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The long-advertised chillier pattern will be in place from Tuesday the 17th through that late part of the month. But there are going to be some ups and downs within the overall mean pattern, rather than a steady-state chilly pattern day after day. By late this week, high temps should be closer to average (low 40s) for a day or 2 and then take another sharp downward trend next weekend by later Saturday into Sunday. There will be several days in which even the high temperature stays below freezing. In the mean, there will be more days when the high temperature passes the 32 degree mark. With that in mind, a slow melt should continue on streams, creeks and in the shrinking snowpack. This kind of pattern may continue to reduce the risk of major ice jam flooding, but there can be “no guarantees” on that.
No major storms are currently indicated in the next week for our vicinity. No one should assume we are through with measurable or even significant snow. It is simply too soon for such expectations, and with a colder than average pattern odds of a true snow drought lasting through most of the month are not all that favorable. And on the other hand, on the day of this posting (Monday the 16th) nearby Cleveland and Pittsburgh both passed the 60 degree mark. So any low pressure system could be–albeit briefly–capable of pumping unseasonably mild air for a day. So, “all is not lost”.
As I mentioned last Friday the 6th, we are done with subzero readings, following a new record low and the 12th subzero low of the winter (the 3rd most subzero total days of any winter going back to 1871). Our temperatures will run a bit above average inland from Lake Erie for a few days this week, before cooler and more unsettled conditions arrive for the St Patty’s parade(s). This modest moderation will continue to shelter us from poor drainage flooding or any threat of ice jamming, unless we were to receive unexpectedly heavy rain this coming Saturday. Temperatures may be just cool enough to allow a bit of a mix to accompany the more widespread periods of rain on Saturday, and the occasional showers or drizzle on Sunday. Neither the First Ward nor the Delaware Avenue parades will be basking in sunshine and mild temperatures, but readings should be tolerably cool/chilly without raising the risk of frostbite which has occurred in some parades in the past. As of this posting, Saturday looks wetter than Sunday, but neither day will win any awards. Readings will again moderate on Monday.
However, by the 17th, there are signs a ridge of high pressure will redevelop over western North America, forcing the polar jet stream to go around it over NW Canada where this jet will tap into some modified arctic air, delivering it to the Great Lakes. This means temperatures will again be headed solidly below the average high closer to 40 or 41 at that time. Again, we won’t be returning to a true polar blast for our region but it does currently appear our temperatures will be running more than a couple of degrees below average. Even that colder trend will have some ups and downs within it. In the mean, though, it looks like our daytime highs will be below average most of the time from the 17th through at least the 24th or 25th. At least it can be said this type of pattern will keep the risk of ice jam flooding low.
The extreme pattern which dominated February isn’t going to be so extreme through March 12th or so. However, temperatures will still be below average for this time of the year most days (as of this posting, the average high is 37). The huge western ridge of warm high pressure over the west will slowly flatten out and the polar jet stream which has to go around it will lose its true polar connection. That will allow arctic air masses the chance to moderate a little before they drop down into the Great Lakes, rather than drop down our way staight from northern Siberia and the North Pole. This western ridge will retreat more into the NE Pacific, and the long dip in the polar jet stream over the east will lose some of its definition as well. Within this partial relaxation of the pattern, there will be ups and downs, with quick hits of arctic air (such as on Thursday the 5th), followed by partial recovery to near normal temperatures–but still a little below.
Right around the 14th and 15th, all 3 of the extended range tools we use to predict the overall North American temperature pattern agree the pattern will shift to a more West-to-East flow, instead of NW to SE. The kind of flow keep the true arctic air up in its “zone” to the north and allows milder Pacific air to cross the lower 48 more frequently. As you might imagine, a Pacific flow is considerably milder than a polar or arctic flow.
I’m not saying that at that point we’ll be done with winter and the threat of wintry weather. What I am saying is that the extremes in temperatures as far as truly bitter blasts will become much less likely. As in the previous thread, the more gradual this pattern change is, the better off we’ll be. There is thick ice on all streams and creeks and a huge amount of water stored in our deep snow cover. A sudden, strong thaw would virtually guarantee more serious flood potential, both from ice jams and from snowmelt. Nature will deal out what it deals out regardless of what we “wish” for. All we can do is hope the moderation is gentler than it’s been in years past.
“Less harsh” does not equate to “mild,” for starters. However, after what could still turn out to be the coldest month in Buffalo record-keeping history (not just coldest February), a trend toward “less harsh” will be noticeable, if not exactly cause for wild celebration. During February (and for a large part of January), the Polar branch of the jet stream has been riding far north into the Arctic around a warm ridge of high pressure dominating the western states all the way up into Alaska. At the top of that climb north, the jet stream was grabbing onto polar air masses which have their origin in northern Siberia, and then dumping those air masses around parts of the–yes, it exists, Virginia–polar vortex into the Great Lakes and the NE, along with parts of the midwest.
