How we got here: 1884 to present

The timeline

1. 1884John P. Finley of the Army Signal Corps runs experimental tornado forecasts and publishes forecast rules, in the year of the 19 February Enigma outbreak.
2. 1885–1887The word "tornado" is barred from official forecasts. The Weather Bureau keeps the ban after taking the service over in 1890, on the argument that naming the hazard would cause panic.
3. 1938The word is permitted again, in warnings rather than in routine forecasts. Half a century of silence, and a public tornado forecast programme still fourteen years away.
4. 25 Mar 1948Fawbush and Miller at Tinker AFB issue the first successful tornado forecast, five days after a tornado struck the base.
5. 1952The Weather Bureau stands up a severe weather unit in Washington in March, made permanent as the Severe Weather Unit on 21 May. Renamed SELS, the Severe Local Storms service, in June 1953, it is the direct ancestor of the National Severe Storms Forecast Center and then SPCStorm Prediction CenterThe national office in Norman, Oklahoma that issues severe weather outlooks, mesoscale discussions and watches. It does not issue warnings..
6. 9 Apr 1953The first documented tornadic hook echoA hook-shaped appendage on the reflectivity image, wrapped around the back of a supercell. One of the oldest radar clues that a storm is rotating., filmed by Don Staggs on the Illinois State Water Survey radar at Willard Airport, north of Champaign.
7. 11 Apr 1965The Palm Sunday outbreak. The survey afterwards finds the public could not tell a "tornado forecast" from a warning, and that for many the message never arrived at all.
8. 1966"Tornado forecast" becomes "tornado watchConditions are favourable for severe weather over a broad area for the next several hours. Issued by SPC. It means be ready, not take cover.". Warning practice is tightened, and sirens and spotter networks expand.
9. late 1960s–70sSKYWARNThe National Weather Service's own volunteer spotter programme, formalised in the 1960s, which supplies the ground truth behind warnings. Training is run by local forecast offices, so only a forecast office can make somebody SKYWARN-trained. takes shape. Its impetus and its name come out of Palm Sunday, and the national programme is in place by the early 1970s; organised spotting itself is older, going back to wartime and to local networks in the 1950s.
10. 3–4 Apr 1974The Super Outbreak.
11. 1991–1997NEXRADNext Generation Weather RadarThe programme that developed and deployed the radar network in the 1990s; WSR-88D is the radar itself. The two names are used almost interchangeably. deployment. Roughly 160 WSR-88DWeather Surveillance Radar, 1988, DopplerThe doppler weather radar the National Weather Service runs, roughly 160 of them across the country. When somebody says "the radar", this is the one they mean. radars, counting the contiguous states, Alaska, Hawaii, the territories and Defense Department sites.
12. 1 Oct 2007Storm-based polygonThe shape a warning is drawn on, replacing whole-county warnings in 2007. Being inside the shape is what matters, not which county you are in. warnings replace county-based warnings, for tornado, severe thunderstorm, flash floodFlooding that begins within about six hours of whatever caused it, counted from the causative event rather than from when anyone noticed the water. The cause is usually intense rainfall, but a dam failure, a levee failure or an ice jam qualifies and can do it on a clear day. and marine products.
13. 22 May 2011Joplin. The NWS Central Region Service Assessment, published that July, documents how people actually responded to the warnings they received.
14. 31 May 2013El Reno. The first documented storm-chaser fatalities: Tim Samaras, Paul Samaras and Carl Young, and Richard Henderson. It is the reason spotter safety gets its own module later in this course.
15. 2013The dual-polarizationA radar upgrade that sends pulses both horizontally and vertically, so the returns say something about the shape of what they hit. It is what lets radar recognise lofted debris. upgrade, rolling across the network since 2010, completes. It makes the Tornado Debris Signature an operational confirmation tool.

What the sequence shows

Two patterns run down that list. The first is that capability and permission moved separately. Finley was publishing tornado forecast rules in 1884; the word was barred from forecasts the following year and stayed out of them for half a century. The objection was that naming the hazard would cause panic, not that the forecasts were wrong. That argument still appears whenever a warning is held back over how people might react.

The second is that each technology narrowed the question rather than answering it. Radar told forecasters where to look. Polygon warnings shrank the warned area from a county to a shape. Dual-pol added debris aloft. None of them closed the gap this course is about: whether something is happening at the ground, right now, where people live. Each improvement made the remaining human observation more specific, not less necessary.