Winter 2017-18: Discussion

fraxinus1 wrote: »

Oh great. I return to boards after being away from it for a few weeks and I'm meet with the news that there will be no snow this Winter. Another load of mild muck for us. Oh well I might log back on for the Christmas just to be festive.

Ah would ya stop. Never once have I mentioned the word snow in my forecasts here. I've never said if there's a chance or not. Why? Here's why which I must update sometime:

https://www.boards.ie/vbulletin/showpost.php?p=105178582&postcount=5

I am trying to stay away from mentioning that word for reasons stated in that link.

fraxinus1 wrote: »

Oh great. I return to boards after being away from it for a few weeks and I'm meet with the news that there will be no snow this Winter. Another load of mild muck for us. Oh well I might log back on for the Christmas just to be festive.

Ah Fraxinus,

This is the stuff we want to avoid, nowhere has anyone said it's mild muck, FAR from it. It would be somewhat appreciative if you read the thread a little bit more instead of being so pessimistic.

Even if we were to have a repeat of 2010, we'd always have some doubt in the charts. They're not the gospel by any means, so don't take it with such a poor heart!

Now that's what you call northern blocking!

M.T. Cranium wrote: »

So about that idea of mine to crunch the numbers of past winters (pressure data) and test out the findings of Oneiric3 over a longer period of time -- I now see that the wetterzentrale archives (from NOAA) have been improved in two ways. One is that they now go back 20 years further to 1851. The other is that they have maps for every six hours and also a hover feature on the display that makes it a lot faster to inspect the maps and record the numbers.

Anyway, I can report that I have started the data file, choosing Dublin as my location (I am quite sure it would not matter to the analysis what location we choose), and I have recorded the data from Jan 1 to Mar 15 1851 as well as from Nov 16 1851 to Mar 15 1852, so that's two winters down, 128 to go to reach the start of Oneiric's 1981-2010 analysis. I would probably keep going so I had the same data for 1981-2016. But I am sure it will look almost identical, an average of five locations in central Ireland is going to have almost the same pressure as Dublin every single data point.

What I noted so far, too early to see any trends of course, is that there were some strong lows passing to the north at the expected times from my own earlier reported research (Dec-Jan full and new moons) and that the winter of 1851-52 must have been tedious for anyone interested in the weather back then, it looks almost devoid of interesting events of any kind. The pressure rose quite high for most of late Feb and early March 1852 so probably some sharp frosts each morning. The winter itself looks bland with a weak zonal flow most of the time.

I chose Nov 16 to Mar 15 rather than just Dec-Jan-Feb so that I would have enough "sidebar" data to get three full lunar cycles out of each winter. When I test that part, I will line up the data by lunar dates but I will also test Oneiric's calendar year findings. It's going to take a few weeks at a minimum, especially as I am busy moving out of here and into our new location. When I have the first 30 years done we can start to talk about trends uncovered.

I scanned through winter 1852-53 to see what that looked like, and Feb 1853 looks like it could have been quite a snowy month in Ireland, if anyone has any way to check for evidence of that, have a look (mostly Feb, the good synoptics started in late Jan and lasted into early March too). A lot of cold easterly winds with lows south of Ireland, no nasty warming of oceans back then, surprised I haven't encountered tales about the winter of 1853. Feb 1853 in the CET record was 18th coldest (0.6 C).

Anyway, with the new maps posted, I had my first chance to see a few notable weather events of those two decades, for example Toronto had its highest pressure in a long period of record in Jan 1866 and while Toronto is a bit off the map grid you can see a closed 1055 mb high extending into Quebec (Jan 8 1866). Also some of the synoptics of the very heavy snowfall month of March 1870 in eastern Canada, as you'd expect, a storm track from PA to south of NS.

If you want to see these maps, go to wetterzentrale.de and click on archives, then NOAA in the drop down menus, and choose the dates you want to see. You have to be careful that it doesn't revert to the recent default date in 2014 when you move around from map to map.

If anyone wants to record any winters between my early start and 1981, and send me the data in an excel file, I'll let you know how I am recording the data. This could give us some answers earlier than I will be able to achieve solo.

According to Met Éireann, a violent snowstorm occurred on 14th February 1853. On this same day, the Queen Victoria ship struck rocks off Howth Head which led to the loss of 55 lives. The month had a CET of 0.6c which is -3.3c below the 1821-50 CET average.

I cannot find much information on February 1853, even from Mr Data himself, Kevin Bradshaw.

esposito wrote: »

The last cold snowy February I remember was 2009, at least for Dublin anyway. Around the 8th-13th if i'm not mistaken. We had a few days of lying snow in south Dublin.

The only snow I had that month (which was a big one so I can't complain) was on the 2nd/3rd:

esposito wrote: »

Ah yes, it was at the start of February 2009. Good memories, a nice easterly for a few days that closed Dublin Airport temporarily.

