On May 19th, a tornado hit the north side of town in Edmond and points NE from there as well as later in Shawnee. On May 20th another tornado developed, this time in Newcastle and moved into S OKC and Moore before dissipating. The tornado took 24 lives and mangled property. Here is a brief recap of some posts I made back then as well a look at data today.
Back on May 20th, 2013 I posted this update at 2:15pm with the radar image above while storm chasing south of town. It would end up being the very last thing I could post due to lack of cell connection. I watched this storm evolve so quickly it made me sick that I couldn’t get out more warnings as it became tornadic. I wanted to warn more people but couldn’t. Not a good feeling…”Heads up OKC. These 3 developing storms will hit the city hard. NW Edmond should be okay but from E side of Edmond down along I-44 will have trouble. Tornadoes are a possibility. Stay alert! If by chance a northern storm anchors to the weak cold front on the NW side of town the added vorticity from that boundary will aid in tornado development.”
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The track of the tornado/damage path plotted by the NWS with the accompanying EF rating for damage found.
What’s left of a car after the Moore tornado and why you don’t want to be in one. Found at 149th/Penn pulled out of a creek.
Remember to take forecasts of tornadoes seriously but also remember that the large EF4/5s are very rare. Only about 5% of all tornadoes rank in this category. The majority are under EF3 strength. It takes a perfect set of conditions to form a large destructive tornado and in my experience they typically need a surface boundary to interact with that can be ingested into the updraft to take advantage of streamline vorticity gradients. Here is a detailed look at data from May 20th, 2013 that I put together right after the event. OU is looking at our TDWR data and is able to concur that the outflow boundary to the south from the decaying storm aided in convergence with the weak front as the added ingredient that made this storm go from bad to worse in a very short amount of time. A freak event for sure which is why they are rare.  https://www.youtube.com/watch?v=KMWNPBuWigk
So don’t listen to talk of “May 3rd or May 20th” all over again when we are days out from an event. This meso/micro scale condition is only detectable hours before an event and a storm has to actually form in the area in question. Nowcasting is how you will know. That said, an environment (different from this one) with very strong speed and directional shear (which this one did not have) typically does favor stronger tornadoes in general and can be forecasted 24 hours out before an event. Still though, I caution using certain terminology without understanding how sensitive those that experienced a tragic event like this can be.
So did tornado alley move this year? We’ve only had 5 so far. The answer is no. Depending on time of year there are different areas that see tornadoes and the most general location is E side of the Rockies to the deep South and points in-between as shown the above map. This link shows the number of tornadoes for any given year dating back to 1950 across OK. http://www.srh.noaa.gov/oun/?n=tornadodata-ok-monthlyannual
Regarding the year thus far as a whole across the entire US, tornado production is extremely low (black line in the graph above) and may end up being lower than last year when we saw less than 1,000 tornadoes. So when you hear that every year it’s going to get worse and we’ll get more stronger and more deadly storms due to global warming and climate change, just picture this graph in your head and say wait a minute, that’s clearly not true and not what the data says. Also remember that each year compared to years past more and more tornadoes are seen and reported than ever before with the A) increased population B) social media/smartphones C) boom in storm chaser numbers desperate for action.
So what this should mean is that years/decades past the number should actually be higher than reported/recorded and that will be more comparable to use with today. Now if the numbers today shows an even lower number than average then the pendulum has swung to less deadly storms not more and means maybe this climate change is a good thing after all!
