page_title: Tornado watch
hierarchical_section_title: Tornado watch
caption_attribution_description: English: Tornado watch 232 from the year 2007, issued during the May 2007 tornado outbreak
context_page_description: A tornado watch is an alert issued by national weather forecasting agencies when weather conditions are favorable for the development of severe thunderstorms that are capable of producing tornadoes. A tornado watch therefore implies that it is also a severe thunderstorm watch. A tornado watch must not be confused with a tornado warning. In most cases, the potential exists for large hail and/or damaging winds in addition to tornadoes.
  A watch does not mean that the severe weather is actually occurring, only that atmospheric conditions have created a significant risk for it. If severe weather actually does occur, a tornado warning or severe thunderstorm warning would then be issued. Note that a 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.
  In the United States, the Storm Prediction Center – a national guidance center of the National Weather Service – issues watches for areas likely to produce tornadoes and severe thunderstorms.
context_section_description: A tornado watch (SAME code: TOA) is an alert issued by national weather forecasting  agencies when weather conditions are favorable for the development of severe thunderstorms that are capable of producing tornadoes. A tornado watch therefore implies that it is also a severe thunderstorm watch. A tornado watch must not be confused with a tornado warning. In most cases, the potential exists for large hail and/or damaging winds in addition to tornadoes.
  A watch does not mean that the severe weather is actually occurring, only that atmospheric conditions have created a significant risk for it. If severe weather actually does occur, a tornado warning or severe thunderstorm warning would then be issued. Note that a watch is not required for a warning to be issued; tornado warnings are occasionally issued when a tornado watch is not active (i.e. when a severe thunderstorm watch is active, or when no watches are in effect), if a severe thunderstorm develops and has a confirmed tornado or strong rotation.
  In the United States, the Storm Prediction Center – a national guidance center of the National Weather Service (NWS) – issues watches for areas likely to produce tornadoes and severe thunderstorms. The watch boxes (or weather watches, WWs) are usually outlined in the format of x miles north and south, or east and west, or either side of a line from y miles direction of city, state, to z miles another direction of another city, state. For example: "50 miles either side of a line from 10 miles northeast of Columbia, South Carolina to 15 miles south-southwest of Montgomery, Alabama" ("Either side" means perpendicular to the center line). In addition, a list of all counties included in its area of responsibility is now issued by each NWS forecast office for each watch.
  In the event that a tornado watch is likely to lead to a major tornado outbreak along with possible destructive winds and hail, enhanced wording with the words Particularly Dangerous Situation (PDS) can be added to the watch; this is occasionally issued when atmospheric conditions are deemed sufficient to breed development of severe thunderstorms that are capable of producing significant tornadoes (either from supercells that develop strong, low-level rotation under typical tornadogenesis during the storm's maturation stage, or by thunderstorms that initiate mesocyclone maturation during their early development through a combination of sufficient wind shear and very high convective available potential energy (CAPE) values). Occasionally, a tornado watch may replace a severe thunderstorm watch (or a portion of one) should conditions that were originally forecast to be conducive for non-tornadic severe thunderstorms change to allow possible tornado formation.
  In Canada, the criteria used to issue a tornado watch are the same and watches are issued by regional offices of the Meteorological Service of Canada of Environment Canada in Vancouver, Edmonton, Toronto, Montreal and Halifax, on a county or regional basis.
  The term "red box" refers to the assigned coloring used for watch box outlines used in Storm Prediction Center and National Weather Service products; television stations typically assign other colors (colors used may vary, but very seldom if ever red, which is usually reserved for identifying tornado warnings; yellow is the most commonly used to denote them) to highlight tornado watches in severe weather advisory displays.
caption: An example of a tornado watch for parts of Kansas and Nebraska, issued by the Storm Prediction Center on May 5, 2007.
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