Nope, the site is 100% free. However, donations as little as $1 are appreciated.
No, but there are some features that are only offered to logged in users.
Logged in users can:
- Post in the tornado forums
- Receive notification when users post comments, photos, or videos about a specifc tornado
- Export search results to .csv
All data comes from the Storm Prediction Center's (SPC) historical tornado data file, unless otherwise noted. Enhanced tornado path data for selected tornadoes comes from the National Climatic Data Center (NCDC). NCDC derived path data is shown when available.
The current data covers the period from 1950 through 2015.
- Short answer: The data is updated shortly after it is released by the Storm Prediction Center's (SPC).
- Not quite as short answer: The SPC generally releases data in the Spring for the prior year. So, tornado data for 2016 will be released sometime around March or April 2017. After it is released, it will be checked and processed into a format suitable for this site.
The historical tornado data on this site matches the original source information (SPC or NCDC data), except where noted. However, the Tornado History Project can not guarantee the accuracy of the underlying SPC or NCDC data. If you believe an error had been made in the original data (number of fatalities is incorrect, approximate tornado path is wrong, etc...), please post a comment on the appropriate tornado map/forum page.
The Tornado History Project generates approximate paths through separate historical archives provided by the Storm Prediction Center (SPC) and the National Climatic Data Center (NCDC). Paths generated from the NCDC data are typically more detailed, but neither archive gives exact path information. There are several reasons that paths may be inaccurate:
- Tornado touchdown and liftoff coordinates were recorded with only 2 digits of decimal precision (i.e. [33.72, -86.15] vs [33.71689, -86.15463]). As a consequence, the observed points on the map may be slightly off from actual. Note that beginning in 2009, up to 4 digits of decimal precision are given.
- Coordinates have not historically been calculated via GPS (Global Positioning System). Thus, tornado touchdown and liftoff coordinates should be considered as estimates only.
- Tornadoes may not have been in contact with the ground for the entire path as depicted on the map. Storm damage in any location depicted under the "path" should not be inferred.
- Although paths are drawn as straight lines between any two sets of coordinates, the tornado may have "zigzagged" in some way.
- Although paths are drawn as uniform thin lines on the map, it is likely that the tornado changed size over its lifetime. Damage in any location depicted under (or not under) the "path" should not be inferred.
Even with the above in mind, the data is the best available. If you see a path that is depicted incorrectly, please post a comment in the tornado forum indicating why you belive the path to be incorrect.
Paths generated from NCDC data are typically more detailed due to the way coordinates are listed in each archive:
- SPC database - A maximum of 2 coordinates (touchdown and liftoff) is given for each tornado, or each state segment of a tornado if it is a multi-state tornado. Thus the vast majority of paths are depicted as simple straight lines.
- NCDC database - Some tornadoes have mutliple sets of coordinates within any state, generally corresponding to entry and exit points by county. Thus, since more coordinates have been used to draw the path, the depicted path should be more accurate. Having said that, most tornadoes do not have additional path data in the NCDC archive. When they do, paths are drawn from the NCDC data.
Tornadoes are classified by the National Weather Service (NWS) according to their intensity and damage. Until 2007, the Fujita Scale (F) was used, but as of February 1, 2007, the Enhanced Fujita Scale (EF) was implemented. In both systems, the least damaging tornadoes are rated as F0, while the most damaging tornadoes are rated as F5. The number on the tornado icon simply represents the F Scale or EF Scale. In some cases tornadoes were not assigned F or EF number. In those cases, the tornado icon contains a "?" instead of a number.
So what about those colors? Well, they don't really mean anything except that all tornadoes of the same F or EF rating are of the same color. The specific colors themselves were just chosen to make the map look pretty.
There are many ways to help support the Tornado History Project.
- Contribute comments, tornado videos, or tornado photos - If you have experienced a tornado, consider sharing your memories, photos or videos of the event in the appropriate tornado forum. Or, if you know of another site that contains historical information, photos or videos of any specific tornado, please share that in the forum as well.
- Spread the word
- Use the "Share" button at the top of the page to email a link to your friends, or post a link at a social bookmarking site.
- If you have a web page or blog, consider linking to the Tornado History Project.
- Donate to the Tornado History Project - Consider donating to the Tornado History Project. Donations of all sizes are welcome (as low as $1) and help cover current costs and future development.