Sciency Thoughts: Dallas

Tuesday, 22 October 2019

Thousands left wthout electricity after tornado hits Dallas, Texas.

Around 140 000 people lost their electricity after a tornado hit in Dallas, Texas, on Sunday 20 October 2019. The storm touched down near Love Field Airport, then moved northeast through the city. The storm is known to have injured three people in the city and caused extensive damage to property, with weather monitoring radar systems detecting debris from the storm 6 km in the air, but no fatalities have been reported. One person has died in Arkansas after being hit by a falling tree due to high winds from a related weather system.

Tornado in Texas on 20 September 2019, seen from Rockwall, to the north of Dallas. AP.

Tornadoes are formed by winds within large thunder storms called super cells. Supercells are large masses of warm water-laden air formed by hot weather over the sea, when they encounter winds at high altitudes the air within them begins to rotate. The air pressure will drop within these zones of rotation, causing the air within them so rise, sucking the air beneath them up into the storm, this creates a zone of rotating rising air that appears to extend downwards as it grows; when it hits the ground it is called a tornado.

Tornadoes can occur anywhere in the world, but are most common, and most severe, in the area of the American mid-west known as 'Tornado Ally', running from Texas to Minnesota, which is fuelled by moist air currents from over the warm enclosed waters of the Gulf of Mexico interacting with cool fast moving jet stream winds from the Rocky Mountains. Many climatologists are concerned that rising temperatures over the Gulf of Mexico will lead to more frequent and more severe tornado events.

Simplified diagram of the air currents that contribute to tornado formation in Tornado Alley. Dan Craggs/Wikimedia Commons/NOAA.

Sewage spill leads to closure of Dallas Lake to leasure users.

Authorities in Dallas have closed the White Rock Lake, in the north of the city, to leisure users after a contractor accidentally ruptured a sewage main, leading to around 3.8 million litres of sewage entering the White Rock Creek, which feeds into the lake. The sewage has so far been prevented from entering the lake by a series of booms across the creek, but the lake has been closed to users as a precaution, and it is unclear how the sewage will be recovered.

Leisure boats sitting unused on White Rock Lake in Dallas following a sewage spill. CBS DFW.

As well as the obvious dangers to health presented by sewage, which is likely to contain a variety of Bacteria and other micro-organisms harmful to Human health, sewage provides a source of nutrients which can lead to eutrophication and the rapid growth of blooms of Algae, Bacteria or other micro-organisms, which absorb oxygen from the water leading Fish and other aquatic organisms to asphyxiate.