013  
FXHW60 PHFO 300644  
AFDHFO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HONOLULU HI  
844 PM HST MON MAY 29 2017  
   
SYNOPSIS
 
 
LIGHT WINDS WITH LOCAL NIGHTTIME LAND BREEZES WILL CONTINUE  
ACROSS THE STATE THROUGH EARLY TUESDAY MORNING. THE TRADE WINDS  
WILL GRADUALLY BECOME REESTABLISHED FROM EAST TO WEST ACROSS THE  
ISLAND CHAIN STARTING TUESDAY MORNING, AND CONTINUING THROUGH  
TUESDAY NIGHT. UNTIL THE TRADES RETURN, EXPECT LOCAL SEA BREEZES  
WITH CLOUDS AND ISOLATED SHOWERS MAINLY ACROSS LEEWARD AND  
INTERIOR SECTIONS OVER THE WESTERN END OF THE ISLAND CHAIN TUESDAY  
AFTERNOON. TRADE WIND SPEEDS WILL BECOME LOCALLY BREEZY LATER  
THIS WEEK, WITH PASSING TRADE SHOWERS MAINLY ALONG WINDWARD FACING  
SECTIONS STARTING MID-WEEK.  
 

 
   
DISCUSSION
 
 
A WEAK NEARLY NORTH TO SOUTH ORIENTED SURFACE TROUGH REMAINS IN  
THE VICINITY OF THE CENTRAL HAWAIIAN ISLANDS EARLY THIS EVENING.  
THE TAIL END OF A DISSIPATING FRONTAL BOUNDARY IS ALSO EVIDENT  
LESS THAN 300 MILES NORTH OF KAUAI. ELSEWHERE, A WEAK 1020 MB  
SURFACE HIGH APPEARS TO BE ABOUT 560 MILES NORTH-NORTHWEST OF  
LIHUE, WHILE A 1024 MB SURFACE HIGH IS MORE THAN 1450 MILES EAST-  
NORTHEAST OF HILO. THESE FEATURES ARE MAINTAINING A RELAXED  
PRESSURE GRADIENT ACROSS THE REGION EARLY THIS EVENING. AS A  
RESULT, THE BACKGROUND FLOW REMAINS LIGHT, WITH LOCAL NIGHTTIME  
LAND BREEZE CIRCULATIONS ARE BEGINNING TO DEVELOP ACROSS MOST OF  
THE INDIVIDUAL ISLANDS AS RADIATIONAL COOLING BECOMES ESTABLISHED  
AFTER SUNSET.  
 
ALOFT, LOOPS OF WATER VAPOR IMAGERY CONTINUE TO SHOW MIDDLE AND  
UPPER TROPOSPHERIC LOWS ABOUT 260 MILES NORTHEAST OF HILO. THESE  
FEATURES ARE TRACKING SLOWLY TOWARD THE NORTH-NORTHEAST AWAY FROM  
THE ISLANDS. THE SURFACE TROUGH NEAR THE CENTRAL ISLANDS APPEARS  
TO BE A REFLECTION OF THE LOWS ALOFT. THE LAST LOW-LIGHT VISIBLE  
SATELLITE IMAGERY SHOWS PARTLY TO MOSTLY CLOUDY SKIES OVER MOST  
OF THE STATE, WHICH ARE LEFT OVER FROM THE DAYTIME HEATING AND  
LOCAL AFTERNOON SEA BREEZE CIRCULATIONS. RADAR REFLECTIVITY DATA  
SHOW ISOLATED SHOWERS NEAR THE SOUTHEAST BIG ISLAND. AS THE  
NIGHTTIME LAND BREEZES CONTINUE TO BECOME ESTABLISHED THIS  
EVENING, THIS WILL LIKELY CONTINUE TO SUPPRESS THE CLOUD COVER  
AND SHOWERS OVER THE ISLANDS.  
 
