It can't get much worse than July 2012 in the Midlands.
With virtually no rain falling, Omaha saw its driest July on record. Several other Nebraska and Iowa communities set records or nearly did, according to the National Weather Service.
Omaha received 0.01 of an inch of rain for the month. But it was even worse in Norfolk, Neb., and the Iowa towns of Audubon and Atlantic, where only a trace fell and zero rainfall was officially recorded.
Those four communities were the driest in the region.
Add near-record heat for the month — the past 12 months have been the warmest on record for Omaha — and it's clear why the worst drought in decades is intensifying.
“You couldn't pick a worse time of year for us to be dry,” said Barbara Mayes, a meteorologist for the National Weather Service office that serves Omaha, eastern Nebraska and western Iowa. “Right at the time when we expect to get the most rain, we're getting the least.”
The accumulating weather records are a sign that an unyielding dome of high pressure has parked itself over the Great Plains, shunting rains south into Texas and Mexico and north toward Canada. The resulting stagnation across the Plains has even prompted storm chasers to head to Canada for tornadoes.
Only an unusual weather system — but more likely, the change in seasons — will be enough to dislodge the dome of high pressure, said David Miskus, a meteorologist and drought specialist for the federal agency that does long-term forecasting. The agency, the Climate Prediction Center, has forecast that the drought will last into October.
Seasonal forecasts are dicey, but for now, the Climate Prediction Center says the odds favor a warmer-than-normal fall and winter for Nebraska and Iowa. As is typically the case for this part of the country, the odds lean in no particular direction for precipitation.
The arrival of fall should bring at least some relief for a couple of reasons, said Miskus and Dale Mohler, a senior meteorologist at AccuWeather Inc., The World-Herald's weather consultant.
Temperatures drop as cold air slides down from Canada, as the intensity of the sun's rays weaken and the days get shorter. And a seasonal shift in the jet stream should help shake loose the high-pressure system that has blocked moisture from the heart of the country.
“The odds are that the drought will ease a bit,” Mohler said. “But to totally break down? The odds are against that anytime soon.
“There's going to be some relief. I want people to know there will be some fall rain, but probably not consistent enough that we can say the drought has been completely broken.”
Unfortunately, as fall arrives, the Midlands will move toward the months that bring the least moisture. In Omaha, a normal December generates about one-fourth the moisture of a normal July.
Heavy winter storms will be needed to replenish the soil's moisture, because if the blocking pattern returns next summer, it will very quickly erase any gains made during the winter, Mohler said.
Miskus said an El Niño weather pattern appears to be brewing in the Pacific Ocean. If it develops according to normal fashion, it bodes well for winter precipitation. Typical El Niño winters are wetter than normal across the southern United States.
“That would be a bonus — we need any excess moisture we can get,” Miskus said. A stormy southern United States might steer storms into Nebraska and Iowa, he said.
No one is ruling out the possibility of a series of storms breaking the drought's stranglehold.
But Mohler and Miskus stressed that such storms would be highly unusual because the drought has become self-sustaining.
Hot weather dries out the soil, and dry soil heats up faster than wet soil. The superheated ground then intensifies the air temperature. Mohler estimated that the region's dry ground could be adding 5 to 6 degrees to the temperature.
The cycle continues beyond that, too.
With less moisture in the ground, cornfields expel less moisture into the air, and that results in lower humidity, which means less moisture to generate instability and storms. Storm systems have a hard time dumping widespread rain because the droplets can evaporate before they hit the ground.
Mohler said the most significant source of summer rains — thunderstorms — has been missing this year. About 60 percent of summer rains normally come from these large storm systems, he said.
Instead, spotty rains have fallen. Parts of Bellevue, for example, received slightly more rain than Omaha during the month of July. But nowhere did the Midlands receive a typical overnight storm capable of dousing an entire state with an inch or two of rain.
In the short term, there's a sliver of good news, Mohler said: The high-pressure system has shifted enough to the west and south that the edge now hovers above the Midlands. That will allow some storms to ride up along that edge and drop rain, he said.
“You're not completely out of the blocking pattern,” Mohler said, “but if you're on the edge, you can see rain from time to time.”
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