OKLAHOMA CITY — The remnants of Tropical Storm Isaac could deliver much-needed rain to drought-stricken eastern Oklahoma, although it also could bring flooding and an increased risk of tornadoes, forecasters said Monday.
Associate state climatologist Gary McManus said he believes the potential reward is worth the risk that comes with such a storm. All of Oklahoma is in a drought, with northeastern and western Oklahoma in the worst shape.
“That would certainly go a long way toward alleviating the impacts,” of the drought, McManus said. “We’re down eight to 10 to 15 inches in parts of the state.
“It’s like anything else when you deal with our (Oklahoma) weather, you take the good with the bad,” he added. “But really, I think, to get rid of the drought, it would be worth the risk.”
Meteorologist Pete Snyder said it’s too early to tell how much, if any, potential rainfall eastern Oklahoma could receive from the tropical system. How far west the storm tracks into the Gulf of Mexico and whether there are any lingering weather systems in the region could be factors.
“I don’t know that it would bring so much into the state of Oklahoma,” Snyder said. “It would be more likely to go to the east of us.”
Isaac remained a tropical storm over the Gulf of Mexico on Monday, but was expected to make landfall as a Category 1 Hurricane along the Gulf Coast on Tuesday, according to the National Hurricane Center. It would reach Oklahoma on Friday and perhaps mix with other instability and increase the chance of rain and storms.
Any tropical system that makes landfall can produce tornadoes, as its winds interact with weather systems already in the area and friction along the ground changes the air flow further, said Bill Bunting, of the Storm Prediction Center in Norman, Okla.
The strongest quadrant of a tropical storm is its northeastern corner, where winds roar from the southeast. If it approaches a pre-existing weather pattern that has winds from a different direction, tornadoes can develop quickly — often before a warning can be issued.
“Tropical cyclones are very efficient producers of wind shear,” said Bunting, the center’s operations branch chief. “Friction increases the vertical wind shear, and when combined with the instability you get a pretty good environment for the rapid spin-up of tornadoes.”
Even hundreds of miles inland a storm can produce a tornado, or several tornadoes, as it mixes with the air flow already in place, he said.
McManus noted that in August 2007, the remnants of Tropical Storm Erin spun in from the west, then stalled over central Oklahoma and dumped about a foot of rain on the region. Erin was blamed for the deaths of seven people in Oklahoma.
Oklahoma Department of Emergency Management spokeswoman Keli Cain said the agency has its eye on the storm and is prepared to respond as needed.
“We’ve just been watching that and monitoring that,” Cain said. “We work very closely with the National Weather Service, both in Norman and in Tulsa.”