579
FXHW60 PHFO 021331
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
331 AM HST THU APR 2 2026
SYNOPSIS
TYPICAL MODERATE TO LOCALLY BREEZY TRADE WINDS WILL CONTINUE
THROUGH THIS WEEKEND AND BRING MAINLY NIGHT AND MORNING SCATTERED
SHOWERS TO WINDWARD AND MAUKA LOCATIONS. BY EARLY NEXT WEEK, A
DEEPENING TROUGH NORTHWEST OF THE STATE WILL PULL UP A MORE
MOISTURE RICH TROPICAL AIR MASS OVER THE STATE AND INCREASE
PRECIPITATION CHANCES. SOME OF THE RAIN COULD BE HEAVY, ESPECIALLY
MID- TO LATE NEXT WEEK.
DISCUSSION
WATER VAPOR IMAGERY LOOP FROM THIS MORNING SHOWED VERY DRY AIR IN
THE MID AND UPPER LEVELS ENTRENCHED OVER AND EAST OF THE STATE,
ASIDE FROM A THIN LAYER OF HIGH CLOUDS PASSING OVER THE BIG
ISLAND. THIS CAN ALSO BE NOTED ON THE LATEST 12Z RAOB SOUNDINGS
FROM BOTH HILO AND LIHUE, WITH A RATHER DRAMATIC DRY LAYER
RESIDING ABOVE A 6000 FT DEEP BOUNDARY LAYER TEMPERATURE
INVERSION. AT THE SURFACE, AN AREA OF HIGH PRESSURE, ANCHORED
ROUGHLY 1000 MILES NORTH OF HAWAII CONTINUED TO DRIVE MODERATE TO
LOCALLY BREEZY EAST NORTHEASTERLY TRADES. SCATTERED LOW CLOUDS
CAUGHT UP IN THIS FLOW HAVE BEEN PUSHING TOWARDS WINDWARD PORTIONS
OF THE ISLANDS FOR THE LAST SEVERAL HOURS. SEVERAL WINDWARD
STATIONS ON EACH ISLAND PICKED OF A FEW HUNDREDTHS OF AN INCH OF
ACCUMULATION, BUT NOTHING OF SIGNIFICANCE.
TODAY THROUGH FRIDAY, THE PATTERN WILL CHANGE VERY LITTLE WITH
MODERATE TO LOCALLY BREEZY TRADES DRIVING LIGHT SCATTERED SHOWERS
ALONG MAINLY WINDWARD AND MAUKA LOCATIONS. THE GREATEST SHOWER
ACTIVITY CAN BE EXPECTED TO OCCUR DURING THE NIGHT AND EARLY
MORNING HOURS. BY THIS WEEKEND, THE AFOREMENTIONED HIGH WELL NORTH
OF THE AREA DRIFTS EAST AS A FRONTAL SYSTEM APPROACHES. THIS
SHOULD ALLOW THE LOCAL SURFACE PRESSURE GRADIENT AROUND THE REGION
TO EASE AND TRADES TO WEAKEN SLIGHTLY. LOW CLOUDS AND SHOWERS WILL
BE ISOLATED AT BEST WITH A SHALLOW BOUNDARY LAYER IN THE LOWER
LEVELS AND DRY AIR IN PLACE ALOFT.
BY MONDAY, BOTH THE GFS AND ECMWF BEGIN TO DIG A BROAD UPPER
TROUGH WELL NORTHWEST OF THE STATE. LIGHT BACKGROUND FLOW AROUND
THE ISLANDS WILL BECOME SOUTHEASTERLY, VEERING TO SOUTHERLY LATE
TUESDAY. WITH SUCH LIGHT FLOW AND SLIGHTLY DEEPER LOWER LEVEL
MOISTURE IN PLACE, AFTERNOON SEA BREEZES COULD HELP INITIATE A FEW
SHOWERS OVER INTERIOR PORTIONS OF THE ISLANDS.
