Heavy Rain in Guam, August 7, 2012

Name: Heavy Rain in Guam, August 7, 2012
Start: 2012-08-07T17:00
End: 2012-08-07T22:00
Location: Guam

August 7, 2012 · NWS GUM · 1 event in 1 county or zone

Heavy thunderstorms developed over central and northern Guam the evening of Tuesday 7 August, dropping up to 5 inches of rain and producing widespread flooding. 82 inches at Sinajana.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

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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 GUM wrote it up.

Heavy thunderstorms developed over central and northern Guam the evening of Tuesday 7 August, dropping up to 5 inches of rain and producing widespread flooding. Rainfall reports included 4.73 inches at Guam International Airport and 4.82 inches at Sinajana. About 30 homes sustained damage from the flooding, amounting to an estimated $10,000 in damage.

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 Guam wrote its last area forecast discussion before the first event at Aug 7, 6:35 AM UTC, 25 minutes earlier.

Area forecast discussion, Aug 7, 6:35 AM UTC, 25 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
435 PM CHST TUE AUG 7 2012

.SYNOPSIS...LIGHT WINDS OVER THE MARIANAS AND AFTERNOON HEATING
ALLOWED SHOWERS AND THUNDERSTORMS TO DEVELOP OVER GUAM.
WIDESPREAD SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A SURFACE
TROUGH REMAIN TO THE NORTH OF THE MARIANAS. SHOWERS ASSOCIATED
WITH A DISTURBANCE NEAR CHUUK ARE SITUATED WELL TO THE SOUTHEAST
OF GUAM.

&&

.DISCUSSION...A RATHER STAGNANT WEATHER PATTERN WILL PERSIST
DURING THE NEXT FEW DAYS OVER THE MARIANAS. LIGHT AND VARIABLE
WINDS WILL PROMOTE AFTERNOON THUNDERSTORM FORMATION OVER GUAM ON
WED AND POSSIBLY THU AND FRI. A DISTURBANCE NEAR CHUUK MAY BRING
SOUTHEASTERLY FLOW BY THE WEEKEND BUT MODEL PERFORMANCE CONTINUES
TO POOR EVEN IN THE LONG TERM SO FORECAST CONFIDENCE IN GENERAL
REMAINS LOW.

&&

.EASTERN MICRONESIA...
VERY UNSETTLED WEATHER CONTINUES FROM THE CHUUK AREA ACROSS KOSRAE.
INVEST AREA 91W ROUGHLY NEAR 7N156E NEEDS TO BE MONITORED. A PATTERN
OF UPPER-LEVEL DIVERGENCE PERSISTS ACROSS MUCH OF MICRONESIA...AND
SOUTHWEST TO WEST SURFACE WINDS EXTEND EASTWARD ALL THE WAY TO
KWAJALEIN AND MAJURO. MAJURO IS EXPECTED TO REMAIN IN A RELATIVELY
DRY FLOW WITH NORTHEAST WINDS RE-DEVELOPING IN THE NEAR TERM. THIS
MARGINALLY DRIER WEATHER IS EXPECTED TO SLOWLY SPREAD WESTWARD AS
THE WEEK PROGRESSES.

&&

.WESTERN MICRONESIA...
A DISTURBANCE CENTERED BARELY EAST OF KOROR IS CAUSING AN UNUSUAL
PATTERN OF OUTFLOW THAT IS AFFECTING MOST OF FAR WESTERN MICRONESIA.
THE GFS MODEL INITIALIZES DECENTLY BUT DEVELOPMENT OF THIS SYSTEM
BECOMES ERRATIC AND HARD TO FOLLOW IN ANY LINEAR FASHION.
ALSO...THE MONSOON TROUGH SEEMS TO BE REFORMING FROM JUST NORTH OF
YAP TOWARD INVEST 91W AND MUCH FARTHER INTO EASTERN MICRONESIA. AT
ANY RATE...WEST TO SOUTHWEST SURFACE WINDS ARE EXPECTED TO PREVAIL
AT YAP AND KOROR FOR THE NEAR TERM...WITH WINDS MORE VARIABLE IN
THE LONGER TERM. CHUUK WEATHER WILL BE UNSTABLE AND AFFECTED BY
INVEST 91W AND A LIGHT TO MODERATE SOUTHWEST MONSOON FLOW. MODEL
SOLUTIONS DIFFER TO A VERY LARGE DEGREE ABOUT THE DEVELOPMENT OF
91W AND IT WILL NEED TO BE MONITORED.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...NONE.
MARIANAS WATERS...NONE.
&&

WILLIAMS/SIMPSON

The radar

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

Open the radar archive at this moment

Event by event

1 heavy rain. Local standard time, as filed.

Heavy Rain, Guam

When: August 7, 5:00 PM GST to 10:00 PM GST
Where: Guam County, 0.61 mi ESE of Agana Heights to 0.4 mi NNW of Barrigada
Property damage: $10,000
Reported by: Newspaper
Coordinates: 13.467, 144.759

What these are

Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.

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

The same day elsewhere

Every storm in Guam in 2012 Every state in 2012 This day in weather history Warnings in Guam, August 2012

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: 411182.