Here is the just released Winter Outlook from the National Weather Service’s Climate Prediction Center. It is NOT a high confidence outlook, to be sure. But I agree with the uncertainties the Center has detailed:
This is a time of year in which normal climatology brings us lots of ups and downs in weather. We’ve recently had a few Novembers in which temperatures averaged a fair amount above average. This November often been Windier and occasionally Stormier than in those recent years.
This week of November 18th starts out seasonably cold and shifts over to seasonably mild temperatures before another transition to wintry temperatures occurs this weekend. This weekend: “Aye, there’s the rub.” Lots of uncertainty abounds, with large difference between the models, and their ensemble means. Sunday night, there were signs in the European model of a storm system which would have headed toward eastern New England and which might have given us a chance at some widespread snow. The Euro’s subsequent run took that storm farther north and east, with something of a cold blast moving in by Saturday night and Sunday. The GFS never showed that first Euro storm being close enough to us to give us widespread snow, nor did the Canadian. However, there is good agreement the coldest airmass of the season will be on its way this weekend with gusty winds and snow showers, along with some lake effect snow potential on a NW flow, which would focus the heavier LES on the hills again, well south. The GFS is considerably faster, bringing that arctic airmass in Saturday afternoon. I won’t dismiss that speed, since last week’s late week GFS wasn’t bad on the speed of Sunday night’s cold front. As of this Monday evening (bottom line) there are no good signs of a widespread heavier synoptic snowfall in WNY this weekend–though I’m not ruling out such signs recurring in future runs. But there’ll be no questioning the wintry atmosphere, with temps probably staying in the mid-upper 20s on a cold, windy Sunday, with a little moderation early next week. The GFS is chillier for Thanksgiving Day than the Euro, which has kept us consistently seasonable for that day. I won’t touch precipitation this far out.
For the bigger picture, the Climate Prediction Ctr (for newcomers…we just call it CPC) expresses high confidence for below average temperatures in the 6-10 day outlook, and average confidence for the 8-14 day outlook. That major 6-10 day cold anomaly may imply much below average temperatures for that whole stretch. However, I’m still expecting some ups within those downs. Here’s why. The indices don’t match up with a western ridge/eastern trough all that well. While I would expect the 2nd half, or even the last 2/3 of the weekend to be much colder than average, the pattern remains too progressive for a stable wrn ridge/ern trough to take up residence for too long a time. Plus, the positive heights which are showing up so frequently over the far SE also may be related to the lack of a persistently -NAO/-AO, and help to flatten the trough in the Grt Lks and NE. There continue to be no signs of a fundamental change in the PNA to cold/+ phase, so a western ridge which could force a cross polar flow simply won’t be there in the next 2 weeks. This doesn’t mean I’m expecting big Ups with any major above average temp periods…just not steady arctic air.
The MJO remains “incoherent”, weakly active, and is not expected to have a measurable impact on global weather in the next 2 weeks, at least not at our latitude. The ENSO forecast remains unchanged…neutral through next spring.
Temperatures will be heading back to near normal, then well above normal as we get into the weekend and next Monday. The initial warming will be tempered by gusty winds, adding a wind chill to the air. These winds will relax on Friday, and Saturday a more southerly flow will boost readings into the 50s. We’ll be even warmer on Sunday, with a gusty SSW wind. However, a deepening area of low pressure to our west will inject moisture into our region. The storm system will bring a strong, moist southerly flow to WNY on Monday. Both the ECMWF and GFS deterministic/operational models are in good agreement now this storm system will be deep as it passes to our north. It will bring more widespread showers into our region on a warm & windy Monday, and I’m seeing signs we may also experience some Sct Tshowers or even TStorms as a strong cold front approaches Monday night.
With this new agreement between the models, it now appears temperatures will drop rather sharply by Tuesday into Wednesday, ahead of some moderation later next week. Post frontal winds may be an issue, possibly reach Advisory criteria (or even stronger–too early to tell).
