Emergency Preparedness
Tornado
Tornadoes are violently rotating columns of air with circulation that reaches the ground. Tornadoes usually start as a funnel cloud and are accompanied by a loud, roaring noise. Tornadoes:
Are the most destructive of all the atmospheric phenomena with wind speeds up to 318 mph.
Often strike with little or no advanced warning.
Are extremely dangerous. One supercell storm can produce a series of tornadoes along the same general line. Tornado Awareness: Tornadoes can occur at any time of the year in the United States.
In southern states, peak tornado occurrence is March through May, while peak months in northern states are June through August, with secondary tornado maximum occurrences in September through November.
Tornadoes occur at all hours of the day and night but are most likely to occur between 3 and 9 p.m.
Typically tornadoes move from southwest to northeast, but they have been known to move in any direction.
The average forward speed of a tornado is 30 mph, but this may vary from nearly stationary to 70 mph.
Tornado Danger Signs: Tornadoes may develop from thunderstorms when warm, moist air is in advance of eastward-moving cold fronts. Watch for skies that turn suddenly dark and greenish (a phenomenon caused by hail) and with increasing wind speeds, and keep a particular lookout for the formation of funnel clouds.
Large Hail: Tornadoes are spawned from powerful thunderstorms that often produce large hail.
Calm before the Storm: Often just prior to tornado touchdowns, the winds may die down and the air may become very still; clear, sunlit skies are not uncommon behind a tornado.
Clouds of Debris: Approaching debris clouds can mark a tornado’s location, even if a funnel is not visible.
Funnel Clouds: A visible rotating extension of the cloud base is a sign that a tornado may develop. Tornadoes are evident when one or more clouds turn a greenish color and a dark funnel descends.
Roaring Noise: High winds can cause a roaring sound often compared with a passing freight train. Tornado Scales: The Enhanced Fujita Scale (EF Scale) rates the strength of tornadoes with intensity estimates through after-the-fact examination of the damage they produced using knowledge of the wind forces needed to damage or destroy various buildings and their component parts to estimate wind speeds.
*Source: NOAA http://www.spc.noaa.gov/faq/tornado/ef-scale.html
Virginia Cooperative Extension has many resources to help before, during and after emergency situations. Whether the need is flood clean-up or financial considerations, Extension offers valuable research-based information to support communities preparing and recovering from disasters. Please explore our website to learn which program or Extension Specialist may be able to best assist you, or contact your local extension office.