Flash Flood Watch 1, NWS Honolulu, HI

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HONOLULU HI
1248 PM HST MON JAN 10 2011

.UPDATE...
WINDS OVER THE BIG ISLAND SUMMITS HAVE INCREASED TO ADVISORY
LEVELS...HENCE A WIND ADVISORY HAS BEEN ISSUED THROUGH THE EVENING.

&&

.SYNOPSIS...
A COLD FRONT WILL SWEEP DOWN THE ISLAND CHAIN TODAY AND TONIGHT...
BRINGING SHOWERS TO THE SMALLER ISLANDS DURING THE DAY AND TO THE
BIG ISLAND TONIGHT. ONE MORE BRIEF ROUND OF COOL AND DRY WEATHER
WILL FOLLOW BEHIND THE FRONT ON TUESDAY. A STRONGER FRONT WILL
PRODUCE WET AND WINDY WEATHER OVER MUCH OF THE STATE DURING THE
SECOND HALF OF THE WORK WEEK. POTENTIALLY HEAVY RAINFALL WILL
DEVELOP ON WEDNESDAY AND CONTINUE THROUGH THURSDAY.

&&

.PREV DISCUSSION.../ISSUED 959 AM HST MON JAN 10 2011/

A COLD FRONT APPROACHING KAUAI WILL BRING CLOUDY SKIES TO THE
STATE TODAY AND MODERATE SHOWERS AS THE FRONT MOVES QUICKLY DOWN
THE THE ISLAND CHAIN. FRONTAL RAINS WILL REACH KAUAI BY
MID-MORNING...OAHU IN THE LATE AFTERNOON...AND MAUI COUNTY AND THE
BIG ISLAND THIS EVENING AND TONIGHT. GUSTY SOUTHWEST WINDS WILL
INCREASE AHEAD OF THE FRONT TODAY...WITH THE STRONGEST WINDS
AFFECTING HIGHER TERRAIN AND WINDWARD AREAS PRONE TO DOWN-SLOPE
ACCELERATING WINDS. THOUGH GUSTY...WIDESPREAD DAMAGING WINDS ARE
NOT EXPECTED. THE FRONT WILL BE WEAKENING AND MOVING QUITE
FAST... KEEPING THE THREAT OF FLOODING VERY LOW.

WINDS ACROSS THE SUMMITS OF HALEAKALA AND THE BIG ISLAND WILL
INCREASE WITH THE APPROACH OF THE FRONT AND A WIND ADVISORY FOR
HALEAKALA GOES INTO AFFECT THIS EVENING. THE BIG ISLAND SUMMIT
WINDS LOOK TO BE JUST UNDER ADVISORY LEVELS AS THE FRONT PUSHES
THROUGH. LAYERED CLOUDS BRING THE CHANCE FOR SNOW SHOWERS OVER THE
BIG ISLAND SUMMITS TONIGHT...BUT ACCUMULATIONS LOOK TO BE LOW...SO
NO WINTER WEATHER ADVISORY HAS BEEN ISSUED.

FOR LATE MONDAY NIGHT AND TUESDAY...NORTH WINDS BEHIND THE FRONT
BRING COOL AND DRY AIR OVER THE SMALLER ISLANDS AGAIN WHILE THE
BIG ISLAND HANGS ON TO SOME LINGERING MOISTURE LEFT BEHIND BY THE
AFOREMENTIONED COLD FRONT. COOL TEMPS ARE EXPECTED OVER THE
SMALLER ISLANDS EARLY TUESDAY MORNING...WITH MOSTLY CLEAR SKIES
PREVAILING THROUGH TUESDAY.

