157
FXHW60 PHFO 070719
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
919 PM HST FRI MAR 6 2026
SYNOPSIS
A SIGNIFICANT CHANGE IN THE WEATHER PATTERN IS EXPECTED EARLY
NEXT WEEK. MODERATE TO BREEZY EAST-SOUTHEAST TRADE WINDS AND
MOSTLY STABLE CONDITIONS WILL PERSIST THROUGH THE WEEKEND.
BEGINNING LATE MONDAY INTO MONDAY NIGHT, A DEEP LOW PRESSURE
SYSTEM EVOLVING NORTHWEST OF THE ISLANDS WILL SHIFT WINDS
SOUTHERLY AND DRAW DEEP TROPICAL MOISTURE NORTHWARD ACROSS THE
STATE. THIS WILL BRING INCREASING CHANCES FOR HEAVY RAINFALL,
THUNDERSTORMS, AND STRONG WINDS STARTING OVER THE WESTERN ISLANDS
LATE MONDAY, THEN SPREADING STATEWIDE THROUGH MIDWEEK. UNSETTLED
WEATHER MAY PERSIST THROUGH MUCH OF NEXT WEEK DUE TO THE SLOW-
MOVING NATURE OF THE SYSTEM.
DISCUSSION
A NOTABLE SHIFT IN THE LARGE-SCALE PATTERN IS EXPECTED TO UNFOLD
ACROSS THE HAWAIIAN ISLANDS DURING THE UPCOMING WEEK. THE CURRENT
DRY AND FAIRLY STABLE REGIME, CHARACTERIZED BY MODERATE TO LOCALLY
BREEZY EAST-SOUTHEAST TRADE FLOW, WILL HOLD IN PLACE THROUGH THE
WEEKEND. CONDITIONS WILL THEN BEGIN TO CHANGE LATE MONDAY INTO
MONDAY NIGHT AS A DEEP UPPER TROUGH DEVELOPS AND AMPLIFIES
NORTHWEST OF THE ISLANDS, BRINGING A MULTI-FACETED WEATHER EVENT
TO THE STATE THAT COULD INCLUDE HEAVY RAINFALL WITH FLASH FLOODING
POTENTIAL, STRONG TO SEVERE STORMS, AND STRONG KONA WINDS.
MODEL GUIDANCE CONTINUES TO INDICATE A STRONG JET STREAK, WITH
CORE WINDS AROUND 120 TO 140 KT AT 250 MB, DIGGING SOUTHEAST
ALONG THE WESTERN FLANK OF THE EVOLVING TROUGH. AS THIS OCCURS,
THE TROUGH IS EXPECTED TO ACQUIRE A MORE NEGATIVE TILT AND EXPAND
TOWARD THE ISLAND CHAIN. THE ISLANDS WILL INCREASINGLY COME UNDER
THE INFLUENCE OF THE JET STREAK’S LEFT-EXIT REGION, PROMOTING
ENHANCED UPPER-LEVEL DIVERGENCE AND DIFLUENT FLOW ALOFT. THIS
LARGE-SCALE ASCENT, COMBINED WITH SMALLER SHORTWAVE DISTURBANCES
ROTATING AROUND THE BASE OF THE TROUGH, COULD GENERATE PERIODS OF
ORGANIZED CONVECTION THROUGH MUCH OF NEXT WEEK, POTENTIALLY
BEGINNING AS EARLY AS TUESDAY.
AT THE SURFACE, GLOBAL AND ENSEMBLE GUIDANCE ARE FAIRLY
CONSISTENT IN DEPICTING A BROAD CYCLONIC CIRCULATION DEVELOPING
NORTHWEST OF THE STATE BY EARLY NEXT WEEK IN RESPONSE TO STRONG
UPPER HEIGHT FALLS. CENTRAL PRESSURES NEAR 985 TO 990 MB ARE
POSSIBLE WITH THIS FEATURE REMAINING WELL NORTHWEST OF THE
ISLANDS. THE RESULTING PRESSURE PATTERN WILL SUPPORT STRENGTHENING
SOUTH TO SOUTHEAST WINDS ACROSS THE STATE, ALLOWING A PLUME OF
DEEP TROPICAL MOISTURE TO SURGE NORTHWARD INTO THE REGION.
PRECIPITABLE WATER VALUES ARE EXPECTED TO CLIMB INTO THE 1.7 TO 2
INCH RANGE BY TUESDAY OVER THE WESTERN ISLANDS, THEN SPREAD ACROSS
THE REMAINDER OF THE STATE BY MIDWEEK.
THE EVOLVING THERMODYNAMIC AND KINEMATIC ENVIRONMENT, INCLUDING
UPPER HEIGHT FALLS, COOLER AIR ALOFT, AND INCREASING DEEP-LAYER
SHEAR, WILL FAVOR EPISODES OF HEAVY RAINFALL WITH EMBEDDED
THUNDERSTORMS. COMBINED WITH BROAD CONFLUENT SOUTH-SOUTHEAST FLOW
AND ISLAND TERRAIN EFFECTS, THIS PATTERN COULD SUPPORT TRAINING
AND ANCHORED CONVECTION, PARTICULARLY ALONG FAVORED TERRAIN. THIS
RAISES THE POTENTIAL FOR SIGNIFICANT FLOODING CONCERNS IF HEAVIER
RAINFALL BANDS PERSIST OVER THE SAME AREAS. IN ADDITION TO THE
HEAVY RAINFALL THREAT, SOME STORMS COULD BECOME STRONG, AND
OCCASIONALLY SEVERE, BY THE MIDDLE OF NEXT WEEK WITH LOCALLY
DAMAGING WINDS POSSIBLE.
