As snow lovers, readers of this blog are probably amateur meteorologists as well, studying forecasts for snow and temperatures when planning ski days and trips. The consensus for this winter among professional meteorologists is for a strong El Nino, which will have an impact on ski areas across North America.
To understand a skier’s perspective on weather forecasting in general and El Nino specifically, I spent some time with Drew Jackson, a meteorologist (with a BS and MS in Meteorology from Penn State University) turned ski area marketing guy. Jackson was Marketing and Communications manager at Mt. Bachelor for 5 years and is now the CRM manager at Camelback.
I was always under the impression that long term weather forecasts, like the Farmer’s Almanac, were just weather’s version of an old wives’ tale – good for small talk at the water cooler but of highly dubious accuracy. Jackson, however, educated me that long-term forecasts can actually be relatively reliable. The answer to the question of how reliable, like many questions related to meteorology, is, “it depends.”
“Long-term, seasonal forecasts from credible sources, such as NOAA’s Climate Prediction Center, can be quite accurate,” Jackson said. Long-term forecasts depend heavily on looking at “past years where similar conditions were present (called ‘analog’ years) and then predicting an outcome based on what happened during similar past circumstances.” For example, El Nino episodes frequently (but not always) deliver milder temperatures in the north central part of the US, and historically (but not always) greater than average precipitation in the southern US.
The concept of long-term weather forecasts is more about the overall chances of something occurring, rather than predicting specific temperatures or precipitation amounts. For example, “a long-range forecast by NOAA for above average temperatures is really just an adjustment of these odds,” says Jackson. “Long range forecasts should be viewed as ‘tipping the probability scale’ in a certain direction, rather than a deterministic and specific forecast.”
Precipitation and Temperature 3-Month Forecasts
Right now, the NOAA forecast for January through March of 2016 shows below average precipitation from eastern Washington through the Idaho panhandle to central Montana, and through much of the upper Midwest. On the other hand, southern California and Arizona, southwestern Texas, and most of Florida show the best chance for an above average level of precipitation this winter.
In terms of temperatures, the January to March 2016 period is forecast to exhibit chances for below average temperatures in the southern third of the country, and warmer temperatures in the coastal areas of the Pacific Northwest and Alaska, along with the far upper Midwest – just as Jackson described.
The consensus seasonal forecast for this winter is for a strong El Nino pattern, which historically has had somewhat predictable outcomes in different regions of the US.
El Nino is a weather pattern that happens every three to seven years. Its effect on the weather in the US – and indeed, across the globe – originates with a slowing of the easterly trade winds in the Pacific Ocean near the equator, which causes a change in the average temperature in that large body of water. “This results in above-average ocean water temperatures off the coast of South America, and, oppositely, the water temperature in the western Pacific near Indonesia can become cooler than average,” explains Jackson. While this phenomenon is quite complicated, the gist is that the typical atmospheric circulation pattern is altered across the planet.
In the US, El Nino typically manifests itself as a split jet stream. Like a skier approaching a fork in the trail, the storms coming from the Pacific shear apart into a northern and southern track just off the coast of the US. During an El Nino, the southern branch tends to garner most of the storm energy. “This why the Pacific Southwest tends to get more snow during strong El Nino winters,” explains Jackson. Good news for southern California ski areas like Bear Mountain, Snow Summit, and Mountain High!
On the other hand, Jackson notes that the northern storm track is relatively less potent. “The weaker northern branch of the jet stream drives the remnants of the splitting storms into British Columbia and the Alaska panhandle, with only ‘glancing blows’ or ‘brush-bys’ to the Pacific Northwest and northern Rocky Mountain regions. Lower than average winter snowfall totals and milder winter temperatures are common in these areas courtesy of this typical El Nino weather pattern.”
How about the eastern half of the country during an El Nino? Jackson suggests that the effects of El Nino aren’t as pronounced in the eastern US, although that’s not to say that there aren’t some impacts. “The Great Lakes States can often be warmer and drier than average. The Northeast is also susceptible to milder conditions during very strong El Nino winters, but it’s not uncommon for the northern and southern branches of the jet stream to ‘phase’, or merge, over the Mid-Atlantic States, allowing for large coastal storms to spin up and deliver big snows to the Northeast.” Keep your fingers crossed, New England skiers and riders.
So how will the 2015/16 winter shape up for skiers and snowboarders in the US? The general weather outlook for the ski season seems relatively certain, but how those patterns will actually play out in terms of total snow and specific temperatures … well, it depends.