705
FXHW60 PHFO 070702
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
902 PM HST MON APR 6 2026
SYNOPSIS
A SIGNIFICANT PATTERN CHANGE IS THEN EXPECTED BY TUESDAY AS AN
UPPER LEVEL TROUGH AND SURFACE LOW PRESSURE EVOLVE NORTHWEST OF
THE ISLANDS. THIS SYSTEM IS EXPECTED TO DRAW DEEP TROPICAL
MOISTURE NORTHWARD OVER THE STATE, LEADING TO AN EXTENDED PERIOD
OF STRONG SOUTHERLY WINDS, INCREASED CHANCES FOR WIDESPREAD
RAINFALL AND THUNDERSTORMS, AND RENEWED FLOODING CONCERNS FROM
FROM THE MIDDLE OF THE WEEK THROUGH THIS WEEKEND.
SHORT TERM UPDATE
ISSUED AT 901 PM HST MON APR 6 2026
THE LATEST FORECAST REMAINS ON TRACK, SO NO AMENDMENTS WILL BE
REQUIRED WITH THIS UPDATE. LIGHT TO MODERATE TRADES ACROSS
PREDOMINATELY WINDWARD PORTIONS OF THE STATE AND LAND-SEA BREEZES
HOLDING PRESENT ACROSS LEEWARD PORTIONS, NAMELY ALONG THE KONA
COASTLINE OF BIG ISLAND. SHOWER ACTIVITY IS SLOWLY DETERIORATING
ACROSS THE HAWAIIAN ISLANDS; THE CALM BEFORE THE STORM, SO TO
SPEAK. GUIDANCE CONTINUES TO DEPICT AN UPPER-LEVEL TROUGH AND
ASSOCIATED SURFACE LOW TO EVOLVE NORTHWEST OF THE ISLANDS TUESDAY,
THE CATALYST TO AN INCREASE OF MOISTURE ACROSS MUCH OF THE STATE.
PREV DISCUSSION
WATER VAPOR IMAGERY SHOWS AN APPROACHING UPPER LEVEL TROUGH OVER
THE NORTHWEST HAWAIIAN ISLANDS THIS AFTERNOON. OCCASIONAL CIRRUS
CLOUDS ALONG THE EASTERN FLANK OF THE TROUGH WILL CONTINUE OVER
THE NEXT DAY OR SO. AT THE SURFACE, A RIDGE IS NORTHEAST OF THE
STATE WITH THE AXIS PASSING THROUGH 30N140W. TO THE NORTHWEST, A
COLD FRONT AROUND 575 MILES NORTHWEST OF KAUAI TRACKING EAST AT 10
MPH. GENTLE TO MODERATE SOUTHEAST WINDS PREVAIL WITH LIGHTER
WINDS/LAND BREEZES SETTING UP LEEWARD DUE TO THE BIG ISLAND WIND
BLOCKAGE. MOST ISLANDS WILL SEE DECREASING SHOWERS AND CLEARING
TONIGHT EXCEPT FOR KAUAI WHERE CLOUDS AND SHOWERS WILL BEGIN TO
ENHANCE DUE TO THE UPPER TROUGH.
A BROAD SURFACE TROUGH IS EXPECTED TO DEVELOP AHEAD OF THE FRONT, JUST
NORTHWEST OF THE ISLANDS EARLY ON TUESDAY, REINFORCING AND
STRENGTHENING SOUTH WINDS ACROSS THE ISLANDS. A MOISTURE BAND
ASSOCIATED WITH THE TROUGH WILL ALSO SET UP AROUND KAUAI ON
TUESDAY AROUND THE TIME THE UPPER TROUGH MOVES ACROSS THIS AREA
BRINGING A CHANCE FOR HEAVY SHOWERS. DEEP TROPICAL MOISTURE WILL
BE DRAWN NORTHWARD IN THE SOUTH FLOW. THE COMBINATION OF DAYTIME
HEATING, SEA BREEZES, AND A POTENT SHORTWAVE TROUGH MOVING
THROUGH, MAY EVEN TRIGGER SOME HEAVY SHOWERS OR THUNDERSTORMS OVER
INTERIOR AREAS ON TUESDAY. 0-6 KM BULK SHEAR VALUES IN EXCESS OF
60 KNOTS MAY ALLOW SOME OF THESE THUNDERSTORMS TO BECOME ORGANIZED
AND PRODUCE BRIEF STRONG GUSTS ON TUESDAY, BEFORE DROPPING OFF
TUESDAY NIGHT. THE UPPER TROUGH EXITS TUESDAY NIGHT WHILE THE
DEEP TROPICAL MOISTURE BUILDS NORTHWARD, BUT THE BRIEF RETURNING
STABILITY MAY BE ENOUGH TO PROVIDE A PERIOD OF LESS-INTENSE
SHOWERS TUESDAY NIGHT INTO WEDNESDAY MORNING.
