Author: Dr. Ray Russell Founder and President of RaysWeather.Com Date: October 10, 2015 RaysWeather.Com 2015-2016 Winter Fearless Forecast Background It's that time of year--leaves change, temperatures gradually fall, October festivals occur every weekend, some folks eagerly wish for coldest winter in the history of the world, and some media outlets always satisfy the snow hounds with forecasts of the worst winter ever. If you have been reading our forecasts for many years, you know we do not always satisfy the desires of the snow hounds; however, this year we will. I always feel the need to quickly temper the reader's expectations for long-range winter forecasts. Many long-range forecasts are never worth the pixels they are displayed on, and no long-range forecast is always correct. Being on the correct side of average seasonal snowfall 60%-70% of the time is geniuslevel forecasting. In spite of a few failed Fearless Forecasts, we have a track record of being better than most. After a near-perfect 2013-14 forecast, 2014-15 did not turn out so well as shown in Table 1. Table 1: Accuracy of Last Year s RWC Fearless Winter Forecast Location Forecast Actual Actual - Forecast Snowfall Snowfall Asheville, NC 18" 13" -5" Banner Elk, NC 60" 41" -19" Beech Mtn, NC 115" 69" -46" Boone, NC 48" 28-20" Hickory, NC 9" 4.5" -4.5" Independence, VA 30" 17" -13" Jefferson, NC 33" 25" -8" Morganton, NC 11" 4" -7" Waynesville, NC 18" 11" -7" Wilkesboro, NC 14" 10" -4" (Actual reports even within each location varied from site to site. I chose a snowfall total that fairly represented the average for each location.) Overall, our total snowfall forecasts were 25% to 40% too high. The bust was largely because we expected a moderate El Niño to develop; however, that did not happen. Instead, generally neutral to weak El Niño conditions developed. Then, the Fearless Forecast was never "bailed out" by the North
Atlantic Oscillation (NAO). If the NAO had become negative for a few weeks, last winter's persistent Mid- Atlantic storm track would have shifted farther south delivering more snow to the Southern Appalachians. As a consolation prize, we did have a very snowy February; in Boone, February 2015 was the 11 th snowiest February in the last 56 years. Temperatures? Last year, we forecast temperatures to be 0-1 degree colder than average; last winter's average was about 2 degrees below average. Summary of the Fearless Forecast for Winter 2015-2016 As Fearless Forecasts go, this one is as bullish a forecast as we will ever make. Here you go, snow hounds! 33% greater snow than the 56-year average for the Mountains and 20% above average snow for the Foothills Temperatures averaging 1 to 2 degrees below the long-term average. This forecast would place the Southern Appalachians in the top 20% of seasonal snowfall totals. (Note: The forecast snowfall total includes snow/ice falling between October 2015 and May 2016.) Table 2: Specific 2015-16 Snowfall Forecasts for Selected Locations Location Expected Total Snow/Ice for Winter 2015-2016 Asheville 20" Banner Elk 67" Beech Mountain 110" Boone 54" Hendersonville 15" Hickory 9" Independence, VA 29" Jefferson and West Jefferson 35" Lenoir 11" Morganton 12" Sparta 31" Spruce Pine 27" Sugar Mountain 105" Waynesville 19" Wilkesboro 13" Happy Skiing and Snowboarding! We ll keep you informed with the most reliable day-to-day forecasts for the Southern Appalachians and Foothills all winter. This forecast does not come out of thin air or some not to be named body part. It comes from serious analysis; continue reading for the explanation. Fearless Forecast Rationale ENSO Analysis The El Niño Southern Oscillation (ENSO) is the starting point for almost any long-range forecast in the United States. Other forecast indices have implications for winters in the Southern Appalachians, but
