The 1951 Pacific typhoon season was a generally average season with multiple tropical cyclones striking the Philippines. With the exception of January, each month saw at least one tropical system develop; October was the most active month with four tropical cyclones forming. Overall, there were 31 tropical depressions, of which 25 became tropical storms; of those, there were 16 typhoons.
The season began with the formation of a short-lived unnamed tropical storm on February 19, well east of the Philippines; Typhoon Georgia became the season's first named storm and typhoon after first developing in the open Pacific on March 20. In April, Typhoon Iris developed before intensifying into a super typhoon the following month; Iris was the first recorded instance of a Category 5-equivalent typhoon in the western Pacific. The final typhoon and storm of the year was Typhoon Babs, which remained at sea before dissipating on December 17.
The scope of this article is limited to the Pacific Ocean, north of the equator and west of the International Date Line. Storms that form east of the date line and north of the equator are called hurricanes; see 1951 Pacific hurricane season. At the time, tropical storms that formed within this region of the western Pacific were named and identified by the Fleet Weather Center in Guam. However, the Japan Meteorological Agency (JMA), which was established five years later, identified four additional tropical cyclones during the season not tracked by the Fleet Weather Center; these analyzed systems did not receive names.
Systems
Typhoon Georgia
A persistent low-pressure area south of Kusaie was first noted on March 14. The origins of the cyclonic circulation remain disputed, with one hypothesis indicating initial development south of Nauru and another suggesting that the system originated from a minor tropical wave east of the Marshall Islands. Nonetheless, southeasterly flow associated with an unusually strong high pressure area positioned over northeastern Australia aided the tropical cyclogenesis of the disturbance, and at 1200 UTC on March 18, the circulation developed into a tropical depression. In its initial stages, the disturbance steadily intensified as it moved in a northeasterly direction, attaining tropical storm strength by 1800 UTC the next day. At 0600 UTC on March 20, Georgia reached typhoon intensity; however, the Guam Fleet Warning Center only issued its first typhoon bulletin on the tropical cyclone at 0600 UTC the following day, by which time Georgia already had winds of , equivalent to a Category 3 hurricane on the Saffir–Simpson hurricane wind scale. At the same time, the typhoon began to develop an eye. Subsequently, Georgia attained its peak intensity with maximum sustained winds of , equivalent to a modern-day Category 4 hurricane. Afterwards, the intense typhoon began to quickly lose organization and strength, and degenerated into a remnant low after 0600 UTC on March 25, coinciding with the last typhoon bulletin issued by the Guam Fleet Warning Center. The remnants tracked westward before dissipating after 0600 UTC on March 28.
As a developing tropical system, the precursor to Georgia and resultant tropical depression moved near Kusaie, producing a peak rainfall total of over a three-day period and gusts in excess of . On March 20, Georgia passed to the south of Kwajalein. As such, the island's station observed "strong surface winds" and of rain in an eighteen-hour period. As a weakening tropical cyclone, Georgia threatened Wake Island and Eniwetok Atoll; the latter of which was expected to be the site of American nuclear testing operations. Though both islands were warned of by the Guam Fleet Weather Center, however, the typhoon had weakened considerably before reaching them, and effects remained marginal. Nonetheless, of rain was reported on a weather station in Eniwetok. The nuclear testing operation, termed Operation George, remained unaffected, though the first test was detonated on July 4, well after Georgia dissipated.
Typhoon Hope
In early April, several cyclonic vortices were noted south of the Marshall Islands. One of these circulation centers tracked westward and later developed into a tropical depression near Micronesia early on April 15. Steadily intensifying, the disturbance intensified into a tropical storm by 1800 UTC the next day. At roughly the same time, Hope began to curve slightly to the north. The Guam Fleet Warning Center estimated that the tropical storm intensified into a typhoon by 1800 UTC on April 17, before strengthening further to reach its peak intensity with maximum sustained winds of at 0000 UTC. At the same time, the weather center at Andersen Air Force Base in Guam began issuing bulletins on the storm. Shortly after, Hope executed a small anticyclonic loop, which resulted in the tropical cyclone tracking westward. After this loop was completed, however, the typhoon began to weaken. This weakening trend continued, and the Guam Fleet Warning Center ceased the issuance of bulletins at 1200 UTC on April 20, by which time Hope was deemed too weak to be classified as a tropical cyclone. However, the China Meteorological Agency (CMA), in analysis of the system, determined that Hope had persisted up until late on April 23 before dissipating.
Super Typhoon Iris
In late April, a well-developed tropical wave began developing east of Chuuk Lagoon. Tracking westward, the easterly wave was analyzed to have organized into a tropical depression by 0000 UTC on April 29. Twelve hours later, Iris was estimated to have strengthened into a tropical storm. At roughly the same time, a vessel in the vicinity of the storm reported winds in excess of , prompting the Guam Fleet Weather Center to initiate reconnaissance flights into the cyclone. Midday on April 30, Iris intensified into the equivalent of a modern-day typhoon as it moved in a slightly oscillatory path towards the Philippines. After a slight fluctuation in intensity during the overnight hours of May 1, Iris rapidly intensified to reach its peak intensity with a minimum pressure of and maximum sustained winds of early on May 4, making it the equivalent of a Category 5 super typhoon; at the time this was the first confirmed instance of a typhoon reaching such intensities. Afterwards, Iris weakened slightly before making landfall on South Luzon around 1800 UTC the following day.
