Posts

John Homenuk

(Premium) Intensity of weekend cold still uncertain

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After many of us geared up for Spring with warm weather in both the early and middle part of March, the atmosphere reminded us that no transition is as smooth as it may seem. Colder, blustery air has returned to the area, and although a mild stretch is expected during the middle of this coming week, very cold air will again surge into the area by this weekend. As we spoke about several days ago, forecast models have done an excellent job of signaling the overall pattern teleconnections and evolution, with a surge of cold air possible during the first week of April.

Over the past few days, however, the intensity and duration of this cold air has come into question. Forecast models have trended slightly weaker overall with the lobe of the Polar Vortex which will break off and head southward into Southeast Canada and Northern New England. Accordingly, the forecast temperatures in our area have moderated a bit. While the overall evoltion of the pattern still suggests anomalously cold air gets to our region, a more south-to-north gradient appears likely, with the coldest temperatures likely north of New York City and more slight to moderate departures from normal to the south.

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John Homenuk

Coldest air of winter to arrive this weekend

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A large arctic airmass, owing to a piece of the polar vortex, will drop southward late this week and weekend from Canada into the Great Lakes and Northeast United States. With it will come the coldest air of the winter — and the coldest air in quite some time, especially aloft. Temperatures at 850mb, or roughly 5000 feet, will drop to nearly -30 degrees celsius, challenging some records for temperatures at that level in the Northeast US for the date.

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Doug Simonian

Wintry pattern change coming by late next week

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For any readers who want to know more about any potential rain tonight, as well as the weather for Friday and the weekend, check out our latest forecast discussion. There may even be some scattered showers and isolated thunder with a cold pool aloft, as mid-level lapse rates will be near 7C/KM tomorrow afternoon.

While our area sits in low level moisture and clouds, former Super Typhoon Nuri has transitioned into an extratropical storm, but is forecast to fall to pressures below 920mb! This would be one of the strongest extratropical cyclones on record.

This extremely strong cyclone will help to release plenty of latent heat and energy towards the Poles, which will generate an anomalously strong ridge in Alaska and western Canada. In short, as the extratropical system becomes a behemoth both at the surface and aloft, the strong jet stream and digging trough in the mid and upper levels create an anomalous ridge to their east, pumping a ridge from the West Coast into British Columbia. This ridge will be so strong that it will also flow into the Arctic, tanking the Arctic Oscillation. This allows the Polar Vortex to be weakened and sent to the south on the downstream side of the ridge.

Accordingly, forecast models are in good agreement that the Polar Vortex will split into two, with a piece sagging southward toward Southern Canada during the middle to latter part of next week.

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John Homenuk

Not-so-polar vortex will make disruptive return next week

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Wait! Don’t go digging into your closet to find your winter jacket in that bin of winter clothes just yet. The Polar Vortex may “technically” be returning next week — but it isn’t so “polar” in air quality, and it may not be by other definitions as well. So is it really a Polar Vortex at all? The meteorological community is up in arms today over the usage of the term — and the end result is, of course, leading to varying opinions and arguments. The cause of the argument itself is the modeled approach of a massive upper level troughing system, which will feature much below normal temperatures both aloft and at the surface. The track, size and orientation of the system bear many resemblances to the Polar Vortex which tracked through the Great Lakes this past January.

Still, the time of year makes the sensible weather results quite different. Temperatures which are 10-20 degrees below normal (or more in some locations) won’t quite drop the thermometer near the freezing mark. But, still, things could get quite cool over the Great Lakes and Ohio Valley. Some meteorologists prefer to call the incoming system a Polar Vortex, others don’t. But the bottom line has to do more with meteorology than terminology — and the sensible weather effects are becoming more clear as we move closer. Figure 1 shows temperature anomalies at 850mb as forecast by the GFS next week. Notice the broad area of well below normal temperatures as a result of the large upper level troughing system with cold air moving south from Canada.

Fig 1. (Atmos Albany)

Fig 1. (Atmos Albany)

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