The ensemble means suggest some weak troughing either over the north central states or the Great Lakes right around Thanksgiving. As per usual, at that time range short waves and their respective amplitudes can’t be seen. The mean may end up being the smoothed mean of a higher amplitude flow. The Canadian mean has that hinted-at troughing moving back toward N & S Dakota, while the ECMWF has the trough axis at the Great Lakes. If the timing doesn’t change (and the odds on it not changing are fairly slim), Thanksgiving Day would be more likely to be cool than warm.
As I type this post, a Freeze Warning will be in effect late tonight for much of WNY. But the overall trending favors a gradual transition to above average temperatures occurring more often than not over the next few weeks. The western ridge will be “beaten down” by Pacific troughs/storm systems, allowing a mainly zonal flow to dominate by the end of the 1st week of November and into the 2nd. This continues to be a fairly high confidence extended forecast…more on that in a moment.
Within this milder than average mean trend, there will–of course–be ups and downs. Short waves will still buckle the flow, starting with a strong storm system late this week (that will produce winds approaching Advisory criteria by Friday). In its wake will be progressively chillier weather over the weekend, though nothing extreme. Some lake effect may develop in a WNW flow on Saturday, as rain showers. Some moderation will return by Monday, with signs of another short wave toward midweek, next week. Beyond that, short waves cannot be seen in the ensembles.
As for the zonal flow, the PNA ensemble has that index going negative/warm; the AO positive/warm; and the NAO positive/warm. None of this can be tied to the MJO which is weak, expected to remain weak for the next 2 weeks, and which is not propagating to the east.
But for snow/winter fans, I call your attention to the 3 words in my headline: “for a While”. This is not necessarily a sign of how trends are going to go later in the cold weather season…due to the usual variables which are not predictable beyond a couple of weeks.
Last week’s headline was telling, concerning “Hints of a Pattern Change.”
The signs are now clear we will be heading into a chillier pattern, in stages. What remains unclear is HOW chilly. And will snowflakes accompany the chilly pattern at any point?
In the broadest sense, the 500mb ensemble means offer good support for below average temperatures most days starting late this week, and amplifying by mid/late week next week. The more erratic deterministic/operational GFS & ECMWF runs at least have decent agreement between themselves on 850 temps dropping to -4 to -5, then -6 by late next week (0 or -1 or-2 generally won’t cut it at this time of the year unless there is unusual upward vertical velocity). In the GFS, the coldest part of the pattern seems to hold off until next Thursday-Friday.
If those temps were to verify, and if we had a cyclonic curvature to the flow, that would favor some snow at high elevations at times, with some possibility of a mix even at lower elevations. While these global models tend to show a predominantly NW flow during that period, they lack the resolution so far out to pick out lesser troughs/short waves which can cause alternate backing and veering of the boundary layer winds. The global models favor some periods of LES or LES/R during this cold period, but amplitudes can lessen between now and then. There may also be a trough in the SW undercutting the amplitude of the western ridge to some extent. So, while there may be some hints of excitement here for snow lovers, the cliche applies; “I wouldn’t get too worked up about it.” Not yet, anyway.
The MJO remains active, but it is weaker and will stay weak to moderate over the next 2 weeks (still considered active) with some possible eastward propagation. That weaker active status is reducing its impact at tropical latitudes to a limited extent. The indices are a mixed bag over the 2 week period. The AO is out of phrase with the NAO, tending to be closer to neutral. The NAO is sharply negative for a while, with a weakening amplitude later in the month, heading upward to neutral or even a little positive by Nov 1. The PNA is positive initially, but there is major spread in its ensemble members in week 2. The ensemble means have a flatter flow close to the end of their runs, which may be reflective of the less favorable NAO & PNA. But I wouldn’t say the mean goes completely zonal…just low amplitude.
Finally, there is continued high confidence for neutral ENSO conditions to continue well into Spring 2014.
There are some signs in the Canadian and GFS ensemble means of some increased troughing from the northern plains into the Grt Lakes sometime around the 18th-22nd. The ECMWF shows very little of that tendency but does not refute it either—it just has a very weak tendency in that direction. Possibly tied into this are hints of a more negative AO and NAO toward that time, and more of a positive PNA. However, those 3 indices have lots of spread between their ensemble members, so they’re anything but “high confidence.” As for the MJO, it is forecast to remain active for the next 2 weeks, but with more uncertainty than in recent weeks both on its strength and how much more it will propagate to the east. There are some fuzzy signs of possible weakening.
