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Moore, Oklahoma Tornado & Enhanced Risk of Large Violent Tornadoes Again Today

21 May 2013, 11:31 am

Our Worst Fear Confirmed: A Violent (Urban) Tornado. The tornado that formed west of Moore, Oklahoma yesterday went from EF-1 to EF-4 strength within 10-15 minutes, responding to favorable conditions aloft (powerful wind shear coupled with an explosively unstable atmosphere). Tornado Watches were posted roughly 2 hours ahead of time, Tornado Warnings issued by the OKC NWS at least 30 minutes in advance. The problem? If you don’t have a basement or underground shelter the odds of surviving a direct hit from an EF-4 are small – even well constructed brick and mortar homes can be scraped down to foundation with an EF-4’s 180-200 mph winds.* 30 square miles impacted by moderate to extensive tornado damage.* This may top Joplin as the most expensive tornado in U.S. history. The May, 2011 Joplin tornado came in at $2.8 billion. I expect the 2013 Moore tornado to be comparable, probably $2-3 billion in total damage. There’s a good chance this will be America’s most expensive tornado on record.

Moore Damage Path. Yesterday’s mile-wide path is in green, the 1999 EF-5 path is in red, the 2003 tornado in blue. KFOR.com has a good interactive map here.

Close-Up Of Damage Path. Again, the green-shaded area shows yesterday’s track, a wider path than 1999 and 2003. Thousands of homes and businesses were impacted. Fewer than 1 in 10 Oklahomans have basements or storm shelters – bedrock makes it costly to excavate. Some have storm shelters, steel and concrete-reinforced closets and garages, but an EF-4 can be unsurvivable if you can’t get below grade, below ground.

 

Ground Zero. Here is an aerial map with path superimposed, showing where some of the most destructive (and deadly) winds hit, including Plaza Towers Elementary School, where loss of life was high.

Plaza Towers Elementary School. The before/after imagery is stark. This tornado will reignite the debate over school safety and the need for reinforced shelters in all public buildings.

Moore Medical Center. Damage is significant at Moore Medical Center; most operations have been shifted to other nearby medical facilities.

War Zone. As meteorologists we’re trained to think clinically, like doctors. Look at the data, evaluate the models, make a prediction. Leave emotion out of the mix. But you can’t look at these images (as a parent, as a human being) without being heartbroken. The damage is consistent with an EF-4 or EF-5 tornado.
More Imagery. Here is a before/after comparison of homes in a neighborhood east of South Eastern Avenue.* before the tornado hit several Oklahoma City TV meteorologists encouraged people in the direct path of this tornado to “drive away”. The reality: if an EF-4 strength tornado is approaching and you don’t have a basement or shelter your odds of survival are small. Statistically it’s better to get into your vehicle and try to outrun the tornado. The problem: as good as Doppler radar is it can be difficult estimating the intensity of a tornado, even 10-15 minutes in advance. We can see rotation, even a hook echo, but is it an EF-1 or a monster EF-5? Unlike hurricanes, where we can see satellite imagery and estimate strength, tornadoes are much more difficult to predict in advance: track and ultimate intensity.* there is no evidence that we’re seeing more EF-4 or EF-5 tornadoes, which comprise less than 1-2% of ALL tornadoes that strike the USA. A warmer atmosphere increases instability and buoyancy, but wind shear in a warming world should decrease over time. More research is needed, but we can’t (yet) connect the dots and claim that there is causal connection.


Today’s Risk Areas. The greatest potential for large, violent tornadoes comes from Dallas and Arlington to Shreveport, Texarkana and the southern suburbs of Little Rock. Yesterday Moore, Oklahoma was (near) the moderate risk, so it’s worth repeating that having a moderate footprint within 50-200 miles should be a tip-off to staff that the risk of large, destructive tornadoes is elevated.

Wednesday Risk. No moderate threat tomorrow, a slight risk of storms capable of hail and damaging straight-line winds from Detroit, Columbus and Cleveland to Pittsburg, State College, Buffalo and Rochester. An isolated tornado can’t be ruled out in and near this region tomorrow, but probably not the scope and severity of the tornadoes that have struck the Southern Plains in recent days.

Summary: It’s our worst fear as meteorologists: a large (urban) tornado. One glaring problem: “tornado fatigue”. As a nation we are still issuing too many tornado warnings (at least that’s the consensus among most private meteorologists I know). Nobody wants to miss a tornado – that’s the cardinal sin, so NWS issues warnings on just about every rotating thunderstorm they find on Doppler. The FAR or false alarm rate is still hovering near 70%. Stated differently, 7 in 10 tornado warnings produce NO tornado. This leads to apathy (“they’re crying wolf!”) and when the big tornado does materalize, when our worst fears are realized, many residents simply aren’t ready to take the measures necessary to protect their lives.In a hurricane you have days to prepare; a tornado: 5-30 minutes. The average lead time, nationally, is 13-15 minutes. Last year I proposed new terminnology, leveraging “Alerts” (for rotation based storms) and “Tornado Emergencies” (for confirmed tornadoes on the ground moving into urban areas). This is a reflection of land-use trends and suburban sprawl. Tornadoes that would have hit farmland 10-30 years ago are now hitting subdivisions. As metropolitan areas expand the probability of a direct strike from major tornadoes goes up steadily over time. Last year I wrote an article for Huffington Post, recounting a severe storm conference, where a well-respected structural engineer/meteorologist predicted that, within our lifetime, a single U.S. tornado will hit an urban area, even a downtown, with over 1,000 fatalities from a single twister. Yesterday was a reminder (to me) that his prediction may not be as far-fetched as it sounds. It’s land-use, statistics and probabilities, another unpleasant symptom of expanding metropolitan areas.

I had the chance to  talk with MSNBC’s Chris Hayes yesterday about the Moore Tornado.  You can click below to watch that interview.

 

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Stay alert, especially those in Texas, Arkansas and Louisiana. Today should be the last day of large, extra-violent EF-3+ tornadoes. The threat diminishes tomorrow, shifting into the northeastern USA with mostly hail and straight-line winds expected. We’ll keep you posted.

Paul Douglas – Alerts Broadcaster

Alerts Broadcaster provides severe weather and natural hazard intelligence to businesses worldwide through Alerts, Briefings, and Business Continuity Consultation.  Alerts Broadcaster meteorologists are working 24×7 to provide analysis and perspective that is crucial to your company’s severe weather response.

 

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