| Current Conditions | ||
| Temp |  | -1.8 C |
| RH | | 96 % |
| Wind | | NNW 17 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 517 FXHW60 PHFO 040211 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 411 PM HST TUE MAR 3 2015 .SYNOPSIS... HIGH PRESSURE TO THE NORTHWEST WILL KEEP MODERATE TO FRESH TRADE WINDS BLOWING OVER THE ISLANDS TONIGHT...BECOMING STRONGER THROUGH FRIDAY. A TROUGH ALOFT NEAR THE STATE WILL RESULT IN HEAVY RAIN AND THUNDERSTORMS ON THE BIG ISLAND AND MAUI THROUGH THURSDAY. TRADE WINDS WILL FOCUS RAINFALL OVER THE WINDWARD SLOPES...WITH SOME SHOWERS CARRYING OVER TO LEEWARD AREAS. && .DISCUSSION... A 1038 MB SURFACE HIGH IS CENTERED 1500 MILES NORTHWEST OF KAUAI AND IS PRODUCING MODERATE TO FRESH TRADE WINDS ACROSS THE ISLANDS. A BROAD TROUGH ALOFT IS LOCATED NORTH OF THE STATE WHILE A WEST TO EAST ORIENTED JET STREAM RUNS ALONG THE BASE OF THIS TROUGH. INFRARED SATELLITE SHOWS THE JET STREAM CARRYING A THICK BAND OF LAYERED AND HIGH CLOUDS OVER HAWAII FROM THE WEST LATE THIS AFTERNOON. CURRENT RADAR SHOWS THUNDERSTORMS OVER THE LEEWARD AND INTERIOR SECTION OF THE BIG ISLAND. THESE THUNDERSTORMS WERE TRIGGERED BY A COMBINATION OF DAYTIME HEATING...INSTABILITY CAUSED BY THE INCOMING TROUGH ALOFT AND ABUNDANT MOISTURE. THE BROAD AND DEEP TROUGH ALOFT WILL PERSIST NORTH OF THE AREA FOR AT LEAST THE NEXT WEEK. A SHORT WAVE TROUGH WITHIN THE LARGER TROUGH WILL APPROACH THE ISLANDS FROM THE NORTHWEST TONIGHT. AS THE TROUGH APPROACHES...THE ATMOSPHERE WILL BECOME MORE UNSTABLE AND THE DEEP LAYERED MOISTURE WILL SPREAD OVER THE ISLANDS. THE FOCUS OF THIS MOISTURE AND INSTABILITY WILL BE ACROSS MAUI AND THE BIG ISLAND THROUGH WEDNESDAY NIGHT. THUS...WE EXPECT HEAVY RAIN WITH EMBEDDED THUNDERSTORMS TONIGHT THROUGH WEDNESDAY NIGHT. A FLASH FLOOD WATCH HAS BEEN ISSUED FOR THE BIG ISLAND AND MAUI AND A WINTER STORM WARNING HAS BEEN ISSUED FOR THE BIG ISLAND SUMMITS...BOTH PRODUCTS GO THROUGH WEDNESDAY NIGHT. CONCERNING THE FLASH FLOOD WATCH...WHILE BOTH ISLANDS ARE ENTIRELY INCLUDED WITHIN THE WATCH...TRADE WINDS WILL FOCUS THE MORE PERSISTENT RAIN ACROSS THE WINDWARD SLOPES. STRONG WESTERLY WINDS ALOFT WILL STRENGTHEN OVER THE BIG ISLAND AS THE SHORTWAVE DEPARTS ON THURSDAY...AND MAY RESULT IN ADVISORY OR WARNING LEVEL WINDS FOR THE BIG ISLAND SUMMITS FROM THURSDAY INTO NEXT WEEK. FOR KAUAI...OAHU AND THE REMAINDER OF MAUI COUNTY...TRADE WINDS WILL STRENGTHEN OVER THE NEXT COUPLE OF DAYS AS THE SURFACE HIGH FAR NORTHWEST OF THE STATE STRENGTHENS AND MOVES