Tornado warning
A tornado warning is a public warning that is issued by weather forecasting agencies to an area in the direct path of a tornado, or a severe thunderstorm capable of producing one, and advises individuals in that area to take cover. Modern weather surveillance technology such as Doppler weather radar can detect rotation in a thunderstorm, allowing for early warning before a tornado develops. They are also commonly issued based on reported visual sighting of a tornado, funnel cloud, or wall cloud, typically from weather spotters or the public, but also law enforcement or local emergency management. When radar is unavailable or insufficient, such ground truth is crucial. In particular, a tornado can develop in a gap of radar coverage, of which there are several known in the United States.
A warning should not be confused with a tornado watch, issued in the United States by the Storm Prediction Center and in other countries by applicable regional forecasting agencies or national severe weather guidance centers, which only indicates that conditions are favorable for the formation of tornadoes. Although a tornado warning is generally a higher alert level than a tornado watch, in the U.S., it can be surpassed by a higher-level alert—structured as wording that can be added to the official warning product—to warn the public of intense tornadoes affecting a densely populated area.
A tornado watch is not required for a warning to be issued; tornado warnings are occasionally issued when a tornado watch is not active, if a severe thunderstorm develops and has a confirmed tornado or strong rotation.
History in the United States
Early history
In April 1899, the Chicago Tribune wrote to the United States Weather Bureau via a news article posing the question on why tornado warnings are not sent out via telegraphs or even the telephone to warn the local population in the path. Cleveland Abbe responded by saying "it is certain that if any such arrangement were possible, the Weather Bureau would have done this many years ago" along with "we must remember that the destructive areas of tornadoes, and even of thunderstorms, are so small that the chance of being injured is exceedingly slight" and that "we do not attempt to prevent that which is inevitable". They also wrote that the change of being injured by a tornado is "one in ten thousand years".In June 1899, U.S. Weather Bureau Oklahoma section director J. I. Widmeyer published that long-range forecasters in Oklahoma were sounding "unnecessary tornado alarms" due to "ignorant predictions" to residents in Oklahoma and that they were causing "frightened men, women, and children" to take shelter, despite no tornadoes occurring. Cleveland Abbe added on to the publication by Widmeyer saying, "it is unnecessary to resort to the caves and cellars, or to stop our ordinary avocations for fear of a tornado, until we see the cloud in the distance, or are positively certain that one is about to pass near us".
In April 1908, the U.S. Weather Bureau published several replies regarding a question posed to the Weather Bureau on: How can we protect against tornadoes?.
- Lieutenant John Park Finley responded with "the best we can do is to watch the distant tornado, and if it seems to approach us then move away toward the left; so far as we have learned, this still continues to be the best rule".
- The Chief of the Weather Bureau responded with the idea to establish a warning system by surrounding a city at a distance of with wires hooked up with alarms. That way, a warning can be given to the city for an impending tornado. The wire system would detect sudden pressure differences, if wires were twisted, or if wires were short circuited. It was also stated that at a distance of four miles from the city, the tornado "would be unable to reach the city from any direction without giving us an alarm".
- Cleveland Abbe responded by saying the idea of a wire-based system around a city is not practical as well as how tornadoes are very infrequent. Abbe ended by saying that "the mere forewarning of a tornado is no protection against its coming" and that it would be wiser to "spend your money to protect yourself against diseases, accidents, lightning, ect…".
The first official tornado forecast was made by United States Air Force Capt. Robert C. Miller and Major Ernest Fawbush, on March 25, 1948. The first such forecast came after the events that occurred five days earlier on March 20, 1948; Miller – a California native who became stationed at Tinker Air Force Base three weeks earlier – was assigned to work the late shift as a forecaster for the base's Air Weather Service office that evening, analyzing U.S. Weather Bureau surface maps and upper-air charts that failed to note atmospheric instability and moisture content present over Oklahoma that would be suitable for producing thunderstorm activity, erroneously forecasting dry conditions for that night. Thunderstorms soon developed southwest of Oklahoma City, and at 9:30 p.m., forecasters from Will Rogers Airport sent a warning to Tinker that the storm encroaching the city was producing wind gusts of and a "Tornado South on Ground Moving NE!" Base personnel received an alert written by the staff sergeant on duty with Miller; the twister struck Tinker several minutes later around 10:00 p.m., damaging several military aircraft that could not be secured in time before it crossed the base grounds.
