High Surf in Hawaii, April 24 to 27, 2004

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST SAT APR 24 2004

.SYNOPSIS...THE TRADES WILL BE LIGHT ENOUGH THIS WEEKEND TO PROMOTE
SOME AFTERNOON CLOUD BUILDUPS OVER THE INTERIOR OF THE ISLANDS. A
FEW SHOWERS WILL POP UP DURING THE AFTERNOONS AND EVENINGS. NIGHTS
AND MORNINGS WILL FEATURE MOSTLY CLEAR SKIES...WITH ONLY A COUPLE
LIGHT WINDWARD AND MAUKA SHOWERS. OUR NEXT SIGNIFICANT WEATHER
FEATURE IS A COLD FRONT THAT WILL REACH KAUAI LATE SUNDAY NIGHT OR
EARLY MONDAY. THIS FRONT WILL PUSH DOWN THE ISLAND CHAIN EARLY NEXT
WEEK...THEN STALL OVER THE SOUTHERN ISLANDS THROUGH MIDWEEK.

&&

.DISCUSSION...WIND PROFILES FROM THE FOUR RADARS AND THE 12Z
SOUNDINGS FROM PHLI AND PHTO SHOW 10-15 KT TRADES IN THE LOW LAYER.
THE OBSERVATIONS FROM THE MORE EXPOSED TRADE WIND LOCATIONS LIKE
MOLOKAI AIRPORT...KAHULUI...AND LIHUE INDICATE THE SAME. HOWEVER...
SATELLITE SUGGESTS WE STILL HAVE SOME SORT OF A HYBRID BETWEEN A
DRY TRADE WIND PATTERN AND A CONVECTIVE PATTERN...AS MOST LAND AREAS
STARTED OFF UNDER CLEAR SKIES THIS MORNING AND ARE NOW QUICKLY
STARTING TO CLOUD OVER.

THE MORNING SOUNDING FROM HILO SHOWED SIGNIFICANT MID-LEVEL
WARMING...WHICH SUGGESTS THAT THE AIRMASS IS NOT AS UNSTABLE AS
YESTERDAY. HOWEVER...NEITHER SOUNDING HAD MUCH OF A CAPPING
INVERSION EITHER. HAVE UPDATED THE SKY...POP...AND WEATHER GRIDS TO
REFLECT A WEAK CONVECTIVE TYPE PATTERN FOR THE REST OF THE DAY.

LITTLE CHANGE TO THE LONGER TERM THINKING AT THIS TIME. WEAKENING
COLD FRONT WILL REACH KAUAI LATE SUNDAY NIGHT OR EARLY MONDAY...THEN
PUSH DOWN THE CHAIN. THE MODELS AGREE REMARKABLY WELL ON THE TIMING
OF THIS FEATURE THROUGH EARLY MONDAY...THEN BEGIN TO DIVERGE...
PARTICULARLY WITH THE TIMING OF POST FRONTAL CLEARING. ETA IS A BIT
SLOWER...WHILE THE GFS AND NOGAPS SWING THE DEEPER LAYERED MOISTURE
TO MAINLY THE SOUTHERN ISLANDS BY TUESDAY MORNING. UKMET IS THE
FASTEST...DEPICTING THE FRONT OVER THE BIG ISLAND AS EARLY AS MONDAY
AFTERNOON. ALTHOUGH IT IS RATHER LATE IN THE SEASON...THIS FRONT
WILL BE ACCOMPANIED BY AN UNUSUALLY STRONG UPPER LEVEL TROUGH THAT
WILL DIG SOUTH ALONG 150W...THUS THE MORE AGGRESSIVE SOLUTIONS MAY
PROVE TO BE THE WINNER.

TOWARD MIDWEEK...THE FRONT WILL INEVITABLY OUTRUN ITS UPPER SUPPORT
AND LIKELY COME TO A HALT OVER THE BIG ISLAND AS CYCLOGENESIS OCCURS
ABOUT 1100 MILES TO OUR NORTHEAST NEAR 33N146W. THIS SHOULD KEEP AN
EXTENDED PERIOD OF RATHER MOIST WEATHER OVER THE SOUTHERN ISLANDS
WHILE THE OTHER ISLANDS EXPERIENCE DRIER WEATHER.

&&

.MARINE...SOUTH SWELL FORERUNNERS WITH PERIODS OF 20 TO 25 SECONDS
REACHED THE ISLANDS THIS MORNING. AT THIS TIME...BUOYS TO THE SOUTH
OF THE STATE INDICATE THAT SURF ALONG SOUTHERN SHORES WILL BUILD
DURING THE DAY AND PEAK OVERNIGHT AND SUNDAY AT HEIGHTS JUST BELOW
THE WARNING LEVEL OF 15 FEET. WE WILL CONTINUE TO CLOSELY MONITOR
BUOYS REPORTS DURING THE DAY TO DETERMINE IF WARNING LEVEL SURF WILL
MATERIALIZE. ALSO...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL
HAWAIIAN WATERS DUE TO THE LARGE SOUTH SWELL.

&&

.WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY.....ALL SOUTH SHORES
SMALL CRAFT ADVISORY...ALL HAWAIIAN WATERS FOR LARGE SWELL

R BALLARD/WROE