Flash Flood Warning 24, NWS Honolulu, HI

843 
WGHW70 PHFO 120026
FFSHFO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
226 PM HST THU DEC 11 2008

HIC009-120035-
/O.CAN.PHFO.FF.W.0024.000000T0000Z-081212T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
MOLOKAI IN MAUI COUNTY-
226 PM HST THU DEC 11 2008

...THE FLASH FLOOD WARNING IS CANCELLED FOR THE ISLAND OF MOLOKAI IN
MAUI COUNTY...

...A FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH LATE TONIGHT FOR 
MAUI COUNTY...

THE HEAVY RAINS HAVE DIMINISHED AND MOVED OFFSHORE TO THE 
EAST...THUS THE FLASH FLOOD WARNING IS CANCELLED.

LAT...LON 2124 15711 2121 15666 2102 15679 2107 15715

$$
KODAMA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
1000 AM HST THU DEC 11 2008

.SYNOPSIS...
A STRONG KONA LOW NORTHWEST OF THE STATE WILL BEGIN TO MOVE TO THE
NORTH TODAY. STRONG SOUTHERLY WINDS WILL GRADUALLY DECREASE THIS
AFTERNOON AND EVENING. THE THREAT FOR HEAVY RAIN TODAY EXTENDS FROM
KAUAI TO MAUI...AND WILL REMAIN THROUGH LATE TONIGHT. A VERY MOIST
AIRMASS WILL PERSIST OVER THE ISLANDS INTO NEXT WEEK...LEADING TO
WET AND UNSETTLED WEATHER.

&&

.DISCUSSION...
THE KONA LOW AFFECTING WEATHER ACROSS THE ISLANDS IS LOCATED ABOUT
850 MILES NORTH NORTHWEST OF HONOLULU...AND IS CURRENTLY NEARLY
STATIONARY. THIS SYSTEM IS EXPECTED BEGIN MOVING TO THE NORTH
NORTHWEST THIS AFTERNOON. THERE IS ABUNDANT MOISTURE FEEDING INTO
THE SYSTEM FROM THE SOUTH. THE POES AMSU TOTAL PRECIPITABLE WATER
SENSOR INDICATES PW FROM 1.7 TO 2.1 INCHES ACROSS THE STATE. THIS
HAS HELPED TO CONTRIBUTE TO EXCESSIVE RAINFALL...WITH RAINFALL RATES
OF 3 TO 4 INCHES PER HOUR REPORTED EARLIER THIS MORNING. REGIONAL
RADARS SHOW A WIDESPREAD BAND OF SHOWERS CURRENTLY FROM OAHU TO
MAUI. INDIVIDUAL CELLS ARE MOVING TO THE NORTHEAST AT 30 MPH...BUT
THE OVERALL AREA OF SHOWERS IS MOVING EASTERLY VERY SLOWLY.

THE LAST FEW RUNS OF THE GFS HAVE SUFFERED PROBLEMS WITH GRIDSCALE
CONVECTIVE FEEDBACK. THE CURRENT 12Z RUN DEVELOPS A BULLSEYE OF QPF
FROM 4 TO 7 INCHES IN DIFFERENT 6 HOUR PERIODS TODAY AND TONIGHT. A
LOOK AT THE QPF ROUTINES SHOW MOST OF THIS WAS GENERATED AS STABLE
RAINFALL...NOT FROM THE CONVECTIVE ROUTINE...A SIGN THAT THE MODEL
IS DEVELOPING CONVECTION AT TOO LARGE OF A SCALE. THIS PROBLEM FEEDS
BACK ON ITSELF...AND RESULTS IN THE MODEL DEVELOPING SPURIOUS
FEATURES SUCH AS STRONG UPPER-LEVEL DIFLUENCE AND LOW- AND MID-LEVEL
HEIGHT FALLS. BASED ON THESE PROBLEMS...FEEL THAT THE GFS IS TOO
BULLISH BRINGING HEAVY RAIN TO THE BIG ISLAND THIS
AFTERNOON/EVENING. THEREFORE WILL LEAVE THE BIG ISLAND OUT OF THE
FLASH FLOOD WATCH. RAINFALL IS EXPECTED /SHOWERS CAN BE SEEN ON
RADAR SOUTH OF THE ISLAND ALREADY/ BUT AT THIS TIME IT APPEARS THE
HEAVIEST RAIN WILL BE CONFINED TO THE WEST OF THE BIG ISLAND.

