Name: Tropical Storm in Guam, June 13 to 15, 2004
Start: 2004-06-13T00:00
End: 2004-06-15T23:59
Location: Guam

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 2

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.

TROPICAL STORM DIANMUAfter developing about 125 miles southwest of Yap on the morning of June 13th, Tropical Depression 09W moved slowly northwest between Yap and Palau that evening. It became a tropical storm early on the 14th, and appeared to be headed safely away from Yap. However, Tropical Storm Dianmu slowed abruptly and turned to an east-northeast track. Dianmu dealt Yap a glancing blow, passing about 75 miles northwest of that island as a 65 mph tropical storm at about 0400 SST on the 15th. Meanwhile, southwest monsoon flow into Dianmu brought gusty winds and heavy rain to Palau on the 13th and 14th. By 1300 SST on the 15th, Dianmu was a typhoon, centered over 150 miles north of Yap and moving quickly away.At Yap, the highest 2-minute wind was 32 mph; from the south-southwest on the 14th at 2353 SST, and from the west-southwest on the 15th at 0650 SST. The maximum gust of 59 mph from the south-southwest was recorded at 2253 SST on the 14th. Since Yap spent most of its time in a dry slot between Dianmu's central cloud mass and its outer rain band, the greatest 24-hour rainfall at the airport was only 0.56 inches through 1600 SST on the 15th. The lowest sea-level pressure at the airport was 998.3 mb at 0457 SST on the 15th. No damage or injuries were reported at Yap.While Palau had less wind than Yap, much more rain fell there as a result of persistent monsoon flow into Dianmu. The maximum 24-hour rainfall was 5.22 inches through 1300 SST on the 14th, while 7.19 inches fell in the 48 hours ending at 0400 SST on the 15th, resulting in minor flooding. The highest 2-minute wind was only 21 mph on the 14th, while the peak gusts of 44 mph were recorded at the Weather Service Office on the 15th at 0902 SST and 1659 SST. No damage or injuries 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 GUA wrote its last area forecast discussion before the first event at Jun 12, 3:47 PM SST, 8 hours 13 minutes earlier.

Area forecast discussion, Jun 12, 3:47 PM SST, 8 hours 13 minutes before

AREA SYNOPTIC DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
1 PM GUAM LST SUN JUN 13 2004

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

NEWLY-FORMED TROPICAL DEPRESSION 09W IS CENTERED BETWEEN YAP AND
PALAU NEAR 8N137E AND IS MOVING WEST-NORTHWEST AT 3 MPH WITH MAXIMUM
SUSTAINED WINDS OF 35 MPH. INFLOW INTO THE DEPRESSION IS PRODUCING
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE REPUBLIC OF
PALAU AND YAP STATE BETWEEN 130E AND 144E SOUTH OF A LINE FROM
9N130E TO 14N137E TO 14N144E. SEE JTWC WARNING WTPN31 PGTW AND NWS
ADVISORY WTPQ31 PGUM FOR FURTHER DETAILS.

A MONSOON TROUGH STRETCHES FROM 9N130E EASTWARD THROUGH TROPICAL
DEPRESSION 09W TO 3N157E. SCATTERED SHOWERS EXTEND ACROSS CHUUK
STATE AND NEIGHBORING ISLANDS IN YAP AND POHNPEI STATE BETWEEN THE
EQUATOR AND 14N FROM 146E TO 157E.

DIVERGENT FLOW ALOFT SOUTH OF AN UPPER-LEVEL LOW NEAR 23N167E IS
GENERATING SCATTERED SHOWERS EAST OF A LINE FROM 25N165E TO 17N167E
TO 6N174E. IN ADDITION...ISOLATED THUNDERSTORMS ARE OCCURRING NORTH
OF 20N FROM 176E TO 180...AND BETWEEN 10N AND 13N FROM 172E TO 177E.

A COLD FRONT SOUTH OF JAPAN IS PRODUCING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS NORTHWEST OF A LINE FROM 22N130E TO 25N136E.

In the hours before

Special weather statement, Jun 12, 7:28 PM SST, 4 hours 32 minutes before

PMZ161-131800-
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TIYAN GU
4 PM GUAM LST SUN JUN 13 2004

...MONSOON WINDS AND RAIN AFFECT TOBI ISLAND AND SONSORAL IN
THE REPUBLIC OF PALAU...

STRONG WINDS ASSOCIATED WITH A SURGE IN THE MONSOON AND A TROPICAL
DEPRESSION EAST OF KOROR ARE PRODUCING STRONG WEST TO SOUTHWEST
WINDS IN THE SOUTHERN PORTION OF THE REPUBLIC OF PALAU. OBSERVATIONS
FROM TOBI INDICATE GUSTS AROUND 35 MPH WITH HIGHER GUSTS IN SQUALLS.
CONDITIONS ARE FAVORABLE FOR THESE WINDS AND OCCASIONALLY HEAVY
RAINFALL TO PERSIST FOR THE NEXT TWO DAYS.

MILLER/ZIOBRO/WELLS

Event by event

2 tropical storm. Local standard time, as filed.

Tropical Storm, Micronesia

When: June 13, 12:00 AM SST to June 15, 11:59 PM SST
Where: Micronesia forecast zone
Reported by: NWS STORM SURVEY

Tropical Storm, Belau

When: June 13, 12:00 AM SST to June 15, 11:59 PM SST
Where: Belau forecast zone
Reported by: NWS STORM SURVEY

What these are

Tropical Storm: A tropical cyclone with sustained winds of 34 to 63 knots (39 to 73 mph).

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

The same day elsewhere

More

Every storm in Guam in 2004 Every state in 2004 This day in weather history Warnings in Guam, June 2004 The 2004 hurricane season

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: 5431931, 5432032.