Thursday, May 23, 2013

The Oklahoma and Tri-State Tornados

The catastrophic tornado that descended on Moore, Oklahoma on May 20th 2013 was one of the most intense yet observed. Now officially rated as an EF 5 system, the highest on the tornado rating scale, it is believed to have generated surface winds of around 340 km/hr (210 mph).

The tornado as it moved to the southwest of Moore - image from Wikipedia Commons (click to enlarge)

The funnel was estimated to have been more than 2 km (1.3 miles) across and during its 50-minute life span travelled some 27 km (17 miles), including a rampage across the highly populated Moore area.

The tragic death toll is, at the time of writing, 24 and more than 200 people were injured.  The damage bill will run into billions of dollars.

Comparisons with the infamous Tri State tornado of March 18 1925 have already been made. In this event a twister ripped through some twenty sizeable townships, including Gorham, Murphysboro, De Soto, West Frankfort and Parrish, all in southern Illinois, causing utter destruction right across the area.

Eventually the tornado crossed the border into Indiana, where it inflicted massive damage to the townships of Griffin and Princeton, before finally abating, after the longest continuous rampage of any known twister.

Contemporary newspaper article following the Tri State tornado of 1925 - image from Wikipedia Commons (click to enlarge)

Subsequent investigation of the damage trail revealed a monstrous gouge of destruction across the countryside, some 353 km (219 miles) long and about 1.2 km (three quarters of a mile) wide. From existing photographic evidence of the damage produced, experts have rated the Tri State as an F5 tornado.

In all, 695 people died - still the record by far for an American tornado. Over 2000 were injured and some 15,000 homes demolished.

It is difficult, if not impossible, to directly compare these tragedies, but one statistic does stand out – the massive difference in the death toll. During the Tri State event there was no organised tornado warning system, no radar imagery and no satellite photographs available. This twister struck virtually without warning.

For the Oklahoma event, effective short-term warnings were issued by the US National Weather Service and these, without doubt, saved many lives. The great strides in public education about tornados, as conducted by the Weather Service and other Government agencies have also been most effective. And this, together with publically available information on the Internet, plus the training and skill of the National Weather Service meteorologists, helped prevent another Tri State scale death toll.

The logo of the National Weather Service of the United States - image from Wikipedia Commons (click to enlarge)

Unfortunately tornados are part of the climatology of the southern parts of the United States but improved forecasting skill, together with technology and public education is making a real difference. Our hearts go out to the people on Moore in Oklahoma who have been devastated by this event.

For an Australian example of the increased effectiveness of weather forecasting see: