2004 Pacific typhoon season

An exceptionally energetic year

Activity ran well above the long-term norm for the western Pacific. JTWC's own warning records show 21 typhoons in 2004, against a 1959 to 2004 average of 17.7, and 30 tropical storms and typhoons against an average of 26.4. Colorado State University's tally of accumulated cyclone energy from JTWC data, 480.6 units, was about 60 percent above normal, and Tropical Storm Risk ranked the season second only to 1997 for intensity.

The season article links the high activity to a Modoki El Niño, in which warmer than usual water shifts farther west than in a classic event and conditions over the western Pacific become especially favorable. Many of the strongest storms formed far to the east, near the Marshall and Caroline Islands, and had long stretches of open ocean in which to strengthen before recurving toward Japan or driving west toward the Philippines.

How the season unfolded

Two weak, unnamed tropical storms in February and March opened the year. Typhoon Sudal followed in April, becoming the first typhoon on April 6 and strengthening to 130 kt after passing just south of Yap. In mid-May Typhoon Nida, Tropical Storm Omais and a short-lived storm in the South China Sea were active at the same time.

June brought the first burst. Five systems formed that month and all reached typhoon strength in JTWC's records: Conson, Chanthu, Dianmu, Mindulle and Tingting. July was comparatively quiet, with only Kompasu and Namtheun, before August produced nine warned systems, the busiest month of the year, including Rananim, Megi, Chaba, Aere and Songda.

September and October each added three storms, among them Meari, Ma-On, Tokage and Nock-Ten, several of which recurved toward Japan. Activity then shifted south. Muifa, Merbok and Nanmadol crossed or approached Luzon between mid-November and early December, and Talas and Noru closed the season near the Marshall and Mariana Islands, with the last tropical-stage observation on December 21.

Four Category 5 typhoons

Typhoon Dianmu and Typhoon Chaba shared the season's highest archive peak, 155 kt one-minute winds and 879 hPa. Dianmu reached it on June 16 in the Philippine Sea after deepening rapidly within about three days of its first warning. Chaba reached the same intensity on August 23 northwest of Guam and held super typhoon strength for several days, and at 468 recorded hours it was also the longest-lived storm of the year.

Typhoon Nida and Typhoon Ma-On completed the four Category 5 storms, each peaking at 140 kt. Nida intensified from 90 kt to 140 kt in less than a day off the eastern Philippines in May, while Ma-On strengthened quickly southeast of Okinawa in October under weak wind shear and strong outflow. Ten other typhoons reached major strength of at least 96 kt, including Sudal and Nanmadol at 130 kt and Mindulle, Songda, Meari and Tokage at 125 kt.

Japan's long run of typhoons

Japan was struck repeatedly. Dianmu crossed Shikoku in June after weakening well below its peak, and Chaba made landfall near Kushikino in southwestern Kyushu around August 30 before moving across Honshu and into Hokkaido. Songda passed over Okinawa and then struck western Kyushu in early September; JTWC's report lists 24 deaths and 15 missing in Japan, and the season article puts its losses at about US$9 billion in 2004 dollars, the costliest typhoon to strike the country up to that time.

Meari made landfall on the southern tip of Kyushu at the end of September, and JTWC's report records 18 deaths with several more missing, mostly from flooding and mudslides. Little more than a week later Ma-On came ashore on the Izu Peninsula on October 9, disrupting flights, trains and ferries around the Tokyo region. Tokage followed later in October, crossing Shikoku and reaching Osaka; the season article attributes 95 deaths to it, the most for a typhoon in Japan since 1982.

The Philippines, Taiwan and China

Typhoon Sudal passed 25 nm south of Yap on April 9, damaging about 90 percent of the island's buildings and leaving 1,500 people homeless, with one death reported. Typhoon Nida crossed the eastern Philippines in May, where JTWC's report lists 31 people dead or missing and about US$1.3 million in crop and infrastructure damage. Typhoon Mindulle killed 31 people with 11 missing in the Philippines and six in Taiwan after striking the island's northeast coast on July 1.

Typhoon Rananim made landfall near Wenling in Zhejiang on August 12, and JTWC's report records 115 deaths, 16 missing and more than 40,000 buildings destroyed, describing it as the worst typhoon to hit China since 1997. Typhoon Aere brushed northern Taiwan and then moved along the coast of Fujian later in August, bringing deadly rain to Taiwan and Luzon.

The season's deadliest disaster came from a weak system. Tropical Depression Winnie, which stayed below tropical storm strength and falls outside the counts above, brought torrential rain to Luzon at the end of November, and Philippine news reports put the number killed or missing at 1,404, mostly in Quezon and Aurora provinces. It arrived between Typhoon Muifa, which left 68 dead in the Philippines, and Typhoon Nanmadol, which reached super typhoon strength before landfall near Casiguran and left 70 dead and 37 missing. Nanmadol was the fourth tropical cyclone to hit the Philippines in two weeks.

Counting methods and retired names

The counts on this page use US-agency one-minute winds from IBTrACS during the tropical stage. The Japan Meteorological Agency, which names storms using ten-minute winds, recognized 29 named storms and 19 typhoons, while JTWC's operational warnings list 21 typhoons among 32 warned systems. Differences arise because ten-minute averages run lower than one-minute winds and because reanalysis revised some storms; Omais, for example, was a typhoon operationally but a severe tropical storm after review. On the same basis, the archive's ACE of 477.3 differs slightly from Colorado State University's 480.6.

The ESCAP/WMO Typhoon Committee retired Sudal, Tingting and Rananim after the season, replacing them with Mirinae, Lionrock and Fanapi. PAGASA also removed the Philippine names Unding, Violeta and Winnie, used for Muifa, Merbok and Tropical Depression Winnie.