The United States’ thermonuclear testing program Operation Castle commences with the first detonation, code named Castle Bravo, on a reef near Bikini Atoll. The most powerful hydrogen bomb detonation carried out by the American military during the 20th century, Castle Bravo has a yield of 15 megatons, three times greater than predicted, with a blast radius of over four miles. Radioactive fallout spreads over 7,000 square miles of the Pacific Ocean, including neighboring islands and a Japanese fishing boat, with both populations showing symptoms of radiation sickness shortly afterward, forcing evacuations and later reparations.
Formerly the Weather Bureau-Army-Navy Severe Weather Unit, the recently-renamed Severe Local Storms Warning Service (SELS) relocates from Washington D.C. to Kansas City, Missouri. The new location puts the SELS closer to the American midwest, a hotbed of severe weather during the spring months, as well as placing it in close proximity to a major telecommunications hub (at this point, the SELS is reliant almost entirely on teletype transmissions). Additionally, precise definitions of what constitutes a severe thunderstorm (winds in excess of 50mph, wind gusts in excess of 75mph, and hail in excess of an inch in diameter) are established, as well as a concerted effort to target its weather bulletins to more precise geographic regions.
The first Godzilla movie, Gojira, debuts in Japan. Directed by Ishiro Honda and starring Akira Takarada, Momoko Kochi and Akihiko Hirata, the film is intended to be an allegory to the ravages of the atomic bomb rather than the beginning of a franchise (though the door is clearly left open to a sequel by dialogue at the close of the movie). The franchise proper will not begin until the first sequel five years later. In the meantime, an American dub of the movie attracts worldwide attention to Gojira, eventually rechristening the character Godzilla for much of the world.