000
FXHW60 PHFO 111330
AFDHFO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST SAT OCT 11 2008
.SYNOPSIS...
TRADE WINDS AND WINDWARD SHOWERS WILL PERSIST THROUGH SUNDAY...BUT A
FRONT APPROACHING FROM THE NORTHWEST WILL BRING PERIODS OF RAIN TO
KAUAI AND OAHU FROM MONDAY NIGHT THROUGH MIDWEEK...WHILE
SOUTHEASTERLY WINDS PRODUCE UPSLOPE SHOWERS OVER THE REST OF THE
STATE. TRADES WILL RETURN EVERYWHERE BY THE END OF THE WEEK.
&&
.DISCUSSION...
LOCAL DATA FROM AROUND THE MAIN HAWAIIAN ISLANDS SHOWED MODERATE
TRADE WINDS BLOWING. GAUGES REPORTED MOST RAINFALL CONCENTRATED OVER
WINDWARD SLOPES...THOUGH IT WAS UNUSUALLY SPARSE SOUTH OF KAUAI.
PERHAPS THE MARINE AIR MASS UPWIND OF THE ISLANDS WAS INHERENTLY TOO
STABLE...OR THE DRY AIR RIGHT NEAR THE SURFACE VISIBLE IN THE HILO
SOUNDING SOMEHOW INHIBITED CLOUD DEVELOPMENT THROUGH THE MIXED LAYER.
GUIDANCE PREDICTS THE TRADES TO PERSIST WITH LITTLE CHANGE THROUGH
SUNDAY. HOWEVER...BY MONDAY A FRONT IS EXPECTED TO APPROACH THE
ISLANDS FROM THE NORTHWEST...SUPPORTED BY A FAIRLY DEEP MID-LEVEL
LOW DIVING TOWARD THE SOUTHWEST OVER THE STATE AT THE SAME TIME. IT
REMAINS TO BE SEEN JUST HOW VIGOROUS THE FRONT AND LOW WILL BE...BUT
THE SEASON FOR SUCH EVENTS APPROACHES RAPIDLY...SO THEY DESERVE
SERIOUS ATTENTION.
THE LATEST SOLUTIONS...INCLUDING THE 06Z GFS...NOW PREDICT THE FRONT
TO STALL OUT NEAR THE KAUAI CHANNEL AROUND EARLY TUESDAY MORNING
BEFORE RETREATING WESTWARD UNDER THE INFLUENCE OF THE RAPIDLY
DEPARTING LOW ALOFT. SUCH A TRACK IS FURTHER WEST THAN IT WAS IN
EARLIER SOLUTIONS...AND IF THE MODELS CONTINUE THIS TREND...THEN
OAHU CAN EXPECT TO RECEIVE LESS RAIN FROM THE EVENT. IT LOOKS LIKE
THE NORTHERLY WINDS BEHIND THE FRONT WILL REACH KAUAI AND NIIHAU
ONLY BRIEFLY...AND THE OTHER ISLANDS NOT AT ALL. LIKEWISE...MOST OF
THE RAIN FROM THIS EVENT WILL REMAIN NORTH OF THE KAIWI CHANNEL. THE
REST OF THE STATE WILL EXPERIENCE LIGHT SOUTHEASTERLIES AHEAD OF
THE FRONT...AND THOUGH IT WILL NOT RECEIVE RAIN DIRECTLY FROM THE
FRONTAL CLOUD BAND...UPSLOPE SHOWERS ALONG SOUTHEAST SLOPES AND
PREFRONTAL CONVERGENCE BANDS MAY PRODUCE SIGNIFICANT ACCUMULATION.
ALTHOUGH THE LOW ALOFT INCLUDES AN IMPRESSIVE COLD POOL...AT THIS
TIME TEMPERATURES OVER THE ISLANDS ARE NOT EXPECTED TO DROP LOW
ENOUGH TO PRODUCE THUNDERSTORMS. HOWEVER...LIGHTNING MAY BE POSSIBLE
WELL OFFSHORE TO THE SOUTHWEST THROUGH NORTHWEST OF KAUAI.
GUIDANCE BRINGS TRADES BACK TO MOST OF THE STATE AS EARLY AS
WEDNESDAY AFTERNOON...BUT THIS TIMING MAY BE A LITTLE FAST EVEN IF
THE FRONT LIFTS OUT PROMPTLY. STILL...LIGHT TO MODERATE TRADES CAN
BE EXPECTED AGAIN BY THE END OF THE WEEK.
&&
.MARINE...
THE FIRST LARGE NORTHWEST SWELL OF THE SEASON MAY ARRIVE SOON FROM A
LARGE STORM LOW OVER THE EASTERN ALEUTIAN ISLANDS. SURF LIKELY WILL
EXCEED THE 15-FOOT HIGH SURF ADVISORY THRESHOLD ALONG NORTH-FACING
SHORES FROM EARLY SUNDAY THROUGH TUESDAY AT LEAST.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
RYSHKO