HEAVY RAIN HAS MOVED EAST OF KAUAI...AND WHILE CLOUDS ARE WIDESPREAD
THEY ARE MUCH MORE STABLE THAN FARTHER EAST ACROSS THE STATE. HAVE
CUT BACK ON POPS ACROSS KAUAI AND NIIHAU AND PULLED THE MENTION OF
HEAVY RAIN. HOWEVER...GIVEN THE AMOUNT OF RAIN THEY RECEIVED LAST
NIGHT TO SATURATE THE GROUND AND LINGERING INSTABILITY ALOFT AND
ABUNDANT MOISTURE...THERE IS ENOUGH OF A CONCERN TO KEEP THEM IN THE
FLASH FLOOD WATCH. OTHERWISE WILL CONTINUE TO THE WATCH AS IS FOR
OAHU AND MAUI COUNTY...WHERE HEAVY RAIN IS CURRENTLY OCCURRING.

IN ADDITION TO THE HEAVY RAIN...STRONG SOUTHERLY WINDS ASSOCIATED
WITH THE CONVERGENCE BAND CONTINUE TO AFFECT THE CENTRAL ISLANDS.
HAVE UPDATED THE WIND ADVISORY TO DROP KAUAI AND EXPAND IT TO
INCLUDE MAUI COUNTY. THE STRONGEST AND MOST DAMAGING WINDS WILL
OCCUR ACROSS DOWNSLOPE AREAS ON THE NORTH SIDES OF THE ISLANDS.
WINDS WILL EASE BY THIS EVENING AS THE PARENT LOW BEGINS TO MOVE
NORTH NORTHWEST AWAY FROM THE STATE.

THE MODEL CONSENSUS HAS BEEN TO WEAKEN THE CONVERGENCE BAND ACROSS
OF THE STATE...AND EDGE IT BACK WESTWARD AS THE KONA LOW STARTS TO
MOVE TO THE NORTH NORTHWEST THIS AFTERNOON AND TONIGHT. THIS
BOUNDARY IS EXPECTED TO LINGER IN THE VICINITY OF THE STATE FOR A
PROLONGED PERIOD OF TIME. EVEN THOUGH THE MAIN LOW MOVES AWAY FROM
THE STATE...AN UPPER LEVEL TROUGH LINGERS TO THE WEST. SHORTWAVE
IMPULSES ROTATING AROUND THIS TROUGH WILL CAUSE THE BAND TO SHIFT
BACK AND FORTH ACROSS THE STATE. SPECIFICS ARE HARD TO PIN DOWN AT
THIS POINT...BUT IT LOOKS AS THOUGH WE ARE IN FOR A PERIOD OF
UNSETTLED WEATHER THROUGH THE MIDDLE OF NEXT WEEK.

&&

.MARINE...
THE STRONG SOUTHERLY WINDS HAVE LEAD TO LARGE AND ROUGH SURF ALONG
SOUTH FACING SHORES OF THE SMALLER ISLANDS FROM NIIHAU TO MAUI. SURF
WILL LOWER OVERNIGHT AS THE WINDS BEGIN TO DIMINISH. IN ADDITION...A
BUILDING NORTHWEST SWELL WILL BRING LARGE SURF TO NORTH AND WEST
FACING OF KAUAI AND NIIHAU TONIGHT AND FRIDAY. THIS NORTHWEST SWELL
WAS GENERATED BY THE KONA LOW FAR NORTH NORTHWEST OF THE STATE.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR NIIHAU-KAUAI-OAHU-
MOLOKAI-LANAI-KAHOOLAWE-MAUI.

HIGH SURF ADVISORY UNTIL 6 PM HST FRIDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD.

HIGH SURF ADVISORY UNTIL 6 PM HST THIS AFTERNOON FOR OAHU SOUTH
SHORE-MOLOKAI LEEWARD-LANAI MAKAI-KAHOOLAWE-MAUI LEEWARD WEST-
MAUI CENTRAL VALLEY-LEEWARD HALEAKALA.

WIND ADVISORY UNTIL 6 PM HST THIS AFTERNOON FOR OAHU NORTH SHORE-
OAHU KOOLAU-OLOMANA-CENTRAL OAHU-WAIANAE MOUNTAINS-MOLOKAI-LANAI-
KAHOOLAWE-MAUI-BIG ISLAND SUMMITS.

SMALL CRAFT ADVISORY UNTIL 6 PM HST THIS AFTERNOON 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-ALENUIHAHA CHANNEL-BIG ISLAND
WINDWARD WATERS-BIG ISLAND LEEWARD WATERS.

&&

MORRISON