTO WINDWARD SLOPES THROUGH THE REST OF THE WEEKEND...ESPECIALLY OVER THE BIG ISLAND...CLOSE TO THE DISSIPATING BOUNDARY. BRIEF MID-LEVEL RIDGING ALOFT WILL PASS OVERHEAD FROM SUNDAY INTO MONDAY...AND THEN A TROUGH ALOFT WILL DIG DOWN EAST OF THE STATE FROM MONDAY INTO TUESDAY...PROVIDING SUPPORT FOR ANOTHER APPROACHING FRONT. GUIDANCE HAD BEEN PORTRAYING THIS FEATURE AS WEAK FOR SOME TIME NOW...BUT RECENTLY IT SUGGESTED THAT THE FRONT MAY NOT EVEN REACH THE ISLANDS...ONLY GATHERING MOISTURE AND LIMITED SUPPORT FOR ENHANCED PRE-FRONTAL SHOWERS. CERTAINLY THIS SCENARIO WAS MORE COMPATIBLE WITH TRADE WINDS CONTINUING THROUGH THE REST OF THE WEEK...AS THE MODELS HAD BEEN SHOWING. IN ANY CASE...SHOWER ACTIVITY WILL TREND TOWARD CLIMATOLOGY BY LATE IN THE WEEK AS THE LINGERING MOISTURE IS RAINED OUT OR BLOWN AWAY TO THE SOUTHWEST. && .MARINE... COMBINED SEAS ACROSS THE STATE CONTINUED TO DIMINISH...BUT A LARGE NEW NORTHWEST SWELL WILL BUILD ACROSS THE ISLANDS THROUGH THE DAY ON FRIDAY...AND THEN PEAK ABOVE WARNING LEVELS ON FRIDAY NIGHT OR SATURDAY. ADVISORY-LEVEL CONDITIONS MAY ARRIVE EARLIER IN THE DAY ON FRIDAY. BASED ON THE DIFFERENT TIMING ACROSS THE STATE...THE HIGH SURF WARNING IS SET TO BEGIN LATE FRIDAY MORNING. ADVISORY-LEVEL SURF MAY REACH WEST-FACING SHORES OF THE BIG ISLAND BY SATURDAY. AS THE NEW NORTHWEST SWELL BUILDS ON FRIDAY...A SMALL CRAFT ADVISORY WILL BE NEEDED FOR LARGE COMBINED SEAS OVER EXPOSED COASTAL WATERS. THESE CONDITIONS LIKELY WILL CONTINUE INTO SUNDAY...BEFORE SUBSIDING BELOW 10 FEET. && .AVIATION... LIGHT SW FLOW WILL CONTINUE FOR KAUAI THROUGH MAUI COUNTY...AS A FRONT APPROACHES FROM THE NW. SCATTERED SHOWERS FROM THE SW AHEAD OF THE FRONT MAY BRIEFLY LOWER CEILINGS TO MVFR AS THEY PASS...OTHERWISE VFR CONDITIONS SHOULD PREVAIL THROUGH THE NIGHT. AS THE FRONT APPROACHES THE ISLANDS BY LATE MORNING...IT WILL BRING PERIODS OF MVFR CEILINGS AND VIS WITH EMBEDDED HEAVY SHOWERS. AIRMET TANGO IS IN PLACE FOR TEMPO MOD TURB N AND NE OF KAUAI THROUGH MAUI COUNTY WITH CONDITIONS CONTINUING BEYOND 1000Z. AS THE FRONT APPROACHES AND THE INVERSION ERODES...IT IS LIKELY THIS WILL BE CANCELED. FOR BIG ISLAND...VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. && .HFO WATCHES/WARNINGS/ADVISORIES... HIGH SURF WARNING FROM 10 AM FRIDAY TO 6 AM HST SUNDAY FOR NIIHAU-KAUAI WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH SHORE-OAHU KOOLAU-OLOMANA-MOLOKAI-MAUI WINDWARD WEST-WINDWARD HALEAKALA. && $$ RYSHKO Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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