NORMAL, Ill. — This “era of extreme weather” patterns is expected to continue over the next several years, according to a meteorologist.

The latest example is the differences between last year’s heat and drought and this year’s milder temperatures and more precipitation.

“The difference is night and day comparing last year to this year — not only during the summer, but even what transpired during last spring, as well,” Mark Russo, Chesapeake Energy Corp. meteorologist, said at the Illinois Farm Bureau Commodities Conference.

He compared weather data collected throughout the central and eastern U.S. between last year and this year, as well as comparing it to the historical data since 1950.

“When we first ran these numbers, we were shocked. We knew last year was warm, but when you take a look at the most reliable data going back to 1950, we’ve never seen anything like this (year-to-year change),” he said.

“We’ve had some changes here and there, but to go from as warm as it was leading into last year’s drought (the warmest year on record) and then you have this year when we had the second coldest March and April dating back to 1950. 1996 was the last time we had anything that similar.”

Russo said this has been described as an era of extremes.

“We’re seeing lots of examples of extreme nature of weather, whether you’re talking localized extremes to macro extremes and extremes from one week to another,” he said. “We think this is something that’s going to continue for some time, as well, that era of extremes we’re in. We do not see that changing, at least as we go through the next several years.”

The National Oceanic and Atmospheric Administration has records dating back to 1895 tracking each state’s temperature and precipitation rates.

According to NOAA data, the first six months of 2013 were the wettest since 1895 in Illinois, Iowa, Wisconsin and Michigan and above normal in Indiana and Missouri.

“What just occurred, especially on the heels of last year’s drought, was a total turnaround in the situation here,” Russo said.

He also reviewed July temperatures and their relationship to corn yields from 1980 to 2010.

During a cooler July, one year had yields below trend, and nine years were above trend, while normal July temperatures, as with this year, resulted in one year’s yield below trend and 10 years above trend. During hot Julys over that period, eight years had yields below trend and three years above trend.

“Corn does not like heat very much, and the data here reflects that. If you factor in 2011 and 2012, it would add more below trend,” Russo said.

In looking at forecasts and potential weather trends, Russo said his group thinks “a little more out of the box when it comes to driving variables for weather patterns.”

“When you look at it from the market standpoint in the world of weather, a lot of focus gets turned to La Niña and El Niño-Southern Oscillation,” he said.

“I used to be a bigger believer in ENSO forcing a pattern, but after observing more years and doing more research on it, I don’t think that there’s much of a correlation here between the oceanic measure of El Niño and La Niña or your sea surface temperatures in the central and eastern Pacific Ocean versus other factors.

“Sea surface temperatures within that area have been pretty normal this year to date. Last year, we were in a La Niña with colder-than-normal water temperatures starting off the year, then it went neutral in the spring and actually there was an El Niño event (with warmer-than-normal water temperatures) during July, August and September.

“When you look at it from a sea surface temperature standpoint, you really don’t get that much in way of relationships between Corn Belt temperatures and precipitation. The correlations are stronger when you look at the atmospheric metric of El Niño and La Niña.”

The atmospheric metric includes tracking global winds up to the stratosphere.

“When the wind index is in a negative stage, that’s more of a La Niña climate. La Niña from an atmospheric standpoint tends to produce more heat and dryness across the middle of the country in areas of the central and eastern U.S.,” Russo said.

El Niño tends to produce wetter, cooler conditions.

“We started out the year with more of an El Niño base state. We think that’s one of the main factors why we had a wet, cold spring. That changed in late May, early June to a warmer, dryer La Niña,” Russo said. “We also think that’s one of the reasons why we had our big drought last year. We were strongly in a La Niña base state in the atmosphere globally.

“The La Niña is weaker this year than last year. In looking ahead, all indications point to neutrality with no signs of any real strong dips toward La Niña or for that matter El Niño over the next several weeks.”

Through the remainder of the growing season “and for that matter I’d even take that to subsequent growing seasons come up, expect this era of extreme and all this variability that you’re seeing right now to continue,” he said.

Commodity markets continue to be very weather-sensitive.

“That’s always the case this time of year, but probably a little bit more so after last year’s weather, and then also South American weather their past growing season and the overall supply and demand table,” Russo said.

“The crops remain ultra weather-sensitive and that will continue as crops mature and corn has seen everything already this season — cold, wet, hot dry.”

The trends in the atmospheric metric of El Niño need to be monitored closely.

“This neutral state results in better rainfall opportunities. Any sharp drop in the La Niña base state would increase the dryness risk, but we don’t see that here,” Russo said. “A sharp rise in the atmosphere ENSO into El Niño levels in September and October would increase the risk of a colder, wetter harvest.

“We’re not calling for an early freeze right now. When you get cold this early in August, then it tends to persist through August and early September.

“I guess I’d be a little more concerned if we were really warm right now and then you go into September and things turn really cold — I’d be more worried about an early freeze then versus now.

“But as variable as it is now, I wouldn’t be surprised that we do have some cold shots sometime during the September-October timeframe, that there will be something colder than normal, but I can’t predict any kind of time.

“The biggest risk would be if the El Niño really starts to take off, and that would be most concerning for a colder, wetter harvest.”