After passing and weakening through the Philippines, Iris emerged into the South China Sea on May 6 as a tropical storm. At the same time, it began to recurve towards the northeast. On May 9, Iris reached a secondary peak intensity south of the Ryukyu Islands with winds of , before subsequently weakening. Afterwards, the tropical cyclone underwent extratropical transition, though the timing of such an event is disputed between the JMA and the CMA, with the former indicating that such a transition occurred on May 11, and the latter indicating a transition on May 14. Nonetheless, Iris made an anticyclonic loop beginning on May 11, before accelerating northeastward and dissipating entirely on May 15. Upon its dissipation, Iris set Guam Fleet Weather Center records for number of tropical cyclone bulletins issued, at 50, and number of reconnaissance fixes, at 54. At its landfall in the Philippines, the typhoon caused nine fatalities and injured an additional 39 people. (subscription required) Rainfall peaked at in Gandara, Samar, with observed winds peaking at in nearby Catbalogan. Damage to highways, bridges, and crops was estimated at ₱19.2 million (US$9.5 million).
Typhoon Joan
A stationary trough of low pressure persisted near Nauru towards the end of April and into early May, producing heavy rains; a station on the island received in a 24-hour period from the system. An interaction between the trough and a passing tropical wave resulted in the formation of an organized disturbance on May 2 that tracked initially northwestward before taking a more westerly course. According to the JTWC, the system became sufficiently organized to be considered a tropical cyclone on May 3, though the JMA indicates cyclogenesis three days later. After some fluctuations in its strength in its nascent stages, Joan curved towards the northeast and strengthened into a typhoon on May 8, peaking that day with winds of and a minimum pressure of . Concurrently, the typhoon stalled and traced out a clockwise loop for roughly a day before resuming a course towards the northwest. Gradual weakening ensued, and the system transitioned into an extratropical cyclone after May 12; the system would dissipate three days later.
Typhoon Kate
A disturbance was first noted in the vicinity of Micronesia on June 17 approximately south of Guam. Aircraft traversing between Guam and the Philippines eventually confirmed the presence of a developing tropical depression by June 25, tracking towards the west. By the following day, the system had strengthened into a tropical storm. The system curved towards the north by June 28 and had begun to trend towards the northeast thereafter, gradually strengthening to a typhoon by 18:00 UTC that day. The storm continued to accelerate towards the northeast, passing just east of the Ryukyu Islands on June 30 before reaching peak intensity offshore Kyushu with maximum sustained winds of and a central pressure estimated at . Kate weakened slightly before making landfall the following day on Shikoku with winds of . The typhoon curved eastward and continued to weaken, tracking through Sagami Bay and emerging over the Pacific Ocean on July 2 as a tropical storm. Kate transitioned into an extratropical cyclone and would later dissipate the following day.
Thirteen people died on Kyushu. Heavy rains flooded 2,000 houses and inundated 8,000 acres of farmland in Kagoshima and Miyazaki prefectures.
Typhoon Louise
The westerly-tracking tropical wave that would develop into Typhoon Louise was closely monitored as it passed Guam on July 25. Strong winds and falling pressures documented in Ulithi strongly suggested that a tropical cyclone was developing in the vicinity. The CMA analyzed the system promptly developing as a strong tropical storm early on July 25; however, the JTWC would not begin issuing bulletins on Louise until reconnaissance aircraft confirmed the presence of an already stout typhoon the following day with winds of . Tracking towards the west-northwest, the storm steadily strengthened, reaching its peak intensity on July 29 east of Luzon with winds peaking at and the central pressure bottoming out at . Typhoon-strength winds began to rake the Filipino province of Isabela that day, ahead of Louise's eventual landfall on July 30 with winds of . The mountainous terrain weakened the storm significantly, and Louise remained weakened system as it traversed the South China Sea before tracking over Wuchuan, Guangdong as a minimal tropical storm on August 2. The tropical cyclone degenerated into a remnant low inland the following day before dissipating entirely on August 5.
Communications were cut in Cagayan on the northeastern portions of Luzon as strong winds felled antennas. In Tuguegarao, 300 homes were blown down by winds estimated at 145& km/h (90 mph), with similar destruction wrought to homes on the coastal city of Vigan. The typhoon brought copious amounts of rainfall to Luzon, peaking at in a 24-hour period in Baguio; this total nearly set an all-time daily rainfall record for the city. There were six fatalities and ten people were injured. Damage was estimated at ₱5.5 million (US$2.7 million).
Typhoon Marge