| Current Conditions | ||
| Temp |  | 3.1 C |
| RH | | 10 % |
| Wind | | NNW 0 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 071 FXHW60 PHFO 301327 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 400 AM HST WED JUL 30 2014 .SYNOPSIS... HIGH PRESSURE FAR NORTH OF THE STATE WILL KEEP TRADE WINDS BLOWING THROUGH THE WEEKEND. DRY CONDITIONS INTO THURSDAY WILL YIELD TO A VERY MOIST AIR MASS BRINGING INCREASING SHOWERS FROM THE SOUTHEAST BY FRIDAY EVENING. CONDITIONS WILL DRY OUT AGAIN SLOWLY OVER THE WEEKEND AND INTO NEXT WEEK AS THE MOIST AIR MASS MOVES AWAY TOWARD THE WEST. && .DISCUSSION... SURFACE OBSERVATIONS AROUND THE MAIN HAWAIIAN ISLANDS STILL REPORTED GENERALLY MODERATE TRADE WINDS...THOUGH AS USUAL SPEEDS WERE HIGHER WHERE THE FLOW ACCELERATED AROUND HEADLANDS AND BETWEEN ISLANDS. CLOUD COVER WAS LIMITED AND PRECIPITATION QUITE SPARSE OVERALL... BUT TWO EXCEPTIONS WARRANTED MENTION. FIRST...SELECT LOWER WINDWARD SLOPES OF THE BIG ISLAND MANAGED TO RECEIVE UPWARDS OF HALF AN INCH OF RAIN AROUND MIDNIGHT...AND MUCH LIGHTER PRECIPITATION SINCE. SECOND...LIGHT SHOWERS MOVED ASHORE OVER WINDWARD SHORES OF KAUAI DURING THE PAST FEW HOURS. THE MOISTER AIR DRIFTING OVER KAUAI FROM THE NORTHWEST SUGGESTED THAT THE SHOWER ACTIVITY THERE WILL REMAIN MORE ACTIVE THROUGH THE DAY...AND THE FORECAST HAS BEEN ADJUSTED ACCORDINGLY...THOUGH ACCUMULATION SHOULD REMAIN ON THE LOW SIDE. ON THE OTHER HAND...THE SHALLOW INVERSION ACROSS ALL THE STATE...AND THE DRIER AIR MASS FROM OAHU TO THE BIG ISLAND...SHOULD LIMIT CONTINUED RAINFALL THERE THROUGH THE SHORT RUN. GUIDANCE AGREED IN PREDICTING GRADUAL CHANGE INTO THE WEEKEND. THE MAIN TWO TRENDS WILL CONSIST OF A SIGNIFICANTLY MOISTER AIR MASS ARRIVING FROM THE ACTIVE ITCZ FROM THURSDAY INTO FRIDAY...AND A MID-LEVEL RIDGE BUILDING IN OVERHEAD FROM THE EAST THROUGH SATURDAY. THE MOISTER AIR WILL PROVIDE MORE FUEL FOR SHOWERS...BUT THE RIDGE ALOFT WILL PRODUCE SUBSIDENCE SUPPRESSING CLOUD DEVELOPMENT. HOWEVER...INCREASED SUPPORT FOR THE SUBTROPICAL RIDGE AT THE SURFACE ALSO WILL BRING SOMEWHAT FASTER WIND SPEEDS...PROVIDING MORE OROGRAPHIC FORCING ALONG WINDWARD SLOPES. FINALLY...IF ENOUGH OF THE MOIST AIR MASS ARRIVES BEFORE THE RIDGE ALOFT REALLY STARTS TO BUILD...THEN A BROAD BUT SHALLOW MID-LEVEL TROUGH LINGERING TO THE NORTH NORTHEAST MAY HAVE A BRIEF OPPORTUNITY TO TRIGGER CONVECTION OVER THE STATE. THIS WINDOW OF OPPORTUNITY APPEARED TO CENTER AROUND FRIDAY NIGHT. ALTHOUGH LOCAL TOOLS RUN ON MODEL OUTPUT DID NOT PREDICT MUCH CHANCE OF THUNDERSTORMS...EVENTS DRIVEN PRIMARILY BY LOW-LEVEL MOISTURE WITH LITTLE SUPPORT FROM ALOFT DID NOT EXACTLY PLAY TO THE STRENGTHS OF THOSE TOOLS. ALSO...TEMPERATURES ALOFT APPEARED TOO WARM TO FAVOR DEEP CONVECTION. FOR NOW...THE BEST COMPROMISE APPEARED TO CONSIST OF SHOWERS INCREASING GRADUALLY FROM THE SOUTHEAST ONTO THE BIG ISLAND FROM THURSDAY INTO FRIDAY...AND THEN LOCALLY HEAVY RAIN CREEPING NORTHWEST FROM THE BIG ISLAND TOWARD THE SMALLER ISLANDS FROM FRIDAY EVENING INTO SATURDAY. THUNDER MAY BE AN OUTSIDE POSSIBILITY FROM THURSDAY INTO SATURDAY...ESPECIALLY TO THE EAST THROUGH SOUTH OF THE BIG ISLAND...BUT AT THIS POINT IT HAS BEEN INTRODUCED INTO THE FORECAST ONLY OFFSHORE TO THE SOUTH OF THE BIG ISLAND ON THURSDAY AFTERNOON. BY LATE IN THE WEEKEND...SOLUTIONS STARTED TO TREND TOWARD CLIMATOLOGY AGAIN. WIND SPEEDS SHOULD DIMINISH SLIGHTLY...WHILE THE MOIST AIR MASS WILL DEPART TOWARD THE WEST...AS DRIER AIR ADVECTS IN FROM THE NORTHEAST. && .AVIATION... VFR CONDITIONS WILL PREVAIL ACROSS THE MAIN HAWAIIAN ISLANDS TODAY AND TONIGHT. PASSING SHOWERS AND ISOLATED MVFR CIGS WILL BE POSSIBLE ON WINDWARD SLOPES. AIRMET TANGO REMAINS IN EFFECT FOR LOW LEVEL TURBULENCE OVER AND IMMEDIATELY DOWNWIND OF THE HIGHER TERRAIN...DUE TO MODERATE TO LOCALLY BREEZY TRADE WINDS. && .MARINE... A SMALL CRAFT ADVISORY REMAINED IN EFFECT FOR TYPICALLY WINDY WATERS AROUND MAUI COUNTY AND THE BIG ISLAND. THESE CONDITIONS ARE EXPECTED TO CONTINUE INTO THE WEEKEND...SO THE ADVISORY LIKELY WILL BE EXTENDED. A SERIES OF SMALL SOUTHERLY SWELLS SHOULD ARRIVE DURING THE NEXT FEW DAYS...BUT A LARGER SOUTH SWELL MAY REACH THE STATE OVER THE WEEKEND. TRADE WINDS WILL CONTINUE TO PRODUCE SHORT-PERIOD CHOPPY SURF ALONG EAST-FACING SHORES. && .HFO WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY UNTIL 6 PM HST FRIDAY FOR MAALAEA BAY- PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST WATERS. && $$ AVIATION...JACOBSON REST...RYSHKO Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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