North Atlantic weather war

The North Atlantic weather war occurred during World War II. The allies (Britain in particular) and Germany vied for access to reliable weather data in the North Atlantic and Arctic Oceans and sought to deny the other weather information. Meteorological data was important as it affected military planning and the routing of ships and convoys. In some circumstances, visibility was necessary (photographic reconnaissance and bombing raids) and in others concealment (keeping ship movements secret or suppressing enemy air activity). D-day planning was greatly affected by weather forecasting; it was delayed by one day in the expectation that a storm would blow out and sea conditions would be acceptable. British sources of data included ships at sea and the weather station at Valentia Observatory and Blacksod Point, in neutral Ireland. German use of weather ships also exposed their secret Enigma codes.

Ocean weather vessels
Starting in 1939, United States Coast Guard vessels were being used as weather ships to protect transatlantic air commerce. The Atlantic Weather Observation Service was authorized by President Franklin Delano Roosevelt on January 25, 1940. By February 1941, five 327-foot Coast Guard cutters were used in weather patrol, usually deployed for three weeks at a time, then sent back to port for ten days. As World War II continued, cutters were needed for the war effort and by August 1942, six cargo vessels were used. The ships were defenseless during the war, which led to the loss of the USCGC Muskeget (WAG-48) with 121 aboard on September 9, 1942. In 1943, the United States Weather Bureau recognized their observations as "indispensable" during the war effort.

The flying of fighter planes between North America, Greenland, and Iceland led to the deployment of two more weather ships in 1943 and 1944. Great Britain established one of their own 80 km off their west coast. By May 1945, 16 ships were in use north of the 15th parallel north in the Atlantic, with six more in the tropical Atlantic. A total of 20 United States Navy frigates were used across the Pacific for similar operations. Weather Bureau personnel stationed on weather ships were asked voluntarily to accept the assignment. In addition to surface weather observations, the weather ships would launch radiosondes and pilot balloons, or PIBALs, to determine weather conditions aloft. Due to its value, operations continued after World War II ended, which led to an international agreement in September 1946 that no fewer than 13 ocean weather stations would be maintained by the Coast Guard, with five others maintained by Great Britain and two by Brazil.

The Germans began to use weather ships by the summer of 1940. However, three of its four ships were sunk by November 23, which led to the use of fishing vessels for its weather ship fleet. Their weather ships were out to sea for three to five weeks at a time. Weather observations from the Germans were ciphered using their Enigma machines. The Munchen and Lauenberg were boarded by the Royal Navy, who managed to gather valuable information in each case. The Wuppertal became trapped in ice and was lost without trace of ship or crew.

Land stations
There were German attempts to set up land based weather stations in contested locations such as Spitsbergen, and even on Allied-held shores, such as Weather Station Kurt in Labrador. The Germans were obliged, by their continental location, to rely largely on long-range aircraft and weather ships, which were vulnerable to attack, and clandestine teams in exposed locations. The Allies had a distinct advantage in the contest, holding all of the major land areas (Newfoundland, Greenland, Iceland) of the North Atlantic. As weather patterns at that latitude generally travel west to east, the Allies could follow the progress of a front as it traveled across the Atlantic. The Germans, with their small number of (impermanent) observation stations, had to rely on a certain amount of luck to detect a weather front before it reached Europe.

In August 1941, in the preparation for Operation Gauntlet, the Royal Navy destroyed the weather station on Bear Island and, later, the one on Spitsbergen (after it had transmitted false information to discourage air observation). Spitsbergen was an important location, however, as it enabled the Germans to monitor weather conditions on the convoy route to northern Russia. The Germans made several attempts to establish and maintain weather reports from the Svalbard archipelago including Spitsbergen and Hopen (Hope Island) and these were never successfully suppressed. Other locations used were on Jan Mayen Island and eastern Greenland with teams and automated stations.