La Niná may have large impact on winter weather, expert says
BY BROOKS TAYLOR
Mt. Pleasant News
While humans have control over a lot of things, one thing they cannot control is the weather, and winter weather could be a factor for area farmers next spring when thoughts of planting come to mind.
Meteorologists say this winter could be a La Niná winter as opposed to last year’s El Ninó winter. Both terms are Spanish with the former meaning “the girl” and the latter “the boy.”
A La Niná winter occurs when ocean temperatures drop 3-5 degrees. Conversely, a similar increase in ocean temperatures create an El Ninó phenomenon.
Meteorologists still are not certain as to the La Niná or its strength, but will know soon. “It (La Niná) is still in the forming stages,” remarked Dave Cousins, a meteorologist with the National Weather Service in the Quad Cities. “That is why there is such a variability in the (winter) forecast.”
A La Niná becomes official when ocean temperatures are one-half degree below average for three straight months,” Cousins explained.
“Right now we are in a La Niná watch,” Cousins said. “There is a 70 percent chance of a La Niná forming and a 55 percent chance of it persisting through the winter. That is what we expect to occur, but we don’t know yet how strong it will be.”
The El Ninó, which impacted the Midwest’s winter last year, is gone, he remarked.
So, what does a La Niná winter mean? Cousins said generally it means colder than average winter temperatures while precipitation could go either way.
Virgil Schmitt, Iowa State University Extension agronomist, said that a La Niná could have an impact on ag land. “A La Niná usually means a more extreme winter. It is colder and dryer than normal with a deeper freeze.
“However, the big thing is whether or not the soil is wet when winter weather comes,” Schmitt continued. “If the soil is wet, it leads to compaction.”
The major factor, Schmitt said, about winter weather for farmers is the number of freeze/thaw cycles. “Freeze/thaw cycles tend to break up soil compaction, which is very good for row crops.
“A significant concern would be if it would get cold and stay cold until spring because then you would have just one freeze/thaw cycle, and the soil would not break up as usual.”
One thing in farmers’ favor this year is the abundance of subsoil moisture, the agronomist said. “Right now, the soils are holding all the water they can and that means a freeze/thaw cycle will create more action because there is more water.
“More water also keeps the freeze from going as deep because water is a heat conduit, much like a brick,” Schmitt continued. “Water stores a lot of heat.”
One of the reasons for the abundance of subsoil moisture, according to Schmitt, is the abundance of late-summer rain. “We’ve had three summers in a row that we’ve had a large amount of rain at the end of the summer. That leaves good subsoil moisture because not all of the subsoil moisture is used by the crop before harvest.”
Flipping the coin, Schmitt said the disadvantage of good subsoil moisture heading into winter is that if it is a wet spring, not only will there be a lot of water runoff but wet conditions could prevent farmers from planting their crops in due time.
As for now, Schmitt said those farmers antsy about applying anhydrous ammonia should wait until the soil temperature is a maximum of 50 degrees and falling regardless if they are or are not using a nitrogen stablilizer.
Cousins verified what area residents know — it has been a great fall weather-wise. Temperatures during the first seven days of November were 10 degrees above normal, October temperatures were four degrees above normal and September temps were 3.2 degrees above normal.
Meanwhile, September moisture was three-tenths of an inch below normal and October rainfall was seven-tenths of an inch below normal.
Cousins said that the first winter forecast, released in October, called for an equal chance of below- and above-normal precipitation and temperatures, which tells us little.
However, should the area be under the influence of a La Niná, meteorologists say winter temperatures would range from six to nine degrees below 2015-2016’s average. The average winter temperature (highs and lows combined) was 32.2 degrees for the area from Dec. 1, 2015 to Feb. 29, 2016, Cousins said. That’s 3.9 degrees above the area average of 28.3 degrees for that time span.
Rainfall last winter was 5.89 inches, or nine-tenths of an inch above normal and the Quad Cities received 11.3 inches of snow. Normal winter snowfall in the Quad Cities is 25.5 inches. Cousins said that his office does not have snowfall data for the Burlington area.
Another bummer for mild winter weather is that insects, like humans, love it, Schmitt said. “A mild winter is good for insects. In fact, if we have snow cover and then it gets cold, the snow will act as an insulator and keep things warm. Many times, a good snow cover will keep the soil temperature above 32 degrees despite what the air temperature may be.”
While the jury is still out on winter weather, Schmitt said there is one certainty. “There is plenty of moisture to get the crops off to a good start next spring.”