High latitude ridge could bring below normal temperatures

High latitude ridging has become a bit of a staple in meteorological terminology over the past several years. Much of this can be attributed to the fact that we’ve seen several record breaking episodes of it. Conversely, we’ve also seen periods which have lacked that blocking, leading to major forecast changes and dramatic pattern evolutions. High latitude blocking, or ridging, occurs when higher than normal heights build into the higher latitudes (here’s a not-so-fancy image of where the high latitudes are defined). This can occur at any time of year, but we’ve seen it in the Autumn and Winter more often over the past several seasons. High latitude ridging and blocking events can be of varying degrees, as well. Some of the less extreme examples, like this upcoming one, can produce mild pattern changes. Other more extreme examples, like the high latitude block that occurred prior to Hurricane Sandy and the Boxing Day Blizzard, can…well, you know.

Nevertheless, without getting overly technical, these high latitude blocks and ridges can “buckle” and slow down the mid and upper level atmospheric pattern. And while much also depends on what’s going on around these blocks, more often than not if they occur on the Atlantic side (Northwest Atlantic Ocean into Greenland), they result in cooler than normal air being displaced to the south of the ridge over Canada. This often leads to cooler than normal air in our region, and this upcoming event likely won’t be an exception to that rule.

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Mid level disturbance leads to epic cloud display in NYC

These NYC clouds weren’t as menacing as they look — we promise. The showers which moved through the area this morning, as a result of a mid level disturbance shifting overhead, created some incredible displays in the New York City area. The surrounding cloud deck made the multiple cloud types even more impressive. Instagram and Twitter users took to their cameras to share some amazing photo’s today — and we’ve compiled some of them below. Chances for showers and an isolated storm will continue today, and a weak coastal storm may bring a period of moderate rain to Long Island and Connecticut tonight into Wednesday.

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In Autumn, all eyes are on the North Pacific

With Autumn officially underway and the leaves starting to turn, many are beginning to wonder about the upcoming winter, and if the Autumn pattern will foreshadow it. Unfortunately, it is not as easy as “cold October yields cold winter” or “warm October yields warm Winter”. If that were the case, we’d have long range forecasting figured out by now, and there would be no need for winter outlooks. The best we have for now are correlations, analogs, physical pattern drivers, and pattern persistence. When added together, the summation of these various factors provide a higher probability of success in medium to long range forecasting, but these methods are far from perfect. The evolution of different atmospheric oscillations during the autumn season can give us a substantial clue as to the ensuing winter’s dominant index modalities.

In this particular case, let’s examine the autumn north pacific pattern of years since 1990, giving us a sample size of 22+ years. The North Pacific pattern is often represented as the East Pacific Oscillation (EPO). Like the North Atlantic Oscillation the EPO has certain, generally predictable outcomes when it oscillates from positive to negative phases. The positive phase of the EPO is usually associated with lower than normal heights across the northeastern Pacific, much of Alaska, and northwestern Canada. Conversely, the negative phase of the EPO generally produces higher than normal heights over the region just described. The positive (+EPO) tends to flood the United States with maritime pacific air due to the low pressure around Alaska, while the negative (-EPO) acts as a block to maritime pacific air due to high pressure over the NE Pacific/Alaska. The -EPO often sets up a cross polar flow with high pressure centered over Alaska and the flow oriented across the north pole from Siberia into Canada. The -EPO pattern has yielded some of most impressive, severe arctic outbreaks on record.

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Coastal storm departs, beautiful weather returns

Our products are a bit late this morning (forgive us, we spent the night at Derek Jeter’s last game at Yankee Stadium) — but they won’t come without any good news! The coastal storm system which marred yesterdays weather, bringing widespread rain and clouds, is shifting well to the northeast of the area this morning. Taking over in its wake are northerly winds, drier air, and a beautiful autumn airmass. Temperatures today will climb into the mid to upper 70’s still, but will feel perfectly comfortable as humidity values drop and moisture moves seaward, associated with the coastal storm.

The best news of all, however, is the fact that this weather looks to continue into early next week. In fact, airmass modification will allow temperatures to climb into the upper 70’s to low 80’s on both Saturday and Sunday with a tremendous amount of sunshine. Dry offshore winds will keep away any marine influence, as well, so the weather really will be exceedingly pleasant. The mid level ridging will keep this pattern in place through the early part of next week.

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