Extended range computer guidance continues to show this strong warm ridge retreating mainly offshore to the Gulf of Alaska and the Aleutians. When that happens, the direct cross polar flow we’ve been receiving will be moderated by some Pacific air blending with the polar air. That would mean, on average, much less chance of the kinds of extremes we’ve suffered during this extraordinary month. That would NOT mean, however, a complete flip-flop to a more springlike pattern. However appealing the latter may sound, a sudden, extensive thaw would almost certainly produce a serious flooding potential from snowmelt and ice jams. While our wishes don’t matter in the least as to how the atmosphere behaves, we will be much better off with a more gradual pattern transition toward more seasonable temperatures (the average high on February 23 is 35). It will not be a smooth ride. As we get closer to March, it appears in the guidance there will be ups and downs, with temperatures still running below average much of the time out to around March 9-10…just not so MUCH below average. This evolution in the pattern also doesn’t clear us from the threat of any snowstorms. We’re nowhere near that time of year, especially not this winter.
But it probably means fewer dead batteries, a little less misery for outdoor workers, and a little less fuel being burned to heat your homes.
After a nearly forgotten very mild and much less snowy than average December, the weather worm turned around January 5th. That’s when we began our downward spiral for most of last month and into this month. A rather persistent western ridge (with minor variations) have keep the west and central US with above average temperatures. An absence of blocking over the North Atlantic has allowed the eastern trough to set up far enough east to restrict most of the really cold weather to the eastern Great Lakes and the NE, into eastern Canada as well.
This high amplitude pattern is going to relax somewhat for a few days, allowing for much less harsh temperatures over the weekend. The price to be paid will be several waves of low pressure moving along a boundary between arctic air to the north and moist Pacific air to the south. Temperatures will be somewhat below average for the first half of next week, but by later in the week, a reamplification of the western ridge/eastern trough will occur. This has been showing up in model ensemble means for quite a while.
With the considerable help of long range forecaster Dr. Judah Cohen, I’m stuck with the unpleasant task of telling people we are nowhere near out of this frigid mess. There is even some chance matters may grow worse. Cohen writes of evidence in the GEFS ensemble and less robust evidence in the ECMWF that the blocking in the North Atlantic which has been absent most of the winter is going to begin to develop. The polar vortex which has been settled lately over the far north of Eurasia is going to drift back toward the north pole. What this favors is a strengthening of the western ridge, which teleconnects with a strengthening of the eastern trough, and more frigid air pouring not only into the NE but retrograding into the central states as well. These teleconnections favor more cross-polar flow. In addition, at about the same time the N Atlantic ridging develops, the MJO will be entering what’s called phase 7 & 8, which correlates with below average temperatures in our part of the country. It’s far from certain that the N Atlantic blocking will become strong, but if it does the NAO would finally go strongly negative–it’s been a nonfactor this winter–and the AO (currently weakly & briefly negative before it goes positive again next week) would go negative as well. The fact that the AO has been positive the majority of the time in the last 4-5 weeks speaks to how poor a predictor in this winter as to cold and snow in the east/NE.
This pattern, with minor variations, is expected to persist into early March in Cohen’s eyes, as I’d speculated the other night on the previous thread. This is a draining, disruptive pattern leading to economic dislocation, high energy costs, and damage to our infrastructure. If we’re correct, this will be one of the longest cold periods in a number of years.
Seasonal snowfall has moved back a little above average over the last few days. After the November lake effect storm(s), the airport (never hit full strength by those events) had gone to 29+ inches with an average to that date of 16+ inches. By midweek last week, the airport had slipped to several inches below average, following an unusually mild December (3.4 degrees above average) and well below average snowfall. We’ve gone back in the other direction this month up to this point. Temperatures have been significantly colder than average, and monthly snowfall has been above average.
