Joseph Shannon, Ph.D.
Gila Community College, Natural Science Division Chair and Biology Instructor
Northern Arizona University, Merriam Powell Center for Environmental Research, Adjunct Biology Professor
Our winter storms roll in from the eastern Pacific Ocean and are driven by the jet-stream. Winter storm formation and amount of moisture in them is dependent on the temperature on the surface water, or the top 300 meters.
The warmer it is, the more moisture is evaporated, and the more likely we get snow. The jet stream is a "river" of high winds (> 150 mph) near 30,000 ft. altitude that snakes across North America, pushing storms along at about 20 mph. If a winter storm forms over the Pacific and the jet stream has "dropped down" to Arizona, the storm will likely be driven to us in the form of low-elevation rain or mountain snow. Sea surface temperature (SST) is monitored by oceanographers and used to make seasonal weather predictions.
If the eastern Pacific Ocean is warmer than average, we call that an El Niño event, or "little boy," because the warm water creates strong storms along the South American coast and great fishing as the storms turn up the nutrient-rich ocean bottom near Christmastime. If the eastern Pacific Ocean is cooler than average, we call that a La Niña event, or "little girl".
Right now the SST data for August through October showed a decrease of 20C or 3.6 F. This may not seem like a lot in terms of cooling a house, but it is a tremendous amount of energy loss when you consider the tens of thousands of square miles of ocean involved. The result is a high probability that the Southwest will have a below-average snow-pack and above-average temperatures this winter. Usually La Niña conditions last for several months, as the ocean circulation will return the temperature balance.
A less scientific way to see what our winter may be like is to check the snow-pack data for the Snowy Range in Australia.
There is an uncanny correlation between the winter there and ours. Probably because they are dependent on the same ocean patterns and circulations we are. This past winter, the Aussies had a very dry and warm winter.
So will you get in enough powder days to warrant buying a season ski pass to your favorite resort this winter?
Probably not in southwest U.S., but the northwest and northern Rockies resorts usually do have good snow in La Niña winters.
Looks like long weekends traveling north are the way go this year to get in good powder runs.
Gila Project -- Regional Water Education and Research is a novel collaborative effort between Gila Community College, Northern Arizona University, and regional natural resource agencies to better understand water-related topics. An important aspect of the Gila Project is to inform the general public about water-related topics such as weather, climate and related technology.