1970 Pacific typhoon season

Few typhoons, but most of them violent

The Joint Typhoon Warning Center counted 24 tropical storms in 1970, one below its 25-year average, and 12 typhoons. By its records that made 1970 the lightest typhoon year in two decades, tying 1950, against an average of about 18 since 1945, and the second year running with below-normal typhoon counts. Storms lived longer, though: the center logged 79 typhoon days, 17 more than in 1969. Hurricane Dot came within about 30 miles of the International Date Line northwest of Midway before veering away, and the center left it out of the western Pacific total.

The site's archive counts 23 tropical storms and 12 typhoons, with an accumulated cyclone energy of 286.9. The archive applies US-agency one-minute winds during the tropical stage to every track observed in 1970, while the JTWC tallied storms from its own warnings, so the two storm totals differ by one. Other season lists describe 27 tropical depressions and 24 tropical storms, following yet another mix of agency records.

What the year lacked in numbers it made up in severity. The JTWC classed seven of its twelve typhoons as super typhoons, with winds of 130 kt or more: Olga, Anita, Georgia, Hope, Joan, Kate and Patsy. The archive, using its own best-track winds, puts 11 typhoons at 96 kt or more and four at Category 5.

A weak ridge and an empty July

The JTWC linked the low typhoon count to the subtropical ridge, which outside August never settled into its usual strength or length during the main typhoon months. Without a steady belt of easterlies across the development zone, the trade winds generated little cyclonic shear and little inflow toward young depressions.

July showed the pattern at its starkest. The month normally averages two typhoons, and in 1970 it produced none for the first time since 1947. A blocking ridge sat over eastern Siberia, and a weak trough reached from east of Japan into the tropics near the Marianas for most of the month, breaking up the easterly flow. Tropical storms Ruby and Sally still formed that month; Ruby crossed northern Luzon and reached China, and the archive lists it as the season's longest-tracked system.

In August and early September the upper-level Mid-Pacific trough took over as the main trigger. Its axis reached west from Midway toward Marcus Island, and the JTWC traced typhoons Wilda, Anita, Clara and Georgia to cyclonic cells that worked down from that trough into the easterlies. Clara became a typhoon at 31.9 degrees north, and a reconnaissance flight into Hurricane Dot in the central Pacific also reached Clara on the same mission.

Nancy in February, then Olga, Wilda and Anita toward Japan

Typhoon Nancy formed south of the Caroline Islands in mid-February and became the season's first typhoon on 22 February, peaking at 120 kt in the archive. The JTWC noted that only one other February typhoon had been recorded since 1945. Nancy's eye passed 35 miles south of Yap, where heavy seas and rain caused an estimated $160,000 in damage and no casualties. The American freighter Antinous rode through the eye east of Samar on 24 February and logged 953 mb, swells over 40 feet and winds above 100 kt. Nancy then skirted Catanduanes, where property damage on that island and Samar came to about $1 million in US dollars of the time, with about 5,000 families left homeless.

Typhoon Olga reached 140 kt over the Philippine Sea on 1 July, then weakened and came ashore south of Osaka as a tropical storm. Its rains caused landslides and floods in Japan and South Korea. The JTWC recorded at least 8 deaths in Japan and 29 in South Korea, with damage near $10 million around Tokyo; it killed 20 people in Japan.

August brought two more strikes on Japan. Typhoon Wilda peaked at 105 kt east of Okinawa and held near 100 kt until it reached the Japanese coast; the JTWC reported at least 11 people killed, 326 injured and rain of up to 18 inches. Typhoon Anita peaked at 135 kt before crossing Shikoku. The JTWC listed at least 23 storm-related deaths, 556 injured, more than 5,000 houses damaged or destroyed and at least 31 vessels sunk. Later that month Typhoon Billie brushed the Ryukyus and South Korea, where the JTWC reported at least 15 deaths from flooding and landslides.

