Flash Flood in Hawaii, October 26 to 27, 2004

Name: Flash Flood in Hawaii, October 26 to 27, 2004
Start: 2004-10-26T19:45
End: 2004-10-27T02:52
Location: Hawaii

October 26 to 27, 2004 · NWS HFO · 1 event in 1 county or zone

A heavy rain event produced flash flooding over the windward slopes of the Koolau Mountains on Oahu. The areas hardest hit included the Kahuku High School campus and the Waikane and Waiahole areas.

Where it happened

Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

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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.

A heavy rain event produced flash flooding over the windward slopes of the Koolau Mountains on Oahu. The areas hardest hit included the Kahuku High School campus and the Waikane and Waiahole areas. Three vehicles became stranded while attempting to cross an overflowing Waikane Stream. All vehicles were successfully recovered with no serious injuries to the vehicles' occupants. Inundation of the Kahuku High School campus damaged portions of the school's athletic complex. No damage estimates were available.

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 Oct 26, 4:00 PM HST, 3 hours 45 minutes earlier.

Area forecast discussion, Oct 26, 4:00 PM HST, 3 hours 45 minutes before

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST TUE OCT 26 2004

.SYNOPSIS...
THE UPPER LOW THAT HAS BROUGHT THUNDERSTORMS TO THE ISLANDS OVER THE
LAST COUPLE OF DAYS IS WEAKENING. SHOWERS WILL REMAIN POSSIBLE OVER
THE STATE TONIGHT ALONG WITH ISOLATED THUNDERSTORMS. TRADE WINDS
ARE EXPECTED TO MOVE INTO THE AREA ON WEDNESDAY BRINGING SHOWERS TO
THE WINDWARD AND MAUKA AREAS ONCE AGAIN.
&&

.DISCUSSION...
THE UPPER LOW THAT BROUGHT THUNDERSTORMS AND HEAVY RAIN TO THE MAIN
HAWAIIAN ISLANDS THE LAST COUPLE OF DAYS CONTINUES TO WEAKEN THIS
AFTERNOON. THE CENTER HAS BECOME HARD TO FIND ON WATER VAPOR IMAGERY
AS IT HAS DEVELOPED MORE INTO AN ELONGATED TROUGH IN THE UPPER
ATMOSPHERE. SUNSHINE BROKE THROUGH THE CLOUDS ENOUGH THIS MORNING ON
OAHU TO SPARK SOME AFTERNOON THUNDERSTORMS...PARTICULARLY OVER THE
KOOLAU RANGE AND THE CENTRAL PART OF THE ISLAND.

THE FLOOD WATCH HAS BEEN EXTENDED OVERNIGHT DUE TO THUNDERSTORM
DEVELOPMENT THIS AFTERNOON...AND THE THREAT OF ADDITIONAL
THUNDERSTORMS AND SHOWERS DEVELOPING OVERNIGHT. A SHORTWAVE TO THE
WEST OF THE ISLANDS MAY MOVE IN AND AID IN THE DEVELOPMENT OF
SHOWERS AND THUNDERSTORMS TONIGHT. THIS AFTERNOON/S SOUNDINGS SHOW
-9 TEMPERATURES AT 500 MB LEVEL AT BOTH HILO AND LIHUE. SHOWERS AND
THUNDERSTORMS TONIGHT WILL NOT BE AS WIDESPREAD AS THEY HAVE BEEN
THE LAST COUPLE OF NIGHTS. HOWEVER RAINFALL AMOUNTS IN THE HEAVIER
SHOWERS AND THUNDERSTORMS COULD STILL CAUSE LOCALIZED FLOODING AND
THUS THE FLOOD WATCH WAS EXTENDED.

HEAVY RAINFALL WAS REPORTED ON THE BIG ISLAND THIS MORNING AS HEAVY
SHOWERS AND THUNDERSTORMS MOVED OVERHEAD. OVERNIGHT SNOW FELL ATOP
MAUNA KEA AND MAUNA LOA. THIS AFTERNOON THAT SNOW WAS VISIBLE ON
SATELLITE IMAGERY AS THE CLOUDS CLEARED THE BIG ISLAND.

THE MODELS CONTINUE TO BE GOOD AGREEMENT WITH THE WEATHER PATTERN
FOR THE NEXT SEVERAL DAYS. THE NORTH TO SOUTH ORIENTED TROUGH TO THE
WEST OF THE ISLANDS IS EXPECTED TO WEAKEN AS IT MOVES TO THE WEST
AWAY FROM THE ISLANDS. DURING THIS TIME THE HIGH PRESSURE RIDGE TO
THE NORTH WILL BUILD BACK IN...BRINGING TRADES BACK TO THE ISLANDS.
&&

.MARINE...
A SOUTH SWELL IS STILL ANTIPICATED TO ARRIVE ON THURSDAY WHICH COULD
BRING SURF NEAR ADVISORY LEVELS OF 8 FEET FOR THE SOUTH SHORES.
&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH FOR ALL HAWAIIAN ISLANDS THROUGH 4 AM WEDNESDAY
&&

M BALLARD

In the hours before

Local storm report, Oct 26, 5:01 PM HST, 2 hours 44 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
501 PM HST TUE OCT 26 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

1133 AM     HEAVY RAIN       4 E HANAPEPE            21.91N 159.52W
10/26/2004  0.20 INCH        KAUAI              HI   TRAINED SPOTTER

            .20 INCHES OF RAIN IN 20 MINUTES

1200 PM     WATER SPOUT      1 SSE KAILUA            21.39N 157.73W
10/26/2004                   HONOLULU           HI   PUBLIC

            WATERSPOUT ABOUT 1 MILE OFF LANIKAI BEACH

1215 PM     FUNNEL CLOUD     1 SSE KAILUA            21.39N 157.73W
10/26/2004                   HONOLULU           HI   PUBLIC

            FUNNEL CLOUD OVER LANIKAI

0430 PM     FLOOD            KAHUKU                  21.68N 157.95W
10/26/2004                   HONOLULU           HI   PUBLIC

            6 TO 8 INCHES OF RAIN PONDED ON KAMEHAMEHA HIGHWAY.

&&

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, Honolulu

When: October 26, 7:45 PM HST to October 27, 2:52 AM HST
Where: Honolulu County, Kahuku
Reported by: OFFICIAL NWS OBS.
Coordinates: 21.455, -157.961 (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 2004 Every state in 2004 This day in weather history Warnings in Hawaii, October 2004

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: 5431863.