Tornado Alley in the United States: Guest Post 3

Spatial Mapping of the Tornado Alley with Respect to Tornado Records of 2000-2010 for the Continental United States :

Parker Capps, 2011 Student, B.S.C.E.
Nathan Mikell, 2011 Student, B.S.C.E.

Nathan Mikell’s geospatial project report, May 2011

The objective of my project was to analyze all recorded tornado events from 2000 till May 25, 2011 to find out my spatial map results coincide with the NOAA’s map of Tornado Alley. The reason I chose this topic research was that I wanted to look at more recent tornado events. After living in the south for so long I remember looking at a map of Tornado Alley, and always thinking is this really accurate. When the opportunity of this project came about and being given the tools of spatial analysis and training I thought that the topic chosen was a valid one.

The Enhanced Fujita (EF) tornado scale ranks tornados on a scale of EF0 to EF5. Weak tornadoes are considered EF0 to EF1. Strong tornadoes are considered EF2-EF4. Killer tornadoes are considered anything EF3 and above. Also killer tornadoes cause more than 95% of all tornado fatalities. In 2009 weak tornados struck 91%, stronger tornados 9%, and no tornados in the last 2 categories of EF4 and EF5. Texas and Kansas have the ability of producing easily over a hundred tornadoes per year. However, most of the tornadoes that these states produce are considered weak tornadoes. On the other hand the EF5 that hit Joplin, Missouri in April 2011 and killed 125 people r, and there was the EF5 that hit Tuscaloosa, Alabama and traveled up through Alabama and went to Birmingham. On that day over 250 fatalities occurred. So when I did the spatial map, I used the ratio of number of fatalities by number of killer tornadoes that was my thought process.

Statewide Tornados since 2000
Tornado Damage Costs ($100,000), 2000-2010

Once all the data used for the year of 2011 was obtained only from 5 tornado outbreaks on: January 1, April 4-5, April 14-16, April 25-28, May22-25. For the 2011 data I used Wikipedia as my source because they had the most recent and largest amount of data on very recent storms. The reason that only these tornadoes were used in the research is they were the best documented events for this year. I used Excel spreadsheet to process the data and the GeoMedia Prosoftware to produce several spatial maps showing fatalities and economic loss by state in the affected region. Once all the compiled data was analyzed andgeospatial maps were created it seemed that NOAA’s Tornado Alley needed to be revised. This conclusion came from the fact that when looking at all the maps, a trend could be seen that some of the same states kept reoccurring. Not only did those states just reoccur but they were always near or at the top of the list of those specific counts.

From what I saw in the data there was a three to four year cycle going on. Where for three to four years activity would be increasing and then fall down drastically, and then start climbing back up to high numbers in the following three to four years.

Mikell's Proposed Tornado Alley Map of south and southeastern states

So the main results I drew from my data as it can be seen on the thematic maps is that when a violent tornado lands in the east it is more likely to cause more fatalities than if one were to hit in the west.

Top 5 states with most damage costs are: Mississippi, Iowa, Missouri, Texas, Tennessee.

Dr. Uddin’s note: Nathan’s topic was timely in May 2011 for his analysis of historical tornado data. I recommend that Nathan Mikell’s proposed Tornado Alley map should be considered by local news media and state emergency management agencies in the region.

During the middle of my geospatial course we heard about the devastating super tornado outbreak from Texas and Oklahoma through Arkansas, Mississippi, and Alabama. I heard the occurrences of multivortex tornadoes.

To benefit the readers and my blog followers, I am providing more info from the National Climatic Data Center.


Tornado Alley Map from NCDC-NOAA

According to the National Climatic Center of NOAA:

  • Tornado Alley is a nickname given to an area in the southern plains of the central U.S. that consistently experiences a high frequency of tornadoes each year. Tornadoes in this region typically happen in late Spring and occasionally the early fall. The Gulf Coast area has a separate tornado maximum nicknamed “Dixie Alley” with a relatively high frequency of tornadoes occurring in the late fall (October through December).”
  • Strong to violent tornadoes (those of EF3 or stronger on the Enhanced Fujita Tornado Damage Intensity Scale), are relatively rare, and do not typically occur outside the United States. Although the boundaries of Tornado Alley are debatable (depending on which criteria you use – frequency, intensity, or events per unit area), the region from central Texas, northward to northern Iowa, and from central Kansas and Nebraska east to western Ohio is often collectively known as Tornado Alley.” 
  • Overall, most tornadoes (around 77%) in the U.S. are considered weak (EF0 or EF1) and about 95% of all U.S. tornadoes are below EF3 intensity. The remaining small percentage of tornadoes are categorized as violent (EF3 and above). Of these violent twisters, only a few (0.1% of all tornadoes) acheive EF5 status, with estimated winds over 200 mph and nearly complete destruction. However, given that on average over 1000 tornadoes hit the U.S. each year, that means that 20 can be expected to be violent and possibly one might be incredible (EF5).”

More info is available from the National Climatic Data Center.


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