Ellen and Fran circle, and Hope deepens

In early September tropical storms Ellen and Fran near Okinawa drew the largest forecast errors of any named storm that year. Post-season analysis showed why: the two storms rotated 220 degrees around each other over 42 hours, closing from 450 to 140 nautical miles apart, and Ellen was probably absorbed near Fran's center. The JTWC called it, to its knowledge, the most extensive example of the Fujiwhara effect ever documented. Fran went on to cross northern Taiwan and reach China.

Typhoon Hope began as a disturbance south of Johnston Island and tracked west north of the Caroline Islands. Aircraft reconnaissance at daybreak on 24 September measured 895 mb, the lowest pressure in the Northern Hemisphere that year and 84 mb below a dropsonde reading 24 hours earlier. The archive records Hope's peak at 150 kt and 900 hPa at that time, making it the season's strongest storm. Hope passed 30 miles east of Chichi Jima on 25 September and then curved east without making landfall.

Georgia, Joan, Kate and Patsy strike the Philippines

Typhoon Georgia reached 140 kt on 10 and 11 September as it neared Luzon, with a 10-mile eye and a reconnaissance pressure of 904 mb. It came ashore near Cape San Ildefonso early on 11 September. Casiguran, 15 nautical miles north of the center, measured 977.5 mb and winds estimated at 120 kt, but only 5.44 inches of rain. The JTWC recorded 95 deaths, 80 missing and property damage near $1.4 million. Georgia crossed the South China Sea at 70 to 75 kt and made a final landfall about 70 miles east of Hong Kong.

Typhoon Joan reached 150 kt early on 13 October and struck the Lagonoy Gulf region of southeastern Luzon near noon that day. The Virac weather station on Catanduanes recorded 950.7 mb and winds estimated near 150 kt, so the storm came ashore close to its peak. Joan passed about 20 miles south of Manila on 14 October, then spread gales more than 250 miles from its center across the northern South China Sea, the largest typhoon of the year by the JTWC's measure. The JTWC reported 575 dead, 1,590 injured and 193 missing in the Philippines, damage near $74 million in US dollars of the time and a 92 percent crop loss in the affected region. Later totals give 768 deaths, a figure that includes the 193 missing.

Typhoon Kate followed within days as a small, tight storm. It came ashore 30 miles south of Davao City on Mindanao, an area that rarely sees typhoons and where light housing is common, yet Davao itself reported winds no higher than 25 kt. Storm surge, rain and floods destroyed more than 5,000 houses and other structures. The JTWC counted 631 dead and 284 missing, with damage close to $50 million, and ranked Kate the deadliest cyclone on record in the Philippines to that date. Kate later reached Vietnam south of Da Nang on 25 October as a tropical storm.

Typhoon Patsy peaked at 135 kt on 18 November and crossed Manila around noon on 19 November with little loss of speed. Manila International Airport logged a gust of 108 kt and 969.3 mb, and ships broke from their anchorages in Manila Bay. The JTWC recorded 241 deaths, including at least 135 at sea, 1,756 injured and 351 missing, damage near $80 million in US dollars of the time and about 31,380 people left homeless in Manila. It called Patsy the most devastating typhoon to strike Manila since the Philippine Weather Bureau began in 1865. Later totals give 611 deaths in the Philippines, plus the 135 at sea, and about 30 in Vietnam, where Patsy made a final landfall on 22 November.

The JTWC gave its damage figures in US dollars of the time. After the season PAGASA retired four of its local names, Pitang for Georgia, Sening for Joan, Titang for Kate and Yoling for Patsy, the most retirements from one season up to then.

Late storms in the South China Sea

Typhoon Iris formed from a shear line in early October and peaked 140 miles south of Hong Kong on 6 October. It was the first October typhoon to develop over the South China Sea since 1957. From late October into November, tropical storms Louise, Marge, Nora, Opal and Ruth formed or tracked across the South China Sea toward Vietnam and the Gulf of Thailand. Nora's remnants crossed the Malay Peninsula on 5 November and contributed to the formation of the 1970 Bhola cyclone, which devastated East Pakistan. The archive's last tropical-stage observation falls on 16 December.