597
FXHW60 PHFO 101953
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
953 AM HST FRI MAY 10 2024
SYNOPSIS
THE THREAT FOR STRONG TO SEVERE THUNDERSTORMS AND HEAVY RAINFALL
WILL CONTINUE ACROSS THE STATE THROUGH TONIGHT AS A STRONG UPPER
LEVEL DISTURBANCE SETTLES SOUTHWARD INTO THE AREA. ALTHOUGH THE
THUNDERSTORM POTENTIAL LATER THIS WEEKEND, PLENTY OF MOISTURE
LINGERING COMBINED WITH AFTERNOON SEA BREEZES AND A BROAD SURFACE
TROUGH NEARBY WILL SUPPORT AFTERNOON SHOWERS OVER INTERIOR AND
LEEWARD AREAS EACH DAY. THE WET PATTERN COULD CONTINUE THROUGH THE
LATTER HALF OF NEXT WEEK AS ANOTHER UPPER DISTURBANCE APPROACHES.
DISCUSSION
WATER VAPOR IMAGERY SHOWED BROAD UPPER TROUGHING OVER THE REGION
WITH A STRONG SHORTWAVE LOW DIGGING SOUTHEASTWARD INTO THE AREA.
THE ASSOCIATED SURFACE TROUGH IS LOCATED OVER KAUAI WITH LOW-LEVEL
CONVERGENT FLOW DRIVING THE POTENTIAL FOR HEAVY SHOWERS AND
EMBEDDED THUNDERSTORMS LATER TODAY. MUCAPES OF 1000 TO 2000 J/KG
COMBINED WITH EFFECTIVE DEEP LAYER SHEAR VALUES OF 35 TO 45 KNOTS
WILL SUPPORT A FEW STRONG TO SEVERE THUNDERSTORMS AND LOCALLY
HEAVY RAINFALL THAT COULD LEAD TO FLASH FLOODING. AS A RESULT, A
FLOOD WATCH REMAINS IN EFFECT FOR THE ENTIRE STATE.
RADAR ACTIVITY SHOWS MOST OF THE HEAVIER SHOWERS HAVE MOVED NORTH
OF THE ISLAND CHAIN FOR THE TIME BEING WITH LINGERING SHOWERS
AROUND MAUI COUNTY LATE THIS MORNING. THE SURFACE TROUGH IS
KEEPING WINDS LIGHT OUR OF THE SOUTH TO SOUTHEAST THROUGH THE NEXT
24 HOURS. DAYTIME HEATING WILL INVOKE SEA BREEZE CONVERGENCE OVER
THE ISLANDS BY AFTERNOON RESULTING IN SHOWERS AND THUNDERSTORMS
DEVELOPING. HI-RES MODELS SHOW OAHU AND EASTWARD FOCUS FOR THIS
ACTIVITY WITH KAUAI, ALTHOUGH WILL BE UNSTABLE, MAY LACK THE
AVAILABLE MOISTURE AND WILL SEE MORE SPOTTY SHOWERS AND
THUNDERSTORMS. 12Z SOUNDING PRECIPITABLE WATER VALUES WERE 1.16
INCHES AT LIHUE COMPARED TO 1.55 INCHES AT HILO. THE FOCUS WILL
SHIFT TO BIG ISLAND AND MAUI COUNTY TONIGHT INTO SATURDAY MORNING,
WHERE THE HIGH SHEAR POTENTIAL SETS UP FOR MORE ORGANIZED
CONVECTION CAPABLE OF PRODUCING SEVERE THUNDERSTORMS (STRONG
WINDS, HAIL, WATER AND LAND SPOUTS). A WINTER STORM WARNING AND
HIGH WIND WARNING ARE ALSO POSTED FOR BIG ISLAND SUMMITS DUE TO
THE HIGH ELEVATION IMPACTS FROM THIS SYSTEM.
GUIDANCE SHOWS THE UPPER LOW BEGINNING TO WEAKEN AS IT LIFTS OFF
TO THE NORTHEAST LATER THIS WEEKEND INTO EARLY NEXT WEEK, WHICH
WILL SUPPORT A DIMINISHING LIKELIHOOD OF THUNDERSTORMS. THE
SURFACE TROUGH WILL FADE AND GENTLE TO MODERATE TRADES WILL EASE
BACK IN BY THE END OF THE DAY SATURDAY. THE RAINFALL CHANCES,
HOWEVER, WILL LIKELY LINGER AS THE AFOREMENTIONED BROAD SURFACE
TROUGH REMAINS OVER OR NEARBY TO THE WEST SUNDAY THROUGH NEXT
WEEK. EXPECT THE LIGHT TO MODERATE EAST TO SOUTHEAST LOW- LEVEL
FLOW TO PERSIST, WHICH WILL ALLOW THE LAND AND SEA BREEZE REGIME
TO HOLD FOR MOST AREAS. THIS COMBINED WITH A SUFFICIENT AMOUNT OF
MOISTURE WILL KEEP THE RAINFALL CHANCES UP EACH DAY, ESPECIALLY
THROUGH THE AFTERNOON AND EARLY EVENING PERIODS OVER
INTERIOR/LEEWARD AREAS WITH THE SEA BREEZES. THE WET PATTERN COULD
PERSIST THROUGH THE SECOND HALF OF THE WEEK AS ANOTHER UPPER LOW
DROPS SOUTHWARD INTO THE AREA DRAWING UP DEEP TROPICAL MOISTURE
AND SOUTHERLY FLOW OVER THE STATE.