ENSO is the only one large-scale index that can be forecast with some confidence from several months away. However, as we saw last winter, even ENSO forecasts can fail. ENSO is a measure of large-scale weather conditions in the Equatorial Pacific. It fluctuates between El Niño (associated with warmer than average sea surface temperatures in the Equatorial Pacific) and La Niña (associated with colder than average sea surface temperatures in the Equatorial Pacific). Both the current ENSO state and the forecast for ENSO are important for understanding weather patterns in the upcoming winter. Currently, the ENSO is classified as a strong El Niño, one of the strongest ever recorded in August. Figure 1 shows the Sea Surface Temperature Anomaly from October 1, 2015. Almost all the Pacific from the Equator northward in the Western Hemisphere has warmer than normal sea surface temperatures. Figure 1: Sea Surface Temperature Anomaly 10/1/2015 (from www.ospo.noaa.gov/products/ocean/sst/anomaly/index.html) However, El Niño may be near or at its peak intensity. Computer modelling used to assist climatologists in forecasting El Niño show the peak and subsequent diminishing of El Niño's intensity. Figure 2, shows an array of model predictions; while they disagree in the details, all forecast a weakening El Niño by late winter or spring 2016. The forecast for El Niño to be near its peak and diminishing by spring 2016 is crucial to our Fearless Forecast. Strong El Niños tend to pull too much heat/energy into the Eastern U. S. producing big storms but with too little cold air to make those "snow" storms for most of the Southern Appalachians. However, a weakening El Niño may "thread the needle" adding energy to systems entering the Gulf and East Coast but not overpowering cold air from the north thus producing a snowy and icy scenario for the Southern Appalachians.
Figure 2: Forecast for ENSO in 3-month Intervals (from www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html) Moderately strong El Niños have produced some of the more memorable winters in the Southern Appalachians. Figure 3 (on the following page) graphically shows total snowfall in the last 56 winters for Boone, NC. The red lines denote strong El Niño winters. The average snowfall in Boone for strong El Niño winters is 51.8" compared to an average of 41.4" for all winters (26% greater in strong El Niño winters). It's obvious from Figure 3 that not all El Niño winters are created equally. Given the forecast for the current El Niño to diminish by spring 2016, we arrived at a smaller set of most comparable winters winters in which El Niño was moderate to strong, but removing the strongest El Niños from consideration. We also eliminated 1987-88 from consideration because the El Niño peaked very early in winter and was weakening by January. So, we decided the following years were the Best-Fit for the upcoming winter: 1957-58, 1963-64, 1965-66, 1986-87, 1991-92, 2002-03, and 2009-10. Figure 4 compares our Best-Fit Winters with all El Niño Winters and all other winters. The amount of snow in the Best-Fit Winters got our attention! Average total snowfall in the Best Comparison Winters in Boone, NC, is 60.1", 45% greater than the 56- year average. However, given the typical challenge of cold air accompanying these energetic storms moving from the Gulf and up the East Coast, we do not believe the same percentage increase holds for lower elevations. So in our final forecast, while still forecasting a snowier than average winter for the Foothills, we are less enthusiastic there than we are for the higher mountain terrain. Also, the wrapping of warm air aloft into these systems tends to increase the threat of icy and "wintry mix" events.
Figure 3: Total Winter Snowfall in Boone, NC, Classified by ENSO (ENSO classifications derived from www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml) Figure 4: Snow totals from our Best-Fit Winters (1957-58, 1963-64, 1965-66, 1986-87, 1991-92, 2002-03, and 2009-10) compared with all El Niño Winters and all other winters. Snow totals shown are from Boone, NC.
