With cold weather on the horizon, Kansans are interested in what they should expect this winter. Below are the NOAA Climate Prediction Center’s outlooks for temperature and precipitation during the winter season -- December through February (Figure 1 and 2).
The temperature outlook calls for a slight increase in the chance for warmer-than-normal temperatures statewide (Figure 1.). That tendency increases as you move further south and west in the Plains. It is important to remember that this is the 3-month average. There could be significant cold periods and still have an overall warmer-than-normal winter. One difficulty with that pattern is that crops and livestock are not able to develop strong winter hardiness. This makes them more susceptible to severe conditions during the occasional extreme cold snap.
The precipitation outlook is neutral, meaning there is an equal chance to have above-, near-, or below-average precipitation this winter (Figure 2.). Winter is normally the driest time of the year for most of the Plains. Southeast Kansas is an exception, with a more even distribution of precipitation across the year.
It is worth noting that neither the temperature nor the precipitation outlook predicts the degree to which conditions will vary. A tenth of a degree (0.1) warmer-than-normal average temperature would validate the outlook to a similar extent as an increase of 10 degrees. A hundredth of an inch (0.01) greater-than-normal average would have a similar result in the precipitation outlook. Significantly wetter-than-normal conditions would be needed to improve the drought conditions in the Northern Plains. In Kansas, only 1% of the state is in moderate drought with 16% of the state abnormally dry. With the equal opportunity for a wetter/drier than normal winter, near-average conditions are likely. This would likely continue as areas of scattered abnormally dry/moderate drought in the central portions of the state.
The major force responsible for the current winter weather outlook is the ENSO (El Niño-Southern Oscillation) signal. At this time, a weak La Niña pattern (cooler-than-normal waters in the Pacific along the Equator) is expected through the majority of winter. Storm tracks during La Niña winters are typically more zonal across the continental US, with the polar jet steering systems pushed northward across the northern tier of the United States.
Given the uncertainty of the La Niña, other factors may have a stronger influence. Two patterns that deserve attention are the North Atlantic Oscillation (NAO) and the Madden-Julian Oscillation (MJO). The NAO is a comparison of high and low pressure in the Atlantic basins. When the NAO is negative (with a weak gradient between high pressure in the subtropics and low pressure over Iceland), the east coast of the United States tends to have stronger cold outbreaks with more snow (Figure 3). Some of that can clip the eastern Plains region.
The MJO is an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days (Figure 4). The position or state of the MJO influences storm generation across the United States. Unfortunately, both the NAO and MJO conditions can change rapidly, and forecasts for these patterns are not as well developed as for the ENSO. That makes it difficult to gauge their impacts on an extended basis.
Mary Knapp, Assistant Climatologist
Christopher “Chip” Redmond, Kansas Mesonet Manager