2022 12/05 Bill Marino Winter 2022-23

Bill noted that since 1991, La Nina winters have trended near normal as far as temperatures. Moderate to strong La Nina events have *never* been wetter than normal. Currently, there is a consensus that La Nina will persist through late winter/early spring. He also mentioned that this will be the third consecutive winter with La Nina conditions. Bill then went into an explanation on what a La Nina event actually means for North America and more specifically, our area. He also mentioned that since 1990, temperatures and storm tracks can be highly variable in the Western Great Lakes region during La Nina.

Digging into the temperature outlook more closely, Bill observed that the temperature trend since 1950, when La Nina conditions are observed several years in a row, there were generally a higher frequency of colder than normal months, especially in January. Normal being defined by the most recent climate period of 1990 – 2020.

Taking a closer look at the precipitation outlook, a general storm track seems to show up over the Ohio River Valley and eastward over the Appalachians. Historically, near normal precipitation has been observed during several-year La Nina events in SW Michigan.

The composite forecast, based on multi-year La Nina events, shows colder than normal temperatures and near normal amounts of precipitation.

Bill then examined the actual historical snowfall numbers for various cities around SW Michigan. Observation methodology varied widely between sites and so the numbers are difficult to draw any solid conclusions from. If we were to believe the observed snowfall totals, La Nina events once again tend to yield below normal snowfall amounts.

November, February and March tend to be the snowy months according to additional La Nina data.

Based on the CPC and other factors like La Nina analogs, Bill believes that we will end up with near normal temperatures and expects that we will have a near normal or slightly drier than normal winter. Considering how much snow we’ve already received in November (Grand Rapids, MI reported its 2nd snowiest November on record with 28.0”), he believes it will be difficult for us to end up in the bottom tercile of observations. La Nina patterns also suggest that the second half of the winter could produce more snowy conditions.

A final note from Bill is that it can take a week to put together a seasonal forecast like this. He looks at all of the trends/historical data and crunches the numbers to put together statistical predictions based on various factors leading up to the season for which one is predicting.