CLOSER. THE TRADES WILL USHER IN SCATTERED SHOWERS THROUGH THURSDAY WITH THE FOCUS OVER THE WINDWARD SLOPES. WE ANTICIPATE OVERALL LESS MOISTURE ACROSS THE WESTERN HALF OF THE STATE...THUS LESS SHOWER COVERAGE AND LIGHTER PRECIPITATION CAN BE EXPECTED. TRADE WINDS WILL REMAIN BREEZY THROUGH FRIDAY NIGHT WHEN THE HIGH BEGINS TO TRACK BACK TO THE NORTH. THE WEEKEND COULD BRING ANOTHER ROUND OF HEAVY RAIN AND THUNDERSTORMS OVER THE EASTERN HALF OF THE STATE. WE WILL CONTINUE TO MONITOR FOR MORE DETAILS IN THE COMING DAYS. && .AVIATION... THE AFTERNOON CONVECTION ON THE BIG ISLAND SLOPES...LEADING TO CB TOPS TO FL300 AND LIGHTNING...WILL BEGIN TO DIMINISH WITH SUNSET. ELSEWHERE...SHOWERS EMBEDDED WITHIN THE TRADE WIND FLOW CONTINUES TO FOCUS OVER WINDWARD AND MAUKA AREAS. AIRMET SIERRA IS POSTED FOR MOUNTAIN OBSCURATION OVER N THRU E SECTIONS OF OAHU AND MAUI. THESE MORE ACTIVE SHOWERS ARE EXPECTED TO CONTINUE OVER THE NEXT FEW PERIODS. THE EASTERN ISLANDS...ESPECIALLY WINDWARD BIG ISLAND AND WINDWARD MAUI...WILL LIKELY EXPERIENCE HEAVY SHOWERS...POSSIBLY SEEING PREVAILING MVFR WITH ISOL TO TEMPO IFR CONDITIONS STARTING LATE TONIGHT. AIRMET SIERRA WILL LIKELY BE EXPANDED LATER THIS EVENING. THE POTENTIAL FOR THUNDERSTORMS REMAINS OVER THE BIG ISLAND THIS EVENING AND THROUGH WEDNESDAY NIGHT AND OVER MAUI COUNTY LATE TONIGHT. THE UPPER LEVEL JET OVER THE ISLANDS IS CARRYING ENOUGH SPEED SHEAR TO KEEP AIRMET TANGO POSTED FOR TEMPO MOD TURB BETWEEN FL250 AND FL400. ADDITIONALLY...A THICK MID TO UPPER LEVEL CLOUD DECK PASSING OVER THE ISLANDS ALONG THE JET. THEY MAY BE THICK ENOUGH TONIGHT TO PROMPT THE ISSUANCE OF AIRMET ZULU FOR LIGHT TO MOD RIME ICING ABOVE 130. && .MARINE... WINDS WILL REMAIN BELOW SMALL CRAFT ADVISORY SPEEDS TONIGHT BUT THE WINDS WILL STRENGTHEN TOMORROW AS A STRONG HIGH BUILDS NORTHWEST OF THE AREA. THIS WILL LIKELY REQUIRE A SMALL CRAFT ADVISORY FOR STRONG TRADE WINDS AND ROUGH SEAS BY WEDNESDAY. THE BREEZY TRADE WINDS WILL PRODUCE ROUGH SURF ALONG EAST FACING SHORES AS WELL OVER THE NEXT SEVERAL DAYS...POSSIBLY RESULTING IN A HIGH SURF ADVISORY LATER IN THE WEEK. OTHERWISE SURF IS EXPECTED TO REMAIN BELOW THE ADVISORY THRESHOLDS. && .HFO WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH LATE WEDNESDAY NIGHT FOR MAUI AND THE BIG ISLAND. WINTER STORM WARNING UNTIL 6 AM HST THURSDAY FOR BIG ISLAND SUMMITS. && $$ DISCUSSION/MARINE...FOSTER AVIATION...EATON Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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