Flash Flood Warning 26, NWS Honolulu, HI

565 
WGHW70 PHFO 130633
FFSHFO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
833 PM HST FRI DEC 12 2008

HIC003-130730-
/O.CON.PHFO.FF.W.0026.000000T0000Z-081213T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
OAHU IN HONOLULU COUNTY-
833 PM HST FRI DEC 12 2008

...A FLASH FLOOD WARNING REMAINS IN EFFECT FOR THE ISLAND OF OAHU IN
HONOLULU COUNTY UNTIL 930 PM HST...

THE AREA OF HEAVY RAINFALL CONTINUES TO MOVE NORTHWARD ACROSS THE 
NORTHERN PORTION OF OAHU. ALTHOUGH RAINFALL INTENSITIES WILL 
GENERALLY DECREASE OVER THE NEXT HOUR...RUNOFF WILL REMAIN HIGH IN 
AREAS PREVIOUSLY AFFECTED BY HEAVY RAIN. 

THE FLASH FLOOD WARNING INCLUDES ALL LOCATIONS ON OAHU.

A FLASH FLOOD WARNING MEANS FLASH FLOODING IS IMMINENT OR OCCURRING
IN STREAMS...ROADS AND LOW LYING AREAS. MOVE TO HIGHER GROUND NOW.

DO NOT CROSS FAST FLOWING OR RISING WATER IN YOUR VEHICLE OR ON FOOT.
TURN AROUND...DON/T DROWN.

THIS WARNING MAY NEED TO BE EXTENDED BEYOND 930 PM HST IF FLASH
FLOODING PERSISTS.

LAT...LON 2159 15831 2176 15796 2130 15763 2127 15813

$$

819 
WGHW70 PHFO 130715
FFSHFO

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE HONOLULU HI
915 PM HST FRI DEC 12 2008

HIC003-130725-
/O.CAN.PHFO.FF.W.0026.000000T0000Z-081213T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
OAHU IN HONOLULU COUNTY-
915 PM HST FRI DEC 12 2008

...THE FLASH FLOOD WARNING IS CANCELLED FOR THE ISLAND OF OAHU IN
HONOLULU COUNTY...

...A FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH SATURDAY AFTERNOON 
FOR OAHU...

RAINFALL HAS DIMINISHED ON THE ISLAND OF OAHU AT THIS TIME AND 
RUNOFF IS SUBSIDING.  

LAT...LON 2159 15831 2176 15796 2130 15763 2127 15813

$$

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST FRI DEC 12 2008

.SYNOPSIS...
A SLOW MOVING UPPER LEVEL TROUGH WEST OF KAUAI WILL MAINTAIN A MOIST
AND UNSTABLE AIR MASS ACROSS THE STATE THROUGH THE WEEKEND AND INTO
THE FIRST HALF OF NEXT WEEK. HEAVY RAINFALL IS POSSIBLE THIS
WEEKEND...MAINLY ACROSS KAUAI AND OAHU.

&&

.DISCUSSION...
WATER VAPOR IMAGERY SHOWS THE DEPARTING UPPER LOW ABOUT 1400 MILES
NORTH NORTHWEST OF HONOLULU. AN UPPER TROUGH EXTENDS SOUTH FROM THIS
LOW TO NEAR 15N170W. A SERIES OF SHORTWAVE IMPULSES CAN BE SEEN
ROTATING AROUND THE TROUGH. ONE SHORTWAVE JUST SOUTHWEST OF KAUAI
IS HELPING TO ENHANCE CONVECTION WEST OF OAHU. THIS CONVECTION IS
DEVELOPING ALONG AN INVERTED SURFACE TROUGH THAT CAN BE SEEN IN THE
MORNING QUIKSCAT PASS EXTENDING SOUTHWEST FROM THE STATE.

REGIONAL RADARS SHOW A WIDESPREAD AREA OF CONVECTION COVERING KAUAI
AND ADJACENT COASTAL WATERS. REPORTS FROM KAUAI HAVE INDICATED THAT
A STEADY MODERATE RAIN IS FALLING...ALTHOUGH THERE HAVE ALSO BEEN
REPORTS OF EMBEDDED THUNDERSTORMS AS WELL. AN AREA OF STRONGER
CONVECTIVE CELLS IS LOCATED JUST SOUTH OF THE ISLAND. THIS AREA HAS
MADE A VERY SLOW BUT STEADY PROGRESS NORTHWARD THROUGH THE
AFTERNOON.

THE 12/18Z GFS AND 12Z ECMWF BOTH HAVE VERY CONVECTIVELY DOMINATED
SOLUTIONS...WITH TRANSIENT MID-LEVEL VORTICITY CENTERS AND WEAK LOWS
AND HIGHS CAUSED BY LARGE AREAS OF CONVECTION THAT THEY DEVELOP.
HOWEVER...IS INTERESTING TO NOTE IS THAT MOST OF THE 12Z GUIDANCE...
INCLUDING THE NOGAPS...UKMET...AND NAM...SHOW A SIMILAR OVERALL
PATTERN. THEY FEATURE A SURFACE LOW DEVELOPING ALONG THE TROUGH...
WHICH TRACKS NORTHWARD JUST WEST OF THE STATE. DIFFERENCES EXIST
WITH TIMING/PLACEMENT/INTENSITY...BUT THE CONSENSUS SUPPORTS THE
IDEA OF ADDITIONAL CONVECTIVE DEVELOPMENT ALONG AND AHEAD OF THE
TROUGH. IT IS DIFFICULT TO PIN DOWN DETAILS...BECAUSE THE DETAILS
RELY ON LARGE-SCALE CONVECTION THAT RESULT FROM SUBTLE UPPER LEVEL
FEATURES...BOTH OF WHICH ARE DIFFICULT TO MODEL.

