SPC Online SeverePlot features official NWS data of tornadoes (since 1950),
along with hail and damaging convective winds (since 1955). This website
replaces the legacy PC-based SeverePlot 2.0 program.
The data is derived from the Storm Data publication by
National Weather Service field offices, with careful review and processing
conducted by the
Climatic Data Center and the
Prediction Center. Finalized official data for an
entire year will typically be made available the following summer (i.e. 2009
available summer 2010). If final data is not yet available for the desired
date(s), preliminary unofficial storm reports can be accessed at:
Damage values are only available for events beginning in 1996. These losses do not include crop damage.
Damage rating scale is the
PLENGTH = Path length in miles.
PWIDTH = Path width in yards.
Convective/thunderstorm related winds only (does not include hurricane or
non-thunderstorm damage). Wind data includes both measured/estimated wind
gusts and wind damage without estimated wind speeds (a default wind query with a
min speed of 0 includes all such reports). Speed is in knots (50 kt/58 mph
and greater is considered severe).
Size is inches in diameter (0.75 inch or larger is severe).
- Testing in various web browsers is ongoing. Online SeverePlot is known to work with Mozilla FireFox versions 2-3 and Internet Explorer 6.0.
- Please allow up to 30 seconds for the requested data to display.
- Complex report queries encompassing a large number of reports over many years may timeout and not plot entirely. If so, please reduce the requested number of years etc.
- To save a graphical image of storm reports, right click on the map and select "Save Picture As" or "Save Image As" pending your web browser.