El Nino is back! Wait, what is El Nino-other than a great wrestling name?
Short and simple: El Nino refers to warmer than normal waters in the Pacific. The warm ocean surface in turn warms the air which in turn has an affect on wind patterns that steer storms, cold air, warm air etc...
How does this affect me?
El Nino's affects on St. Louis climate are more pronounced during Winter (December, January and February). So, when El Nino occurs we can point to something that historically drives our winter climate in a certain direction. Typically we experience a drier than normal and warmer than normal Winter. Don't think that all Winter will be warm and dry, it won't. Some days will be cold, there will be some snow, but overall the climate of this year's Winter is expected to be warmer and drier than normal. Also, one nasty storm can make it a tough Winter for some people. In fact, during the El Nino Winter of 2006-2007, St. Louis had a devastating ice storm with hundreds of thousands of people with no power (click here for more on that ice storm). But after that ice storm, we didn't have much snow and we ended up with slightly below normal precipitation and warmer than normal temperatures.
The Bottom Line:
We expect this winter will be warmer than normal, will have less snow than normal and will have near normal to slightly below normal precipitation (snow/rain/ice all combined). That's the overall trend for most El Nino winter's in St. Louis.
The National Weather Service (and Mark Britt in particular) has put together a fantastic chart showing how St. Louis temperatures, precipitation and snow has departed from normal during El Nino years. (Click here and scroll to the bottom of the page for that chart).
Looking at that chart shows you that not all El Nino winters are warm and dry compared to normal. But it's obviously the trend and it's based on that historical trend that the 2009-2010 Winter Outlook for St. Louis is warmer than normal and near normal to below normal precipitation.
We'll be monitoring this El Nino as we get closer to Winter, so check back with us as we provide more updates.