Flash Flood in Guam, July 31, 2003

Name: Flash Flood in Guam, July 31, 2003
Start: 2003-07-31T12:00
End: 2003-07-31T18:00
Location: Guam

July 31, 2003 · NWS GUA · 1 event in 1 county or zone

Light winds combined with daytime heating caused showers and thunderstorms to form across the island of Guam. The heaviest rain was over the southern portions of the island.

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 GUA wrote it up.

Light winds combined with daytime heating caused showers and thunderstorms to form across the island of Guam. The heaviest rain was over the southern portions of the island. 1.22 inches of rain was recorded at an automated weather observing station in Inarajan between 1200 and 1600. Nexrad 88-D radar showed an area between Inarajan and Merizo with more than two inches of rain falling from 1100 to 1800.

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 Jul 31, 3:58 AM SST, 8 hours 2 minutes earlier.

Area forecast discussion, Jul 31, 3:58 AM SST, 8 hours 2 minutes before

AREA SYNOPTIC DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
1 AM GUAM LST FRI AUG 1 2003

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

A MONSOON TROUGH EXTENDS FROM A CIRCULATION CENTER EAST OF LUZON
NEAR 13N129E...CURRENTLY THE SUBJECT OF A TROPICAL CYCLONE FORMATION
ALERT...EASTWARD TO ANOTHER CIRCULATION CENTER EAST OF GUAM NEAR
12N155E THEN SOUTHEASTWARD TO 6N159E.

LOW-LEVEL CONVERGENCE INTO THE TROPICAL DISTURBANCE EAST OF LUZON IS
GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 100
MILES OF A LINE FROM 17N129E TO 21N136E.

CONVERGENT WESTERLY WINDS SOUTH OF THE TROUGH ARE PRODUCING
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS YAP...CHUUK..AND
POHNPEI STATES BETWEEN THE EQUATOR AND 11N FROM 137E TO 157E.

AN UPPER-LEVEL TROUGH...WHICH STRETCHES SOUTHWARD FROM AN UPPER-
LEVEL LOW NEAR 26N158E...COMBINED WITH A SURFACE TROUGH EXTENDING
NORTHEASTWARD FROM THE SURFACE LOW EAST OF GUAM IS CREATING
SCATTERED SHOWERS FROM THE NORTHERN MARSHALL ISLANDS TO WAKE ISLAND
BETWEEN 11N AND 25N FROM 157E TO 167E...AND ISOLATED THUNDERSTORMS
WITHIN THE SAME AREA NORTH OF 18N.

TRADE-WIND CONVERGENCE IS GENERATING ISOLATED SHOWERS AND
THUNDERSTORMS ACROSS KOSRAE AND THE MARSHALL ISLANDS BETWEEN THE
EQUATOR AND 11N FROM 160E TO 180.

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE LOCATED WEST OF THE
FAR NORTHERN MARIANA ISLANDS BETWEEN 18N AND 21N FROM 140E TO
143E...AND FURTHER NORTH BETWEEN 24N AND 25N FROM 135E TO 149E.

Event by event

1 flash flood. Local standard time, as filed.

Flash Flood, Guam

When: July 31, 12:00 PM SST to 6:00 PM SST
Where: Guam County, South Portion
Reported by: OFFICIAL NWS OBS.

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 2003 Every state in 2003 This day in weather history Warnings in Guam, July 2003

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: 5367321.