Make a Tornado

Weather Maps for Students:

Average Number of Tornadoes per Year: Most tornadoes happen in the “Tornado Alley” area of the United States; Oklahoma and Texas have more tornadoes than any other states. There are also many tornadoes in Florida, but these are often not as destructive as tornadoes in the Midwest.

Tornadoes by Season: More tornadoes happen during the spring & summer because these are the times with the warmest temperatures. We also see that there are many more tornadoes in the middle-eastern states than in the western United States.

Average Number of Thunderstorm Days per Year: There are more thunderstorm days in the southern states due to the abundance of warm, moist air. We can see a correlation in Florida between number of thunderstorms and frequency of tornadoes. However the map of most thunderstorms does not directly align with the map of highest occurrence of tornadoes for the rest of the country. This is because the presence of cool air at high altitudes coming off the Rocky Mountains and from the north, which creates consistent conditions for destructive tornadoes, is missing from the southern states.

Air Masses: The continental polar (cool/dry) air masses collides with the maritime tropical (warm/moist) air masses in the center of the United States, right in Tornado Alley! The movement of these air masses creates consistent conditions for storm fronts, where differing air masses collide. Also apparent from this map is why the coastal areas in the United States have so many storms; cooler air from the north meets warmer air from the tropics, combined with all the moisture air over the oceans is carrying.

 

Map of the Average Number of Tornadoes per Year in the United States

Average number of tornadoes per year (Credit: National Weather Service)

Map of tornadoes by season in the United States during the 1991-2010 NOAA Averaging Period

Tornadoes by season (Credit: www.ustornadoes.com)

Map of Average of Thunderstorm Days Per Year in the United States

Average number of thunderstorm days per year (Credit: National Weather Service)


Air masses with cold air mass in blue and warm air mass in red