213  
FXHW60 PHFO 050630  
AFDHFO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE HONOLULU HI  
830 PM HST SAT FEB 4 2023  
   
SYNOPSIS
 
 
AN UPPER LOW OVER THE STATE WILL MAINTAIN AN UNSTABLE AND MOIST  
AIRMASS, WHICH WILL GENERATE SHOWERS AND ISOLATED THUNDERSTORMS,  
WITH LOCALLY HEAVY RAINFALL, THROUGH THE REMAINDER OF THE  
WEEKEND. THE UPPER LOW WILL WEAKEN AND EXIT EAST OF THE ISLANDS BY  
MONDAY. MUCH DRIER AND MORE STABLE CONDITIONS WILL FILTER ACROSS  
THE STATE TO BEGIN THE WORK WEEK, WHILE A MORE TYPICAL TRADE WIND  
WEATHER PATTERN DEVELOPS ACROSS THE ISLANDS INTO NEXT WEEKEND.  
 

 
   
DISCUSSION
 
 
CURRENT RADAR SHOWS SHOWERS REMAINING ACROSS THE ISLANDS THIS  
EVENING, BECOMING MORE FOCUSED ALONG WINDWARD SLOPES AS LOCALLY  
BREEZY TRADE WINDS CONTINUE ACROSS THE REGION. RADAR ESTIMATES  
SUGGEST LOCALLY ENHANCED RAINFALL RATES REMAINING EMBEDDED WITHIN  
SOME OF THE SHOWERS THIS EVENING. THE LATEST LIGHTNING DATA SHOWS  
A FEW STRIKES IN THE VICINITY OF THE BIG ISLAND, AROUND 200 MILES  
NORTH TO NORTHEAST OF HILO, IN AN AREA OF ENHANCED INSTABILITY  
(SHOWALTER INDEX (SW) AROUND -2C).  
 
TONIGHT THROUGH SUNDAY...THE UPPER LOW WILL REMAIN ANCHORED OVER  
THE STATE TONIGHT, BEFORE SLOWLY MOVING EASTWARD AND BECOMING  
CENTERED ACROSS THE BIG ISLAND SUNDAY NIGHT. THIS PATTERN WILL  
MAINTAIN DEEP LAYERED MOISTURE (PWS GREATER THAN 1.50") AND  
MODEST INSTABILITY (SW AROUND 0 TO -1C) ACROSS THE STATE THROUGH  
SUNDAY AFTERNOON. THE DEEPER MOISTURE AND LINGERING INSTABILITY  
WILL THEN BECOME MAINLY CONCENTRATED ACROSS THE EASTERN END OF THE  
STATE SUNDAY NIGHT INTO EARLY MONDAY. THUNDERSTORM PROBABILITIES  
SHOW THE BEST CHANCE FOR ISOLATED STORMS TO REMAIN ACROSS  
WINDWARD ZONES AND SURROUNDING WATERS, AND VICINITY OF THE BIG  
ISLAND THROUGH SUNDAY AFTERNOON. DRIER AND MORE STABLE CONDITIONS  
WILL THEN BEGIN TO PUSH IN ACROSS THE WESTERN END OF THE STATE  
SUNDAY NIGHT INTO EARLY MONDAY. OVERALL, WILL MAINTAIN THE CURRENT  
FORECAST TREND, WITH SHOWERS AND ISOLATED THUNDERSTORMS BECOMING  
MAINLY FOCUSED ALONG WINDWARD AREAS AND MARINE WATERS THROUGH  
SUNDAY AFTERNOON.  
 
MONDAY AND TUESDAY...THE TRANSITION TOWARD MORE STABLE AND DRY  
CONDITIONS WILL CONTINUE MONDAY, AS THE UPPER LOW WEAKENS AND  
EXITS EASTWARD OF THE STATE. HIGH PRESSURE DRIFTING WELL NORTH OF  
THE REGION WILL FURTHER STRENGTHEN THE TRADE WIND WEATHER PATTERN  
ACROSS THE ISLANDS TO BEGIN THE WORK WEEK. THIS PATTERN WILL  
REINFORCE THE TREND TOWARD DRIER AND MORE STABLE CONDITIONS  
ACROSS THE ISLANDS. HOWEVER, CURRENT TRENDS SUGGEST ENOUGH  
MOISTURE LINGERING AROUND THE ISLANDS (MODELED PW VALUES 1.25 TO  
1.35", MOISTURE DEPTHS 9K-13K FT) TO MAINTAIN INCREASED AREAL  
COVERAGE OF SHOWERS ACROSS WINDWARD LOCATIONS INTO TUESDAY.  
SHOWERS WILL REMAIN FOCUSED ACROSS MAINLY WINDWARD AREAS. HOWEVER  
THE AIRMASS WILL QUICKLY STABILIZE THROUGH THE BEGINNING OF THE  
WEEK, WHICH WILL GREATLY REDUCE THE THREAT OF LOCALLY HEAVY  
RAINFALL.  
 
WEDNESDAY INTO NEXT WEEKEND...THE AIRMASS CONTINUES TO BECOME MORE  
DRY AND MORE STABLE, WITH FORECAST PW VALUES FALLING TO UNDER  
1.00" WHILE MODELED MOISTURE DEPTHS FALL TO AROUND 8K FT OR LESS.  
THIS PATTERN WILL GREATLY REDUCE THE INTENSITY AND AREAL COVERAGE  
OF SHOWERS ACROSS THE ISLANDS. LINGERING TRADE WIND FLOW WILL  
MAINTAIN SHOWERS TO MAINLY FAVORED WINDWARD LOCATIONS, WITH THE  
MOST PERSISTENT SHOWERS AT NIGHT THROUGH EARLY MORNING HOURS.  
 