Those trends will level off following the arctic shot for Tue-Wed, with temperatures slowly recovering to closer to average later this week (still on the cold side, but nothing like last week or Tue-Wed this week). Readings may head a little above average during the weekend. During the time period from around the 18th into the latter part of the month, there will be more occasion for more Pacific air to cut off the kinds of arctic blasts we’ve endured last week. However, the moderating trend will not be a totally smooth ride, and there will be some ups and downs, just fewer if any extremes. Ensemble means show a very broad ridge in the eastern Pacific at the end of the runs (26th-27th) and very broad troughing over the N Central and Great Lakes states. The amplitude is lower than it is now, to be sure. When ridges and troughs are so broad, it’s often a sign of large spread between the ensemble members which make up the ensemble mean. It doesn’t look as though there will be much phasing between the northern jet stream and the southern stream for awhile. However, large ensemble member spread can mask any individual features even more, so the more moderate pattern (not to be confused with truly mild, as would be the case with a well defined eastern ridge) is a very fuzzy one as depicted. In the next week (through the 20th or so) there are no current signs of any significant synoptic storms putting a hit on the eastern Great Lakes. And because there are no current signs of large lake effect potential, my “but Not for Long” headline is probably a safe bet over the next 7 or 8 days.
After some almost unseasonably mild weather before and during the Christmas holiday, the pattern will be shifting to a more wintry one for the last few days of December and the first few days of January. The northern branch of the jet stream is going to buckle again, but this time the trough will be “positive” tilt, with the axis running from Quebec to the Great Basin and SW. That will preclude any deep storm system in our region for at least a few days. A somewhat split, separate southerly branch of the jet may carry a vigorous system far to our south and toward the SE/middle Atlantic seaboard with no impact on us.
However, as the cold air deepens on New Years Eve, a brisk (and bitter-feeling) WSW flow will set up across the eastern Great Lakes. This means late night revelers should be dressed in their warmest, protective gear for any prolonged exposure, even though temperatures look “merely” cold that night. There will probably be some Lake Effect developing downwind of Lake Erie. Working against it will be early model and ensemble projections of this being a dry air mass. Working in favor of it will be some cyclonic curvature to the flow (the arctic anticyclonic ridge will be Well S & SW of us) and a pretty healthy delta T/low level lapse rate. Lake Erie is currently 3 degrees above average at 39. The lower res global models and ensembles are not very good at picking up all but extreme lake effect this far out in time, so they’re not showing much. I do expect some lake response by either late New Years Eve or New Years Day, slowly winding down by the weekend. The pattern will then begin to relax, and more seasonable temperatures (not mild, but seasonable) will return.
Judah Cohen is forecasting the AO to go predominantly negative for much of January, but also says there is uncertainty about the strength and impact of his predicted SSW during the month. Despite the AO showing a general trend toward the negative by the start of the year, the NAO goes positive for a while, so there are mixed signals on that front. But there IS good agreement on this cold period for New Years week, and the WSW flow setting up in the boundary layer, so things may get interesting for a few days.
Confidence is continuing to grow as of this Wednesday evening posting that a major storm system will be taking shape by Christmas Eve into Christmas. Confidence continues to be much lower by comparison as to that storm’s impact in WNY. As you should expect 8 days in advance, there is model disagreement on storm timing and placement, and there is some ensemble disagreement as well. However, there is unusually good agreement this far out between the operational GFS and ECMWF on the broader details. That is, there is good agreement an initial low pressure area and its trough will undergo a transformation as that trough begins to tilt from NW to SE, known as a negative tilt. That tilt encourages more rapid and deeper strengthening of a surface low with a broadening of the precipitation shield associated with the storm. The negative tilt will spawn a deepening frontal wave along the initial low’s cold front. This secondary low will undergo strong cyclogenesis, coming up from the S or the SSE. The new intense low will eventually merge with the original parent low to the N and become a rather powerful cyclone. Both the GFS and ECMWF deterministic runs take the central pressure of the merged low down to 964mb! The ensemble means of the 2 models drop the center to around 978-980mb. The GEM has some similarity, but its cyclogenesis is less impressive than in the GFS and ECMWF. The actual path taken by the new deep low in the GFS is faster and farther east than the ECMWF depiction, which would put us in the cold wraparound snow and strong winds more quickly than in the ECMWF.
Also strong to possibly High winds will be favored. On Wednesday, a strong SE flow will increase coverage and intensity of rainfall, and winds will strengthen, strongest near the Lake Erie shoreline south of Buffalo. As the main low shifts north with its near bombogenesis, the cold wraparound circulation should change the rain into an uncertain amount of snow overnight on Christmas Eve into Chrstmas morning. As of this Wednesday evening, both the ensembles and deterministic models favor strong to possibly High winds in the cold advection as well. It is too soon to speculate as to how much synoptic snow will fall vs lake effect behind the storm. Signs do point to potentially dificult travel by or before Christmas morning, and there will be the chance for damaging gusts and a seiche–depending on the orientation of the pressure field. There may also be especially strong gusts immediately following passage of the cold front, with an isallobaric coupling (pressure fall/rise couplet) possibly causing additional problems.
