Long term models

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Just a few days ago, the long term model data was showing a significant storm moving through the central US on Christmas Eve then turning NE-ward across the Ohio Valley then heading into the St Lawrence River Valley and New England states on Christmas day. A low such as this with cold air to the north/west would have brought significant snows to the Great Lakes regions, maybe even western New York and the ski areas of northern New England.

Today, the same long term models doesn’t show the low and now doesn’t show that much cold air moving across the northern States. In fact a good portion of the country is looking to have fair skies versus clouds and precipitation……Granted this model data is forecasting the movement of air parcels where they will be in 13-15 days, so this far out there is bound to be some error, but what I find interesting is how much of a swing this data can make and in such a short period of time. If a more gradual shift in the pattern was happening over a period of 7 days, then that would indicate that the data is good and the errors were getting less as we get closer to that day. But when you go from the chance of snow and cold temps in the model data a day ago to no storm, no precip and milder temps the next day…… that’s a bit concerning.

Such big swings are not uncommon with these models. Yes, they are trying to forecast for as many as 16-17 days out. So far out that the local news won’t even forecast out that far. They’ll stick to the standard 5 days forecast and may dangle an extra day or two without much detail or as aside to the broadcast…..but I digress.

The important thing to remember about the long term model data no matter how far out it goes is to watch for the forecast trend it is showing and a one day flip/flop isn’t a major concern as of yet. Watching this data and looking at the movement of cold air and does it start to show consistency in upcoming runs. That is what will more accurately show what is to be expected in the longer term. So, even though this big swing is not a big concern today and the subsequent runs could show a return to the low center moving across the Great Lakes and into New York…..we shall see.