Florida Prescribed Fire Had Unexpected Drop In RH

According to TampaBay.com, the prescribed fire in Florida that escaped and may have added smoke to existing fog, contributing to Wednesday's 50+ vehicle pileup, experienced an unexpected 30% drop in relative humidity. A spokesman said the minimum RH was forecasted to be 60%, but it dropped to 30% in the morning an hour after they started the Rx burn.

"A weather forecast from the forestry staff showed that the humidity would not drop below 60 percent all day, a crucial factor in determining whether to proceed with a burn. If humidity dropped to 30 percent or below, the Division of Forestry would have denied the permit.

A form that Burger filled out to document the controlled burn showed that the humidity measured 63 percent at 10 a.m. on Tuesday, so he and a crew of five other employees started the burn at 10:15 a.m. They expected to be finished by noon.

"They do a lot of prescribed burning, and they do a good job at it," said Department of Agriculture spokesman Terry McElroy. "But something apparently went awry."

To the crew's dismay, within an hour after they started the fire, the humidity abruptly dropped to 30 percent, Morse said. That wasn't part of the forecast, he said."