The decade of the 1940s featured the 1940–49 Pacific typhoon seasons. The seasons had no official bounds, but most tropical cyclones tend to form in the northwestern Pacific Ocean between June and December. These dates conventionally delimit the period of each year when most tropical cyclones form in the northwestern Pacific Ocean.
On January 16, the remnants of a weakening cold front to the east of the Philippines spawned an area of low pressure. The system became better organized as it moved to the northeast, however remained rather shallow. The low was absorbed by a cold front advancing from the north early on January 18, just to the north-northwest of Guam. Based on data from Chin's Atlas the system achieved typhoon strength between the 16 and the 18 of January, however historical weather maps indicated the system never strengthened to a tropical storm.
A tropical low formed to the southwest of Guam and west of Palau on April 8. It moved westward over the next few days and continued to gradually deepen. Discrepancy in the location and strength of the system between Chin's Atlas and weather maps makes it difficult to pinpoint where the system went to after this point. The Chin's Atlas data set has the system moving to the north of Palau and eventually dissipating to the northeast of Catanduanes as a tropical storm on April 16. Historic weather maps has the low moving straight west towards Mindanao, and curving sharply to the north on the 13. Afterwards the low strengthens to a tropical storm while paralleling the coast to the east during April 14. On April 15 the storm made landfall in Eastern Samar with a pressure below 1000 millibars. Afterwards the storm weakened and moved north in response to a nearby front and stalled to the east of Luzon. An area of low pressure soon evolved to the north near Taiwan, on April 18, and moved the stalled depression to the north east. Later the system became absorbed with a cold front.
Chin's Atlas has a tropical storm moving to the northwest of the Mariana Islands between the 15 and 16 of April. Weather maps indicate a weak low pressure area attached to a cold front, likely indicating the storm was extra-tropical in nature.
A small, yet powerful typhoon, Connie, was first spotted on June 1 by the Weather Central Guam, moving northeast. Winds were reported to have been as high as 140 mph. But by June 7, it began to weaken. Its final fate is unknown. The US Navy's Fifth Fleet (formerly Third Fleet) was hit by Connie. The same fleet had previously been hit, with great loss of life, by Typhoon Cobra, in 1944. Connie being lesser, only one officer and five USN men were lost or killed because of Connie, and around 150 airplanes on its carriers were either lost or damaged.
Typhoon Helen formed on August 29. It moved west-northwest and strengthened into a category 3 typhoon with 120 mph winds. It weakened slightly to a category two and struck Taiwan. It briefly was over waters before it hit China as a tropical storm. It dissipated on September 4.
Louise was first seen developing on October 2, 1945 in the Caroline Islands. It unexpectedly veered north and slowed down, only to intensify as it passed over Okinawa on October 9 with 90 mph wind gusts and a minimum central pressure of 968.5 mbar. Shortly after, Louise began to weaken, and hit Japan as a strong tropical storm. The tropical cyclone became extratropical shortly after on October 12. In Okinawa, 36 people died, 47 people were reported missing, and 100 people were seriously injured. In Buckner Bay, the US military were occupying a temporary base. 30 ft (9.1 m)–35 ft (11 m) waves were reported to have crashed ashore, tearing into their Quonset huts and other building. The Bay was being used as port for the US military. Fifteen merchant cargo ships were grounded, with a few unrecoverable. 3 US Navy Destroyers were grounded beyond salvage, and over 200 various other US military boats, including 6 tank and truck amphibious landing craft, a number of special purpose boats, patrol boats, and amphibious landing craft were grounded or severely damaged, and beyond. Eighty percent of the buildings in the bay were completely wiped out while all 60 airplanes at the local airports were damaged.
Typhoon Barbara formed on March 27, and moved west. It strengthened briefly to a category three with 115 mph winds. But shortly after, it began to weaken. Typhoon Barbara curved northward and then westward, in turn hitting the Philippines as a category one. After making landfall, it curved back to the east and continued to weaken until April 7, when it dissipated.
