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Don Paul: WNY keeps riding the weather roller coaster

Don Paul

After Wednesday’s freezing rain comes Thursday’s brief bubble of balmy. Brief is the operative word. Allow me to make your eyes squint. This National Weather Service hourly graphic display wind forecast has directional wind barbs on it. Note the orientation of the barbs later Thursday.

The winds originate from the southeast, then the south from around 3 until 9 p.m. Thursday. That is a wind which accelerates coming down the slopes of the Southern Tier, known as a downslope wind. A downslope wind heats up as it rolls down the slopes from compression, and it dries out as well. That will give us the short-lived bubble of balmy. Models often underforecast downslope warming. In the ultimate example back in 1943, Spearfish, S.D., went from minus 4 degrees to 45 degrees in two minutes from a Chinook/downslope monster coming down from the Rockies. For the Niagara Frontier, our paltry-by-comparison downslope wind should bring temps to around the mid 50s later Thursday. That won’t last long. In this forecast depiction for 7 p.m. Thursday from NWS HQ, we are still on the warmer side of a strengthening low pressure system crossing the northern Great Lakes.

After that cold front goes by, the falling barometric pressure ahead of the front will suddenly jump upward, and the rush of rising pressure behind the front will produce strong to possibly high winds (the latter is a severe weather term, for peak gusts over 58 mph or sustained winds of 40+ mph for at least one hour). All this will be preceded by gusty showers and thunderstorms ahead of the front. The strong, cold winds behind the front will gust to 55 or 60 mph toward and into Friday morning, as I see it at this writing. Some wind damage may occur. As the cold air deepens during Friday, temperatures will fall through the 20s, and some limited lake snow will develop. Yes, Lake Erie is mostly ice-covered, but the ice is not thick well away from the shores.

I believe these southwest winds will destabilize this still young ice and break up portions of it to produce new openings. Models can’t handle this kind of a setup very well, so how much lake snow can be generated remains very much an open question. Here is what one high-resolution model is showing, keeping in mind the ice cover uncertainty:

With so much ice out there, I wouldn’t think the lake effect will be ALL that organized. However, the temperatures will be falling into the low 20s. As the arctic air deepens, should the winds punch open some large areas in the ice, it will bear watching. With multiple openings, given enough size, multiple bands might develop. Whatever is falling should settle southward into the hilly terrain later in the day, after beginning on the Niagara Frontier.

A seasonably cold weekend, mostly dry, follows with some sun both days. After that, uncertainty increases into Monday night out through midweek. There is poor model agreement on another storm system approaching Monday night-Tuesday. The Canadian/GEM model is the most aggressive for Tuesday, though even it suggests a transition to mixed precipitation and possible rain.

The overall ensembles of models further out in time are having problems with the upper air pattern. The European/ECMWF ensemble mean shows a cold pattern across most of the lower 48 by mid/late week, next week. The breadth of this pattern, without a warm western ridge and cold eastern trough (such as last week’s brutal high amplitude pattern) is somewhat unusual.

The American/GFS upper air ensemble shows a different forecast, with the cold confined to the West and seasonably milder temps in the East.

The GEM ensemble is even more emphatic on this trend by around Feb. 17.

If the GFS and the GEM were to prevail, this would differ significantly for mid-February from what ensembles were showing late last week.

Even within the ECMWF ensemble, there are vast differences between the 51 member model runs which make up the ensemble mean. Hence, courtesy of Dr. Michael Ventrice of IBM’s the Weather Company, note the huge disparity in the ECMWF:

And these wild swings within the ensemble are, in turn, due to wild uncertainty in a vast, shifting oscillation with roots in the Indian and western Pacific oceans called the Madden-Julian Oscillation/MJO. Here is what I wrote about the MJO back on Dec. 14: “Moreover, there is an inordinately complex oscillation out over the Indian and western Pacific oceans called the Madden-Julian Oscillation/MJO. There is no nice and neat graphic I can use to explain its complexity.” The MJO forecasts from different models and ensembles usually are in better agreement than they have been for the last 7 to 10 days. If we have very low confidence in which of the MJO’s eight phases will dominate (and the effects of each of those eight phases varies with the time of the year) in the next few weeks, and how strong the MJO will be, we can’t have much confidence in the extended range for the second half of the month. Back in mid/late December, confidence about the mid/late January polar outbreak was rather good. No such higher confidence exists at this writing. I hope the models get their MJO act together soon. I like to eat waffles, not use them for an excuse.

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