Climatologists don't have the ability to predict how extreme a trend will be. Jim Newman, the retired climatologist who contributed to the understanding of the El Nino and La Nina cycles, always said that a long-range forecaster was doing good to get the trend right – nobody can tell the extremes.
That bit of philosophy rang true last week. The National Weather Service in its long-term forecast is predicting somewhat cooler than normal temperatures for all but the northeast corner of Indiana continuing through February.
Cooler than normal can be anywhere from less than a degree on average to a few degrees lower than the normal average. A break-out week with 10 degree-below-normal will add to the colder than normal average, but doesn't mean the entire period will be anywhere near that cold.
Even when the prediction is cooler than normal and it holds true over a long period, there can be a week of warmer than normal weather thrown in. It's the overall trend that climatologists want to get a handle on.
Associate State Climatologist Ken Scheeringa says there still appears to be an El Nino, or warm water front, forming in the Pacific Ocean. However, he doesn't believe it will affect Indiana's winter. In the absence of a strong El Nino other forcing functions that can control weather may take over, he notes.
The same period through February is also expected to be drier than normal for all of Indiana. The degree of drier than normal varies somewhat, but it continues a trend that set up late last fall. Average precipitation totals are typically lower in the winter months than summer months over most of the state anyway.
Assuming the rest of the winter will be like last week would likely be a mistake, Scheeringa would predict. He's holding to the cooler than normal, drier than normal pattern, with drier than normal being the overriding, strongest factor over the past several months.