Flash Flood in Hawaii, August 4, 2004

Name: Flash Flood in Hawaii, August 4, 2004
Start: 2004-08-04T03:45
End: 2004-08-04T12:45
Location: Hawaii

August 4, 2004 · NWS HFO · 1 event in 1 county or zone

Heavy showers and isolated thunderstorms produced flash flooding near the community of Waiahole in the windward coastal part of Oahu. 5 feet across the roadway.

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 and isolated thunderstorms produced flash flooding near the community of Waiahole in the windward coastal part of Oahu. Kamehameha Highway was closed for a time because water was as deep as 1.5 feet across the roadway. No serious injuries or property damage were reported.

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 3, 8:30 PM HST, 7 hours 15 minutes earlier.

Area forecast discussion, Aug 3, 8:30 PM HST, 7 hours 15 minutes before

HAWAIIAN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
830 PM HST TUE AUG 3 2004

.SYNOPSIS...
THE REMNANT TROPICAL MOISTURE FROM TROPICAL STORM DARBY WILL
CONTINUE TO BRING SHOWERS...SOME HEAVY...TO THE ISLANDS TONIGHT AND
INTO WEDNESDAY. TRADE WINDS...WITH THEIR MORE NORMAL PATTERN OF
WINDWARD AND MAUKA...NIGHT AND MORNING SHOWERS...WILL RETURN ON
THURSDAY.

&&

.DISCUSSION...
HEAVY SHOWERS WHICH HAVE BEEN AFFECTING MOSTLY THE BIG ISLAND AND
MAUI LAST NIGHT AND TODAY...ARE MOVING WEST. A SURFACE TROUGH...THE
REMNANT OF EX-TROPICAL STORM DARBY...IS NOW ORIENTED SOUTHWEST
THROUGH NORTHEAST AND LIES THROUGH THE KAIWI CHANNEL BETWEEN OAHU
AND MOLOKAI. A PLUME OF MOIST TROPICAL AIR IS BEING PULLED
NORTHWARD ALONG THE EAST SIDE OF THIS TROUGH...WITH DRIER NORTH TO
NORTHEASTERLY FLOW ALONG THE WEST SIDE OF THE TROUGH. SHOWERS...SOME
BRIEFLY HEAVY...MARK THE TROUGH AND EXTEND EAST TO BEYOND THE BIG
ISLAND. THE TROUGH AND SHOWERS ARE MOVING WESTWARD AT ABOUT 10 MPH
AND WILL AFFECT ALL ISLANDS THROUGH THE NIGHT TONIGHT AND INTO
WEDNESDAY. IT APPEARS MOISTURE MOVING UP FROM THE SOUTH WILL
CONVERGE WITH MOISTURE MOVING WESTWARD NORTH OF THE ISLANDS RIGHT
OVER OAHU LATER TONIGHT.

BY THURSDAY AND FRIDAY MORE TYPICAL TRADE WIND WEATHER IS EXPECTED
THANKS TO HIGH PRESSURE FAR NORTH OF THE STATE. TRADE WINDS WILL BE
IN THE 10 TO 20 MPH RANGE WITH SHOWERS MAINLY CONFINED TO WINDWARD
AND MAUKA AREAS.

&&

.LONG TERM...
WE ARE ALSO WATCHING ANOTHER AREA OF SHOWERY WEATHER THAT MAY
APPROACH THE ISLANDS OVER THE WEEKEND. TROPICAL DEPRESSION SIX-E IS
LOCATED ABOUT 1500 MILES EAST SOUTHEAST OF HONOLULU. THE NATIONAL
HURRICANE CENTER IN MIAMI HAS ISSUED ITS LAST ADVISORY ON THIS SYSTEM
BUT THE GFS AND NOGAPS MODELS STILL BRING A LARGE AREA OF REMNANT
TROPICAL MOISTURE OVER THE STATE LATE FRIDAY INTO SATURDAY BRINGING
THE THREAT OF HEAVY RAINFALL ONCE AGAIN TO THE STATE.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH ALL ISLANDS.
HIGH SURF ADVISORY EAST SHORES OF KAUAI OAHU MOLOKAI MAUI AND THE
BIG ISLAND.

&&

FARRELL

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: August 4, 3:45 AM HST to 12:45 PM HST
Where: Honolulu County, 2 mi N of Kahaluu
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, August 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: 5431599.