Forecast for October, Fall, and Winter – Warmer Than Average

The NWS Climate Prediction Center released their latest outlook for October and beyond. It looks like the warm-than-average weather is expected to continue for the next several months. The primary driver in the forecast is the ongoing El Niño in the Pacific Ocean basin.

October

Illinois has an increased chance of above-average temperatures for October. There is not much to report on precipitation in Illinois. We are between drier-than-average conditions to our northeast and wetter-than-average conditions to our southwest.

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October-December

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Updated El Nino Forecast

There is a 95% chance that El Niño will continue through winter and gradually weaken through spring 2016, according to the NOAA Climate Prediction Center today. That remains essentially unchanged from last month’s outlook. As noted in a earlier post, this increases the chances of a mild winter in Illinois.

Here are the recent sea surface temperatures, as a departure from the average, in the Pacific Ocean basin. The units are in degrees Celsius, so just double the number to get the approximate departure in degrees Fahrenheit.  This represents an impressive amount of heat, considering that these warmer water temperatures cover thousands of square miles.

The traditional area for El Niño formation is circled and labeled on the map. The one wild card in the current situation is that we have exceptionally warm waters farther to the north than what I have seen in past El Niño episodes (green circle). This could potentially change the impacts of El Niño over North America.

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Click to enlarge. Source NOAA http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/

Last Two Big El Nino Events – Milder Winters in Illinois

The latest NWS forecast for the winter months of December-February has Illinois with an increased chance of above-average temperatures. In general, the core winter months of December, January, and February, were much warmer in Illinois and the Midwest during the last two major events in 1997-98 and 1982-83.

Along with the warmer temperatures was a noticeable drop in snowfall across most of Illinois during the core winter months. Some places in eastern and southern Illinois saw their snowfall totals cut in half. However, while the overall pattern was for less snowfall, it still snowed. And some places saw significant snowfall events in November and March, outside the core winter months.

Precipitation (rainfall + water content of snow) was closer to average and in some places, such as western and northern Illinois, wetter than average. This suggests that many of the snowfall events were replaced by rain events under the much warmer conditions.

1997-98 El Niño

The 1997-98 El Niño event saw much above average winter temperatures across Illinois and the Midwest. For Illinois, it was the 3rd warmest December-February on record at 34.6 degrees, and 5.6 degrees above average.

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1997-98 temperature departures. Click to enlarge.

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