UPPER-LEVEL FORCING IS FORECAST TO STRENGTHEN AGAIN WEDNESDAY AS
A STRONG SECOND SHORTWAVE ROUNDS THE BASE OF THE TROUGH,
POTENTIALLY ENHANCING LIFT OVER THE REGION WHILE SURFACE LOW
PRESSURE CENTER ORGANIZES WEST OF THE ISLANDS. THE COMBINATION OF
DEEP TROPICAL MOISTURE ENGULFING THE STATE, INCREASING LARGE-
SCALE FORCING FOR ASCENT POINT TOWARDS ANOTHER WIDESPREAD AND
ORGANIZED RAINFALL EVENT FOR THE STATE. THEREFORE, A FLOOD WATCH
HAS BEEN ISSUED FOR ALL ISLANDS FROM WEDNESDAY MORNING THROUGH THE
DAY FRIDAY.
SOUTH WINDS WILL RAMP UP LIKELY TO ADVISORY LEVELS WEDNESDAY NIGHT
THROUGH FRIDAY MORNING. STRONG WINDS WILL OCCUR IN AND AROUND
HEAVY SHOWERS AND THUNDERSTORMS, AS WELL AS AROUND MOUNTAIN RIDGES
AND DOWNSLOPING GUSTS OVER NORTHERN AND WINDWARD SLOPES OF ALL
ISLANDS. SEVERE WIND GUSTS (58 MPH+) WILL BE POSSIBLE, THOUGH MOST
AREAS WILL SEE MAX IN THE 40-50 MPH RANGE, AND LIKELY MORE OF A
WIND ADVISORY SETUP. STAY TUNED FOR MORE INFORMATION ON THAT.
FINALLY, A WINTER STORM WATCH HAS BEEN POSTED FOR A COMBINATION OF
FREEZING RAIN AND SNOW ON THE BIG ISLAND SUMMITS ABOVE 12,500
FEET ALSO RUNNING WEDNESDAY THROUGH FRIDAY.
DIFFERENCES REMAIN IN THE GLOBAL MODELS FOR THE WEEKEND, BUT THE
GENERAL CONSENSUS IS THAT THE ACTIVE PATTERN COULD LINGER IN THE
AREA. THE ECMWF CLEARS OUT MUCH OF THE STATE OF THE BULK OF THE
RAIN, BUT THE GFS CONTINUES THE POTENTIAL FOR RAIN ACROSS AT LEAST
PORTIONS OF THE STATE THROUGH THE WEEKEND AND BEYOND, WHERE THE
DEEP MOISTURE AXIS ANCHORS.
AS PREVIOUS DISCUSSIONS HAVE MENTIONED, ONE IMPORTANT CONSIDERATION
WITH THIS WEEK'S RAINFALL IS ANTECEDENT CONDITIONS. THE ISLANDS
EXPERIENCED SIGNIFICANT FLASH FLOOD EVENTS IN RECENT WEEKS, AND
DESPITE SEVERAL DAYS OF DRIER TRADE WIND WEATHER, SOILS REMAIN
VULNERABLE IN MANY AREAS. AS A RESULT, ANY TIME PERIOD OF HIGHER
RAINFALL RATES COULD QUICKLY LEAD TO ENHANCED RUNOFF, RENEWED
RISES IN STREAMS AND RESERVOIRS, AND LOCALIZED FLASH FLOODING
CONCERNS.
AVIATION
TRADES WILL CONTINUE TO WEAKEN HEADING INTO THE EVENING AS AN
UPPER-LEVEL DISTURBANCE MOVES IN AND INITIATES A WET WEEK ACROSS
THE ISLANDS. VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH AT
LEAST SUNRISE TOMORROW, HOWEVER RAIN MAY START TO MOVE IN FOR
KAUAI AND EVEN HILO BY LATE MORNING TUESDAY. RAIN IS THEN EXPECTED
TO SLOWLY SPREAD ACROSS THE ISLANDS AFTERWARD.
