Click on any county to see information about tornado activity in that county, anc click on any tornado symbol to see information about that tornado. If you click on a tornado, the county data will appear initially, but in the upper-right corner of the popup you will see "1 of 2" (or more than 2 if there are nearby tornadoes). Click on the arrows to cycle through the different features.
A tornado touchdown is defined as the location where a funnel cloud first makes contact with the surface
of the earth, officially confirming that a tornado has occured.
There are two main regions in Pennsylvania where tornado touchdown density is high. The Appalachian Mountains (Pennsylvania's Ridge and Valley physographic province) lie between these two areas, and often serve to break up the low-level circulations needed for tornado formation. As you zoom around the map above, you can clearly see this trend.
The below table details tornado touchdown information since 2004 for both Pennsylvania and the nation as a whole.
|PA % of U.S. Total||1.37||0.90||0.62||0.55||0.23||0.54||0.98|