As Tornado and Severe Weather Awareness Week continues in Wisconsin, we take a closer look at the forecasting factors that can help people know when the risk for these storms can take place.
Severe weather comes from thunderstorms, but not every thunderstorm is capable of creating severe weather.
“The three main ingredients are moisture, instability and lift,” says Tim Halbach, Warning Coordination Meteorologist at the National Weather Service office in Sullivan. The last ingredient needed is wind shear in the atmosphere that will make storms strong or severe. “Whether its a long ling of thunderstorms that produces those damaging winds and sometimes even some embedded tornadoes, or if it is the type of storm called a supercell thunderstorm which typically produces your long-track tornadoes.”
These factors allow each National Weather Service office to work in cooperation with the Storm Prediction Center in Norman, Oklahoma to determine when an area is under a threat for severe weather.
If conditions look favorable for a severe weather event to possibly occur in the near future, Halbach says they will do their part to let the public know. First it with messaging prior to the storms. “We’re putting it on our social media pages and putting in on our website, telling everybody this potential exists for the next day.”
Several hours before storms occur, the National Weather Service will issue the appropriate watch to continue the alert process. Halbach says there is a difference between a watch and a warning. “The watch means that the ingredients are there, but maybe those storms aren’t there yet. It’s kind of like a get ready. Storms are about to develop over the next few hours here. Some entities that need a little more heads up time to kind of prepare in case some warnings get issued.”
A warning will only get issued when one of two events occur:
- There is a confirmed severe weather event happening. That means winds are causing damage (gusting over 58 mph), hail is falling that is at least one-inch in diameter, or a tornado or funnel cloud has been spotted.
- Radar has indicated rotation within a storm or wind speeds and hail are estimated to be at severe level.
Overall, Halbach says their goal is simple. “People get as much heads up time as possible.”
Listen to the full interview with Tim Halbach regarding how severe weather threats are forecast, and how certain words may be added to warnings in order to properly describe the risk of severe weather that is occurring.