CURRENTLY IT LOOKS LIKE THE WESTERN HALF OF THE STATE WOULD BE MOST
IMPACTED...MAINLY KAUAI AND NIIHAU. HOWEVER THE CURRENT ACTIVITY HAS
MADE A STEADY PROGRESS EASTWARD ACROSS THE KAUAI CHANNEL. ALSO...
WITH THE MOIST AIRMASS IT WILL NOT BE DIFFICULT FOR ADDITIONAL
CONVECTION TO DEVELOP OUT AHEAD OF THE TROUGH /AS HAS STARTED
HAPPENING NEAR OAHU OVER THE PAST HOUR/. THEREFORE...HAVE EXTENDED
THE FLASH FLOOD WATCH FOR KAUAI...NIIHAU...AND OAHU THROUGH
SATURDAY AFTERNOON. ELSEWHERE ACROSS MAUI COUNTY AND THE BIG
ISLAND...THE THREAT FOR FLOODING RAIN HAS DIMINISHED AND THE FLASH
FLOOD WATCH HAS BEEN CANCELLED.

THROUGH THE REMAINDER OF THE FORECAST...THERE IS GENERAL AGREEMENT
FEATURING A PERSISTENT LONGWAVE TROUGH WEST OF THE STATE...WHICH
WILL MAINTAIN A MOIST SOUTH TO SOUTHEASTERLY FLOW ACROSS THE
ISLANDS. A STRONGER IMPULSE IS EXPECTED TO SWING AROUND THE TROUGH
LATER IN THE WEEKEND...AND MAY PROPEL THE SURFACE TROUGH FARTHER
EAST ACROSS THE STATE SATURDAY NIGHT/SUNDAY. DEPENDING ON THE TRACK
OF THIS FEATURE...IT MAY PULL THE HEAVIEST RAIN NORTHEAST FROM KAUAI
AND MISS THE REMAINING ISLANDS...OR IT MAY BRING ANOTHER AROUND OF
HEAVY RAIN TO OAHU AND POSSIBLE MAUI COUNTY. THE STRONGER SOLUTIONS
THAT TAKE THE TROUGH FARTHER NORTH OF THE STATE...SUCH AS THE
GFS...DO SO BECAUSE THEY DEVELOP STRONGER SURFACE LOWS ALONG IT.
THIS MAY BE AN ARTIFACT OF FEEDBACK FROM THE CONVECTION THAT
DEVELOPS ALONG THE TROUGH. WILL CONTINUE TO LEAN THE FORECAST IN THE
DIRECTION OF THE 12Z NOGAPS...WHICH TAKES THE TROUGH SLOWLY EASTWARD
BEFORE WEAKENING IT LATE SUNDAY/SUNDAY NIGHT. ANOTHER PIECE OF
ENERGY REAMPLIFIES THE LONGWAVE UPPER TROUGH WEST OF THE STATE EARLY
NEXT WEEK...STARTING THE PATTERN ALL OVER AGAIN.

&&

.MARINE...
THE HIGH SURF ADVISORY FOR NORTH AND WEST FACING SHORES OF KAUAI AND
NIIHAU AND NORTH FACING SHORES OF OAHU HAS BEEN EXTENDED THROUGH
TONIGHT. THE SWELL AT BUOY 51001 HAS MAINTAINED AT ADVISORY LEVELS
THROUGH THE AFTERNOON...AND HAS ONLY SHOWN SIGNS OF DROPPING AS OF
01Z. 18Z WAVEWATCH III GUIDANCE SHOWS A SIMILAR TREND...WITH THE
SWELL STEADY THROUGH MUCH OF THE NIGHT BEFORE BEGINNING TO SLOWLY
SUBSIDE. HAVE ALSO EXTENDED THE SMALL CRAFT ADVISORY THROUGH TONIGHT
AS WELL. THE COMBINATION OF THE NORTHWEST SWELL AND WIND WAVES NEAR
THE ISLANDS WILL CREATE COMBINED SEAS OF 10 FEET.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR NIIHAU-KAUAI-
OAHU.

HIGH SURF ADVISORY UNTIL 6 AM HST SATURDAY FOR NIIHAU-KAUAI
WINDWARD-KAUAI LEEWARD-OAHU NORTH SHORE-OAHU KOOLAU.

SMALL CRAFT ADVISORY UNTIL 6 AM HST SATURDAY FOR KAUAI NORTHWEST
WATERS-KAUAI WINDWARD WATERS-KAUAI LEEWARD WATERS-KAUAI CHANNEL-
OAHU WINDWARD WATERS.

&&

BRAVENDER