| Current Conditions | ||
| Temp |  | 3.5 C |
| RH | | 9 % |
| Wind | | SSE 12 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 577 FXHW60 PHFO 260646 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 846 PM HST FRI JUL 25 2014 .SYNOPSIS... MODERATE TRADE WINDS WILL FOCUS SHOWERS MAINLY ACROSS WINDWARD AND MAUKA AREAS. AN INCREASE IN SHOWER ACTIVITY IS EXPECTED TO MOVE FROM EAST TO WEST ACROSS THE STATE DURING THE WEEKEND. TRADES MAY STRENGTHEN SOMEWHAT EARLY NEXT WEEK. && .DISCUSSION... A QUIET LATE JULY EVENING IS IN PROGRESS ACROSS THE STATE. RADAR LOOPS AND RAIN GAUGE DATA SHOW PASSING TRADE SHOWERS ACROSS SOME WINDWARD AREAS...WITH RAINFALL ACCUMULATIONS GENERALLY REMAINING ON THE LIGHT SIDE. A TYPICAL SUMMERTIME SURFACE PATTERN PREVAILS... WITH THE NORTHEAST PACIFIC HIGH CENTERED ABOUT 1400 MILES NORTHEAST OF HONOLULU. A WEAK LOW PRESSURE AREA IS LOCATED ABOUT 720 MILES SOUTH SOUTHEAST OF SOUTH POINT ON THE BIG ISLAND...AND IS BEING MONITORED FOR SIGNS OF DEVELOPMENT WHILE MOVING TO THE WEST. WATER VAPOR IMAGERY DEPICTS A MID LEVEL RIDGE EXTENDING FROM THE BIG ISLAND EASTWARD...WITH AN UPPER LEVEL TROUGH LOCATED SEVERAL HUNDRED MILES NORTHEAST OF KAUAI. THE 00Z SOUNDINGS SHOW A WELL DEFINED INVERSION BASED AROUND 7000 FEET...WITH NEAR NORMAL PRECIPITABLE WATER VALUES OF BETWEEN 1.3 AND 1.4 INCHES. MIMIC-TPW IMAGERY SHOWS AN AREA OF HIGHER MOISTURE (PWATS 1.5 TO 1.7 INCHES) APPROACHING THE STATE FROM THE EAST...WITH THE LEADING EDGE ABOUT 100 MILES SOUTHEAST OF THE BIG ISLAND. THROUGH THE OVERNIGHT...WOULD EXPECT TRADE SHOWERS TO INCREASE ACROSS WINDWARD AREAS IN THE TYPICAL MANNER...WITH A FEW OF THE SHOWERS SPILLING OVER INTO SOME LEEWARD AREAS. THE HIGHEST RAIN CHANCES SHOULD OCCUR ACROSS WINDWARD SLOPES OF THE BIG ISLAND AND HALEAKALA...AS THE AREA OF ENHANCED MOISTURE MOVES IN LATE TONIGHT. THE EXISTING FORECAST REFLECTS THE ABOVE THINKING... AND NO UPDATES ARE PLANNED FOR THIS EVENING. LITTLE CHANGE IS EXPECTED TO THE OVERALL MODERATE TRADE WIND PATTERN THROUGH THE WEEKEND. MODELS APPEAR TO INITIALIZE THE AREA OF HIGHER MOISTURE CURRENTLY JUST EAST OF THE STATE REASONABLY WELL...AND MOVE THIS AREA STEADILY WESTWARD THROUGH SUNDAY. DURING THIS TIME...THE UPPER LEVEL TROUGH INITIALLY NORTHWEST OF KAUAI WILL MOVE EASTWARD...PASSING NORTH OF THE STATE SUNDAY AND SUNDAY NIGHT. WOULD EXPECT THE TRADE INVERSION TO RISE AND WEAKEN A BIT IN RESPONSE...WHICH COMBINED WITH THE ADDITIONAL MOISTURE MOVING THROUGH COULD PRODUCE A FEW LOCALLY HEAVIER SHOWERS AT TIMES. PERSISTENT MODERATE TRADE FLOW SHOULD KEEP THE SHOWERS MOVING ALONG HOWEVER. POPS WILL REMAIN QUITE HIGH OVER WINDWARD AND MAUKA SECTIONS ESPECIALLY DURING THE NIGHT AND