Flash Flood Warning 126, NWS Honolulu, HI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
415 AM HST MON AUG 7 2006

.SYNOPSIS...
SHOWERY TRADE WIND WEATHER WILL CONTINUE FOR THE NEXT COUPLE OF
DAYS...WITH THE HEAVIEST RAIN OVER KAUAI TODAY. ALTHOUGH TRADE WINDS
WILL EASE A LITTLE TODAY...THEY WILL REMAIN BREEZY THROUGH THE WEEK.

&&

.UPDATE...
HAVE ISSUED A FLOOD WATCH FOR KAUAI THROUGH NOON TODAY...AS RAIN
CONTINUES TO FALL...AND MOVE IN FROM THE EAST. GAGES ON THE HANALEI
AND WAILUA RIVERS INDICATE ELEVATED WATER LEVELS...AND ADDITIONAL
RAINFALL WILL LIKELY LEAD TO THE CLOSURE OF THE ROADWAY IN HANALEI
DUE TO FLOODING. THINKING THAT THE THREAT WILL MINIMIZE AS THE DAY
WEARS ON...HENCE THE RELATIVELY SHORT VALID TIME FOR THE WATCH.

&&

.DISCUSSION...
A 1029 MB HIGH LOCATED FAR NORTH OF THE ISLANDS CONTINUES TO SUPPLY
THE ISLANDS WITH BREEZY TRADE WINDS...AND AMPLE LOW LEVEL MOISTURE.
THIS INCOMING MOISTURE IS BEING ENHANCED NEAR THE ISLANDS...MOST
ESPECIALLY NEAR KAUAI...DUE TO THE PRESENCE OF AN UPPER LEVEL TROUGH
LOCATED JUST TO OUR NORTH. SATELLITE SHOWS BROKEN SHOWERY LOW CLOUDS
EXTENDING WELL TO THE EAST...WITH RADAR DETECTING LOTS OF SMALL
SHOWERS STREAMING WESTWARD WITHIN THE TRADE FLOW. THE INTERACTION
OF THIS LOW LEVEL MOISTURE...THE UPPER TROUGH...AND THE TERRAIN OF
KAUAI HAS LED TO QUITE A SOAKING ON KAUAI OVERNIGHT...WITH MORE THAN
10 INCHES OF RAIN ON MOUNT WAIALEALE OVER THE PAST 24 HOURS...AND
1.32 IN LIHUE IN THE THREE HOUR PERIOD ENDING 2 AM. MOST OTHER
WINDWARD AREAS HAVE RECEIVED A STEADY DIET OF SHOWERS
OVERNIGHT...BUT RAINFALL TOTALS ARE NOTHING LIKE THOSE SEEN ON
KAUAI.

WATER VAPOR IMAGERY SHOWS THE SHOWER-ENHANCING UPPER TROUGH LIFTING
NORTHWARD...AND THE UPPER FLOW BECOMING ZONAL OVER THE ISLAND CHAIN.
HOWEVER...A DIFFICULT TO ANALYZE WEAK MID LEVEL TROUGH IS SHOWN JUST
NORTH OF THE ISLANDS IN MODEL INITIAL STATES...AND THIS FEATURE IS
FORECAST TO LINGER THROUGH A GOOD PORTION OF THE UPCOMING WEEK.
GUIDANCE INDICATES THE MIXED LAYER WILL BE 8 TO 10 THOUSAND FEET
DEEP THROUGH THE WEEK...THEREBY MAINTAINING A STEADY SUPPLY OF TRADE
SHOWERS...MAINLY WINDWARD THOUGH...AS TRADE SPEEDS WILL BE EASING.
THIS INSTABILITY WILL BRING THE THREAT OF HEAVY RAIN OVER THE KONA
SLOPES THIS AFTERNOON...AS DAYTIME HEATING TRIGGERS SEA BREEZE
CONVERGENCE.

THE SURFACE HIGH FAR NORTH WILL WEAKEN SOMEWHAT AND MOVE WEST OVER
THE NEXT 24 HOURS...AS A FRONT DIGS SOUTHWARD FROM 40N TO 30N
BETWEEN 150W AND 160W. ALTHOUGH THE TRADES WILL CONTINUE TO
BLOW...THEIR SPEEDS WILL DECREASE A NOTCH DUE TO THE POSITION OF THE
HIGH. AS THE FRONT WEAKENS TUESDAY AND WEDNESDAY...THE HIGH WILL
BUILD EAST AGAIN...AND TAKE UP RESIDENCE IN ITS CLIMATOLOGICAL
POSITION IN THE NORTHEAST PACIFIC...THEREBY MAINTAINING TRADES AT
MODERATE TO FRESH SPEEDS.

IN SUMMARY...A WET TRADE WIND PATTERN THROUGH THE WEEK...BUT EASING
TRADES WILL PUSH LESS SHOWERS LEEWARD. HEAVY SHOWERS ON KAUAI AT
LEAST THIS MORNING...AND POSSIBLY ON THE KONA SLOPES THIS AFTERNOON.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY EAST FACING SHORES THRU 4 PM TODAY.
SMALL CRAFT ADVISORY THRU 6 PM TODAY FOR WATERS SOUTH OF THE BIG
ISLAND...ALENUIHAHA CHANNEL...MAALAEA BAY AND PAILOLO CHANNEL.
FLOOD WATCH THROUGH NOON TODAY FOR KAUAI.

&&

BIRCHARD