Was the F5 tornado in Moore, Oklahoma caused by global warming? Probably not. There hasn't been an increase in tornado activity in recent years.
F4 and F5 tornadoes are extremely rare:
Graphs and most images are from Jeff Masters' Wunderblog.
Yes, there is more warm, moist air to power the tornado because of climate change, but there is also less wind shear because of climate change. This is great for hurricane development, but a tornado needs that wind shear. A tornado needs air going at a different direction on the ground vs. in the upper atmosphere in order to create that rolling barrel of air that gets rotated 90 degrees to create the tornado. (See one of Weatherdude's diaries for an excellent description of tornado formation.)
So we have two changes in the climate that are at odds with each other. On the one hand we have warmer, wetter air that helps tornado formation, but on the other hand we have less wind shear that hurts tornado formation.
At this time, we do not have enough data to know which change will have the most effect on tornado formation in the future. One theory is that the distribution over time of strong tornadoes will be less homogeneous. That is, one year will have a lot of tornadoes and another year will have very few. Another change could be to shift the peak tornado activity from June into May.
I would like to share some multimedia that I found while researching the Moore tornado.
This is the well-known tornado from the air with the annoying closed captions covering part of the screen:
The camera amazes me. It is under the aircraft and must be somewhat autonomous to perform like that. The helicopter is in rough air and turning around to maintain position, but somehow the camera remains dead steady on the tornado.
The beginning of the tornado from fairly close up:
That one is better in high-rez.
The tornado track compared to the May 3rd tornado:
A more zoomed in track:
Notice that Briarwood Elementary School is near the edge of the track while Plaza Towers Elementary School is pretty close to dead center.
If you have 3-D glasses this image will give you an idea of how high the cloud tops were on that day. Save it to disk because the size is too large for this web site:
I don't believe that the geology in Oklahoma prohibits building basements or below ground shelters. It just costs a little more. We are Americans and we want everything as cheap as possible. We don't build one house at a time, we build them a dozen or a hundred at a time. Placing a wood frame house on a concrete slab is the cheapest way to do it.
It's the 21st century. Would could dig a hole in the ground if we wanted to. Waterproof floor and walls aren't a problem either.
Oklahoma County has 6,489 tornado shelters out of approximately 260,000 residential properties, according to the county's chief deputy assessor, Larry Stein. FEMA has invested in more tornado shelters for Oklahoma than in any other state.
I don't know the percentage of these shelters that were above ground in the tornado's path. I am curious about how well the above ground shelters did. (They are a recent development) I don't see any in the aerial photos and can't find any information in the news.
This is the type of shelter that I am talking about:
I assume that these rectangular safe rooms are then bolted onto the concrete slab. Will those bolts hold in the face of such wind loading?
Gratuitous weather photo from Orlando, Florida: