CHANGES COMING TO THE LONG RANGE WEATHER PATTERN?
Since mid October we have been locked in this weather pattern where weather fronts and storm systems march through every couple of days. Hurricane Michael set the pattern change in motion and it appears that we are going to start seeing a realignment going forward though where we are going exactly is a bit of a mystery. That of course makes weather fun. It is the intrigue that we all seem to enjoy and we thrive on the uncertainty.
The signals from the tele-connections were rather interesting today. These measure pressure changes in different areas of North America. Some of these areas tend to overlap but they give us an idea of the relative strength of any particular pattern. For example, the PNA or Pacific North America index gives a feel for the strength of a high pressure ridge in the west plus low pressure trough in the East (positive reading). Notice that the PNA index is strongly positive early next week which makes sense since we are dealing with a deep trough and storm system in the Eastern US. What it doesn’t tell us is where exactly that trough is because the Eastern US is a pretty big place. The position of that trough means everything in the winter with regards to storm track and rain verses snow issues. Notice that the PNA goes negative which means that the ridge in the west weakens combining with a lack of a trough in the East. Weather models show this idea to some degree later next week after the storm system for Monday and Tuesday pulls out. At least that is the general idea of the GFS model last night.
However today’s runs (and this is supported by the European model this afternoon) offer an entirely different scenario. Rather than pulling out the trough in the East and crashing the ridge in the west, models have now decided that we will hold that trough in the East and keep the ridge in the west stronger.
This development to me suggests that the pattern may instead of changing, just relaxes for while after whatever happens next weekend. This scenario suggested by the model brings a low up the East Coast but there won’t be any cold air around until the very end of the event. It might be enough to bring some snows to New England however especially the interior. Another shot of cold air likely follows into Thanksgiving week before we seen a bit of a moderating trend but nothing on the order of a ridge in the East or what is lovingly referred to as the blow torch. For you cold weather snow lovers I would actually be somewhat encouraged by the way the pattern is evolving at the moment for the months that count which is December through March.
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