Severe weather season is already here and we want you to be ready. The week of April 16-20 is Tornado and Severe Weather Awareness Week in Wisconsin. On Thursday April 19th there will be a statewide tornado drill. That starts at 1 pm when a mock tornado watch will be issued. It will be followed a mock tornado warning issued at 1:45 pm.
So let’s go into more detail about severe weather, starting with the definitions of watches and warnings. When conditions are favorable for severe weather to develop, a Watch is issued. This means meteorologists at the Storm Prediction Center in Norman, Oklahoma are looking at various forecasts and feel the threat for thunderstorms capable of producing severe weather are imminent sometime soon. If conditions are favorable for some of the storms to produce tornadoes, a TORNADO WATCH will be issued. Here we see an example of that from June 21, 2011 when much of the Chippewa Valley was under a tornado watch.
In this case, the tornado watch was in effect from 2:15 pm to 9:00 pm. All the counties within the red outline are within that watch and where the storms are expected to be. Just because it is labeled a tornado watch does NOT mean other types of severe weather aren’t possible. Storms without tornadoes can also occur within the watch box, with damaging winds and/or large hail possible.
Now in the case of a SEVERE THUNDERSTORM WATCH, the atmosphere is capable of producing severe storms, but storms producing tornadoes aren’t likely. Not to say a tornado isn’t possible, but in these cases strong winds and large hail are the most immanent threats. Here is an example of a Severe Thunderstorm Watch from June 26, 2010.
The severe thunderstorm watch was in effect from 7:45 pm to 3:00 am. All the counties within the blue outline are within that watch and where the storms are expected to be.
So what makes a storm severe? Basically 3 criteria need to be met.
#1) Can hail one inch or larger fall from the storm?
#2) Are winds stronger than 58 mph (50 knots) possible?
#3) Is the storm capable of producing a tornado?
A WARNING means that one or all of those criteria have been reached and severe weather is imminent or is already occurring. In the case of a Severe Thunderstorm Warning, National Weather Service meteorologists have identified a storm capable of producing winds in excess of 58 mph and/or hail larger than 1”. They do this by looking at Doppler Radar, reports from storm spotter reports, or other sources.
In a Tornado Warning, a storm capable of producing a tornado has been identified using Doppler Radar, or storm spotters have relayed a report of a storm capable or already with a tornado.
The watches and warning are then relayed to the public by local TV stations, like WEAU, radio stations, NOAA Weather Radios, websites, or even through phone by text message or other alerts.
Local public safety officials like police officers and emergency managers also receive the watches and warning. They will be on standby to activate local warning systems to alert the public and assist of any damage is reported.
Ready Wisconsin has put together a great website outlining a number of things to get you and your family ready for severe season. Here is the link to that website...READY WISCONSIN...
That link will get you home and school tornado safety tips, lightning safety, NOAA Weather Radio information, more detail on severe weather watches and warnings, a family disaster plan, severe weather statistics and more…