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Don Paul: Don't look to the forecast for signs of spring

We do get early springs, on occasion. March of 2012 comes to mind; there were four consecutive days of 80 degrees or higher, as well as a boatload of days in the 60s and 70s. The monthly mean temperature was an astounding 13.4 degrees above the March average.

This year, we have reached 40 degrees only once in March so far, on the first. Our mean temperature as of the 12th is 1 degree below average. We’ve had 12.9 inches of snow at Buffalo-Niagara Airport in March, which is 6.6 inches above average for the date … and that’s going up significantly more between this week.

Whither the warmth? So as not to bury the lead, there are no signs of an extended warm breakout (read: 50s or 60s) looking toward the start of April.

Some of you may scoff about predictions that go out that far in time. For precipitation, you’d be perfectly correct in scoffing. With temperatures, it can be another story.

When a pattern is well established, and the variables in the atmosphere supporting that pattern are well established, there can be real forecasting skill (read: “definitely better than a coin flip”) going out two to three and occasionally three to four weeks. Of course, uncertainty increases further out in time, so all hope is not lost as we head into weeks three and four.

For example, in January I had reasonable confidence February would be another colder-than-average month. The first two weeks held true to form, but the second half of the month was extraordinarily mild, with two days in the upper 60s and a 59-degree finish on Feb. 28. That gave us a mean temperature 5.6 degrees above February’s average. That late warming was greater than could be seen in January data.

Click here to see a quick overview of the upper-level pattern expected over the next two weeks with an ensemble of model runs at National Weather Service headquaters. Smoothed out over time, it doesn’t have the appearance of an extremely cold pattern, and it isn’t. If you look at the first few days, you’ll note a sharp deepening of the dip in the polar jet stream associated with the monster nor’easter heading up to Nova Scotia.

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But as time goes on, the pattern seems to smooth out, with the dip or trough in the northeast taking on a flatter appearance. And you don’t see a sharp, warm ridge of high pressure over western North America that would lead the polar jet to take a sharper dive over the east in reaction, delivering truly polar air masses to the east, as was the case earlier this winter.

All that said, there are no signs of a warm ridge taking up residence in the southeast United States that would force the polar jet to retreat to the north for a lengthy period. The mean pattern will allow it to stay cold enough often enough for this week’s nor’easter to not be the last beast of its type for the season. It gets cold enough for another snowstorm, or a winter storm with mixed precipitation, along the coast again next week. Worst of all with these not-too-cold monsters is the accumulating snow is heavy, destructive stuff. Combined with strong winds, this snow brings down trees and powerlines.

Let’s look at an ensemble of the vaunted European model going out 10 days. The term “ensemble” applies because the European Center located in England takes the European model and changes the startup/initial conditions slightly, adding 51 runs, each with slightly different initial conditions into the ensemble. This is extremely valuable because we can never be certain of the precise state of the atmosphere when initializing, so the European Center’s superior computer crunch power puts out the most data-intense ensemble. The United States will be making big improvements in our crunch power but, for now, our ensemble has 21 different runs, rather than 51. The European is more accurate much — but not all — of the time. Here is the European ensemble mean at about 18,000 feet up. (Click on the middle arrow to animate.)

This week’s monster stands out for its strength or amplitude. Then, you’ll notice a flatter trough reappears in the east next week, beginning around March 20. The flatter appearance does not imply a weak system at this point. Further out in time, the 51 individual members of the ensemble spread out more from one another with greater uncertainty, and that spread give a flatter appearance to the wave. When we get closer to March 20, I have fairly good confidence that next system will again sharpen up and produce still another strong nor’easter storm that could send limited backwash moisture to Western New York in its wake.

The upper-air ingredients and the oscillations that lead to the polar jet buckling in the east look fairly persistent. There is actually a 46-day European upper-air ensemble that suggests next week’s system will not be the last, either. That ensemble shows some brief warm-ups later in the month between systems into early April. And it’s possible the systems at that time will make more rain than snow, even when they are strong.

Eventually, the blocking that buckles the polar jet will dissipate and what’s called the North Atlantic Oscillation in its cold phase will relax and let springtime in.

It’s not an encouraging pattern for most, though it will lengthen ski season and keep some snowmobile trails open more. That very warm March of 2012 led to major, costly problems when frosts and freezes returned in April. Blossoms had opened prematurely, and farmers took major hits from the damage that followed the strangely hot March.

As of this writing, it at least looks dry and bright for both parades this weekend, with slightly milder temperatures on Sunday than for Saturday.

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