The 2004 Pacific typhoon season was an extremely active season that featured the second-highest ACE ever recorded in a single season, second only to 1997, which featured 29 named storms, nineteen typhoons, and six super typhoons. It was an event in the annual cycle of tropical cyclone formation, in which tropical cyclones form in the western Pacific Ocean. The season ran throughout 2004, though most tropical cyclones typically develop between May and October. The season's first named storm and also the first typhoon, Sudal, developed on April 4, later was reached typhoon status two days later, and became the first super typhoon of the year three days later. The season's last named storm, Noru, dissipated on December 21.
The scope of this article is limited to the Pacific Ocean to the north of the equator between 100°E and 180th meridian. Within the northwestern Pacific Ocean, there are two separate agencies that assign names to tropical cyclones, which can often result in a cyclone having two names. The Japan Meteorological Agency (JMA) names a tropical cyclone should it be judged to have 10-minute sustained wind speeds of at least anywhere in the basin, whilst the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) assigns names to tropical cyclones which move into or form as a tropical depression in their area of responsibility located between 135°E and 115°E and between 5°N and 25°N, regardless of whether or not a tropical cyclone has already been given a name by the JMA. Tropical depressions that are monitored by the United States' Joint Typhoon Warning Center (JTWC) are given a number with a "W" suffix.
Seasonal summary
The activity of the season was extremely high, while the impacts of the typhoons were damaging and deadly, including four consecutive typhoons that struck them in the Philippines. In August, Typhoon Rananim struck Taiwan and China causing widespread damage, killing 169 people and with an estimated $2.44 billion (USD 2004) in damage. Typhoon Aere also caused heavy damage in China after Rananim killed 107 people there with minimal damage. Typhoon Songda was the costliest typhoon of the season to hit Japan, with damage estimated at $9.3 billion (US$2004) and 28 people killed. In October, Typhoon Tokage hit Japan as a tropical storm, causing a total of 95 deaths and damage estimated at $2.3 billion (2004 USD). Tropical Depression Winnie struck the Philippines killing a total of 1,593 people, making Winnie the deadliest storm of the season since Tropical Storm Thelma in 1991. After the month of November, the seasonal activity onwards decreased. The activity during the month included two typhoons. Muifa struck the Philippines after Winnie, killing 68 people and subsequently bringing heavy rains to Thailand killing 40 people. The fourth and last consecutive typhoon to hit the Philippines was Nanmadol which made landfall as a Category 4 typhoon in that country, killing a total of 77 people.
The Accumulated Cyclone Energy (ACE) index of this season amounted to 60% above the normal level for Pacific typhoon seasons, calculated by Colorado State University using data from the Joint Typhoon Warning Center to be 480.6 units. This makes the season the second-most intense Pacific typhoon season in recorded history, only after 1997. Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of .
Systems
Tropical Depression 01W (Ambo)
The first tropical storm of the 2004 Pacific typhoon season developed on February 10 west of Chuuk. It tracked to the west, organizing slowly due to persistent vertical wind shear. On February 13 and 14, the depression executed a clockwise loop. When the storm turned to the southwest, the wind shear overcame it, and the cyclone dissipated on February 19. The remnants of Tropical Depression Ambo dissipated, affecting Luzon by bringing flash floods and heavy rainfall on February 20 until February 22.
Tropical Depression 02W (Butchoy)