Severe Thunderstorm Warning 2, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST THU DEC 9 2010

.SYNOPSIS...
SOUTH WINDS WILL INCREASE IN ADVANCE OF A COLD FRONT APPROACHING
FROM THE NORTHWEST. HEAVY SHOWERS AND THUNDERSTORMS NOW OVER AND
NEAR KAUAI AND OAHU WILL SPREAD OVER THE ENTIRE STATE TONIGHT AND
FRIDAY. LOCALLY HEAVY RAINFALL IS POSSIBLE...WHICH COULD RESULT IN
FLASH FLOODING.

&&

.DISCUSSION...
FORTUNATELY...THE HEAVY SHOWERS AND THUNDERSTORMS HAVE STAYED OVER
THE KAUAI CHANNEL WHERE NEXRAD ESTIMATED RAINFALL TOTALS WERE IN
EXCESS OF 21 INCHES AS OF 2 PM. COASTAL WATERS NORTHWEST OF KAUAI
ALSO HAD IMPRESSIVE RAINFALL TOTALS IN EXCESS OF 10 INCHES. THE
ISLANDS HAVE BEEN LUCKY SO FAR...BUT IT WOULD NOT TAKE MUCH TO HAVE
THE HEAVY CONVECTION SHIFT TO OVER LAND. HENCE THE FLASH FLOOD WATCH.

CONVERGENT LOW LEVEL FLOW OUT OF THE SOUTHEAST...SOUTH AND SOUTHWEST
WILL BRING MOIST AIR UP OVER THE ISLANDS THROUGH FRIDAY. THE SOUTH
FLOW IS IN ADVANCE OF A COLD FRONT LOCATED NORTHWEST OF KAUAI. THE
FRONT IS MOVING SLOWLY TO THE SOUTHEAST...AND IS EXPECTED TO REACH
KAUAI FRIDAY NIGHT. IT WILL THEN MOVE DOWN THE ISLAND CHAIN TO EAST
OF THE BIG ISLAND BY SATURDAY NIGHT. THE MOIST AIR WILL SHIFT TO THE
EAST IN ADVANCE OF THE FRONT.

INSTABILITY ASSOCIATED WITH AN UPPER LEVEL TROUGH NORTHWEST OF THE
STATE WILL SET OFF HEAVY SHOWERS AND THUNDERSTORMS IN THE MOIST AIR
AHEAD OF THE FRONT. THE TROUGH IS FORECAST TO MOVE TO THE SOUTHEAST
AND IS EXPECTED TO BE EAST OF THE ISLANDS SATURDAY NIGHT. THE FLASH
FLOOD WATCH PRESENTLY IN EFFECT FOR NIIHAU...KAUAI AND OAHU WILL
EXPAND TO COVER ALL ISLANDS TONIGHT.

WINDS ON THE SUMMITS OF THE BIG ISLAND AND MOUNT HALEAKALA MAY REACH
WIND ADVISORY CRITERIA THIS EVENING. ALSO...WINTER WEATHER
CONDITIONS ARE POSSIBLE OVER THE BIG ISLAND SUMMITS FRIDAY NIGHT
INTO SATURDAY MORNING. A WINTER STORM WATCH HAS BEEN ISSUED FOR THE
POTENTIALLY HEAVY SNOW.

WITH THE FRONT AND THE TROUGH ALOFT EAST OF THE BIG ISLAND SUNDAY...
A SURFACE HIGH PRESSURE WILL MOVE NORTH OF THE STATE AND TRADE WINDS
WILL RETURN. ALSO...A RIDGE ALOFT TRAILING THE TROUGH WILL MOVE OVER
THE ISLANDS FROM THE WEST RESULTING IN A MORE STABLE ATMOSPHERE.

&&

.MARINE...
THE CURRENT LARGE NORTH SWELL WILL GRADUALLY DIMINISH THROUGH THIS
WEEKEND. THE HIGH SURF ADVISORY FOR NORTH AND EAST FACING SHORES
WILL LIKELY BE CANCELED EARLY FRIDAY MORNING.

