Tornado “weather” is an atmospheric condition typified by hot, humid days, southerly winds and darkening skies. Huge greenish-black thunderclouds usually appear an hour or two before tornadoes form. Rain, and frequently hail, precede and follow tornadoes. The time of greatest frequency is between 3:00 p.m. and 7:00 p.m. When close by, tornadoes sound like the roar of jet planes at takeoff.
A tornado is recognizable by the funnel-shaped cloud which appears from the southwest and travels at about 30 miles per hour. It spins rapidly (with whirling winds which exceed 300 miles per hour on the perimeter) and extends toward the earth from the base of a thundercloud. When it touches down, it is often 300 yards wide. Its destructive force results from the speed of its exterior winds and the vacuum in its interior which creates large differences in air pressure.
A severe thunderstorm watch means that damaging winds and hail are expected. It often precedes the issuance of a tornado watch.
A tornado watch means that conditions are favorable for the development of tornadoes. (WATCHES may be issued frequently. Except for keeping informed via radio or television, they do not require immediate action.)
A tornado warning requires immediate action, because a tornado has been sighted, either visually or on radar and is in our area!
When a tornado warning is issued by the National Weather Service, the St. Joseph County Civil Defense tornado warning system will activate the siren atop the North Dining Hall. For tornadoes, the siren issues a steady tone for three to five minutes. The siren will not issue an all clear. All clear signals are issued by the National Weather Service via radio and television announcements.
Specific tornado safety procedures vary from location to location, building to building, at the University, however, general safety precautions include:
- Taking shelter in the nearest substantial building immediately.
- Going to the basement or to an interior corridor.
- Avoiding windows, large rooms, auditoriums or gymnasiums.
Siren tests are made at 11:30 a.m. on the first Thursday of the month and consist of a one-minute steady tone, one minute of silence and a one-minute wailing tone.
These instructions and more detailed information on tornado and severe weather conditions is found in the front of the University Telephone Directory.