George Lessens' Winter Forecast 2011-12 | News
Chief Meteorologist George Lessens forecasts cold and snowy weather in his Winter 2011-12 Forecast.
Defining What 'Winter' Means
Weeks before winter actually settles in meteorologists are called upon to make their predictions for what type of season it will be. Long-range forecasting is one the more difficult tasks for meteorologists (my profession), so we turn to climatologists to help us analyze and interpret worldwide weather patterns that affect us locally.
Typically when we speak of winter temperatures we usually mean average temperatures for the months of December, January, and February. When we talk about snowfall we usually mean the total snowfall for the entire season (September-May.) The average winter temperature for Grand Rapids is 26.8°F while the average snowfall is 74.9" (based on the 30-year average from 1981-2010).
Last Year's Forecast Results
Last year, I forecast the winter of 2010-11 would feature temperatures near average (25.5°F, +0.5°F); it turned out 0.2°F below average in Grand Rapids (24.8°F). I also predicted snowfall would be well-above average (95", +21"); it turned out 1.8" above average in Grand Rapids (74.0").
La Niña Explained
This year, a weak-moderate La Niña pattern is in progress - a cool pool of surface water centered along the equator in the Pacific Ocean, which is not as strong as last winter. This pattern is expected to continue through the winter season.
La Niña Snowfall
Snowfall in Grand Rapids in the sixteen episodes of La Niña since 1949-1950 (not including 2010-11) ranges from 54.5" to 107.0" with an average of 74.8". Interestingly, the 30-year average from 1981-2010 is almost identical - 74.9". Nine episodes have had less snow than average while seven episodes have had more snow - almost equally split. This year, the snowfall season will probably start out slowly with November, December, and January seeing lower snowfall amounts but quickly pick up in February and March and then quickly taper off in April. In these graphics, Anomalies indicate how far away from average, with the blue colors indicating more snow and brown colors indicating less snow; Composite indicates how often this occurs, with blue colors meaning less often and red colors meaning more often.
La Niña Temperatures
Temperatures during these same La Niña episodes in Grand Rapids have ranged from 22.7°F to 31.6°F with an average of 24.7°F. The 30-year average from 1981-2010 is 26.8°F. Eleven episodes have been colder than average while only five have been warmer - decidedly cooler. This year, temperatures will probably start out close to average in November, December, and January but get colder in February - April. In these graphics, Anomalies indicate how far away from average, with the blue colors indicating colder and red colors indicating warmer; Composite indicates how often this occurs, with blue colors meaning less often and red colors meaning more often.
In general, I believe West Michigan will have temperatures that are near to slightly below average (26.3°F, or -0.5°F for Grand Rapids); snowfall will probably be around average or slightly above average (80", or +5.2" for Grand Rapids).