797  
FXHW60 PHFO 240141  
AFDHFO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HONOLULU HI  
341 PM HST WED SEP 23 2020  
   
SYNOPSIS
 
 
TRADE WINDS CAN BE EXPECTED FOR THE NEXT FEW DAYS AS HIGH  
PRESSURE PASSES BY FAR TO OUR NORTH. AN AREA OF ENHANCED MOISTURE  
WILL PROVIDE FOR A PERIOD OF PASSING SHOWERS THROUGH TONIGHT  
PRIMARILY FOR WINDWARD AND MAUKA AREAS. WINDS WILL BE LIGHTER OVER  
THE WEEKEND AND ON INTO EARLY NEXT WEEK AS A FRONTAL SYSTEM MOVES  
CLOSER TO THE AREA FROM THE NORTHWEST. THE AIRMASS WILL BE FAIRLY  
DRY AND STABLE SO JUST A FEW SHOWERS ARE EXPECTED.  
 

 
   
DISCUSSION
 
 
SURFACE HIGH PRESSURE CENTERED FAR TO THE NORTH NORTHWEST OF THE  
AREA IS PROVIDING FOR MODERATE TRADE WINDS ACROSS THE STATE. AN  
AREA OF ENHANCED MOISTURE IS SEEN ON SATELLITE IMAGERY MOVING INTO  
MAUI COUNTY AND THE BIG ISLAND. RADAR SHOWS NUMEROUS SHOWERS FALL  
OVER EASTERN AND INTERIOR SECTIONS OF THE BIG ISLAND AS WELL AS  
OVER THE WINDWARD SLOPES ON MOLOKAI AND MAUI. A FEW LIGHT PASSING  
SHOWERS ARE SEEN ELSEWHERE PRIMARILY OVER WINDWARD SLOPES AND  
SUMMITS. THE AREA OF MOISTURE IS EXPECTED TO SPREAD UP OVER OAHU  
AND KAUAI THIS EVENING AND OVERNIGHT. SHOWER ACTIVITY IS EXPECTED  
TO INCREASE ESPECIALLY OVER WINDWARD AND MAUKA AREAS WITH THE  
TRADE WINDS SUFFICIENTLY STRONG ENOUGH TO BLOW OVER SHOWERS OVER  
TO SELECT LEEWARD AREAS AT TIMES.  
 
THE SURFACE HIGH WILL MOVE SLOWLY EASTWARD OVER THE NEXT FEW DAYS  
WITH AN UPTICK IN TRADE WINDS EXPECTED. PASSING LIGHT SHOWERS WILL  
CONTINUE TO FAVOR WINDWARD AND MAUKA AREAS WITH MOST LEEWARD  
LOCATIONS REMAINING DRY.  
 
AS WE HEAD INTO THE WEEKEND, THE HIGH WILL HAVE MOVED TO A  
POSITION FAR TO THE NORTHEAST OF THE STATE WHILE A FRONTAL  
BOUNDARY FAR TO THE NORTHWEST NUDGES THE HIGHS ASSOCIATED RIDGE  
AXIS A BIT SOUTH. THIS WILL CAUSE THE TRADE WINDS TO BECOME LIGHT  
TO MODERATE ALLOWING DAYTIME SEA BREEZES AND NIGHTTIME LAND BREEZES  
TO BECOME WIDESPREAD. THE SEA BREEZES WILL PRODUCE AFTERNOON CLOUDS  
AND SPOTTY SHOWERS, BUT A RIDGE ALOFT WILL KEEP THE ATMOSPHERE STABLE,  
SO RAINFALL WILL BE LIGHT.  
 
BY EARLY NEXT WEEK, THE FRONT WILL BE LOCATED A FEW HUNDRED MILES  
TO THE NORTH NORTHWEST OF THE STATE. WINDS WILL BECOME RATHER  
LIGHT WITH LAND AND SEA BREEZES DOMINATING. THE AIRMASS WILL  
REMAIN RATHER DRY AND STABLE SO SHOWER ACTIVITY WILL BE RATHER  
LIMITED.  
 