A STRONGER COLD FRONT LOOMS ON THE HORIZON FOR WEDNESDAY AND
THURSDAY. THE FRONT IS EXPECTED TO BRING STRONG AND GUSTY
SOUTHWEST WINDS AND HEAVY RAINFALL WITH THE LARGEST IMPACTS OVER
THE SMALLER ISLANDS. THE ATMOSPHERE BECOMES INCREASINGLY UNSTABLE
WEDNESDAY NIGHT AS THE FRONT APPROACHES...BRINGING THE POSSIBILITY
THUNDERSTORMS ALONG WITH THE HEAVY RAINFALL. ALSO...THE 12Z RUN OF
THE GFS DEPICTS 5 THOUSAND FOOT WINDS OF 35 TO 45 MPH OVER KAUAI AND
OAHU WEDNESDAY AFTERNOON AND NIGHT WHICH WOULD BRING
HAZARDOUS...DOWNSLOPING SOUTHWESTERLY WIND GUSTS OVER WINDWARD
AREAS AND LOCALES NORTH OF TERRAIN. THE HEAVY RAINFALL THREAT
WILL CONTINUE INTO THURSDAY AS THE FRONT STALLS OVER THE SMALLER
ISLANDS...BUT WINDS WILL DIMINISH. A HYDROLOGIC OUTLOOK...
ESFHFO...HAS BEEN ISSUED HIGHLIGHTING THE POTENTIAL FOR FLASH
FLOODING AS THE FRONT EFFECTS THE ISLANDS WEDNESDAY AND THURSDAY.

THE STALLED FRONT WILL WEAKEN THURSDAY NIGHT AS THE SUPPORTING UPPER
TROUGH LIFTS OUT TO THE NORTHEAST AND WEAK UPPER RIDGING REBUILDS.
REMNANT FRONTAL MOISTURE MAY LINGER THROUGH FRIDAY...KEEPING SHOWER
CHANCES A BIT HIGH AS SOUTHERLY WINDS PERSIST. FORECAST CONFIDENCE
DROPS CONSIDERABLY AS DOES MODEL AGREEMENT HEADING INTO THE WEEKEND.
THE ECMWF BUILDS TRADE WINDS OVER THE ISLANDS ON SATURDAY THEN
WEAKENS WINDS AS ANOTHER FRONT APPROACHES. THE GFS TRIES TO PUSH IN
ANOTHER WEAK FRONT CLOSE TO KAUAI BY SUNDAY...KEEPING THE ISLANDS
UNDER SOUTHERLIES. HAVE OPTED TO GO WITH THE GFS...WHICH HAS
PERFORMED BETTER IN RECENT WEEKS.

&&

.AVIATION...
CURRENT COLD FRONT TO BRING MVFR AND ISOL IFR CONDITIONS AS IT
CROSSES THE FA TODAY AND INTO TUE. AIRMETS HAVE BEEN POSTED FOR MT
OBSC/TURB/ICING. PLEASE SEE THE AVN PRODUCTS FOR MORE DETAILS.

&&

.MARINE...
THE SMALL CRAFT FLAG WILL BE UP FOR AT LEAST PORTIONS OF HAWAIIAN
WATERS INTO THURSDAY. SMALL CRAFT ADVISORIES CURRENTLY COVER ALL
WATERS AROUND THE WESTERN END OF THE STATE NORTH AND WEST OF MAUI.
COMBINED SEAS ARE EXPECTED TO BE NEAR THE 10 FOOT THRESHOLD
TODAY...WHILE WINDS WILL PEAK AROUND 25 KT AHEAD OF THE FRONT.

A LARGE NORTHWEST SWELL WILL BUILD TONIGHT...PRODUCING HAZARDOUS
SEAS. THIS SWELL WILL BE CONFUSED...MEANING IT WILL HAVE BOTH LONG
AND SHORT PERIOD ENERGY. IT WILL GENERATE SURF ABOVE ADVISORY
LEVELS BEGINNING LATER TONIGHT...AND A HIGH SURF ADVISORY HAS BEEN
POSTED. ANOTHER PULSE OF LONG PERIOD WEST NORTHWEST SWELL IS DUE
TUESDAY NIGHT...POSSIBLY PUSHING SURF TO WARNING LEVELS. SURF WILL
REMAIN ELEVATED THROUGH WEDNESDAY...WITH ADDITIONAL BOUTS OF HIGH
SURF POSSIBLE THROUGH THE WEEKEND.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM HST WEDNESDAY
FOR NIIHAU-KAUAI WINDWARD-KAUAI LEEWARD-WAIANAE COAST-OAHU NORTH
SHORE-OAHU KOOLAU-MOLOKAI-MAUI WINDWARD WEST-MAUI CENTRAL VALLEY-
WINDWARD HALEAKALA.

WIND ADVISORY UNTIL MIDNIGHT HST TONIGHT FOR HALEAKALA SUMMIT-
BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST TUESDAY 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-MAALAEA BAY-
PAILOLO CHANNEL.

&&

MORRISON