It was one of the few times that a SSW event destroyed the chances of cold. If it weren't for the SSW event in February 2009, some people say the cold would have went on for longer.

Donegal Storm wrote: »

February 2009 and 2010 had plenty of days with falling snow in Donegal though not much accumulation.

We had about 5 or 6cm of totally unexpected snow in Letterkenny in early February 2011, I went to bed around midnight with no mention of snow in the forecast and nothing on here, woke up at 7am to torrential snow about ankle deep, lasted about 3 or 4 days on the ground iirc

Don't think I've seen snow in February since then, we must surely be due a cold one at this stage

I do remember seeing a BBC chart with some snow to the northwest of Ireland for 3 February 2011.

Donegal Storm wrote: »

Just looked back through my photos and it was on the morning of the 7th. It was frontal snow where cold air was dragged into the back edge of the front, very localised and wasn't picked up by forecasters or anyone on here. I've rarely been as confused as I was waking up that morning :pac:

Aw yeah, I remember that too now that you mentioned it. It was an unexpectedly sunny day for me after what was a soaking weekend of downpours.... I was meant to have heavy rain especially through the morning but I had little to none.

Gonzo wrote: »

I always lean towards the milder outcomes, because 8 times out of 10 that's what we get, especially over Ireland, we are more prone to mild outcomes than anywhere else in Europe. Even a proper easterly over the UK doesn't mean that Ireland is going to join in the fun, Winter 2012 being a classic example of that. They are also far more likely to see snow from mild/cold battles than we are.

I've witnessed enough non events and chart changes in my life time to not take the threat of snow/cold too seriously until it comes into the 24-36 hour timeframe and even then it's often knife edge stuff, wondering is the temperature or due points correct, will the Irish sea develop any showers, will the Isle of Man spoil things, how far will the showers make it across Ireland from the west, wind directions, The high pressure too close to Ireland, it's often too early or too late in the season for real snow, all these scenarios.

But on rare occasions it does work out, and when that happens it makes the snow all the more truly magical.

Yep agree! In a nutshell!!

Buffalobill29 wrote: »

I hate when headline say "Ireland's cold snap is about to end and we can enjoy mild weather for the next week"...i don't enjoy mild weather, i really hate mild weather in November and especially Winter...are they clueless that people actually want snow and cold weather, not bloody mild weather!

Most, if not all, of those who work in the media assume that we, the great unwashed, subscribe to a kind of group think, where all our wishes and desires are the same, and they, the great enlightened, merely put in to words what we unthinkingly want to hear.

Needless to say, most of those who work in the media are as thick as two short planks.

I don't see much irony, when it comes to weather reporting the media tend to beat two drums constantly, the lower grade portion are constantly banging on about some unprecedented cold winter or hot summer just around the corner, and the higher grade dutifully spoon feed us the latest "proven science" that requires us to pay higher taxes that still won't be enough to change the human-disturbed weather (and when you ask, so why are we paying these taxes if it won't work anyway, then we are reminded not only is this proven science from the 99% lock-step consensus, but it's the Right Thing to Do).

The irony is that if we paid less tax, all the civil servants would stay home and global warming would presumably end.

There will be snow some day in late November or December and itl make up for Danish exhibition match

M.T. Cranium wrote: »

the lower grade banging on about some unprecedented cold winter or hot summer just around the corner, and the higher grade...

I really wonder if there is any real disparage between the so called 'higher' and 'lower' grade media outlets in terms of actual quality output. The higher grade may have more long-winded articles with the odd fancy word thrown in the attempt to give it some illusion of substance, but IMO, they are no less biased, and no less out of touch, when it comes to pretty much any topic to be honest.

Oneiric 3 wrote: »

If one was to make a long range prediction based long term averages alone, I wonder if one could make maybe make fairly reasonable long-range forecast? though of course, weather rarely follows a set pattern on a year by year basis.

However, this chart I generated showing the 1981-2010 MSLP pattern (based on a running 7 day period) for the country as a whole for the winter season, does show a fairly interesting pattern, with 3 major 'dips', occurring at specific intervals, namely: end of December, mid-late Jan and mid Feb, which would indicate that, on average, the most unsettled spells of the Winter season are likely to occur at these times. Same would with peaks, which would suggest 3 or 4 relatively settled periods to occur at fairly specific intervals in the season.




Data from the ECMWF.

_________________________________________________

As far as the December pattern shown above, the longer-term data have a similar appearance although the amplitude (as you might expect taking more data) is about half or perhaps a little more than half of this recent period (it is a higher fraction if you average the data on the assumption of a gradual forward shift in time). It may look larger than that but keep in mind that I am using unsmoothed data and Oneiric3 was using a 7d running mean which will tend to make for smaller amplitudes (timing would be less affected).

I have lined up with Oneiric's graph (visually as close as I can) the actual lowest pressure readings after 21 December (to 2 Jan) in the following graph of 20-year averages starting 1851-70 and ending with 1991-2010. Times are from the four-daily series. Pressures are in each case 1000 mb plus amount shown. This series strayed over into 1 Jan during 1931-50 then back into late December.

