1973 Pacific typhoon season

Six empty months and a short season

The western North Pacific stayed quiet for the first half of 1973. The Joint Typhoon Warning Center noted that only 1952 had seen such a late start since the Second World War, and statistics from the Royal Observatory, Hong Kong, showed no comparable dearth in the first six months since 1917. On average five tropical cyclones form in that half-year, three of them typhoons. The archive's first tropical-stage observation falls on 29 June, and Tropical Storm Wilda, the first named storm, crossed Luzon and reached southern China in early July.

The JTWC named 21 tropical cyclones, 12 of them typhoons, well below its average of 19 typhoons since 1959; only 1969 and 1970 had come close. It issued warnings on just 77 days, about half the 14-year average, and typhoon days fell to a record low of 42, against 121 in 1972. The site's archive, using US-agency one-minute winds during the tropical stage, also counts 21 tropical storms and 12 typhoons, with 4 major typhoons and an accumulated cyclone energy of 146.7.

The JTWC traced the lull to the upper atmosphere. The near-equatorial ridge that usually forms south of the Tropical Upper Tropospheric Trough was missing for most of the season, so upper westerlies blew over the Caroline and Marshall Islands, where deep easterlies normally prevail. The resulting vertical shear suppressed development south of 20°N and east of 135°E. The monsoon trough did not settle south of Guam until the second half of the season.

Billie, Dot and a crowded July

Once activity began, several storms overlapped: the JTWC logged 27 days with two or more cyclones and nine with three or more. Typhoon Billie formed east of the Philippines on 12 July and strengthened rapidly to 130 kt, its peak in the archive, before heading north and weakening over northeastern China. The JTWC ranked Billie as a super typhoon at its 130 kt threshold, while the archive places it at Category 4. Typhoon Ellen formed from a trough trailing Billie and meandered south of Japan, and its rain fell on Shikoku and Kyushu while much of Japan was in drought.

Typhoon Dot crossed near Hong Kong in mid-July, flooding low-lying parts of the New Territories and damaging crops and farm buildings. The JTWC reported one person killed by a landslide there. In mid-September Typhoon Marge struck central Hainan with sustained winds estimated near 80 kt and made a final landfall north of Vinh, North Vietnam. It killed 903 people on Hainan.

Nora, Patsy and Ruth in October

In the first half of October the monsoon trough south of Guam spawned three typhoons in quick succession. Typhoon Nora formed south of Yap on 30 September and, over 20 hours on 5 and 6 October, its pressure fell 66 mb to 877 mb with surface winds estimated at 160 kt. The JTWC ranked the pressure among the lowest on record. The archive gives Nora's peak as 160 kt and 875 hPa on 6 October, the strongest storm of the season, and that pressure was the lowest then recorded.

Nora weakened before it skirted the northeastern tip of Luzon with sustained winds of about 100 kt, then passed within 60 nautical miles of Kaohsiung and came ashore near Amoy, China, on 10 October. The JTWC reported 6 deaths on Luzon, more than 100,000 people homeless and over $2 million in damage. On Taiwan, 12 people died, 28 were unaccounted for, and nearly 8,000 lost their homes. In the Taiwan Strait the Greek freighter Baltic Klif capsized with three crew drowned and others missing.

Typhoon Patsy reached 140 kt and 895 hPa on 10 October, the season's second Category 5 storm in the archive, then weakened sharply and crossed northern Luzon as a tropical storm. Typhoon Ruth followed, reaching Luzon on 15 October with sustained winds of 85 kt. The JTWC reported 27 killed, 30 injured and 23 missing on Luzon, thousands of homes destroyed and property damage above $5 million. Ruth then crossed Hainan and died on the North Vietnam coast on 19 October.

November storms and a year Japan escaped

The JTWC listed Nora, Ruth and tropical storms Sarah and Vera as the storms behind most of the year's casualties, with Taiwan, South Vietnam and the Philippines bearing the brunt. Its casualty table credits Sarah with 50 deaths. Sarah later crossed into the Bay of Bengal, and Vera, which never reached typhoon strength, affected about 3.4 million people in the Visayas in late November. The archive's last tropical-stage observation falls on 27 December.

The main Japanese islands saw no typhoon cross their coast in 1973, which the JTWC described as a first in records since 1945. Typhoon Iris, the archive's longest-tracked storm of the year, affected Japan and North Korea in August, but it peaked at only 85 kt.