AVIATION
A BROAD SURFACE TROUGH AND UPPER LEVEL DISTURBANCE WILL SLOWLY
MOVE SOUTH ACROSS THE STATE TODAY. THIS WILL BRING ENHANCED
SHRA ACTIVITY ALONG WITH THE THREAT OF A FEW TS WITH INCREASED
COVERAGE OVER THE WESTERN ISLANDS THIS MORNING THEN SLOWLY SHIFT
SOUTHEASTWARD LATER TODAY. EXPECT PERIODS OF MVFR CONDS WITH
OCCASIONAL IFR POSSIBLE UNDER HEAVIER SHRA.
AIRMET SIERRA REMAINS IN EFFECT FOR TEMPO MTN OBSC ACROSS THE
SMALLER ISLANDS AND WINDWARD SECTIONS OF THE BIG ISLAND, WITH
LITTLE CHANGE EXPECTED TODAY.
AIRMET TANGO MAY BECOME NECESSARY FOR MODERATE MID TO UPPER LEVEL
TURBULENCE AS THE UPPER LEVEL DISTURBANCE MOVES ACROSS THE STATE.
AMD NOT SKED FOR PMDY CONTINUES DUE TO EQUIPMENT ISSUES, WITH NO
TIMELINE FOR RESTORATION.
MARINE
AN UPPER DISTURBANCE MOVING INTO THE AREA FROM THE NORTH WILL
KEEP THE THREAT OF STRONG, POSSIBLY SEVERE, THUNDERSTORMS IN THE
FORECAST THROUGH SATURDAY. ANY THUNDERSTORMS THAT DEVELOP WILL
HAVE THE POTENTIAL TO PRODUCE STRONG WIND GUSTS, HAIL, AND
FREQUENT LIGHTNING. MARINE INTERESTS SHOULD CONTINUE TO MONITOR
FOR ANY SPECIAL MARINE WARNINGS THAT MAY BE ISSUED TODAY THROUGH
SATURDAY. LIGHT AND VARIABLE WINDS WILL REPLACE THE USUAL TRADE
WIND FLOW AT THE SURFACE TODAY AND SATURDAY AS A TROUGH NEAR KAUAI
STRENGTHENS AND EXPANDS ACROSS THE ISLAND CHAIN. LIGHT TO
MODERATE EASTERLY TRADE WINDS WILL RETURN ON SUNDAY.
A LONG-LIVED SOUTH SWELL WILL AFFECT THE ISLANDS INTO THE
WEEKEND. SURF ALONG SOUTH FACING SHORES IS EXPECTED TO REMAIN AT
THE HIGH SURF ADVISORY THRESHOLD OF 10 FEET THROUGH THIS
AFTERNOON, THEN GRADUALLY DECLINE SATURDAY THROUGH TUESDAY AS THE
PERIOD SHORTENS. A SERIES OF OVERLAPPING LONG-PERIOD SOUTH SWELLS
WILL GIVE ANOTHER SIZABLE BOOST TO SOUTH SHORE SURF WEDNESDAY
THROUGH LATE NEXT WEEK.
NORTH SHORE SURF WILL REMAIN TINY THROUGH THIS MORNING. A SMALL
REINFORCING SHORT-PERIOD NORTH-NORTHWEST SWELL WILL BUILD IN THIS
AFTERNOON AND CONTINUE THROUGH THE WEEKEND. A SMALL LONG-PERIOD
NORTHWEST SWELL WILL BUILD SUNDAY NIGHT, GIVING NORTH SHORE SURF A
BOOST EARLY NEXT WEEK. SURF ALONG EAST FACING SHORES WILL BE WELL
BELOW NORMAL LEVELS THROUGH THE MIDDLE OF NEXT WEEK.
HFO WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH LATE TONIGHT FOR ALL HAWAIIAN ISLANDS.
HIGH SURF ADVISORY UNTIL 6 PM HST THIS EVENING FOR SOUTH FACING
SHORES OF NIIHAU, KAUAI, OAHU, MOLOKAI, LANAI, MAUI AND BIG
ISLAND.
HIGH WIND WARNING UNTIL 6 AM HST SATURDAY FOR BIG ISLAND
SUMMITS.
WINTER STORM WARNING FROM NOON TODAY TO 6 AM HST SATURDAY FOR
BIG ISLAND SUMMITS.
DISCUSSION...FOSTER
AVIATION...WALSH
MARINE...VAUGHAN
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