1851-70 ____________ 09.4 _ 26th 00z
1871-90 _____________09.4 _ 28th 18z
1891-1910 ___________ 04.9_ 29th 12z
1911-30 ______________02.3_ 30th 12z
1931-50 ______________ 08.5 _ 1st 06z
1951-70 ______________07.7 _ 30th 06z
1971-90 ___________06.7_ 20th 12z
1991-2010 ____________08.1 _ 30th 06z

The phenomenon came a bit early 1971-90, which half overlaps Oneiric3's period of 1981-2010 so I generated a separate 30-year filter for Dec 1981-2010 and found that the lowest pressure in that was

1981-2010 ___________09.5 _ 25th 06z

This is quite similar to what Oneiric3 found and is 9 mb lower than the earlier peak (12th 00z).

Meanwhile, for the entire period of record this is the late December pressure minimum.

1851-2010 ____________09.4 _ 30th 12z


The late December troughs of pressure are in some cases not the lowest in December altogether (as was the case in 1981-2010). But there is usually a peak in pressure around mid-December too, as in 1981-2010, those values (maximum for the second half of the month, except 1971-1990 where the effect was noted earlier than other periods and a higher pressure occurred towards the end of the month) are as follows ... this graphic also shows the drop in pressure towards the end of the month:

1851-70 ______ 14.2 (17th 18z) ______ -4.8 mb (8.25 d)
1871-90 __________ 15.7 (26th 12z) __ -6.3 mb (2.5 d)
1891-1910 ______ 18.5 (21st 12z) ____-13.6 mb (8.0 d)
1911-30 ______ 17.4 (17th 12z) ______-15.1 mb (13.0 d)
1931-50 __________ 20.1 (23rd 12z) __-11.6 mb (8.75 d)
1951-70 _________16.9 (21st 12z) ____ -9.2 mb (8.75 d)
1971-90 ______ 11.0 (16th 00z) ______ -4.3 mb (4.5 d)
1991-2010____ 21.1 (15th 12z) ______-13.0 mb (14.75d)

and for comparison

1981-2010 ____16.4 (15th 12z) _______ -6.9 mb (9.75d)
___ note higher before 15th by 2-3 mb __

for the entire period of record (1851-2010)

1851-2010 _______13.4 (21st 12z) ____ -4.0 mb (9.0 d)
_______________________________________________________

ANALYSIS:

The first thing worth noting is that my grid point which is slightly northeast of Oneiric3's data grid has not led to any obvious discrepancies in the analysis, the 1981-2010 data look very similar. I did not run a 7-day smoothing function on my data so we're looking at actual timing of max and min values.

It appears that this pressure wave has been a constant except for some period in the 1970s which was an interval of frequent blocking patterns. It was particularly strong from about 1891 to 1950 (perhaps a longer overlap of other intervals) and seems to be getting stronger again recently.

One possible cause that fits the slight lateward drift in the 20-year intervals would be a Sun-galactic centre resonance effect. It is possible that this amplifies lunar tides as well around late December. So the effect may be related to ocean circulations and might be discernible in other climate regions. It would make sense to find opposite pressure signals in different climate regions too, as it must balance out somehow.

The Sun is crossing the galactic equator a bit later each century, for example in the first century the Sun crossed the galactic equator around 30 Nov rather than 21-22 Dec as nowadays (this is due to the long cycle (26,400 y) of precession of the earth's axis) although the drift shown for the pressure signal here is slightly larger than the drift in dates implied by precession, which is about 2d per century. I may get a better insight into this by studying the time drift shown by any other pressure oscillations. Another factor that would speed up the lag effect (making it go faster with relation to the calendar) would be any connection to the earth's magnetic field since the North Magnetic Pole has been moving more westward in recent decades, so if anything is generated within that grid it would arrive later downstream, differentials in the 19th century would be smaller as the NMP was then either nearly stationary or moving slowly northward. Having the field stronger and focused further south could also be factors that would generate an earlier arrival. My working idea (early stages yet) would be some sort of effect generated over eastern North America or the western Atlantic around the time of solar-galactic alignment then sent downstream by travelling systems that would normally take 3-5 days to reach Ireland. I am aware of a similar effect in Toronto temperatures indicating a slight second-order peak around the time of this effect (without the 3-5 day lag).

But the main point is that the effect that Oneiric3 discovered in the data was not confined to the interval 1981-2010, and may have been stronger at times in the past, as we might expect in a stronger magnetic field with greater air mass contrasts.

I will take a similar look at the pressure wave that he found for 1981-2010 in January in the next few days. A caveat is of course that this is a background phenomenon, a 10-15 mb pressure wave while quite significant is the equivalent of a weak frontal wave, a stronger low will create a pressure wave of 30 to 50 mbs at least. But if we could find a cause and effect explanation for any of this, it would advance our understanding considerably.