Flash Flood Warning 22, NWS Honolulu, HI

225 
WGHW70 PHFO 141712
FFSHFO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
712 AM HST SAT NOV 14 2009

HIC003-141720-
/O.EXP.PHFO.FF.W.0022.000000T0000Z-091114T1715Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
OAHU IN HONOLULU COUNTY-
712 AM HST SAT NOV 14 2009

...THE FLASH FLOOD WARNING HAS EXPIRED FOR THE ISLAND OF OAHU IN
HONOLULU COUNTY...

HEAVY RAIN ON THE KOOLAU SLOPES HAS EASED...BUT MODERATE SHOWERS 
CONTINUE. WHILE THE THREAT OF FLASH FLOODING HAS EASED...RUNOFF IS 
STILL OCCURRING AND STREAMS WILL REMAIN HIGH FOR SEVERAL HOURS.

A FLASH FLOOD WATCH REMAINS IN EFFECT.

LAT...LON 2163 15805 2170 15795 2155 15786 2151 15792
      2152 15797

$$

BIRCHARD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 AM HST SAT NOV 14 2009

.SYNOPSIS...
UNSETTLED WEATHER CONTINUES WITH LOCALLY HEAVY RAINS AND
THUNDERSTORMS POSSIBLE THROUGH TODAY. STRONG TRADE WINDS WILL
LAST THROUGH THE WEEKEND...ALONG WITH ABOVE AVERAGE RAINFALL.
RAINFALL WILL TAPER OFF A BIT EARLY NEXT WEEK...BUT WILL STILL
LIKELY REMAIN HIGHER THAN NORMAL...ESPECIALLY FOR WINDWARD AREAS.

&&

.DISCUSSION...
HEAVY SHOWERS AND THUNDERSTORMS CONTINUE TO PINWHEEL AROUND THE MAIN
HAWAIIAN ISLANDS...AFFECTING LOCAL WATERS FOR THE MOST PART BUT ALSO
MOVING ACROSS THE ISLANDS FROM TIME TO TIME. A WEAKENING UPPER LOW
ABOUT 300 MILES WEST OF KAUAI HAS KEPT OUR AIRMASS UNSTABLE...WHILE
EAST SOUTHEASTERLY WINDS CONTINUE TO BRING ABUNDANT MOISTURE ACROSS
THE STATE. THE FOCUS OF HEAVY SHOWERS AND THUNDERSTORMS IS NEAR
KAUAI AND OAHU THIS MORNING...WITH THE HEAVIEST ACTIVITY ACROSS THE
KOOLAU RANGE OF OAHU. MODERATE TO OCCASIONALLY HEAVY SHOWERS ALSO
FORM ACROSS THE MAUKA SECTIONS OF KAUAI FROM TIME TO TIME. LIGHTER
SHOWERS PERSIST ACROSS WINDWARD AND SOUTHEAST SECTIONS OF THE BIG
ISLAND. SATELLITE LOOP SHOWS THE SURFACE LOW...NOW NEAR 20N170W OR
ABOUT 700 MILES WEST SOUTHWEST OF KAUAI...CONTINUES MOVING WEST. THE
SURFACE LOW HAS LONG SINCE DECOUPLED FROM THE UPPER LOW...WHICH HAS
NOT MOVED MUCH OVER THE PAST 24 HOURS. THIS MOVEMENT OF THE SURFACE
LOW AWAY FROM THE ISLANDS HAS ALLOWED LOW LEVEL WINDS ACROSS LOCAL
WATERS TO BACK TO ALMOST A TRADE WIND DIRECTION. THE PRESSURE
GRADIENT BETWEEN THE SURFACE LOW AND SURFACE HIGH PRESSURE FAR NORTH
OF THE ISLANDS REMAINS STEEP ENOUGH TO SUPPORT STRONG AND GUSTY
WINDS THIS MORNING...AT OR ABOVE SMALL CRAFT ADVISORY CRITERIA FOR
THE TRADITIONALLY WINDY WATERS AND CHANNELS.

SINCE HEAVY SHOWERS AND THUNDERSTORMS REMAIN CLOSE BY...WE ASSESS
THE FLOOD THREAT TO BE HIGH ENOUGH TO CONTINUE THE FLASH FLOOD WATCH
THROUGH THIS AFTERNOON. HOWEVER...SATELLITE LOOP SHOWS THAT LAYERED
CLOUDS HAVE MOVED NORTHEAST OF THE BIG ISLAND...LIKELY REMOVING THE
MOISTURE NEEDED FOR SNOW ON THE BIG ISLAND SUMMITS. THE WINTER
WEATHER ADVISORY FOR THE BIG ISLAND SUMMITS IS THEREFORE CANCELLED.

THE UPPER LOW WILL DRIFT SLOWLY WEST OVER THE WEEKEND AS IT FILLS.
BOUNDARY LAYER MOISTURE SHOULD REMAIN ABUNDANT THROUGH TODAY AS
WELL. AS TRADES GRADUALLY SWING TO A MORE TYPICAL NORTHEASTERLY
DIRECTION...SHOWERS WILL BECOME MORE TERRAIN FOCUSED AS TOPOGRAPHY
TAKES OVER THE MAIN FORCING MECHANISM. TRADES WILL STAY BREEZY AND
INCREASE INTO NEXT WEEK WITH POPS REMAINING HIGHER THAN NORMAL
THROUGH THE FORECAST PERIOD ALONG WINDWARD ZONES.

&&

.MARINE...
LARGE EAST NORTHEAST SWELL PERSISTS THIS MORNING...WITH THE MOKAPU
POINT BUOY SHOWING ABOUT 14 FT 12 SEC AS OF 115 AM HST. BOTH THE
HIGH SURF WARNING AND ADVISORY HAVE BEEN EXTENDED THROUGH 6 PM HST
THIS AFTERNOON. CONTINUED BREEZY TRADES WILL LIKELY KEEP EAST FACING
SHORES AT OR JUST ABOVE ADVISORY LEVEL THROUGH THE WEEKEND...PERHAPS
LONGER. ONCE THE SURF DROPS BELOW 15 FEET ALONG WINDWARD KAUAI AND
OAHU...WARNINGS WILL BE DOWNGRADED TO ADVISORIES.

THE SMALL CRAFT ADVISORY COVERS ALL WATERS AND CHANNELS FOR A
COMBINATION OF STRONG WINDS AND HIGH COMBINED SEAS. TRADE WINDS AND
LOCALLY GENERATED SEAS MAY STAY AT OR NEAR ADVISORY CRITERIA INTO
NEXT WEEK.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH THIS AFTERNOON FOR ALL HAWAIIAN ISLANDS.

HIGH SURF WARNING UNTIL 6 PM HST TODAY FOR KAUAI WINDWARD-OAHU
KOOLAU-OLOMANA.

HIGH SURF ADVISORY UNTIL 6 PM HST TODAY FOR MOLOKAI-MAUI
WINDWARD WEST-MAUI CENTRAL VALLEY-WINDWARD HALEAKALA-BIG ISLAND
NORTH AND EAST.

SMALL CRAFT ADVISORY UNTIL 6 PM HST SUNDAY FOR ALL HAWAIIAN
WATERS.

&&

POWELL