2004 Western Pacific typhoon season
Typhoon Dianmu 2004
Typhoon Dianmu reached Category 5 strength in the Philippine Sea in June 2004. It weakened before reaching Japan, where rain and wind caused damage and deaths as the storm accelerated northeast.
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178 mph
Jun 16, 2004 during the tropical stage
Full archive record, including non-tropical stages if present
Along the recorded center positions
STORM HISTORY
Rapid development near Yap
Dianmu began as disturbed weather southeast of Palau within the monsoon trough. It organized into a depression, became a tropical storm on June 14 and paused west of Yap while strengthening. A northward turn followed as its eye and central thunderstorms developed.
The archive records maximum one-minute winds of 155 kt on June 16, equivalent to Category 5. PAGASA tracked the typhoon under the name Helen as it entered the agency's warning area east of the Philippines.
A weaker storm reaches Japan
After its peak, Dianmu moved northwest and then turned toward Japan. It weakened before crossing the country and became extratropical on June 21. The saved account attributes four deaths and about US$68.3 million in damage to its effects in Japan, in 2004 currency, with two additional deaths in South Korea.
Dianmu's remnants continued beyond the tropical phase. The archive follows the system through June 28, extending its recorded life well past the intense Philippine Sea stage.
Further reading
QUICK ANSWERS
Dianmu in brief
What was Typhoon Dianmu's highest wind speed?
178 mph, the highest one-minute sustained wind in its tropical stage, recorded on Jun 16, 2004, 06:00 AM UTC.
What category was Typhoon Dianmu?
Category 5 at its peak on the Saffir–Simpson one-minute wind scale, first reaching Category 5 on Jun 15, 2004, 06:00 PM UTC. Other agencies classify storms differently.
What was Typhoon Dianmu's lowest pressure?
879 mb, the minimum central pressure recorded during its tropical stage, on Jun 16, 2004, 06:00 AM UTC.
When did Typhoon Dianmu occur?
The archived track runs from Jun 11, 2004, 06:00 PM UTC to Jun 28, 2004, 12:00 PM UTC, with the tropical stage from Jun 12, 2004, 06:00 PM UTC to Jun 21, 2004, 03:00 PM UTC.
Where did Typhoon Dianmu form?
In the Western Pacific basin, in the 2004 season. Its first archived position is 6.5°N, 139.4°E on Jun 11, 2004, 06:00 PM UTC.
Did Typhoon Dianmu make landfall?
No archived position places Typhoon Dianmu's center over land, but positions are six-hourly and a brief landfall can fall between them.
METHODOLOGY
Data sources and limitations
The map and summary are generated from NOAA's IBTrACS v04r01 archive. Wind and category use US-agency records; minimum pressure is calculated during the tropical stage, with the archive's pressure source retained. Category 5 refers to the Saffir–Simpson one-minute wind scale; local agencies may use different classifications. Coastlines use Natural Earth's 1:10m land data.
Track distance adds great-circle distances between consecutive observations, excluding gaps over 12 hours. This track has no gaps over 12 hours. The line shows the storm's center, not its size, rainfall or flood extent. Converted wind speeds are rounded to the nearest whole unit.
Archive retrieved
NOAA IBTrACS archive and Field documentation
Sources & methodology