Winter Forecast 2009-2010
Well, as fall fades away to meteorological winter on Tuesday, it’s time for the winter forecast. Many things to consider this year with a bit of an El Nino, a cold PDO (Pacific Decadal Oscillation) and stratospheric warming. Let’s talk a bit in brief about how each of these plays into creating a forecast. First, El Nino. As of this writing the ENSO 3.4 is about 0.5 C above average, just barely an El Nino. In looking at past El Nino’s similar to this, many winters have started cold and ended warm. We will start with this and then use the other two modify. Next is the PDO. This is a cooling of the north Pacific waters, It tends to run in a 20 -35 year cycle as shown by this graph. We are currently in the front 1/3 of this cycle so the next 10-15 years could see colder than average winters and summers. This does not mean they will all be cold but most of them. While a weak El Nino tends to bring more storms to the northwest coast it also tends to reduce the effect of storms along the southern California coast due to cooler water and sinking air. Major winter fires over southern Cal cannot be ruled out because this sinking will tend to evaporate cloud cover. This will likely reduce the number of Pacific storms that track to the Midwest but will increase them along the east coast. Look out for a rough winter there. Now on to the stratospheric warming. The reason it’s warm is the heat from the earth is escaping through the tropopause and into the stratosphere. Hence, if greenhouse gasses were being trapped so readily, it would not be this warm. It could also be a result of a sun which is running about 3% cooler than average due to a lack of sunspots. Whether or not we are going into a prolonged solar minimum will likely not be known for several more years. Without getting into to many smaller items, we have a consensus from these events that winter will likely start out cold and warm toward the end. What does that mean for snowfall? Well, considering the lack of Midwest storms due to the cold PDO, snow is likely to be less than last year. So let’s say 35-45 inches. Remember, one big storm can blow this up so I like to take all the storms from winter and drop the biggest and the smallest to reach an average. No, it’s not a scientific “trick”. Temps for December through February will be about average to slightly below. Maybe one degree. To break it down, December 3-5 degrees below, January, average to 2 below and February 2-4 above. I will leave this up for about a week and then we will talk about what all this “Climategate” really means to all of us.