Flash Flood in Hawaii, August 7, 2006

Name: Flash Flood in Hawaii, August 7, 2006
Start: 2006-08-07T05:00
End: 2006-08-07T08:21
Location: Hawaii

August 7, 2006 · NWS HFO · 1 event in 1 county or zone

Heavy showers over northern sections of Kauai produced flash flooding conditions near Hanalei. The rain caused flooding along Kuhio Highway, forcing officials to close the Hanalei Bridge.

Where it happened

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS HFO wrote it up.

Heavy showers over northern sections of Kauai produced flash flooding conditions near Hanalei. The rain caused flooding along Kuhio Highway, forcing officials to close the Hanalei Bridge. Omao Road was also closed for a time. Because of the problems with the roadways, the Hanalei School was closed all day on the 7th. However, there were no reports of serious property damage or injuries.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Honolulu, HI wrote its last area forecast discussion before the first event at Aug 7, 4:15 AM HST, 45 minutes earlier.

Area forecast discussion, Aug 7, 4:15 AM HST, 45 minutes before

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

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Kauai

When: August 7, 5:00 AM HST to 8:21 AM HST
Where: Kauai County, Hanalei
Reported by: LAW ENFORCEMENT
Coordinates: 22.011, -159.705 (the zone’s center; the record gives no point)

What these are

Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Hawaii in 2006 Every state in 2006 This day in weather history Warnings in Hawaii, August 2006

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5528998.