On June 17, Typhoon Dolly formed. It moved northwestward, only to strengthen. After passing by the Philippines, it reached its maximum intensity of 125 mph, a strong major hurricane. It rounded around Taiwan and made landfall on China's shoreline. It dissipated hours after on June 23.
Tropical Storm Ingrid formed July 12, immediately moving west. After strengthening, it briefly became a category four on July 15. It weakened to a category two and struck the northern part of the Philippines. Ingrid retained its strength until it hit China. Right after it made landfall in China, it moved north and dissipated on July 20.
Janie formed on July 23. It moved northwest and then curved west. It was then that she became a major hurricane with 115 mph winds. After heading westward for a while, Janie began curving the opposite direction. But that was short-lived; it began moving northwest and struck southern Japan. Janie traveled over the island and dissipated near Russia's coast on July 31.
On August 10, a disturbance managed to organize itself enough to be designated Tropical Storm Lilly. It moved in a generally northwest direction while intensifying at a moderate pace-becoming Typhoon Lilly shortly after its formation. Before Lilly moved over cold waters, it attained a peak intensity of 145 mph. It narrowly missed Japan's shoreline as a category two before striking Korea as a moderate tropical storm. Lilly dissipated on August 21, after eleven days of the traveling of the western Pacific Ocean.
Carol formed east of the Philippines on June 17. It moved northwest and skimmed right past the most northern island as a 115 mph typhoon. After that, it began to weaken. Carol passed by Taiwan, and was about to hit mainland China, but it suddenly took a northeast track. Shortly thereafter, Carol dissipated on June 23.
The Joint Typhoon Warning center (JTWC) best tracks lists this system as 03W.
Typhoon Kathleen struck the Boso Peninsula and the entire Kanto Region in Japan on September 15. Heavy rains caused the Arakawa and Tone Rivers to overflow. The resulting floods killed 1,077 people and left 853 people missing.
Tropical Storm Irene formed on November 30 between the Philippine Islands. It strengthened to a tropical storm with 50 mph winds before it made landfall on one of the islands. It curved northeast and weakened to a tropical depression. But after exiting land, it restrengthened to a moderate tropical storm. But shortly thereafter, it became extratropical on December 3. The Japan Meteorological Agency analyzed it as a tropical depression, though it was actually a moderate tropical storm.
Typhoon Karen, the strongest cyclone of the season, developed on January 11, well west of the Philippines. It curved westward while slowly intensifying. After a prolonged period of the slow intensification, the tropical cyclone began to rapidly strengthen. It became a super typhoon on January 16. Shortly after, it weakened and dissipated on January 19.
Ophelia formed on June 10 in the South China Sea. It moved west and struck southern China. It dissipated the next day, without attaining maximum sustained winds any higher than 45 mph.
Typhoon Ione struck Japan in mid-September killing 838 people.
Typhoon Della struck Japan in mid-June killing 468 people.
In July, tropical storm Irma killed 1,600 people and destroyed more than 63,000 houses in Shanghai, China, the worst typhoon on record in the city.
Typhoon Gloria struck Okinawa on July 23. Gloria killed 38 people and destroyed 42,502 buildings on the island. Typhoon Gloria then continued westward and struck Shanghai, China killing 29 people.
Typhoon Kitty struck the Tokyo/Yokohama area August 31 through September 1, 1949. From reconnaissance reports the maximum sustained winds were near 110 knots 12 hours prior to landfall, but had fallen to minimum typhoon strength by the time it reached Honshū. The death toll reached 123 due to rainfall induced flooding and landslides (NY Times, 9/3/1949), and caused about 15 billion yen in damages. As its center passed near Tokyo, the JMA's Central Meteorological Office was able to launch eight rawindsondes in the typhoon environment. Researcher Dr. Hidedoshi Arakawa was able to analyize these soundings to make a vertical analysis of the storm.