Extremely hot for this period across most of the U.S.

Extremely hot for this period across most of the U.S., where the latest pulse of heat from the south is breaking December heat records, more to come on that.

The pulse of heat from the tropics is very intense.Some places east of the Rockies are recording temperature values 15-20°C (20-35°F) above seasonal average.The unfortunate combination with strong upper-level winds and high instability throughout the atmosphere caused a severe tornado outbreak which ravaged parts of the South and Midwest Friday night, devastating entire towns and killing several people.A particularly severe setup for December fuelled by insane warmth & moisture transport under a vigorous short-wave trough.

The storms marched across Arkansas, Missouri, Tennessee, Kentucky and Illinois, ripping homes off their foundations and tossing cars like toys.A path of damage more than 100 miles long from Arkansas into Kentucky may have been caused by a single tornado that might have remained on the ground for hours.The tornado outbreak was potentially historic in track length: 250 miles is eye-watering.Most of it’s life cycle had an extremely violent tornado. Radar suggests debris was lofted over 30,000 feet, hundreds of miles away from its origin, from Arkansas to Kentucky.