Another important characteristic of strong El Niño winters can be seen in Figure 4. On average, they begin similar to or even warmer than other winters. Note that through December, strong El Niño winters have less snow than other winters in Figure 4. In strong El Niño winters, the snow tends to begin in January and then Februarys tend to be very snowy. Strong El Niño winters also tend to keep snow going longer into spring. Strong El Niño winters produce the most snow on average because warmer waters in the equatorial Pacific become breeding grounds for storms that travel from the Pacific to California then across the Southern U. S. Some of these storm systems breed Nor'easters moving up the Atlantic Coast. Figure 5 graphically illustrates what we expect the primary storm path to be this winter. Temperatures do not tend to be brutally cold in El Niño Winters; Figure 5: El Nino Winter Climate Pattern (from www.meted.ucar.edu) however, because of persistent wet, cloudy conditions with storms moving up the East Coast. We do expect cooler than average temperatures. Figure 6 shows a comparison of temperatures from Boone, NC for: the Best-Fit Winters, strong El Niño winters, and all other winters. The main takeaways from the analysis of ENSO forecast for the coming winter are: 1. We have high confidence for a wet winter because of the storm track across the Pacific into the Gulf and up the East Coast. 2. We expect a much snowier-than-average winter in the Southern Appalachians, particularly at higher elevations. The effect may not be as great for the Foothills. 3. Icing may be an increased threat this winter. Figure 6: Average temperatures from our Best-Fit Winters (1957-58, 1963-64, 1965-66, 1986-87, 1991-92, 2002-03, and 2009-10) compared with all El Nino Winters and all other winters. Temperature data is from Boone, NC.
Recent Winter Trends Figure 7 shows the 10-year average winter snowfall for Boone NC for each year since 1968. Figure 7: 10-year Snowfall Average for Boone NC Figure 7 shows a decrease in yearly snowfall for Boone NC between 1985 and 2007. The 10-year average increased from 2008 to 2011; however, it should be noted that only 2 of the last 11 years (and 6 of the past 26 years) have had more than the 56-year average (see Figure 3). The main takeaway from recent winter trends is that our cold and snowy enthusiasm regarding the strong El Niño should be constrained by snowfall trends over the past 30 years. Arctic Ice Figure 8 shows current ice cover in the Arctic relative to average and ice cover in 2012. 2012 had the least Arctic ice coverage ever recorded. The extent of Arctic ice has recovered somewhat from 2012 but is still 2 standard deviations below the long-term average. Initially, one would think that less ice would contribute to a warmer atmosphere since ice reflects more solar radiation (compared to liquid water that absorbs more solar radiation). However, some scientists believe that this phenomenon may have contributed to high latitude blocking and high magnitude troughs in the northern hemisphere during the last few winters. Figure 5: Extent of Arctic Ice (from nsidc.org/arcticseaicenews/)
The main takeaway from the Arctic Ice section: Due to uncertainty regarding its impact on snow and cold in the Eastern U. S., we did not use the ice extent as a factor in the winter forecast. The North Atlantic Oscillation Wildcard Every year, the North Atlantic Oscillation (NAO) is the wild card for long-range winter forecasts. Without belaboring the details, the NAO is the North Atlantic's distant cousin of ENSO. (See https://climate.ncsu.edu/climate/patterns/nao.html for details on both the Arctic Oscillation and NAO.) I know of no reliable way to forecast the NAO three to four months in advance. Whoever "cracks that nut" will deserve a Nobel Prize in Physics. In the snowy winter of 2009-10, a moderate El Niño combined with a persistently negative NAO to produce the third snowiest winter on record. The 2009-10 pattern featured high latitude blocking in Greenland and Eastern Canada producing a persistent trough in the Eastern U. S. Figure 1 shows sea surface temperatures that might result in a negative NAO (warm water in the Gulf of Alaska and warm water just off the Northeast U. S. Coast), but betting on the NAO can cost anyone the mortgage money. The main takeaway from the NAO is no clear signal but a hunch that snowier is smarter. Summary Long-range winter forecast is always a risky proposition. Don't put much stock in this or any other longrange forecast. But here's what we think: High confidence in a wet winter Medium confidence in a slow start to winter A snowier than average winter in the Foothills A much snowier that average winter In the Southern Appalachians A slightly colder than normal winter The heart of our snowy winter will be in late January and February Increased risk of ice and wintry mix events Now, quit fretting over winter and enjoy a beautiful fall. Winter is still two months away. "You're still here? It's over. Go home... go!" -- Ferris Bueller