Spring of 2011 will go down in history as the season of tornadoes. Most Americans are aware of the devastation in Tuscaloosa, Alabama, Joplin, Missouri, Oklahoma City and many other locales, caused by this powerful weather phenomena. Tornadoes have been a part of life for many that reside in Tornado Alley and Dixie Alley. A tornado can occur anywhere, and it is a matter of life or death to be prepared for it. The earliest warning of possible tornado activity comes from the National Weather Service in the form of a tornado watch.
A tornado watch means that atmospheric conditions are favorable for severe thunderstorms to produce tornadoes. A watch does not mean that a tornado is already occuring, which is the purpose of a tornado warning. When a tornado watch is issued, the watch is also a severe thunderstorm watch. Do not be fooled by the bright, sunny skies when a tornado watch is issued. Those nice conditions can change very quickly.
The Storm Prediction Center is a branch of the National Weather Service that oversees the prediction of severe weather in the United States. On their website, they have maps outlining the risk areas and probabilities. The SPC issues the probability of severe weather three days in advance. As the event day gets closer, their guidance may prompt the issue of a tornado watch by the NWS, if necessary. With enough confidence, the National Weather Service will broadcast a tornado watch early that morning. But, given that atmospheric conditions could rapidly change, a watch may pop up just a few hours or less before the event occurs.
If you search your local weather on the National Weather Service website (insert your zip code into the city/state search box on the homepage and hit enter), your local weather page will come up. Any watches or warnings for your area will be posted as red links on the page. When you click those links, the details will be shown on another page. The tornado watch bulletin will contain important information such as when the expect the bad weather, details on the areas of concern, what to do to prepare, a short synopsis of why they believe tornadic activity could occur, and the time when the watch will end. If they say that the watch will end at 7pm, don't proceed to plan activities soon after, watches have been extended before, and for good reason.
The Weather Channel also has a scale they use to broadcast tornadic probabilities based on their forecast. The tornado conditions, or TOR:CON, is a scale from 1 to 10 with 10 being the highest chance of severe and tornadic weather occuring within 50 miles of a location. Their TOR:CON map will outline areas of concern related to tornadoes in red and areas of severe weather concern in orange.
While tornadoes and severe thunderstorms cause damage within a smaller area scale than say, hurricanes, the watches will outline a broad area. The reasoning is because the atmospheric conditions are favorable for it over that entire area and due to the fact that while the meteorologists know how tornadoes form, modern science still can not pinpoint exactly where a tornado will form or how long it will last. For extreme cases, the SPC and NWS will issue a PDS watch.
A Particularly Dangerous Situation, or PDS watch, is issued when meteorologists feel that a major tornado outbreak is likely. This watch is saved for only the most dire of situations and should never be taken lightly. The residents located within the entire area outlined in a PDS watch are encouraged to prepare for not only the possibility of many tornadoes, but also the high chance of strong to violent tornadoes forming that have the potential to last for many miles.
The point of the NWS posting tornado watches is to give people enough time to prepare and plan for any chance that a tornado could bear down on them later. The watches are posted on the NWS website, SPC website, The Weather Channel, Accuweather, and do broadcast over the television and NOAA weather radios. If your area is outlined in the watch, do not ignore it. Get your safe area or shelter ready and keep an eye on the radar throughout the day. Residents within the areas of highest risk, like Tornado Alley, would greatly benefit by purchasing a weather radio so that they can stay informed if the power goes out.