MID TO LATE NEXT WEEK, MODELS CONTINUE TO DEEPEN THE UPPER LEVEL
TROUGH WEST OF THE ISLANDS AND INDUCE A LOW AND COLD FRONT AT THE
SURFACE. GUIDANCE HAS BEEN CONSISTENT WITH THIS SOLUTION FOR THE
LAST SEVERAL RUNS, SO CONFIDENCE IS INCREASING. THIS WOULD SET THE
STAGE FOR TROPICAL MOISTURE BEING DRAWN NORTHWARD ACROSS THE
HAWAIIAN ISLANDS BY DEEP LAYER SOUTHERLY OR SOUTH SOUTHWESTERLY
FLOW OUT AND A DESTABILIZING ATMOSPHERE ALOFT. AS IT STANDS, THE
ECMWF GENERATES A MORE COMPACT AND ROBUST PARENT SURFACE LOW
COMPARED TO THE GFS. NONETHELESS, BOTH MODELS INDICATE THE
POTENTIAL FOR GUSTY SOUTHERLY WINDS AND ROUNDS OF MODERATE TO
HEAVY RAIN. THUS, FLOODING MAY ONCE AGAIN BE A CONCERN. THE
DETAILS FOR TIMING, LOCATION, AND STRENGTH WILL NEED TO BE REFINED
IN THE COMING DAYS.
AVIATION
MODERATE TO LOCALLY BREEZY ENE TRADES PERSIST THROUGH THE PERIOD,
WITH A GRADUAL WEAKENING EXPECTED THROUGH THE REMAINDER OF THE
WEEK. EMBEDDED ISOLATED TRADE SHOWERS CONTINUE, PRIMARILY
AFFECTING WINDWARD AND MAUKA AREAS, OCCASIONALLY LOWERING CEILINGS
AND VISIBILITY TO MVFR AT TIMES. OTHERWISE, VFR CONDITIONS ARE
EXPECTED TO PREVAIL.
NO AIRMETS ARE CURRENTLY IN EFFECT.
MARINE
WEAKENING HIGH PRESSURE NORTH OF THE ISLANDS WILL SHIFT EASTWARD
OVER THE NEXT FEW DAYS, LEADING TO A WEAKENING OF THE TRADE WINDS
INTO THE MODERATE RANGE. WINDS COULD THEN VEER OUT OF THE
SOUTHEAST NEXT WEEK AHEAD OF AN APPROACHING FRONT. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE TYPICALLY WINDIER WATERS AROUND MAUI
COUNTY AND THE BIG ISLAND THROUGH TONIGHT.
THE CURRENT MID PERIOD NORTHEAST SWELL (7 FT, 9-11 SECONDS AT 040
DEGREES) WILL GRADUALLY DECREASE TODAY AS THE NORTHEAST TRADE
WINDS SLOWLY DECREASE. AS A RESULT, EAST SHORE SURF WILL GRADUALLY
DECLINE TODAY THROUGH THE REST OF THE WEEK, BUT WILL STILL RETAIN
A LITTLE SIZE AND CHOP DUE TO THE MODERATE TO LOCALLY BREEZY
TRADES.
THE NEXT SMALL, MEDIUM-PERIOD NORTHWEST (310 DEGREE) SWELL WILL
ARRIVE THIS WEEKEND INTO NEXT WEEK AND BRING A SMALL BUMP IN SURF
FOR NORTH AND WEST FACING SHORES. A LARGER MID PERIOD NORTHWEST
SWELL IS THEN POSSIBLE BY THE MIDDLE OF NEXT WEEK. ALONG SOUTH
FACING SHORES, EXPECT SMALL REINFORCEMENTS TO SUSTAIN SMALL SURF
THROUGH THE WEEK UNTIL A SLIGHTLY LARGER LONG PERIOD SOUTH SWELL
FILLS IN EARLY NEXT WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY FOR MAALAEA BAY-
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG
ISLAND SOUTHEAST WATERS.
DISCUSSION...THOMAS
AVIATION...PIERCE
MARINE...TSAMOUS
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