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COMMENTARY

A milder weekend in store, but also a chillier future

Don Paul

As I wrote this past Monday, some warming would arrive just in time for this weekend. Saturday will start out frosty inland from the lakeshore, and then temperatures move above average into Monday. For activities other than Bills football, it will be ideal for leaf-peeping across much of Western New York or, if you must, raking up those leaves that have already abandoned ship.

Bike rides, walks and hikes – including the big, charitable Ridge Walk & Run just outside of Wellsville – will be mood elevators. Just skip the flip flops and penny loafers. Paths will be muddy from Thursday's rainfall. Plenty of sunshine will prevail Saturday with some high clouds mixing with the sun on Sunday. Sunday will be the warmer of the two days … and if you’re off Monday it will be warmest of all.

As for game day, early tailgaters will be greeted by morning lows in the 40s, rising quickly through the 50s and into the low 60s during the game and probably warmer in the stands and on the field. Note the very wide spacing between those thin, black isobars in this Sunday model. That translates to very light winds, probably variable in direction, with little effect on kicking and passing.

Monday, those isobars will be more closely packed, bringing us our warmest day of the week on a southerly, downslope wind. Downslope means winds will be accelerating down the slopes from the Southern Tier, heating up and drying out as they do so.

Some parts of the Niagara Frontier should approach 70 on Monday, ahead of an area of low pressure, some showers, and a cooler pattern arriving by Tuesday, with a brisk breeze. This cooler pattern, however, will be nothing out of the ordinary. High temps will run in the 50s midweek, not too far below average.

By next Friday, we’ll be back a little above average, with some colder air looming in the northern plains. The wettest day next week will be Tuesday, with a few spotty showers possible on a drier Wednesday, and a renewed chance for showers around Friday.

When might we see a more significantly colder pattern setting up? There are signs of it showing up near the end of the month into early November in the American GFS ensemble (called the GEFS) near surface temps, as posted by Dr. Jason Furtado, who teaches at the University of Oklahoma.

This is a reflection of the upper-air pattern at the same time in the GEFS.

The European extended range ensemble also favors a similar pattern in at least early November, with upper-level warm ridging near the Pacific coast and colder low pressure troughing of the jet stream closer to our region.

As we head into the colder months, don’t count on any particular pattern to persist for weeks at a time. The National Oceanic and Atmospheric Administration (NOAA) took a gambit at explaining a greater likelihood of more erratic patterns this winter in their just-released Winter Outlook text on Thursday. NOAA’s Climate Prediction Center is mandated to make such an outlook, which gets a lot of publicity at the time of its release. If you skipped their text discussion and just looked at the temperature probabilities graphic, you might get a sense of confidence we’re simply going to have a milder than average winter.

Actually, the graphic shows a weak positive anomaly slightly favoring milder-than-average temperatures from December through February, which is known as meteorological winter, when all is said and done at the end of February. What it can’t depict are all the many ups and downs that will occur during this period, with a greater likelihood of erratic changes at least partially tied to a warming climate in the arctic. (You may also note no part of the country is favored for below-average temperatures over those 90 days. The EC (equal chance either way) is the region of greatest uncertainty and may imply colder outbreaks may be a bit more likely in NOAA’s estimation.

Precipitation, an even tougher call than temperatures, looks like this:

We are in a region by which NOAA’s expected most frequent storm track gives us a slight edge toward above-average precipitation. They expect significant drought to develop over parts of Texas and Louisiana, as well as in parts of central and northern California.

The “erratic” part comes in with arctic warming, and you can see as an example high confidence in anomalous warmth for Alaska, which will also be expected for large parts of the high latitudes around the globe. This warming lessens the thermal contrast between the polar region and mid-latitudes, which is linked to episodic weakening of the polar jet stream and the polar vortex. When the vortex weakens in these episodes, it tends to buckle southward, allowing periodic regional invasions of polar air and wintry outbreaks, sometimes for one to two weeks at a time. These episodes are not predictable more than a very few weeks in advance, and cannot be timed within a “winter outlook.”

In recent decades, scientists in my field and related fields have discovered more and more variables in trying to make a seasonal forecast, and I have become less and less a fan of seasonal outlooks. They simply don’t work very well, and are not comparable to seven-day weather forecasts. With the arctic warming at twice the rate of the rest of the hemisphere (as expected), the erratic periods are getting more erratic, more often. NOAA recognizes this, but they also recognize there is value in offering some scientific guidance to the public on what appears more likely, however slim the margin. My thoughts are summed up in this article I wrote a month ago:

Climate change likely to throw wrench into winter outlooks

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