Following an inquiry the next day before a tribunal of five generals who traveled to Tinker from Washington, D.C., who ruled that the March 20 tornado was an "act of God... not forecastable given the present state of the art", base commander Gen. Fred Borum tasked Miller and Fawbush to follow up on the board's suggestion to consider methods of forecasting tornadic thunderstorms. Over the next three days, Miller and Fawbush studied reports and charts from previous tornado events to determine the atmospheric conditions favorable for the development of tornadic activity, in an effort to predict such events with some degree of accuracy. At the time, there had not been studies on how tornadoes formed; however, military radars were being adapted for forecasting use, allowing forecasters to see the outlines of storms but not their internal attributes such as rotation. Miller and Fawbush's findings on atmospheric phenomenon present in past outbreaks would aid in their initial forecast, as the day's surface and upper-air analysis charts determined the same conditions present on March 20 were present on the 25th, concluded that central Oklahoma would have the highest risk for tornadoes during the late-afternoon and evening.
Borum, who had put together a severe weather safety plan for base personnel, then suggested that Miller and Fawbush issue a severe thunderstorm forecast, and then asked the men if they would issue a tornado forecast based on the similarities between the conditions that produced the tornado which hit the base five days earlier, which they were reluctant to do. Fawbush wrote the forecast message that Miller would type and issued it to base operations at 2:50 p.m. as thunderstorms were approaching from North Texas. Defying the high odds against two tornadoes hitting the same area in five days, one hit the Tinker campus around 6:00 p.m., to the surprise of Miller, who found out about the storm via a radio report. Miller and Fawbush would not put out another tornado forecast until March 25, 1949, when they successfully predicted tornadic activity would occur in southeastern Oklahoma.
Miller and Fawbush soon would distribute their tornado forecasts to the American Red Cross and Oklahoma Highway Patrol, after giving William Maughan, chief meteorologist at the U.S. Weather Bureau's Oklahoma City office, permission to relay their forecasts to those agencies. The relative accuracy of the forecasts restarted a debate over their reliability and whether military or civilian agencies should have jurisdiction over the issuance of weather warnings. The USAF had pioneered tornado forecasting and tornado warnings, although John P. Finley had developed the first experimental tornado forecasts in 1885. Two years later, he and other officials with the agency were prohibited by the United States Signal Service's weather service from using the word "tornado" in forecasts. They were instead directed to refer to "severe local storms". This position on tornado forecasting would be shared by the U.S. Weather Bureau after its formation in 1890, fearing that tornado forecasts were insufficiently reliable and that such warnings would incite panic among the public. The side effect of this policy was that the lack of warning resulted in a steady increase in the number of tornado-related fatalities through the 1950s, with some events prior to 1948 having death tolls well over 100.
The Air Force began issuing severe weather forecasts relayed to Weather Bureau offices and emergency personnel in tornado-prone regions through the formation of the Severe Weather Warning Center in 1951, before the Bureau's contention that the USAF intruded on its responsibility to relay such forecasts led to the SWWC limiting the release of its tornado forecasts to military personnel; however, the move to prohibit the USAF from widespread releasing of tornado forecasts led to disapproval and heavy criticism from Oklahoma media outlets, given the agency's continued refusal to provide public tornado warnings. The Weather Bureau issued its first experimental public tornado forecast in March 1952, which proved inaccurate and was released too late to become widely available for public consumption; however, a forecast issued the following evening managed to predict an outbreak of tornadoes across most of the warned seven-state area.
Even after the U.S. Weather Bureau lifted their ban on tornado warnings, the Federal Communications Commission continued to ban television and radio outlets from broadcasting tornado warnings on-air for the same reasoning cited in the Bureau's abolished ban. Broadcast media followed this ban until 1954, when meteorologist Harry Volkman broadcast the first televised tornado warning over WKY-TV in Oklahoma City, due to his belief that the banning of tornado warnings over broadcast media cost lives. Through an alert issued by the USAF Severe Weather Warning Center, Volkman opted to interrupt regular programming to warn viewers of a reported tornado approaching the Oklahoma City area; although station management and U.S. Weather Bureau officials were displeased with his move, WKY-TV received numerous telephone calls and letters thanking Volkman for the warning.