Flash Flood in Guam, August 5, 2004

Name: Flash Flood in Guam, August 5, 2004
Start: 2004-08-05T00:00
End: 2004-08-05T23:59
Location: Guam

August 5, 2004 · NWS GUA · 1 event in 1 county or zone

Several days of heavy rain brought flash flooding to Saipan. At least four families were evacuated.

The toll

Deaths: 0
Injuries: 0
Property damage: $10,000
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 GUA wrote it up.

Several days of heavy rain brought flash flooding to Saipan. At least four families were evacuated. Several roads were closed by water that was knee-deep in places. Rainfall from the 3rd through the 5th of August totaled 4.39 inches at Saipan International Airport on the southern end of the island, and 5.16 inches at Capitol Hill in central Saipan.

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 GUA wrote its last area forecast discussion before the first event at Aug 4, 4:15 PM SST, 7 hours 45 minutes earlier.

Area forecast discussion, Aug 4, 4:15 PM SST, 7 hours 45 minutes before

AREA SYNOPTIC DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
1 PM GUAM LST THU AUG 5 2004

WESTERN NORTH PACIFIC BETWEEN EQUATOR AND 25N FROM 130E TO 180.

TROPICAL STORM MERANTI IS CENTERED NORTH OF WAKE ISLAND NEAR 25N166E
AND IS MOVING NORTH-NORTHEAST AT 9 MPH WITH MAXIMUM SUSTAINED WINDS
OF 50 MPH. INFLOW SOUTHEAST OF MERANTI IS PRODUCING NUMEROUS SHOWERS
AND ISOLATED THUNDERSTORMS NORTH OF 23N FROM 167E TO 175E...AND
SCATTERED SHOWERS BETWEEN 20N AND 23N FROM 170E TO 176E. SEE JOINT
TYPHOON WARNING CENTER BULLETIN WTPN31 PGTW FOR FURTHER DETAILS.

A MONSOON TROUGH EXTENDS FROM 18N130E EASTWARD THROUGH TWO
CIRCULATION CENTERS NEAR 16N139E AND 15N149E THEN NORTHEASTWARD INTO
MERANTI. MONSOON FLOW SOUTH OF THE TROUGH IS GENERATING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE MARIANA ISLANDS...THE
REPUBLIC OF PALAU AND YAP STATE BETWEEN 130E AND 152E FROM THE
TROUGH AXIS SOUTHWARD TO A LINE FROM EQ130E TO EQ140E TO 10N152E.

CONVERGENT SURFACE FLOW COMBINED WITH DIVERGENT FLOW ALOFT IS
CREATING NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS WEST OF WAKE
ISLAND BETWEEN 18N AND 21N FROM 151E TO 165E...AND SCATTERED SHOWERS
EAST OF SAIPAN BETWEEN 13N AND 18N FROM 150E TO 155E.

CONVERGENCE OF MONSOON WINDS AND TRADE WINDS IS PRODUCING SCATTERED
SHOWERS ACROSS POHNPEI STATE...KOSRAE...AND THE MARSHALL ISLANDS
BETWEEN THE EQUATOR AND 10N FROM 155E TO 171E.

A TROUGH OF LOW PRESSURE ALONG 133E FROM 22N TO 30N IS GENERATING
NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS BETWEEN 20N AND 25N
FROM 136E TO 138E AND BETWEEN 18N AND 20N FROM 137E TO 141E.

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Saipan

When: August 5, 12:00 AM SST to 11:59 PM SST
Where: Saipan County, Countywide
Property damage: $10,000
Reported by: NEWSPAPER

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 Guam in 2004 Every state in 2004 This day in weather history Warnings in Guam, 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: 5432263.