So, to avoid cherrypicking, I feel it’s appropriate to write about hints, rather than imply there are clearcut trends. There aren’t, at least not yet. On the last thread, it was brought up that Joe Bastardi spoke/wrote of the greater significance of early October positive snow anomalies in October compared to the rest of the month. Having read at least 2 technical papers by Judah Cohen, I know of no such suggestion on Cohen’s part. I could be wrong. But I doubt Bastardi is right, particularly in light of his history of cherrypicking and sensationalizing in the past.
There can be no doubt that temperatures will run well above average at least into Saturday. Despite the record deluge 2 Saturdays back, September rainfall is running a little below average for Buffalo as the month runs out, with 15 above average temperature days in the month. October will begin on a similar note, with at least a brief shakeup by Sunday or Monday as a better defined cold front crosses the region with some Showers & possible Tstorms. Even then, the ensemble means don’t establish any lasting deep trough over the Great Lakes which would allow sharply colder air to enter the picture. I should add, though, deterministic/operational models are in disarray by Sunday-Monday, with the GFS holding that cold front up until Monday in its latest run this evening. The European is faster, with a Sunday frontal passage. An observer familiar with operational models might be tempted to say, based on the past, “go with the European–it’s the best global model out there.” The European has been showing major inconsistencies from run to run, though, so there’s no auto pick here. All in all, there are no current signs of a fundamental pattern shift to a strong western ridge/eastern trough. The AO/NAO/PNA indices will be even less favorable by mid-October. And, the MJO will continue to be active for the next 2 weeks, propagating more to the east. That could have had a negative effect on cooling even while we had the negative AO/NAO.
The active MJO is probably one of the key factors in suppressing Atlantic basin tropical cyclone activity this past month. We’re up to “J”, the 10th letter in the alphabet. I have no time to look up the numbers, but I’ll venture a guess that this has been one of the least active Septembers on record, when September is normally a climatology peak period. October will begin in a similar vein, with the predicted active MJO and eastward propagation.
A slow moving ridge will keep the big features in our sensible weather rather predictable into the weekend. After a cool start, very gradual warming by mid and late week will bring temperatures back above average into and through the weekend. Readings will be Seasonably mild, not “summery”. The next chance of showers at this writing appears to be no earlier than late Sunday night and more likely Monday.
In the longer range, confidence is much lower. The indices are still pointing in roughly the same direction as they did last week. However, -NAO and -AO still have a fair amount of spread in their ensemble members, as does the +PNA. Possibly working against the climatology of those indices is the still-active MJO, which is expected also to continue unseasonably lower activity in the Atlantic hurricane basin over the next 2 weeks. The Canadian ensemble mean shows clear signs near the end of its run of a west central US ridge and troughing in the midwest and Great Lakes. However, the GFS and European means do not show such a clear trend. Both point to an ill-defined, broad trough across the upper midwest and Grt Lks which would bring less cooling than the outlierish Canadian. CPC prog discussions are also low confidence with, again, no reference to the indices above. Still, I’m not in agreement with CPC’s positive temperature anomaly for the the northern tier of the US for the whole 6-14 day period. Short waves in that range can’t be reliably predicted, especially in the 8-14 Day. But given the high uncertainties, I would have favored a neutral/normal temp outlook for the latter part of the extended range.
There are still no signs of a truly extended period of abnormally cold or warm weather over the next couple of weeks. Our extended range guidance still favors–in the mean–more ups and downs. At this time, we’re not looking at heat & humidity matching the 2 days last week, or many days as chilly as was today/Monday the 16th. But the ups and downs are fairly common as we get into autumn. This week’s warmup will bring a few days of 70s (maybe close to 80 on Friday) followed by passage of another cold front on Saturday. Cooler–but not truly cold– temperatures will return for Sunday and early next week. The Sct Tstorms reaching our region by Friday afternoon or evening will be out ahead of a cold front with enough upper air dynamics to possibly strengthen some of these cells. The showers & tstorms should exit our region by Saturday afternoon, giving way to a pleasantly cool and dry Sunday.