AIRMET TANGO REMAINS IN EFFECT FOR UPPER LEVEL TURBULENCE BETWEEN
FL300 AND FL350 OVER THE ISLANDS AND IS EXPECTED TO CONTINUE
THROUGH THE PERIOD. AIRMET SIERRA WAS DROPPED FOR WINDWARD OAHU,
BUT ANOTHER MAY BE ISSUED FOR OTHER ISLANDS AS THIS AFOREMENTIONED
DISTURBANCE MOVES IN WITH MORE MOISTURE.
MARINE
MODERATE TO LOCALLY FRESH TRADES WILL GRADUALLY EASE AND SHIFT
SOUTHEASTERLY TONIGHT THROUGH WEDNESDAY AS A FRONT STALLS JUST
WEST OF THE ISLANDS AND HIGH PRESSURE FAR NORTH OF THE ISLANDS
MOVES SLOWLY EASTWARD. THE WINDS WILL TURN MORE SOUTHERLY AND
INCREASE TO MODERATE AND STRONG LEVELS ON THURSDAY AS A LOW
PRESSURE SYSTEM DEVELOPS ALONG THE STALLED FRONTAL BOUNDARY.
SMALL NORTHWEST SWELLS WILL KEEP SOME SMALL SURF ALONG NORTH FACING
SHORES THROUGH THIS EVENING. A MODERATE LONG-PERIOD NORTHWEST
SWELL WILL FILL IN TONIGHT AND TUESDAY, GIVING MORE OF A BOOST TO
NORTH SHORE SURF LATE TUESDAY THROUGH WEDNESDAY. A SMALL, SHORT-
PERIOD NORTH-NORTHEAST SWELL WILL FILL IN DURING THE DAY TUESDAY
BEFORE PEAKING WEDNESDAY AND SUBSIDING THURSDAY. THIS OVERLAP WILL
MAKE FOR SOME ROUGH CHOPPY CONDITIONS ALONG NORTH FACING SHORES.
A SMALL SOUTHERLY SWELL WILL KEEP SOME SMALL SURF IN PLACE ALONG
SOUTH FACING SHORES THROUGH THIS EVENING. A SLIGHTLY LARGER, LONG-
PERIOD SOUTH SWELL, WILL FILL IN TONIGHT, GIVING A MORE NOTICEABLE
INCREASE TO SOUTH SHORE SURF TUESDAY. SURF COULD REACH ADVISORY
LEVELS BY WEDNESDAY BEFORE SLOWLY EASING THURSDAY INTO THE WEEKEND.
STRENGTHENING SOUTHERLY WINDS WILL MAKE FOR ROUGH AND CHOPPY SURF
BY LATE NEXT WEEK.
EAST SHORE SURF WILL REMAIN SMALL AND BELOW THE SEASONAL AVERAGE DUE
TO A LACK OF STRONG TRADE WINDS OVER AND UPSTREAM OF THE ISLANDS,
EXCEPT FOR SOME WRAP FROM THE NORTHERLY SWELLS.
HFO WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY AFTERNOON FOR
BIG ISLAND EAST-BIG ISLAND INTERIOR-BIG ISLAND NORTH-BIG ISLAND
SOUTH-BIG ISLAND SOUTHEAST-BIG ISLAND SUMMITS-CENTRAL OAHU-EAST
HONOLULU-EWA PLAIN-HALEAKALA SUMMIT-HONOLULU METRO-KAHOOLAWE-
KAUAI EAST-KAUAI MOUNTAINS-KAUAI NORTH-KAUAI SOUTH-KAUAI
SOUTHWEST-KIPAHULU-KOHALA-KONA-KOOLAU LEEWARD-KOOLAU WINDWARD-
LANAI LEEWARD-LANAI MAUKA-LANAI SOUTH-LANAI WINDWARD-MAUI
CENTRAL VALLEY NORTH-MAUI CENTRAL VALLEY SOUTH-MAUI LEEWARD WEST-
MAUI WINDWARD WEST-MOLOKAI LEEWARD SOUTH-MOLOKAI NORTH-MOLOKAI
SOUTHEAST-MOLOKAI WEST-MOLOKAI WINDWARD-NIIHAU-OAHU NORTH SHORE-
OLOMANA-SOUTH HALEAKALA-SOUTH MAUI/UPCOUNTRY-WAIANAE COAST-
WAIANAE MOUNTAINS-WINDWARD HALEAKALA.
WINTER STORM WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY
AFTERNOON FOR BIG ISLAND SUMMITS.
SHORT TERM UPDATE...PIERCE
DISCUSSION...FOSTER
AVIATION...EVANS
MARINE...TS
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