| Current Conditions | ||
| Temp |  | 3.6 C |
| RH | | 11 % |
| Wind | | SSE 9 mph |
| Road | | Open |
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Hawaiian Islands Synoptic Discussion and Guidance 934 FXHW60 PHFO 261346 AFDHFO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HONOLULU HI 346 AM HST SAT JUL 26 2014 .SYNOPSIS... MODERATE TRADE WINDS WILL FOCUS SHOWERS MAINLY ACROSS WINDWARD AND MAUKA AREAS. AN INCREASE IN SHOWER ACTIVITY IS EXPECTED TO SPREAD FROM EAST TO WEST ACROSS THE STATE TODAY THROUGH SUNDAY. TRADES MAY STRENGTHEN SOMEWHAT BY EARLY NEXT WEEK. && .DISCUSSION... A QUIET LATE JULY NIGHT IS IN PROGRESS ACROSS THE STATE. RADAR LOOPS AND RAIN GAUGE DATA HAVE NOT SHOWN MUCH INCREASE IN WINDWARD SHOWERS DURING THE NIGHT...WITH MOST GAUGES REPORTING EITHER ZERO OR LIGHT RAINFALL AMOUNTS. 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 ANY 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 12Z SOUNDINGS SHOW INCREASED MOISTURE DURING THE PREVIOUS 12 HOURS... WITH PWATS RANGING FROM 1.4 TO 1.5 INCHES. THE HILO SOUNDING ALSO SHOWED A PRONOUNCED WEAKENING OF THE TRADE INVERSION NEAR 7000 FEET...WITH ANOTHER ISOTHERMAL LAYER DEVELOPING BETWEEN 10K AND 12K FEET. 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 ALMOST TO THE BIG ISLAND. MODEL AND SOUNDING DATA SUGGEST THAT A WEAK LOW LEVEL TROUGH IS MOVING THROUGH THE STATE AT THIS TIME...WITH WINDS IN THE 850-700 MB LAYER VEERING TO THE SOUTHEAST AT HILO IN THE WAKE OF THE TROUGH AXIS. TODAY THROUGH SUNDAY...THE AREA OF ENHANCED MOISTURE WILL CONTINUE MOVING WESTWARD ACROSS THE STATE AS THE LOW LEVEL TROUGH SHIFTS WEST OF THE AREA. 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 A HIGHER/WEAKER TRADE INVERSION...AS HAS ALREADY BEEN OBSERVED AT HILO THIS MORNING. THE WEAKER INVERSION COMBINED WITH THE ADDITIONAL MOISTURE MOVING THROUGH COULD PRODUCE A FEW LOCALLY HEAVIER SHOWERS AT TIMES. FAIRLY HIGH POPS WILL PREVAIL STATEWIDE ACROSS WINDWARD/MAUKA AREAS TONIGHT AND SUNDAY...WITH SOME OF THE SHOWERS SPILLING OVER INTO LEEWARD AREAS. WITH SOMEWHAT VEERED LOW LEVEL FLOW POSSIBLE...WILL NEED TO KEEP AN EYE ON WINDWARD OAHU WHERE MORE PERSISTENT SHOWER ACTIVITY MAY TEND TO DEVELOP ALONG THE KOOLAU RANGE. 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 NIGHT... WITH PASSING SHOWERS MAINLY AFFECTING WINDWARD AND MAUKA AREAS. TOWARD THE LATER PART OF NEXT WEEK AND INTO NEXT WEEKEND...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 REMAINS 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 THROUGH THE MORNING HOURS... MAINLY OVER WINDWARD AND MAUKA SECTIONS...AS LOW CLOUDS AND ACCOMPANYING SHOWERS RIDE THE TRADE WINDS. VFR WILL OTHERWISE PREDOMINATE. && .MARINE... AN 08Z ASCAT PASS SAMPLED THE EASTERN HALF OF THE HAWAIIAN COASTAL WATERS...FINDING SOME 20 KNOT WINDS IN THE ALENUIHAHA CHANNEL AND SOUTH OF THE BIG ISLAND...WITH WINDS MOSTLY AROUND 15 KNOTS ELSEWHERE. EXPECT LITTLE CHANGE THROUGH TODAY AND TONIGHT. THE NORTHEAST PACIFIC SURFACE HIGH WILL CHANGE LITTLE IN STRENGTH WHILE MOVING SLIGHTLY FURTHER AWAY FROM THE STATE DURING THE WEEKEND...BUT A WEAK LOW PRESSURE AREA PASSING WELL SOUTH OF THE AREA MAY TIGHTEN THE GRADIENT ACROSS THE ISLANDS SOMEWHAT. WINDS MAY INCREASE TO SCA LEVELS BY SUNDAY OR SUNDAY EVENING ACROSS THE TYPICALLY WINDIER AREAS AROUND MAUI COUNTY AND THE BIG ISLAND. SCA CONDITIONS WILL THEN 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 TONIGHT INTO 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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