The number of tornadoes spawned by the serial derecho of December 15th continues to rise.
Rod Donavon, a meteorologist at the National Weather Service in Johnston, says that single storm spun off 63 verified tornadoes across the state, a one-day record of tornadoes in Iowa. Donavon adds that weather analysts have done a lot of work to verify the twisters, including checking out anywhere anybody reported damage, plus using high-resolution satellite data to help track down all of these tornadoes.
The NWS in LaCrosse says there were eight tornadoes total that day between Floyd, Chickasaw and Howard counties. The strongest were EF-1 twisters south of Marble Rock, over Marble Rock, North Washington, Rudd, the hardest hit with max wind speeds of 110 mph. EF-0 tornadoes were verified in Elma; Maple Leaf, Schley and Cresco.
The NWS in Des Moines says an EF-1 tornado also confirmed west of Greene that impacted Butler and Floyd counties. The strongest tornadoes were EF-2s with wind speeds reaching 115-120 mph. One tracked from Rowan in Wright County northeast through a part of Franklin County and into southwest Cerro Gordo County near Meservey. An EF-2 was also verified near Hansell in Franklin County.
The NWS has also confirmed three separate EF-1 twisters in Franklin County, two separate EF-0 tornadoes in Cerro Gordo County, and an EF-0 in Worth County.
Donovan says the second most one-day tornado total in Iowa was 35 on August 31st of 2014 and number three was 28 tornadoes on April 11th of 2001. He notes that, added together, those two days equal the one-day record of 63 tornadoes set on December 15th.