THE FORECAST MODELS INDICATE THAT THE SURFACE TROUGH WILL  
EVENTUALLY DEPART THE REGION BY LATE TUESDAY. AT THE SAME TIME,  
THE MIDDLE AND UPPER TROPOSPHERIC LOWS WILL CONTINUE TO SHIFT  
SLOWLY NORTH-NORTHEAST AWAY FROM THE ISLANDS, WHILE SURFACE HIGH  
PRESSURE WILL GRADUALLY BUILD NORTH OF THE STATE. THESE FACTORS  
WILL CAUSE THE PRESSURE GRADIENT TO SLOWLY REBOUND FROM EAST TO  
WEST ACROSS THE ISLAND CHAIN TUESDAY AND TUESDAY NIGHT, SO WE  
EXPECT THE TRADES TO EVENTUALLY RETURN. NOTE THAT THE TRADES MAY  
NOT BECOME REESTABLISHED ACROSS KAUAI AND OAHU UNTIL TUESDAY  
NIGHT. THEREFORE, EXPECT LOCAL SEA BREEZE CIRCULATIONS WITH CLOUDS  
AND ISOLATED SHOWERS MAINLY OVER THE LEEWARD AND INTERIOR SECTIONS  
OF THE WESTERN END OF THE ISLAND CHAIN TUESDAY AFTERNOON.  
 
THE TRADES WILL STRENGTHEN TO LOCALLY BREEZY SPEEDS LATE IN THE  
WORK WEEK AS THE SURFACE HIGH PRESSURE CONTINUES TO BUILD NORTH  
OF THE REGION. ALSO, THE ATMOSPHERE WILL LIKELY BECOME  
INCREASINGLY STABLE DUE TO A WEAK MIDDLE TROPOSPHERIC RIDGE  
SETTING UP ABOVE THE ISLANDS. ONCE THE TRADE WINDS ARE BLOWING  
ACROSS THE ISLANDS, EXPECT LOW CLOUDS AND SHOWERS TO MAINLY AFFECT  
WINDWARD AND MAUKA AREAS STARTING TUESDAY NIGHT, AND CONTINUING  
THROUGH NEXT WEEKEND. ONCE THE TRADES STRENGTHEN LATER IN THE  
WEEK, THEY MAY TRANSPORT SOME OF THE SHOWERS OVER TO THE LEEWARD  
SECTIONS OF SOME OF THE SMALLER ISLANDS. OVERALL, RAINFALL  
AMOUNTS ARE FORECAST TO REMAIN LIGHT INTO NEXT WEEKEND.  
 
THE LONG-RANGE GFS AND ECMWF FORECAST MODELS CONTINUE TO SUGGEST  
A WEAK UPPER-TROPOSPHERIC TROUGH SETTING UP OVER THE AREA STARTING  
AROUND SUNDAY. IF SO, THIS FEATURE COULD PROVIDE A SLIGHT  
ENHANCEMENT OF THE LOW CLOUDS AND TRADE SHOWERS STARTING EARLY  
NEXT WEEK. THE MODELS ALSO SHOW A FRONT MOVING DOWN FROM THE  
NORTH-NORTHWEST TOWARD THE REGION EARLY NEXT WEEK. THIS MAY CAUSE  
THE WESTERN END OF THE SURFACE RIDGE NORTH OF THE STATE TO ERODE,  
SO THE TRADES MAY EVENTUALLY START TO WEAKEN EARLY NEXT WEEK.  
 

 
   
AVIATION
 
 
A WEAK PRESSURE PATTERN WILL REMAIN IN PLACE TONIGHT, WITH  
LAND BREEZES EXPECTED IN MOST AREAS. THE TRADES WILL RETURN FROM  
EAST TO WEST ACROSS THE ISLAND CHAIN ON TUESDAY, WITH LOCALIZED  
SEA BREEZES DEVELOPING IN MANY AREAS PRIOR TO THE TRADE WINDS  
KICKING BACK IN. ISOLATED SHOWERS WILL FAVOR THE COASTAL WATERS  
AND WINDWARD AREAS OVERNIGHT. ON TUESDAY, SEA BREEZES WILL LIKELY  
LEAD TO SCATTERED SHOWER DEVELOPMENT OVER THE INTERIOR OF THE  
ISLANDS DURING THE AFTERNOON HOURS, WITH THE SHOWER FOCUS THEN  
SHIFTING TO WINDWARD AREAS AS THE TRADES KICK BACK IN. SOME BRIEF  
MVFR CIGS/VSBYS WILL BE POSSIBLE IN SHRA OVER THE INTERIOR OF THE  
ISLANDS TUESDAY AFTERNOON, AND WINDWARD LOCALES DURING THE LATE  
AFTERNOON AND EARLY EVENING HOURS. PREDOMINANTLY VFR CONDITIONS  
ARE EXPECTED AT THE TAF SITES THROUGH 06Z WEDNESDAY, WITH THE  
EXCEPTION OF PHNY WHICH WILL LIKELY SEE MVFR CIGS FROM MID MORNING  
THROUGH LATE AFTERNOON ON TUESDAY.  
 