A MARINE WEATHER STATEMENT HAS BEEN ISSUED FOR HARBOR SURGE IN THE
KAHULUI AND HILO HARBORS DUE TO THE LARGE NORTH SWELL. THE STATEMENT
ALSO ALERTS MARINERS TO THE THREAT OF ADVERSE WEATHER CONDITIONS
ASSOCIATED WITH THE THUNDERSTORMS.

A SMALL CRAFT ADVISORY /SCA/ CONTINUES FOR ALL OF THE COASTAL
WATERS...EXCEPT MAALAEA BAY AND THE BIG ISLAND LEEWARD WATERS DUE TO
THE LARGE NORTH SWELL. SEAS WILL DECREASE BELOW SCA CRITERIA TONIGHT
FOR MOST COASTAL WATERS. HOWEVER...INCREASING SOUTH TO SOUTHWEST
WINDS...AS WELL AS LARGER SEAS DUE TO LOCALLY GENERATED WIND
WAVES...WILL REQUIRE THE SCA TO REMAIN IN EFFECT THROUGH FRIDAY
MORNING FOR THE COASTAL WATERS AROUND KAUAI AND OAHU.

&&

.AVIATION...
WDSPRD TSRA CONTINUE TO AFFECT THE AREA FROM THE KAUAI CHANNEL WWD
WITH PREVAILING MVFR/IFR CIGS AND VIS. LOCAL LIFR CONDITIONS ARE
LIKELY NEAR THE STRONGEST CONVECTION. TOPS ARE EXCEEDING FL500
PRODUCING SEV TURB AS WELL. HAVE FAIR CONFIDENCE IN THE 00Z TAF
CRITICAL PERIOD. HAVE TRIED TO REPRESENT TRENDS IN THE LONGER TERM
GROUPS IN THE TAFS...BUT STILL HAVE LOW CONFIDENCE DUE TO SHORT TERM
DIFFERENCES IN GUIDANCE. ANTICIPATING FURTHER AMDS TO THE TAFS/FA
THROUGH THE PERIOD. WILL DO OUR BEST TO KEEP THE FORECAST
REPRESENTATIVE. SIGMET UNIFORM CONTINUES TO OVERLAP THE AREA AND
WILL LIKELY STICK AROUND FOR QUITE SOMETIME. WDSPRD TSRA EXPECTED TO
PERSIST THRU FRI...TRACKING SLOWLY EWD. AIRMET SIERRA CONTINUES FOR
KAUAI...BUT HAVE BACKED UP THE ONSET FOR OAHU TIL AFT 04Z. WILL FINE
TUNE THIS AS WELL AND TRY TO PIN POINT AT LEAST A WINDOW OF
DEVELOPING CONDITIONS FOR TONNIGHT.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 600 AM HST SATURDAY FOR OAHU KAUAI AND
NIIHAU.

FLASH FLOOD WATCH FROM 600 PM HST TODAY UNTIL 600 AM HST SATURDAY
FOR MOLOKAI...MAUI...LANAI...KAHOOLAWE AND THE BIG ISLAND.

WINTER STORM WATCH IN EFFECT FROM 6 PM FRIDAY EVENING TO 12 PM
SATURDAY AFTERNOON FOR THE SUMMIT AREAS OF MAUNA LOA AND MAUNA KEA.

HIGH SURF ADVISORY UNTIL 600 AM HST FRIDAY MORNING FOR NORTH AND
EAST FACING SHORES OF NIIHAU...KAUAI...OAHU...MOLOKAI...MAUI AND THE
BIG ISLAND.

SMALL CRAFT ADVISORY UNTIL 600 PM HST TODAY FOR MAUI COUNTY WINDWARD
WATERS...MAUI COUNTY LEEWARD WATERS...PAILOLO CHANNEL...ALENUIHAHA
CHANNEL...BIG ISLAND WINDWARD WATERS AND BIG ISLAND SOUTHEAST WATERS.

SMALL CRAFT ADVISORY UNTIL 600 AM HST FRIDAY FOR THE COASTAL WATERS
AROUND NIIHAU...KAUAI AND OAHU.

&&

CRAIG/DEJESUS