 
   
AVIATION
 
 
WITH HIGH PRESSURE ENTRENCHED NORTH OF THE ISLANDS, TRADE WINDS  
WILL BE MODERATE TO LOCALLY BREEZY THROUGH THURSDAY.  
 
AN AREA OF SHOWERS, AND ACCOMPANYING MVFR CONDITIONS, IS MOVING  
FROM THE EAST AND WILL MAINLY AFFECT WINDWARD AND MAUKA SECTIONS  
ACROSS THE STATE, WITH THE BIG ISLAND, MAUI, AND MOLOKAI STILL  
SEEING THE MOST ACTIVITY THIS AFTERNOON. OTHERWISE, VFR WILL  
PREVAIL.  
 
AN AIRMET FOR MOUNTAIN OBSCURATION IS CURRENTLY IN EFFECT FOR  
WINDWARD PARTS OF THE BIG ISLAND, MAUI, AND MOLOKAI.  
 

 
   
MARINE
 
 
A SECONDARY AREA OF HIGH PRESSURE BUILDING IN BEHIND AN EASTERN  
PACIFIC COLD FRONT WILL MAINTAIN THIS ONGOING NORTH-SOUTH PRESSURE  
GRADIENT ACROSS THE STATE. THIS WILL RESULT IN MODERATE TO FRESH  
TRADES WITH A SLIGHT STRENGTHENING THROUGH LATE THURSDAY. THESE  
ANTICIPATED HIGHER TRADES WILL OCCASIONALLY BECOME LOCALLY STRONG  
WITHIN THE CHANNELS SURROUNDING MAUI COUNTY, MAALAEA BAY AND THOSE  
WATERS SOUTH OF THE BIG ISLAND. THUS, A SMALL CRAFT ADVISORY  
(SCA) REMAINS IN EFFECT FOR THESE WATERS THROUGH AT LEAST FRIDAY  
MORNING. EXPECT WINDS TO WEAKEN BELOW SCA CRITERIA FRIDAY WITH  
WEAKENING WINDS TO A LIGHT BREEZE SUNDAY.  
 
BUOY 51001 BEGAN REPORTING THE PASSAGE OF HIGH PERIOD FORERUNNER  
NORTHERLY SWELLS EARLY THIS AFTERNOON. WHILE THE BULK OF THIS  
EARLIER WEEK GULF OF ALASKA ENERGY WILL RIDE EAST OF THE ISLANDS,  
THE STATE WILL STILL GET CLIPPED BY THIS ENERGY. THERE WILL BE A  
SIGNIFICANT JUMP IN SURF ALONG ALL NORTH-FACING SHORES OVER THE  
NEXT 36 TO 48 HOURS. WAVE HEIGHTS WILL PEAK OUT TOMORROW WHILE  
STAYING BELOW ADVISORY LEVELS WITH A GRADUALLY DOWNTREND FRIDAY  
AND SATURDAY. A NICE BUMP IN THE LONG PERIOD SOUTHWEST SWELL  
MOVING UP FROM A GENERATION AREA SOUTH OF NEW ZEALAND A COUPLE OF  
DAYS AGO SHOULD PICK SOUTHERN-FACING SHORE SURF UP ANOTHER FOOT OR  
SO THROUGH THURSDAY. ANOTHER DAY OR THREE OF MODERATE TO FRESH  
TRADES WILL RESULT IN THE MAINTENANCE OF SEASONAL EAST-FACING SURF  
INTO THE WEEKEND. AFTER A WEEKEND OF WEAKER TRADES AND LOWERING  
SURF, EASTERN SWELL FRONT RUNNERS MAY ARRIVE FROM (WHAT WILL BE  
LEFT OF) TROPICAL CYCLONE LOWELL'S EAST PACIFIC EASTERLY FETCH.  
 

 
   
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...BURKE  
AVIATION...KINEL  
MARINE...BLOOD  
 
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