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John Homenuk

Cold risks emerging to end November

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There is something about this time of year that features more fanfare than the rest. Maybe it’s the approach of winter, or the first surge of cold air into the middle latitudes. Either way, it seems that the first week of November almost always features a bit more drama to the forecast than most weeks, and this year is no different. Forecast models have offered hints this week that the pattern may be set to undergo some significant changes as we look towards the end of Autumn. 

As most are aware, the middle latitude pattern in the Northern Hemisphere has been stagnant for quite some time now. Granted, there have been periods of colder than normal air – especially recently in the Northern Plains where departures neared -10 F on a 7 day average. But for the most part, East of the Mississippi River, temperatures have averaged above normal as a Southeast Ridge anomaly has remained stout, owing to La Nina background forcing from the tropical Pacific Ocean. 

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John Homenuk

EPO ridging a sign of changing pattern across USA

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A pattern in fluctuation has led to several changes in sensible weather conditions across the Continental USA over the past few weeks. Stagnant warmth gave way to several shots of cold air, first affecting the Northern Plains and eventually leaking southward into the Tennessee and Ohio River Valleys. The change in wavelengths and  increased amplitude led to the development of a few significant storm systems; namely one which brought snow to the Upper Midwest, and another which delivered damaging winds and torrential rain to the Northeast.

The hemispheric pattern is set to change again  as we approach the middle part of this week, with appreciable changes already occurring in the Pacific Ocean. As we discuss quite often, what occurs in the Pacific Ocean from the Bering Sea towards the Gulf of Alaska (more affectionately known as the North Pacific) can often have major implications on the weather in the USA. There are other factors to consider, always, but we can often look there for clues, and the coming weeks will be no different.

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John Homenuk

How long will Winter’s hiatus last? Look to the Pacific

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Before the warmth has even arrived, signals of a changing weather pattern have begun once again. This is, honestly, par for the course in the hemispheric pattern that we have been locked into over the past several months. The progressive nature of the pattern itself has not allowed any particular regime to become stagnant. In other words, the pattern is changing quite consistently, and no overly cold or overly warm regime has become established locally.

While this idea fits within our overall winter forecast, there is something to be said for emerging signals of a return to a colder, more active pattern before a warmer pattern has already begun. Lets not get confused, though — the warmer than normal pattern is still on the way. In fact, temperatures are likely to average above seasonal normals in the Northeast US for quite some time from late this week through Christmas and into the first week of January.

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John Homenuk

In Autumn, many eyes drawn to the North Pacific

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With Autumn very obviously and officially underway (have you been outside the past few days?), the questions have begun to surface regarding the upcoming winter — and if the Autumn pattern will foreshadow it. Unfortunately, it isn’t quite as simple as “A cold October means a cold winter” or ” A warm November means a warm winter”. If that were the case, we’d have long range forecasting figured out by now, and there would be much less urgency to winter outlooks. The best we have for now are correlations, analogs, and pattern drivers. When used together, the summation of these factors provide a higher probability of success in medium to long range forecasting. But these methods are far from perfect. The evolution of these different atmospheric oscillations during the autumn season can often give us substantial clues into the ensuing winter’s dominant index modalities.

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