EARLY MORNING HOURS...WITH SOME SPILLOVER INTO LEEWARD SECTIONS OF THE SMALLER ISLANDS. HEADING INTO NEXT WEEK...THE NORTHEAST PACIFIC HIGH IS FORECAST TO WEAKEN SOMEWHAT AS A COLD FRONT MOVES EASTWARD NORTH OF 30N...BUT AT THE SAME TIME A TROPICAL LOW PASSING WELL SOUTH OF THE STATE MAY BE ABLE TO MAINTAIN OR EVEN TIGHTEN THE PRESSURE GRADIENT LOCALLY. OVERALL WOULD EXPECT A TYPICAL TRADE WIND PATTERN TO PREVAIL FOR MONDAY THROUGH AT LEAST TUESDAY...WITH PASSING SHOWERS MAINLY AFFECTING WINDWARD AND MAUKA. TOWARD THE MIDDLE TO LATER PART OF NEXT WEEK...SOME OF THE MODEL GUIDANCE CONTINUES TO BRING ANOTHER SURGE OF DEEP TROPICAL MOISTURE UP TOWARD THE STATE FROM THE SOUTHEAST. THIS MOISTURE WOULD BE ASSOCIATED WITH THE REMNANTS OF CURRENT EAST PACIFIC TROPICAL STORM GENEVIEVE. THE GUIDANCE SUITE HAS BEEN RATHER INCONSISTENT WITH BOTH THE TIMING AND EXTENT OF ANY POSSIBLE MOISTURE SURGE. THERE IS THE POTENTIAL FOR ANOTHER ROUND OF HEAVY SHOWERS ACROSS THE STATE LATER NEXT WEEK AND INTO NEXT WEEKEND...BUT FORECAST UNCERTAINTY REMAINS QUITE HIGH AT THIS POINT. && .AVIATION... TEMPO MVFR CONDITIONS WILL LIKELY OCCUR THIS EVENING THROUGH SATURDAY MORNING...MAINLY OVER WINDWARD AND MAUKA SECTIONS...AS LOW CLOUDS AND ACCOMPANYING SHOWERS RIDE THE TRADE WINDS. VFR WILL OTHERWISE PREDOMINATE. && .MARINE... THERE IS NO RECENT ASCAT DATA AVAILABLE ACROSS THE HAWAIIAN COASTAL WATERS...BUT AN EARLIER ASCAT PASS ACROSS THE WESTERN WATERS AND CURRENT MESONET DATA IMPLY THAT WINDS ARE LIKELY BELOW SMALL CRAFT ADVISORY /SCA/ CRITERIA THROUGHOUT THE AREA. THE NORTHEAST PACIFIC SURFACE HIGH WILL MOVE SLIGHTLY FURTHER AWAY FROM THE STATE DURING THE WEEKEND...BUT A LOW PRESSURE AREA PASSING WELL SOUTH OF THE AREA MAY TIGHTEN THE GRADIENT ACROSS THE ISLANDS SOMEWHAT. WINDS MAY INCREASE TO SCA LEVELS AS EARLY AS SUNDAY EVENING ACROSS THE TYPICALLY WINDIER AREAS AROUND MAUI COUNTY AND THE BIG ISLAND...BUT THIS REMAINS UNCERTAIN. SCA CONDITIONS WILL REMAIN POSSIBLE IN THE TYPICALLY WINDY AREAS THROUGH MUCH OF NEXT WEEK. AS FOR SURF...A SMALL SSW SWELL MAY PRODUCE A MINOR BUMP ON SOUTH FACING SHORES SATURDAY NIGHT AND SUNDAY. SHORT PERIOD TRADE WIND SWELL WILL CONTINUE ACROSS EAST FACING SHORES...POSSIBLY INCREASING A BIT EARLY NEXT WEEK IF TRADES STRENGTHEN. NO SIGNIFICANT NORTH THROUGH WEST SWELLS ARE EXPECTED THROUGH THE NEXT SEVERAL DAYS. OVERALL...SURF WILL REMAIN WELL BELOW ADVISORY LEVELS ON ALL SHORES THROUGH THE WEEKEND AND INTO THE FIRST PART OF NEXT WEEK. && .HFO WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION/MARINE...JACOBSON AVIATION...KINEL Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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