Much can and probably will change over the days to come, of course. We’ll keep you updated. If things get really hectic, watch on air and/or go to wivb.com for details.
As I type this post Monday evening, all of WNY is under a Winter Storm WATCH which begins late Tuesday night and continues into late Thursday night. For our 8 WNY counties, snow begins as a light mix Tuesday evening and turns to light snow later at night. Accumulations will slowly build from E to W on Wednesday and increase further later Wednesday night into Thursday. The wraparound “deformation zone” snow will pile up the most on hills from southern Erie & Wyoming counties into the Chautauqua Ridge and parts of interior Chautauqua & northern Cattaraugus Cos with much less accumulation closer to the PA line. The N to NW flow will also enhance the snowfall amounts N & NE of the City in locations such as Batavia, Medina, and parts of inland Niagara County. Amounts near the City will be somewhat reduced.
Beyond the storm, the warming for this weekend will be slowed a little by the slow departure of the vertically stacked, weakening storm system. Temperatures should edge up to a few degrees above average by Sunday and Monday, ahead of some cooling for a few days by midweek, next week. The overall pattern will return to warmer than average in the mean much of the time out to December 22 or so. CPC, in fact, shows not a hint of a pattern change nor do they discuss one in their 8-14 Day Prognostic Discussion. On the other hand, I am seeing signs of a change in the making. The GEM and GFS 500mb ensemble means seem to clearly show a western ridge rebuilding by the 23rd with somewhat increase troughing in the east. This may or may not be tied to a forecast weakening of the currently active MJO, which is still propagating to the east. Ensemble output favors the MJO weakening considerably by later in week 2, so that its propagation would not have much of an impact compared to what would have happened had it retained its strength. There is also the question about how much influence we can expect from a poorly mixed SSW.
In any case, I’m a little perplexed why CPC isn’t putting much effort into their prog discussions for the 6-10 & 8-14 day outlooks as of late. I would rather they also pointed to what I’m pointing to, but absent their agreement I’ll stand by what I’ve said. A pattern change to colder weather is coming by Christmas Eve and the rest of the month. How MUCH colder I can’t say yet…it may or may not be a big deal.
Now that nature is done doing its worst (let’s hope!) we’ll be catching a relative break on the majority of days over the next 2 weeks. Temperatures will run below average through Friday, with some weekend moderation. Readings will drop back early next week for a couple of days before rebounding midweek. Lake effect will be strictly limited in supply with no indications of moderate or heavy accumulations into next week. In general, the upper level flow will allow some ridging in the east–in the mean–though there will be ups and downs within this pattern. So, anyone looking at smoothed temperature anomalies on CPC maps as being the whole story will be disappointed from time to time. Near the end of the 2 week period, Arctic Oscillation ensemble members have a tendency toward becoming Negative/Cold, but there is still quite a bit of spread at the end of the run–as there usually is. And the PNA seems to be taking on a Positive phase late in the period as well. Model ensemble means hint at the rebuilding of western heights late in the run, with the GEM being the strongest on that ridging. However, it can’t be foreseen if this a temporary ridging in a progressive pattern of ups and downs, or if it is going to be the beginning of a new western ridge/eastern trough amplification. Having seen the 2 links on the previous thread (http://www.cpc.ncep.noaa.gov/products/intraseasonal/temp10anim.shtml) and (https://www.aer.com/science-research/climate-weather/arctic-oscillation) posted by Dave from Rochester and Ayuud, I’m inclined to think if the end of those runs isn’t yet indicative of a return to colder conditions, it might follow shortly beyond the 14-16 day range.
As for ENSO, we still can’t say an el nino event is now occurring because the standard calls for 3 consecutive months of el nino conditions to have occurred. However, warming has continued across most of the tropical Pacific east of the dateline, and key Nino region 3.4 is now at .9 degrees above climatology. So, it’s not an event, and CPC by definition says we still have a neutral ENSO in place for now. Nonetheless, we have el nino conditions in place. This warming was in place during the recent extreme pattern, so no one should jump to conclusions that this el nino condition is bound to be a match for the probable Sudden Stratospheric Warming which seems to have taken shape. We just have no evidence at this point such would be the case. Most ENSO models still indicate a weak el nino is taking shape, but there are now a couple more members (out of more than 20) which point to a short period of moderate el nino conditions than there were a few weeks ago. An interesting note: the CFS v.2 is an outlier for next year, showing a weak el nino weakening by spring and then redeveloping more strongly toward next summer. That time range is far beyond the window of known reliability for predicting ENSO phases in the first place, but it’s also the only model showing that redevelopment.