We’re all familiar with the idea of Tornado Alley and the tornadoes that occur across the continental United States.  Regions from the Great Plains all the way east across the Appalachians and beyond experience tornadoes annually; even areas along the West Coast including California and even Oregon and Washington regularly experience tornadoes.   What about areas of the United States outside of the lower-48?  Such as Alaska, Hawaii, and Puerto Rico?

Related: Monthly tornado averages by state and region

Using a combination of the Storm Prediction Center tornado database and the National Climatic Data Center (NCDC) storm events page it was possible to investigate the number of tornado events that have occurred in these areas from 1950-2012.

Alaska

Google Physical map of Alaska showing tornado events since 1950.  Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

Google Physical map of Alaska showing tornado events since 1950. Note: One tornado does not have coordinates so it is not shown on the map. Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

Out of all 50 states, Alaska is the state that has the lowest number of recorded tornadoes.  There have only been four recorded tornado events since 1950, the last of which occurred on August 25th, 2005.  All tornadoes have been rated at the F/EF0 level.  Referring to the map, the majority of the tornadoes have occurred in the southwestern part of the state, where the terrain is flatter and the climate is moderated and more maritime in nature due to proximity to the Gulf of Alaska.

Alaska is the largest state in the United States, with a land area of 570,380 square miles.  Considering it only has four confirmed tornadoes since 1950, this equates to a ratio of one tornado for every 142,595 square miles.  In comparison, Oklahoma currently boasts a ratio of one tornado for every 20 square miles!

Basically, Alaska is not a tornado state — it currently experiences one tornado roughly once every 15 years.

Puerto Rico

Google Physical map of Puerto Rico showing tornado events since 1950.  Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

Google Physical map of Puerto Rico showing tornado events since 1950. Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

Puerto Rico is a marginal region for tornado activity.  Characterized by steep and rugged terrain over the western and northwestern portion of the territory, most tornadoes occur on the west coast over flatter land where the easterly trade winds collide with the sea breeze.

There have been 23 tornado events since 1950, with the most recent one occurring fairly recently on September 13th, 2012.  Similar to Alaska, the recorded tornadoes over Puerto Rico have all been week, with only one attaining higher than F0/EF0 status.

Hawaii

Google Physical map of Hawaii showing tornado events since 1950.  Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

Google Physical map of Hawaii showing tornado events since 1950. Tornado data courtesy of the Storm Prediction Center. Map by Kathryn Prociv

When it comes to discussing U.S. regions outside of the continental United States, Hawaii is the “tornado alley” of them all.

There have been about 40 tornadoes since 1950, with the last tornado occurring on March 9th, 2012.  Like Alaska and Puerto Rico, the tornadoes have predominantly been F0/EF-0 in rank, but a handful of F2s have also struck several of the islands.  Referring to the map, most tornadoes occur on the island of Oahu (where Honolulu is located); one reason could be that Oahu holds the highest population of all the islands, and it is also the island with a National Weather Service WFO.

It is important to note the 41 tornado reports do not include waterspouts which don’t come ashore!  The National Climatic Data Center shows a record of 31 waterspout reports from 1996-2012 across the entire island chain, and again with most waterspout reports are from Honolulu.

Conclusion

Tornadoes do in fact occur in the states and territories of the United States outside of the continental and lower 48, but the number pales in comparison.  A single state in tornado alley can experience more tornadoes in one year (or even a day!) than Alaska, Hawaii, and Puerto Rico combined.

While it is important to note that one possible reason why the total tornado numbers are low is likely due to the sparse population in parts of these areas, it’s also likely that regardless of a low reporting rate these areas actually experience low tornado rates.

Additional research of tornado climatology for other United States territories outside of the lower 48 likewise yielded paltry results: neither American Samoa, nor Virgin Islands, nor Guam have any tornado reports to date.  (Although the British Virgin Islands has one tornado report!)

Bottom line: for those interested in studying the science behind tornadoes and witnessing this particular wonder of nature, stick to the continental United States!

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B.A. and M.S. at Virginia Tech in geography with an emphasis in geospatial technology and meteorology. Meteorologist and contributor for the Washington Post’s Capital Weather Gang. See full bio.
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6 Responses to U.S. tornadoes that occur outside the U.S. … the continental…

  1. Joel Bader says:

    Does for the tornadoes in Puerto Rico and Hawaii account for tornadoes spawned by hurricanes? I know that Puerto Rico is in a region for hurricanes and tropical storms as is Hawaii (indeed, Hawaii was hit by Hurricane Iniki in 1992).

  2. Kathryn says:

    Good question John! I cannot answer your question fully without additional research, but I would guess tropical storms/hurricanes definitely play a role for Puerto Rico, but am guessing less so for Hawaii. As you noted, Hawaii DOES experience tropical systems, but not nearly as often as they experience tornadoes on a yearly basis.

  3. Ashley says:

    Just wanted to say how much I enjoyed this article! Great job Kathryn! DOMINATE.

  4. Jim Dahlem says:

    Neat post. Now of course as usual I have questions! : )

    -I would think Alaska would obviously have more tornadoes than the 4 shown because of all the open land where it may never be noticed. Does the NWS track radar for hook echos or signs of rotation in areas that aren’t occupied? I would think that may be a waste of resources but didn’t know if they did track that on radar (If radar even exists over most of AK) and thus the 4 tornadoes may actually be representative.

    -Have you ever done a post of non-USA tornadic activity? I know this site is “US” tornadoes, but other than parts of Canada in the northern great plains, tornadoes are very rare outside of this country. Is there any database you know of that show where the few other tornadoes may actually occur?

    • Hi Jim! Always happy to hear from you!

      You and I are on the SAME page regarding Alaskan tornadoes. I’m sure several more tornadoes have occurred across the huge landscape of Alaska, but it is simply so rural and remote they were never seen and damage has never (and will never) be noticed. However, without sounding too dramatic I still don’t think the total number of Alaskan tornadoes is very high…

      A non-US tornado post would be neat. I actually did a lecture on that very topic when I taught my class at Virginia Tech. The US gets 75% of the world’s tornadoes. Canada comes in 2nd with 5%, and the other 20% is split between Russia, Bangladesh, Australia, and Argentina (among a few other localized spots across the world)!

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