068
FXHW60 PHFO 192000
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST SAT APR 19 2025
SYNOPSIS
A SOMEWHAT WET WEATHER PATTERN TODAY AS THE STATE REMAINS UNDER
THE INFLUENCE OF UPPER LEVEL TROUGHING. TRADE WINDS ALSO RETURN
TODAY, BUT WILL BE LIGHT ENOUGH FOR LOCALIZED SEAS BREEZES THIS
AFTERNOON. MODERATE TRADES THEN CONTINUE THROUGH MONDAY, WITH
CLOUDS AND SHOWERS FAVORING WINDWARD AND MAUKA AREAS. ANOTHER
STORM SYSTEM WILL MOVE INTO THE STATE FROM THE NORTHWEST THROUGH
THE MIDDLE OF NEXT WEEK BRINGING A CHANCE OF HEAVY RAIN AND
THUNDERSTORM.
DISCUSSION
RADAR AND SATELLITE IMAGERY SHOW WIDELY SCATTERED SHOWERS ACROSS
THE STATE THIS MORNING WITH CLOUDS FAVORING WINDWARD AND MAUKA
AREAS. RECENT OBS CONTINUE TO SHOW THE REGION UNDER THE INFLUENCE
OF A RELATIVELY UNSTABLE AND MOIST AIR MASS WITH AN UPPER LEVEL
TROUGH TO THE NORTHEAST OF THE ISLANDS. EXPECT THIS TROUGH TO
GRADUALLY WEAKEN LATER TODAY AS UPPER LEVEL RIDGING EXPANDS
TOWARDS THE WEST.
TRADE WINDS ARE EXPECTED TO RETURN TODAY AS HIGH PRESSURE FAR
NORTH OF THE ISLANDS BUILDS. HOWEVER, TRADES WILL BE LIGHT ENOUGH
THIS AFTERNOON TO ALLOW FOR THE DEVELOPMENT OF AFTERNOON SEA
BREEZES. COULD SEE SOME LOCALIZED FLOODING THIS AFTERNOON AS SEA
BREEZE SHOWERS ARE ENHANCED BY LINGERING INSTABILITY. MODERATE
EASTERLY TRADES RETURN BY SUNDAY AND CONTINUE INTO MONDAY, WITH
CLOUDS AND SHOWERS OVER MAINLY WINDWARD AND MAUKA AREAS.
THE NEXT WEATHER MAKER WILL COME IN THE FORM OF AN CLOSED-OFF UPPER
LOW THAT WILL SINK DOWN ALONG AND NEAR 170W LONGITUDE AND COME
WITHIN 600 MILES NORTHWEST OF KAUAI. THE WEST NORTHWEST POSITIONING
OF THIS LOW WILL PULL UP A MORE MOISTURE-RICH AIR OVER THE STATE
FROM THE SOUTHWEST. AS HEIGHTS BEGIN TO LOWER AND MID TO UPPER
LAYERS COOL FROM THE WEST, ENHANCED INSTABILITY WITHIN A MOISTENED
AIR MASS WILL LIKELY INDUCE ANOTHER ROUND OR THREE OF WIDESPREAD
SHOWERS AND THUNDERSTORMS. ENSEMBLE GUIDANCE PLACES THE HIGHER
PROBABILITY FOR MEASURABLE PRECIPITATION ALONG THE UPPER TROUGH
AXIS (CENTERED ON MAUI COUNTY AND POINTS NORTHEASTWARD) AND ON
WINDWARD SLOPES THIS WEEK. WITH THE APPROACH OF EITHER A BROAD
OPEN WAVE TROUGH OR A CLOSED LOW NORTHWEST OF THE ISLANDS NEXT
WEEK, THE HIGHEST RAIN PROBABILITIES (OR AREAS TO RECEIVE MORE
FREQUENT RAIN EPISODES) WILL BE ACROSS THE WESTERN HALF OF THE
STATE. FLOODING CONCERNS MAY BE RE-AWAKENED NEXT TUESDAY THROUGH
THURSDAY AS LOCALLY HEAVY PRECIPITATION FALLS UPON SATURATED
SOILS.
AVIATION
MODERATE TRADES WILL RETURN TODAY AND CONTINUE TO USHER IN CLOUDS
AND SHOWERS TO WINDWARD AND MAUKA AREAS. HOWEVER, WINDS WILL
STILL BE LIGHT ENOUGH TO SUPPORT SEA BREEZE DEVELOPMENT BY THE
AFTERNOON, WHICH WILL BRING ADDITIONAL CLOUDS AND SHOWERS TO
LEEWARD AND INTERIOR AREAS THAT WILL DIMINISH OVERNIGHT WITH THE
LOSS OF DAYTIME HEATING. MVFR CONDITIONS WILL BE POSSIBLE IN ANY
SHOWERS, OTHERWISE VFR CONDITIONS SHOULD PREVAIL.
AIRMET SIERRA IS IN EFFECT FOR MOUNTAIN OBSCURATION FOR WINDWARD
MAUI AND OAHU THROUGH THE MORNING.
MARINE
GENTLE TO MODERATE TRADES CONTINUE THROUGH MONDAY, THEN VEER TO
SOUTHEASTERLY IN ADVANCE OF A DEEP LOW THAT WILL DEVELOP NW OF THE
ISLANDS. WINDS FURTHER VEER THROUGH MIDWEEK AND THEN HOLD STEADY
OUT OF THE SOUTHERLY QUADRANT WHERE THEY WILL REMAIN FOR THE
BALANCE OF THE WEEK. THERE WILL BE A CHANCE OF THUNDERSTORMS
DURING THIS TIME, PARTICULARLY OVER THE WESTERN WATERS.
A MODERATE, MEDIUM PERIOD NNW SWELL HAS SHIFTED MORE N AND WILL
GRADUALLY TREND DOWN THROUGH SUNDAY PRODUCING BELOW AVERAGE SURF
ALONG N AND W FACING SHORES. A TINY, LONG PERIOD NW SWELL WILL
FILL IN MONDAY INTO TUESDAY BEFORE SUBSIDING WEDNESDAY WHICH WILL
PREVENT SURF FROM GOING FLAT. IN THE LONG RANGE, GUIDANCE DEPICTS
A GALE FORMING MONDAY NEAR THE KURILS THEN TRACKING NORTHEAST TO
THE WESTERN ALEUTIANS BY WEDNESDAY. IN THIS SCENARIO, HAWAII
WOULD EXPERIENCE AN UPTICK IN THE NW SWELL NEXT WEEKEND.
SURF ALONG E FACING SHORES WILL REMAIN BELOW THE APRIL AVERAGE
THROUGH THE WEEKEND. E SHORE SURF COULD BECOMES TINY BY MID WEEK
AS SOUTHERLY WINDS EMERGE.
A TINY, LONG PERIOD S SWELL WILL MOVE THROUGH THIS WEEKEND
PROVIDING A SMALL BOOST IN SURF ALONG S FACING SHORES. A LARGER,
LONG- PERIOD SSW SWELL WILL FILL IN MONDAY INTO TUESDAY AND
PRODUCE NEAR TO ABOVE AVERAGE SURF ALONG S FACING SHORES.
HFO WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...AHUE
AVIATION...FARRIS
MARINE...JVC
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