IMPACTS MAY BEGIN TO DEVELOP ACROSS THE WESTERN ISLANDS AS EARLY
AS MONDAY NIGHT AS THE LEADING EDGE OF THE MOISTURE PLUME REACHES
THE STATE. THE RISK FOR HEAVY RAIN AND THUNDERSTORMS WILL LIKELY
EXPAND EASTWARD ACROSS THE REMAINDER OF THE ISLAND CHAIN TUESDAY
INTO WEDNESDAY AS DEEPER MOISTURE AND STRONGER FORCING FOR ASCENT
OVERSPREAD THE REGION.
WHILE DETAILS REGARDING THE EXACT TIMING AND LOCATION OF THE
HEAVIEST RAINFALL REMAIN UNCERTAIN, CONFIDENCE CONTINUES TO
INCREASE THAT A PROLONGED PERIOD OF UNSETTLED AND POTENTIALLY
IMPACTFUL WEATHER WILL AFFECT THE ISLANDS NEXT WEEK. FLOODING
IMPACTS COULD BECOME MORE PRONOUNCED OVER TIME AS SOILS BECOME
SATURATED AND STREAM LEVELS AND RESERVOIRS BECOME ELEVATED.
RESIDENTS AND INTERESTS ACROSS THE STATE SHOULD CONTINUE TO
MONITOR FORECASTS THROUGH THE WEEKEND AS THIS SYSTEM COMES INTO
BETTER FOCUS AND DETAILS REGARDING THE TIMING AND LOCATION OF
IMPACTS BECOME CLEARER.
AVIATION
TRADES ARE PREDOMINATELY EXPECTED THROUGH THE PERIOD, WITH VFR AT
MOST SITES SAVE FOR WINDWARD SITES THAT MAY SEE INTERMITTENT MVFR
DUE TO LOWER CIGS AND SHOWER ACTIVITY. NO AIRMETS ARE CURRENTLY IN
EFFECT FOR THE PERIOD, BUT LOW TO MODERATE TURBULENCE IS POSSIBLE
DURING THE DAY TOMORROW FOR LEEWARD SITES AS TRADES INCREASE IN
STRENGTH.
MARINE
STRONG HIGH PRESSURE FAR TO THE NORTHEAST OF THE STATE WILL
MAINTAIN FRESH TO STRONG TRADE WINDS THROUGH THE WEEKEND, WITH
THE STRONGEST WINDS OVER THE TYPICALLY WINDY AREAS AROUND MAUI
COUNTY AND THE BIG ISLAND. A SMALL CRAFT ADVISORY REMAINS IN
EFFECT FROM THE WINDWARD OAHU WATERS AND KAIWI CHANNEL EASTWARD
THROUGH 6 AM SUNDAY, WITH THE EXCEPTION OF MAALEA BAY. THIS SCA
WILL LIKELY NEED TO BE EXTENDED FOR PORTIONS OF THE MARINE AREA
THROUGH AT LEAST SUNDAY. A FRONT APPROACHING FROM THE WEST WILL
EASE THE TRADES AND SHIFT THEM SOUTHEASTERLY ON MONDAY, WITH THE
WINDS THEN BECOMING SOUTHERLY AND INCREASING TO FRESH TO STRONG
LEVELS TUESDAY AND WEDNESDAY.
SURF ALONG EAST FACING SHORES WILL REMAIN ELEVATED AND CHOPPY
THROUGH MONDAY, FOLLOWED BY A DOWNWARD TREND TUESDAY THROUGH LATE
NEXT WEEK.
A SERIES OF WEST-NORTHWEST SWELLS WILL KEEP SOME SMALL SURF IN
PLACE ALONG NORTH AND WEST FACING SHORES DURING THE NEXT 7 DAYS,
BUT SURF WILL REMAIN WELL BELOW ADVISORY LEVELS. A SMALL TO
MODERATE SIZED NORTH SWELL IS POSSIBLE AROUND THURSDAY AND FRIDAY
OF NEXT WEEK.
SURF ALONG SOUTH-FACING SHORES WILL REMAIN SMALL THROUGH EARLY
NEXT WEEK, WITH THE EXCEPTION OF AREAS EXPOSED TO TRADE WIND SWELL
WRAP. ROUGH AND CHOPPY CONDITIONS APPEAR TO DEVELOP TUESDAY AND
CONTINUE THROUGH LATE NEXT WEEK AS SOUTHERLY WINDS INCREASE IN
ADVANCE OF A FRONT. A SERIES OF SMALL LONG PERIOD SOUTH SWELLS
WILL ALSO MOVE THROUGH MONDAY THROUGH LATE NEXT WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY FOR OAHU WINDWARD
WATERS-KAIWI CHANNEL-MAUI COUNTY WINDWARD WATERS-MAUI COUNTY
LEEWARD WATERS-PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND
WINDWARD WATERS-BIG ISLAND LEEWARD WATERS-BIG ISLAND SOUTHEAST
WATERS.
DISCUSSION...GIBBS
AVIATION...EVANS
MARINE...JELSEMA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page