What should we expect during the upcoming winter? This is a question being asked increasingly often as daylight dwindles and temperatures cool off. Unfortunately, it is a question with no easy answer.
Many folks across western Kansas expect a “bad winter.” The first week in August was warmer than normal, some tall milkweed has been observed, and even the caterpillars agree as many woolly worms with more black than brown have been seen across Kansas. These are all folk lore indications of a severe winter ahead. While there is little scientific validity to these sorts of predictions, they are not necessarily at odds with the science this year.
Winter weather across the United States is expected to be dominated by El Nino. El Nino is characterized by a pronounced warming of the waters of the eastern equatorial Pacific Ocean and results in a more active subtropical jet stream across the southern United States. While the effects of El Nino are complicated, this active jet stream generally results in winter storms being displaced further south than normal.
El Nino has a documented, significant effect on the character of winter weather across the northern plains and the southern part of the United States, but its effects on winter weather are less obvious in the central plains. Statistically, there is a small chance of seeing above normal temperatures over the central plains and the signal gets stronger and more significant the further north you go. However, warmer temperatures on average over an entire season do not suggest the absence of cold weather. Imagine a season where the temperature is 35 F the whole time and one in which it is 70 F half the time and 0 F the other half. Both seasons average to 35 F, but imagine the difference in the weather! Furthermore, local research has shown an increase in snow and ice storms over western Kansas during El Nino years. This makes sense conceptually as an active southern jet stream should result in more moisture and more active storms across the southern United States. Cold air can and will still be drawn south into these storms, and when you put moisture and cold air together, winter storms can be the result.
Official forecasts are for El Nino to continue through the winter of 2009-2010 and perhaps weaken late in the winter or early in the spring of 2010. Based on this expectation, the outlook for southwest Kansas is for near normal temperatures and normal to above normal precipitation – on average. Extreme winter weather events are not only still possible this winter, but we may be more likely to see snow and ice storms this year than normal – especially late fall through early winter (Nov 2009 – Jan 2010). In fact, one suggestion is that an early season heavy snowstorm is possible (Maybe in November?) with the snow remaining on the ground in some areas well into the winter. Persistent snow cover can result in a feedback that keeps things cool and increases the chance for snow and ice later on.
While we cannot be sure about any specifics for an upcoming season, many things are pointing to a more severe winter than normal, including the science!
by Tom Wright, Meteorologist, NWS Dodge City, KS