NO AIRMETS ARE CURRENTLY IN EFFECT.  
 

 
   
MARINE
 
 
WATER LEVELS HAVE PEAKED AT 2.7 FT (RELATIVE TO MLLW) THIS  
EVENING AT THE HONOLULU TIDE STATION AND WILL DROP THROUGH THE  
OVERNIGHT HOURS (LOW TIDE AT 3 AM HST). THESE DAILY PEAK TIDES  
THAT HAVE LED TO COASTAL FLOODING PROBLEMS OVER THE PAST WEEK WILL  
TREND BACK DOWN TOWARD NORMAL LATE TUESDAY EVENING, THEN  
POTENTIALLY BELOW NORMAL WEDNESDAY THROUGH THE UPCOMING WEEKEND.  
AS A RESULT, THE COASTAL FLOODING THREAT IS EXPECTED TO DIMINISH.  
THE NEXT SEQUENCE OF KING TIDES (SLIGHTLY LARGER THAN THIS MONTH'S  
KING TIDES) WILL OCCUR LATER THIS MONTH BETWEEN JUNE 21ST AND  
JUNE 27TH.  
 
LIGHT WINDS WITH LAND-SEA BREEZE CONDITIONS PREVAILING NEAR THE  
COASTS WILL CONTINUE INTO TUESDAY DUE TO A WEAK SURFACE TROUGH  
LOCATED NEAR MAUI COUNTY. TRADE WINDS WILL GRADUALLY RETURN TUESDAY  
THROUGH MIDWEEK AS THIS WEAK TROUGH SHIFTS NORTHWEST AND HIGH  
PRESSURE BUILDS NORTH OF THE AREA. SMALL CRAFT ADVISORY CONDITIONS  
WILL RESULT DUE TO STRONG WINDS BEGINNING TUESDAY NIGHT AND  
CONTINUING INTO THE UPCOMING WEEKEND. THESE STRONGER WINDS ARE  
EXPECTED TO SETUP OVER THE CHANNELS, MAALAEA BAY AND SOUTH OF THE  
BIG ISLAND. AS A RESULT, ROUGH AND CHOPPY SURF ALONG EAST FACING  
SHORES IS EXPECTED THROUGH THE SECOND HALF OF THE WEEK INTO THE  
UPCOMING WEEKEND.  
 
AN OUT OF SEASON SMALL TO MODERATE NORTH-NORTHWEST (330-340 DEG)  
SWELL ASSOCIATED WITH A GALE THAT DEVELOPED NEAR THE DATE LINE OVER  
THE WEEKEND AND TRACKED EAST TO AROUND 1400 NM NORTH OF THE STATE IS  
EXPECTED TO FILL IN THROUGH THE OVERNIGHT HOURS ACROSS THE LOCAL  
WATERS. SURF ALONG NORTH AND WEST FACING SHORES ASSOCIATED WITH THIS  
SOURCE SHOULD PEAK THROUGH THE DAY TUESDAY WELL BELOW ADVISORY  
LEVELS, THEN TREND DOWN INTO THE SECOND HALF OF THE WEEK.  
 
THE LARGE SOUTH SWELL THAT PEAKED SATURDAY AND LED TO ADVISORY-LEVEL  
SURF ALONG SOUTH FACING SHORES HAS DROPPED AND WILL CONTINUE TO FADE  
THROUGH MIDWEEK. THE LATEST OBSERVATIONS AT THE BUOYS SOUTH OF THE  
ISLANDS REFLECT THE BULK OF THE REMAINING ENERGY HOLDING WITHIN THE  
14 TO 15 SECOND BANDS SLOWLY TRENDING DOWN.  
 
ALTHOUGH NO SIGNIFICANT SOUTH SWELLS ARE EXPECTED INTO THE FIRST  
WEEK OF JUNE, A SERIES OF SMALL BACKGROUND LONG-PERIOD SOUTHERLY  
PULSES MOVING THROUGH WILL KEEP THE SURF ALONG SOUTH FACING SHORES  
FROM BECOMING FLAT EACH DAY.  
 

 
   
HFO WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
 
DISCUSSION...HOUSTON  
AVIATION...JELSEMA  
MARINE...GIBBS  
 
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