![]() Now, I actually care what they show (of course, the U.S. But as our knowledge of the atmosphere and models improve, so have the forecasts. Until recently, specific computer model forecasts were not considered useful by most forecasters. These recent changes need to be considered when making seasonal forecasts. The combination of more blocking and more water vapor due to the warming climate is a recipe for big snowstorms - IF it’s cold enough. It is probably not a coincidence that 3 of the 4 biggest snowstorms in Philadelphia occurred in the past decade or so (2009, 2010, and 2016). One of the impacts is in more blocking patterns, including the –AO and –NAO. It has become more and more obvious to many forecasters and climate scientists that the massive Arctic ice melt is influencing weather patterns. The Eurasia snow connection mentioned earlier may be connected to –AO. A negative NAO is often one of the ingredients in our biggest Nor’easter snowstorms. This pattern favors slower-moving coastal storms in the Eastern U.S. When the NAO is negative, HIGH pressure is centered near Greenland. The record winter of 2013-14 featured several giant snowstorms with a strongly negative AO. And it forces the Polar Jet Stream farther south than normal. This forces the coldest air south into Canada and the U.S. So, they are always considered a “wild card.”Ī negative AO means unusually HIGH pressure at high levels over the Arctic. But things like the Arctic Oscillation and the North Atlantic Oscillation have been just about impossible to predict months in advance (unlike El Nino, QBO, and “The Blob”). What is going on in the Arctic and North Atlantic can be just as important as the Pacific. Major El Ninos can still be counted on to give us warm winters with little snow. Quiz: How Well Do You Know Philly Winters?įew winter forecasts are as straightforward as the one in 1997.Now, a winter forecast is expected every year in November. We had a record warm winter and our TOTAL snow was less than an inch. So, I went on the air and predicted an unseasonably warm winter with very little snow. ![]() ![]() They called it an “El Nino.” I had just read research showing the potential connection between strong El Ninos and warm, wet, and un-snowy winters in the eastern U.S. ![]() A huge area in the Tropical Pacific, bigger than the size of the United States, was getting MUCH warmer than normal. It started in 1997 with a look at something I’d only seen a couple of times before. But how much snow? And how low will the temperatures go? I measure several important factors to reach that conclusion.
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