 
   
AVIATION
 
 
BREEZY EASTERLY TRADE WINDS WILL PREVAIL THROUGH THE 24-HR  
FORECAST PERIOD, WITH CLOUDS AND SHOWERS FAVORING WINDWARD AREAS.  
SHOWER COVERAGE MAY INCREASE OVERNIGHT AS AN AREA OF MOISTURE  
CONTINUES WESTWARD THROUGH THE AREA. SOME SHOWERS WILL MAY BE  
HEAVY AT TIMES AND A THUNDERSTORM OR TWO CAN'T BE RULED OUT WITH  
THE ADDED INSTABILITY ASSOCIATED WITH AN UPPER LOW OVER THE  
ISLANDS. WITH THE BREEZY TRADES IN PLACE, SOME SHOWERS WILL MANAGE  
TO REACH LEEWARD AREAS.  
 
AIRMET SIERRA FOR TEMPO MOUNTAIN OBSCURATION WILL BE POSSIBLE  
LATER THIS EVENING AND THROUGH THE SECOND HALF OF THE OVERNIGHT  
PERIOD AS THE AFOREMENTIONED AREA OF MOISTURE MOVES THROUGH.  
 
AIRMET TANGO FOR MODERATE LOW-LEVEL TURBULENCE WILL CONTINUE OVER  
AND DOWNWIND OF ISLAND MOUNTAINS.  
 

 
   
MARINE
 
 
A STRONG HIGH PRESSURE SYSTEM PASSING NORTH OF THE HAWAII REGION  
WILL CONTINUE TO PRODUCE FRESH TO STRONG TRADE WINDS OVER THE  
COASTAL WATERS THROUGH NEXT WEEK. AN UPPER LEVEL LOW OVER THE  
EASTERN ISLANDS WILL CONTINUE TO SLOWLY DRIFT EASTWARD. THIS LOW  
WILL ENHANCE SHOWER ACTIVITY MAINLY OVER SOUTHERN AND EASTERN  
WATERS ON SUNDAY BEFORE DRIFTING AWAY FROM THE REGION. A SMALL  
CRAFT ADVISORY (SCA) REMAINS IN EFFECT FOR ALL WATERS DUE TO WINDS  
AND SEAS THROUGH TONIGHT. WINDS AND SEAS WILL DECREASE ON SUNDAY  
WITH STRONGER TRADE WINDS WITH THE SCA DECREASING IN COVERAGE TO  
THE TYPICAL WINDIER WATERS AND CHANNELS AROUND THE ISLANDS IN MAUI  
AND HAWAII COUNTIES. MORE STABLE CONDITIONS ARE FORECAST FOR  
SUNDAY, THOUGH A CHANCE FOR THUNDERSTORMS WILL LINGER LONGER OVER  
EASTERN WATERS.  
 
A MEDIUM PERIOD NORTH-NORTHWEST TO NORTH SWELL (340-350 DEGREES)  
WILL HOLD INTO SUNDAY BEFORE FADING. ON MONDAY, THE NEXT LONG  
PERIOD NORTHWEST SWELL (310-320 DEGREES) WILL ARRIVE AND SLOWLY  
FILL IN, PEAK ON TUESDAY AND WEDNESDAY, AND THEN LOWER DURING THE  
LATTER HALF OF NEXT WEEK. ON THURSDAY, A LARGER SWELL FROM THE  
NORTH- NORTHWEST (340 DEGREES) WILL ARRIVE AND MAY PRODUCE SURF  
NEAR ADVISORY LEVELS FOR EXPOSED NORTH AND WEST FACING SHORES.  
SURF ALONG SOUTH FACING SHORES WILL EASE THROUGH THE WEEKEND AS A  
LONG- PERIOD SOUTH SWELL ENERGY FADES. SURF ALONG EAST FACING  
SHORES WILL TREND UP THROUGH THE EARLY PART OF THE NEW WEEK AS A  
BELT OF FRESH TO STRONG EASTERLY TRADES DEVELOPS OVER AND FAR  
UPSTREAM OF THE ISLANDS.  
 

 
   
HFO WATCHES/WARNINGS/ADVISORIES
 
 
SMALL CRAFT ADVISORY UNTIL 6 AM HST SUNDAY FOR KAUAI NORTHWEST  
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-  
OAHU WINDWARD WATERS-OAHU LEEWARD WATERS-KAIWI CHANNEL-MAUI  
COUNTY WINDWARD WATERS-MAUI COUNTY LEEWARD WATERS-BIG ISLAND  
WINDWARD WATERS.  
 
SMALL CRAFT ADVISORY UNTIL 6 PM HST SUNDAY FOR MAALAEA BAY-  
PAILOLO CHANNEL-ALENUIHAHA CHANNEL-BIG ISLAND LEEWARD WATERS-BIG  
ISLAND SOUTHEAST WATERS.  
 

 
 

 
 
DISCUSSION...SWR  
AVIATION...GIBBS  
MARINE...BOHLIN  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HI Page Main Text Page