ROCKFORD (WREX) — Severe weather season in Illinois generally lasts from April through June. While images of spinning tornadoes may dance in many people's minds, severe weather can come in a variety of forms.
The most obvious form of severe weather comes in the form of tornadoes. For some, the first tornado they see in life is found on-screen. I am one of those people, having first seen a tornado in "The Wizard of Oz." The weather-centric drama "Twister" solidified by choice to get into meteorology.
Tornadoes can be among the most powerful force on earth. The damage they can cause is nothing short of catastrophic in some instances. The United States has a long history of tornadoes. In no other region of the world do the ingredients necessary for tornado development come together so neatly than in the U.S. midsection.
Tornado Alley comprises the states of Texas, Oklahoma, Kansas, Nebraska, South Dakota, Iowa, Missouri, and eastern Colorado. In this region, warm and moist air is often found in the lower levels from the Gulf of Mexico. Thousands of feet above the surface, winds are pulling in warm and dry air from the Desert Southwest. Even further aloft, cold and dry air is pulled in from Canada. It is this combination of ingredients that primes the environment for tornado production.
A tornado is likely to be the most scary type of severe weather a person can go through in the nation's midsection, but it is far from the only type of severe weather.
It's obvious that most tornadoes in the Midwest come from severe thunderstorms, but not all severe thunderstorms produce tornadoes. In fact, luckily, a relatively small percentage of severe thunderstorms that impact the Stateline actually produce tornadoes.
Hail and strong winds are all possible when severe thunderstorm warnings are issues. In order for the National Weather Service to issue a severe thunderstorm warning, hail has to be at least 1" in diameter or wind gusts must be nearing 60 miles per hour. Severe thunderstorm warnings are not issued for frequent lightning! Nor are they issued when heavy rain is falling.
As thunderstorms dump rain on an area, flooding may become a concern. This threat can be confusing, especially because there are multiple types of warnings and watches for flooding. There can be flash flooding, but there can also be slowly rising flood waters. What's the difference and how does it impact how you seek shelter?
Flash flooding occurs when a heavy amount of rain falls at a time, resulting in water rises along low-lying or flood-prone areas. The danger flash flooding presents pertains to the fact that water is quick to rise. In a matter of just a few minutes, conditions can go from dry to covered in water quickly. Highly urbanized areas are also prone to flash flooding, as water often has fewer places to go.
Slower rising of flood waters is easier to communicate in a timely manner, but still very dangerous. According to the National Weather Service, flooding is "an overflow of water onto normally dry land." The definition is continued further explained as "the inundation of a normally dry area caused by rising water in an existing waterway." Flooding, as we often find during the spring months, can last for days or weeks at a time.