Posts

John Homenuk

The science behind a wintry intrusion this week

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Any time the pattern gets as anomalous as it is forecast to get over the next several days, a meteorologist’s job becomes very interesting. We can either simply say “It’ll be very cold this week”, or we can take the time to explain the science behind it. We’ll choose the latter. The pattern change, which will undoubtedly be noticeable by the middle to end of the upcoming work week, is occurring as a result of several impressive atmospheric events. Global circulations are changing the pattern — and it will be a sight to see. But the change goes far beyond the fact that unseasonably low heights will dip into our area by Thursday morning.

The pattern is already unbelievably anomalous well to our west, over the Northeast Pacific and British Columbia. The extratropical transition of Typhoon Nuri and its phase with a piece of Pacific Energy led to a tremendously anomalous trough — and an incredibly strong storm system with minimum central pressures down to 924mb (The strongest storm in the history of the Bering Sea and the North Pacific). But, more importantly, the anomalous storm system is amplifying a tremendous ridge to its east over the West Coast of the United States, northward into British Columbia and toward the poles.

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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

Rain, cold and even snow possible this weekend

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There, we used the “S word” in one of our posts for the first time this season. An energetic mid and upper level disturbance will shift from Central Canada through the Northeast United States late this week into the early part of this weekend, helping to develop a coastal storm. In addition to the coastal storm will come a strong cold front, and a cold Canadian airmass which will drop temperatures into the 30’s and 40’s at times after its passage. With models hinting at the development of multiple surface lows off the coast, the potential exists for not only rain and wind — but some snow in the higher elevations and the first flakes for others.

But the setup remains extremely complicated. The source region of the disturbance means forecast models are already working with a somewhat limited dataset. And, as is often the case with storms in our area, the mid level disturbances will be involved in fragile interactions, all of which will have a major impact on exactly how the storm develops. Confidence, as a result of these small nuances and features, remains very low.

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John Homenuk

Cold air, winter weather returns to the forecast

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Par for the course this winter, as one storm exits we are already looking ahead at another system which is modeled to potentially bring additional winter weather to the Northeast US. On the heels of a major winter storm for interior and northern New England, which brought a significant cold front and 30-40 degree temperature drop Thursday morning, forecast models are honing in on Pacific energy which will eject into the Southwest US later this week into the weekend. With a lobe of the Polar Vortex hanging around to our north providing cold air, any energetic or moisture filled disturbance would bring the potential for snow. The disturbance late this weekend could do exactly that.

Much of the forecast, however, hinges on the exact positioning and strength of the disturbance as it ejects northeastward from the Southwest US towards the Mid Atlantic. And not surprisingly, forecast models are up in arms as to exactly how consolidated the system will be as it does so. The Canadian, SREF and DGEX extension models all like the idea of the system ejecting as one consolidated trough with significant moisture, while the Euro and GFS are adamant in the idea that the system will be faster and split into multiple pieces.

GFS model showing the important piece of energy entering the Western US and Rockies.

GFS model showing the important piece of energy entering the Western US and Rockies.

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