Heavy Rain in Hawaii, December 3 to 4, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST THU DEC 3 2009

.SYNOPSIS...
A COLD FRONT WILL BE MOVING DOWN THE MAIN HAWAIIAN ISLANDS FROM THE
WEST TONIGHT AND FRIDAY. BREEZY SOUTHERLY WINDS AND LOCALLY HEAVY
SHOWERS LAY AHEAD OF THE FRONT THAT WILL AFFECT THE SMALLER ISLANDS
TONIGHT. WEAK HIGH PRESSURE FOLLOWS BEHIND THE FRONT AND LINGERS
THROUGH THE WEEKEND. THIS WILL BE FOLLOWED BY A WEAKER COLD FRONT
SLATED TO REACH THE MAIN HAWAIIAN ISLANDS MONDAY OF NEXT WEEK.

&&

.DISCUSSION...
THE FORECAST IS PANNING OUT NICELY. PRE FRONTAL CONVERGENCE
CONTINUES THIS HOUR WITH INCREASING SHOWERS WELL AHEAD OF THE COLD
FRONT. SHOWERS HAVE DEVELOPED RATHER RAPIDLY JUST IN THE PAST 3
HOURS OVER KAUAI COUNTY AND TO THE SOUTH THROUGH WEST OF OAHU. SOME
OF THESE SHOWERS ARE HEAVY IN INTENSITY ALREADY. THE COLD FRONT WAS
225 MILES NORTHWEST OF KAUAI AT 2 PM HST MOVING SOUTHEAST AT 25 TO
30 MPH.

THE SOUTHWEST WINDS AHEAD OF THE FRONT WILL CONTINUE TO STRENGTHEN.
WIND ACCELERATING DOWN THE WINDWARD OR NORTH FACING SIDE OF THE
KOOLAU AND WAIANAE MOUNTAINS ON OAHU IS A PRIMARY CONCERN THIS
EVENING. WIND GUSTS TO 40 TO 45 MPH ARE IN THE FORECAST FOR THIS
EVENING FOR OAHU AND KAUAI. THE SOUTHWEST WINDS ARE ALSO QUITE STIFF
THIS AFTERNOON OVER ON THE CENTRAL VALLEY OF MAUI. SO THE WIND
FORECAST FOR THIS AREA AND MAALAEA BAY HAS BEEN BEEFED UP AS WELL.

TIMING WITH THE ARRIVAL OF THE FRONT APPEARS ON TRACK SO FAR WITH
THE FRONT REACHING KAUAI BEFORE MIDNIGHT TONIGHT...OAHU EARLY FRIDAY
MORNING...MAUI AT AROUND SUNRISE FRIDAY...AND FRIDAY AFTERNOON FOR
THE BIG ISLAND. AGAIN... PRE FRONTAL ACTIVITY LOOMS LARGE...PERHAPS
MORE SIGNIFICANT THAN THE ACTUAL FRONT FOR THE SMALLER ISLANDS.

THE COLD FRONT IS EXPECTED TO WEAKEN BY THE TIME IT REACHES THE BIG
ISLAND. THE PRE FRONTAL ACTIVITY FOR THE BIG ISLAND ARE NOT EXPECTED
TO BE AS DRAMATIC AS TO ITS NEIGHBORS.

WIND SENSORS ATOP HALEAKALA SUMMITS ON MAUI IS READING 18 MPH WITH
GUST TO 35 THIS HOUR. ON THE BIG ISLAND SUMMITS...THE SENSORS ARE
REPORTING SOUTHWEST WINDS IN THE LOW 30'S. SO THE WIND ADVISORY
REMAINS IN EFFECT WITH GUSTS POSSIBLY REACHING 55 MPH THIS EVENING.

AFTER THE FRONT CLEARS OUT...WE EXPECT PARTLY CLOUDY SKIES WITH
ISOLATED SHOWERS AND LIGHT WINDS THROUGH THE WEEKEND. LIGHT TRADES
WILL FOLLOW IN BEHIND THIS FRONT...BECOMING LIGHT SOUTHERLY SATURDAY
AFTERNOON OR EVENING...AHEAD OF THE NEXT FRONT SLATED FOR MONDAY.

THIS FRONT CURRENTLY NORTHWEST OF KAUAI WILL ALSO USHER IN A
SLIGHTLY COOLER AIR MASS. EXPECT DAYTIME HIGHS IN THE LOW 80S INTO
THE WEEK END...AND OVERNIGHT LOWS MOSTLY IN THE 60S.

&&

.MARINE...
THE LARGE NORTHWEST SWELL HAS PEAKED AND IS NOW LOWERING. THEREFORE
AREAS UNDER THE HIGH SURF WARNING WILL BE LOWERED TO AN ADVISORY.
THESE AREAS ARE THE NORTH AND WEST SHORES OF NIIHAU AND KAUAI AND
THE NORTH FACING SHORES OF OAHU. THE HIGH SURF ADVISORY REMAINS IN
EFFECT FOR THE NORTH AND WEST FACING SHORES OF MOLOKAI AND THE NORTH
FACING SHORES OF MAUI THROUGH TONIGHT.

THIS CURRENT NORTHWEST SWELL IS THE FIRST OF 3 SIGNIFICANT NORTHWEST
SWELLS. THE NEXT NORTHWEST SWELL IS ON TAP FOR SATURDAY WITH AN EVEN
LARGER ONE SLATED FOR MONDAY. SEE MARINE SECTION AND SURF PRODUCTS
FOR MORE DETAILS.

ALSO A SMALL CRAFT ADVISORY HAS BEEN EXTENDED TO 6 AM FRIDAY...
EITHER DUE TO WIND OR SEAS OR BOTH.

&&

.AVIATION...
AIRMET FOR TURBULENCE DUE TO THE STIFF AND BREEZY SOUTHWEST WINDS
HAVE BEEN POSTED FOR THE MOUNTAINS NORTH THROUGH EAST OF THE SMALLER
ISLANDS THROUGH TONIGHT.

THIS IS ON TOP OF MOUNTAIN OBSCURATION ABOVE 2500 OR 3 THOUSAND FEET
FOR THE ISLANDS OF KAUAI AND OAHU. MOLOKAI AND MAUI MAY FOLLOW SUITE.

PLEASE REFER TO THE AVIATION PRODUCTS FOR MORE DETAILS.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY UNTIL 6 AM HST FRIDAY FOR THE NORTH AND WEST
FACING SHORES OF NIIHAU...KAUAI...OAHU...MOLOKAI...AND NORTH FACING
SHORES OF MAUI.

SMALL CRAFT ADVISORY UNTIL 6 AM HST FRIDAY 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
AND BIG ISLAND WINDWARD WATERS.

WIND ADVISORY UNTIL 6 AM HST FRIDAY FOR BIG ISLAND SUMMITS AND
HALEAKALA SUMMIT.

&&

H LAU