High Surf in Hawaii, September 25 to 28, 2004

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SAT SEP 25 2004

.SYNOPSIS...
A SURFACE RIDGE NORTH OF THE ISLANDS WILL MAINTAIN TRADE WINDS INTO
NEXT WEEK. AN UPPER TROUGH WILL ENHANCE THE USUAL TRADEWIND
SHOWERS...TYPICALLY FAVORING WINDWARD AND MOUNTAIN AREAS DURING THE
NIGHTS AND MORNINGS. A FEW SHOWERS WILL SPREAD LEEWARD ON THE
SMALLER ISLANDS. SHOWERS ON THE BIG ISLAND LEEWARD SLOPES WILL
FAVOR THE AFTERNOON AND EVENING HOURS...AND MAY BE BRIEFLY HEAVY.

&&

.DISCUSSION...
SCATTERED BUT SHOWERY LOW CLOUDS CONTINUE TO STREAM INTO THE MAIN
HAWAIIAN ISLANDS THIS MORNING...BUT ARE LESS PRONOUNCED VERSUS 24
HOURS AGO. THE HILO SOUNDING THIS MORNING REMAINS MODERATELY
UNSTABLE...BUT THE LIHUE SOUNDING INDICATES A WEAK INVERSION TRYING
TO FORM. WILL MAINTAIN THE POPS FOR WINDWARD AND MAUKA AREAS
TODAY...BUT KNOCK DOWN THE PERCENTAGES A CATEGORY FOR LEEWARD
AREAS. WITH MODERATELY UNSTABLE CONDITION PERSISTING THROUGH THE
WEEKEND DUE TO THE UPPER TROUGH OVER THE ISLANDS...ISOLATED HEAVY
SHOWERS ARE STILL POSSIBLE. TRADE WINDS ARE DOWN A NOTCH THIS
MORNING AND WILL DECLINE FURTHER SUNDAY AND MONDAY AS A MID LATITUDE
FRONT WEAKENS THE HIGH PRESSURE TO OUR NORTH. THE FRONT IS NOT
EXPECTED TO REACH THE ISLANDS. MODELS CONTINUE TO ADVERTISE THE
MIGRATION OF A SUBTROPICAL JET TOWARD THE STATE...PLACING THE JET
ENTRANCE REGION OVER THE ISLANDS SOMETIME SUNDAY. MODELS DEPICT
THE CURRENT LOCATION OF THE JET...SOUTHEAST OF THE BIG
ISLAND...FAIRLY WELL...LENDING SOME CREDENCE TO THIS SOLUTION. IF
THE JET MIGRATIONS PANS OUT...AM UNCERTAIN TO WHAT DEGREE THIS MIGHT
FURTHER ENHANCE SHOWER ACTIVITY...BUT THE PATTERN LOOKS
SUSPICIOUSLY SIMILAR TO A SCENARIO A COUPLE OF WEEKS BACKS THAT
PRODUCED A FAIR AMOUNT OF RAINFALL. A NUMBER OF THINGS HAVE TO COME
TOGETHER JUST RIGHT TO RECREATE THAT EVENT...SO FOR NOW WILL TAKE A
MORE CAUTIOUS APPROACH AND MAINTAIN CURRENT SHOWER ACTIVITY LEVELS
THROUGH THE EARLY PORTION OF NEXT WEEK.

AT THE SURFACE...GLOBAL MODELS HAVE COME INTO MUCH BETTER AGREEMENT
WITH THE FORMATION...MOVEMENT...AND INTENSITY OF A SURFACE LOW
EXPECTED FORM ALONG THE AFOREMENTIONED FRONT SOMETIME SUNDAY OR
MONDAY. THE LOW SHOULD REMAIN WELL NORTH OF THE STATE AND HAVE
LITTLE TO NO IMPACT ON ISLAND WEATHER OTHER THAN A PRODUCING A NORTH
NORTHEAST SWELL...MORE ON THAT IN THE MARINE SECTION BELOW.

BY MIDWEEK...MID LEVEL RIDGING WILL ASSIST THE INVERSION IN
BUILDING BACK IN...FOR A RETURN TOWARD DRIER TRADE WIND CONDITIONS.

&&

.MARINE...
A SERIES OF LOWS SOUTHEAST OF NEW ZEALAND LAST WEEKEND PRODUCED A
TRAIN OF SOUTH SWELLS...THE FIRST OF WHICH HAS ALREADY REACHED THE
ISLANDS. RESULTANT SURF FROM THE CURRENT SWELL WILL REMAIN BELOW
ADVISORY LEVELS TODAY .A MORE SIGNIFICANT PULSE OF ENERGY IS
EXPECTED TO ARRIVE EARLY SUNDAY AND PRODUCE SURF ABOVE THE HIGH SURF
ADVISORY THRESHOLD OF 8 FEET. THE SURF IS EXPECTED TO REMAIN
ELEVATED THROUGH TUESDAY OR WEDNESDAY. A HIGH SURF ADVISORY WILL
LIKELY BE ISSUED LATER TODAY. ON THE OPPOSITE END OF THE ISLANDS A
SMALL NORTHWEST SWELL IS EXPECTED SUNDAY...WITH A LARGER NORTH
NORTHEAST SWELL ARRIVING TUESDAY AND WEDNESDAY. THE LATTER SWELL MAY
CAUSE MINOR HARBOR SURGES AT KAHULUI AND HILO.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

TANABE