What’s interesting now is that the ensemble forecasts for our 3 most-discussed oscillations–the AO, NAO & PNA–are all showing tendencies which would eventually favor colder weather in the NE & Great Lakes. This trend (noticed by Think Snow last week) has now been showing up for a number of consecutive days. At this time of the year, the influence of these indices is less than it would be in the cold weather months, to be sure. But it is not a nonexistent or totally insignificant effect in late September, which is when these tendencies are forecast to take hold. I’m not yet seeing a reflection of any such impacts at the ends of the ensemble means. Frankly, however, if the indices continue in this direction (positive PNA, Negative NAO & AO), I would expect some reflection to begin showing up in the ensemble means soon. It’s possible there’s more of a lag than I recall between the indices and their reflection in the atmosphere of eastern North America. Or there may be other variables, such as the currently active MJO, which are dampening any such impacts. By the way, CPC says the 2 week MJO forecast favors suppressed tropical cyclone development in the Atlantic basin. This is in the middle of the climatological peak for that basin. I believe the more active trend will continue in comparison to mid-summer, but the activity will remain below average for this time of year through much of the remainder of the month.
As I type this post, we’re about to enter into a 2 day period of Midsummer Heat (with some accompanying humidity), to be followed by a sharp cool down late in the week. For some spots well north & northeast of the immediate metro area, the 90 degree mark should be cracked. A gusty SW wind tends to force more heating over northern Niagara, Orleans and Genesee Counties, while it keeps the temps from soaring so high in the metro area. A cold front crossing the region early Thursday will be accompanied by scattered showers & tstorms, which will have to be monitored for intensity, ushering in rather chilly air by Friday morning. On Friday, an upslope flow from the N or NE will favor more cloudiness developing during the day, along with some possible minor lake response for a few showers. The weekend which follows will feature tons o’ sun, with cool temps on Saturday, and some moderation for Sunday. Another set of fronts will approach our region early next week. The ensemble means (average trends in upper level winds) still suggest above average temperatures prevailing by later next week and possibly into the following week on most days.
The latest ENSO forecast still strongly favors neutral ENSO (no el nino, no la nina) into late winter or early spring next year. By itself, this neutral ENSO would allow more variability and more frequent cold outbreaks in the cold weather season. But ENSO does not operate “by itself” and quite a few other variables/oscillations cannot yet be determined so far in advance. The Climate Prediction Ctr is still indicating better than even odds of another milder than average winter over large swaths of the country, including our region. Me? I’m not so sure, and choose to take a wait-and-see attitude about how this winter may go. I was surprised to learn the Buffalo News actually gave the scientifically worthless gibberish of the Farmers’ Almanac prominent placement while I was off, with their ridiculous prediction for a big storm in the NY area for the Superbowl. Even if it happened, it would have not the slightest thing to do with the Farmers’ Almanac prediction, because their predictions are based on the aforementioned gibberish with no scientific validity or foundation.
The MJO/Madden-Julian Oscillation is expected to weaken by week 2, which will again make conditions for tropical cyclones to develop more unlikely again in the Atlantic hurricane basin. We are close to the all time record for a latest first hurricane in record-keeping history in the Atlantic. September is typically the most active month of all, and there is bound to be more activity by the end of the month than we’ve seen this season. But for the MJO to move toward an unfavorable phase makes even that climatology less likely to bear that much fruit. For a year with a neutral ENSO to have such little activity is unexpected. One of the culprits has been a rich plume of Saharan dust coming off Africa way out into the Atlantic, which discourages tropical development. Another negative is a large area of dry air over the central Atlantic, where cooler sea surface temps prevail…larger than usual. Tropical Storm Humberto, brewing as I type, will probably become a hurricane. But most track models take the storm northwestward and then northward into this dry air, so it will be not be a threat to the US or the Caribbean. An unusual year, to say the least.