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03-08-2017, 23:55   #1
snowstorm445
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Winter 2017-18: Discussion

Well after a fairly mixed summer thus far perhaps we can now turn toward the end of the year for the season that draws the most interest from boards.ie users (and which provides the most emotional volatility): winter.

It's now been 7 years since the famous spell of late 2010, a world away from the consistently average-to-mild winters we've seen up until now. Since then there hasn't been a major cold spell lasting more than a day or two, with some parts of the country, particularly the east and south, having seen very little lying snowfall at all.

Will we strike gold this year? Are there any indications of major patterns in long range forecasts? Any hunches?
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04-08-2017, 01:23   #2
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I'll go over it all tomorrow .
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04-08-2017, 12:26   #3
cena
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winter weather

Does Ireland get cold enough for water to freeze each year?
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04-08-2017, 12:32   #4
Dr Crayfish
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I'll take a mild dry (if I remember correctly) winter like last year again please
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04-08-2017, 12:35   #5
Elmer Blooker
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Well ... the sun has gone quiet, note we have already had more spotless days in 2017 (with four months left in the year) than all of 2010. Nothing like '09 though when the sun was as dead as a door nail!
There was only THREE spotless days in the five years 2011-15 inclusive.
I'm not saying a snowy winter is on the cards but a quiet sun greatly improves the prospects.
http://www.spaceweather.com/
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04-08-2017, 13:13   #6
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If we end up with another snowless winter, i'll easily take a dry mild winter over a wet, stormy and cold one.
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04-08-2017, 13:16   #7
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Quote:
Originally Posted by cena View Post
Does Ireland get cold enough for water to freeze each year?
by water freezing I take it you mean rivers, small lakes and harbours. It rarely happens in this country. Last time that happened was 2010, and before that I can't even remember, maybe 1991.
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04-08-2017, 13:16   #8
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Ok so I'm going to be doing a couple of posts on different aspects. In the ENSO thread here: http://www.boards.ie/vbulletin/showt...p?t=2057713492, I've been discussing about Winter 2017/18 on what it could be like given the possible outcomes of ENSO.

I will go over what I have been talking 'bout since I made that thread in regards to Winter 2017/18. So yes, the topic of this post is ENSO.

Back in the Spring, it looked like we could have been heading into an El Nino event and quite a moderate one at that. Normally, a moderate El Nino is actually a very good sign for a cold Winter. Winter 2009/10 had a moderate El Nino - though there were plenty of other factors at play also. This is my reanalysis on historical moderate El Nino winters:



The reanalysis clearly showed a high chance of a cold Winter with a southerly tracking jet stream and very intense Northern Blocking as the winds go clockwise into an easterly direction.

As we eventually got past the Spring unpredictable barrier, the models were pointing more towards a weak El Nino and then ENSO neutral. I started looking at weak El Nino winters then, this is my reanalysis for them:



The reanalysis shows plenty of Northern Blocking but the jet stream is going through the country. This is very evident of Winter 2013/14 which had a similar chart. A weak El Nino is not a good sign at all for Winter. This was the trend on the models for a while then until late June and July. I decided to look at weak El Nino winters that were preceded by weak La Nina winters because as we know, Winter 2016/17 was a weak La Nina winter.



This was even worse than the previous weak El Nino chart as the jet stream is on a perfect westerly regime. With the very low heights and the intensified westerlies, it would be very stormy.

Fortunately, there was also the chance of ENSO neutral so I had a look at ENSO neutral winters that were preceded by weak La Nina winters.

This is the reanalysis of said winters.



It shows clearly Northern Blocking. It also shows a trough to the south with the winds coming in a clockwise direction from an easterly. This means it would be a rather unsettled but cold Winter. If the cold is intense then a very snowy Winter. This is a beautiful chart if that's the case.

The Pacific then started to significantly cool down during late June and July. As a result, the models reacted to this cooling and then started showing the possibility of a weak La Nina - once again for 2017/18. El Nino by this stage was dead and long gone.

I looked at the weak La Nina winters that were preceded by weak La Nina winters then. This is the reanalysis of said winters.



This was quite similar to the ENSO neutral chart but even better! It shows a very January 1982 or December 1995-esque kind of setup. This means extreme cold is possible - both months got down to -27c in Scotland.

What I think is the most possible outcome for ENSO is ENSO neutral. However, as can be seen from last year's extremely weak La Nina, a weak La Nina is certainly possible.

I will explain how similar 2012 is to the situation now in regards to ENSO in a post soon.
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04-08-2017, 13:47   #9
pauldry
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Has to be a fairly cold november and december or else our IMT in Sligo will be higher than any year by far

Though having said that July was well over a degree below average after jan to jun above.
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04-08-2017, 13:57   #10
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If it so not going to me snowy and cold well then Mild and Dry will be better off
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04-08-2017, 14:03   #11
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In May 2012, SST anomalies towards the eastern side of the ENSO region - over towards Peru, were increasing significantly. In Winter 2011/12, a weak La Nina took place just like in Winter 2016/17.



It was a very similar situation in the February-April 2017 timeframe with the SST anomalies showing El Nino status towards the eastern side of the ENSO region thus why the models reacted to the situation of showing an El Nino event for 2017/18. However, by May 2017, these SST anomalies were beginning to cool down unlike in 2012.



Eventually by the end of August 2012, the SST anomalies were beginning to cool down significantly. By November, the Pacific was in a cooler state and was on the negative side of neutral. Models such as the CFSv2 reacted to the situation of the cooling just like here in 2017 and they predicted a La Nina for Winter 2012/13. Of course that did not come off however as it was an ENSO neutral Winter. This goes back to me saying Winter 2017/18 will be an ENSO neutral Winter. Winter 2012/13 was a cold one but also an unsettled one. Then of course you had that cold Spring and of course the coldest March since 1962. As you saw from the reanalysis, Weak La Nina to ENSO neutral winters are good for a higher chance of a cold Winter.

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04-08-2017, 14:16   #12
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Now onto the North Atlantic and the NAO. As you can see from the current Atlantic SST anomalies, the Atlantic is in quite a mix with some cold blobs here and there but also some warm bands. Near the end of July, I looked to see if there are any matches in regards to the distribution of the Atlantic SST anomalies. There have been some matches though of course not perfect matches - see them below.



2016:



2010:



2005:



2004:



2001:



Overall, I think 2010 provides the best match.
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04-08-2017, 14:25   #13
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Last winter was the most boring from what I remember...any weather is better than no weather
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04-08-2017, 14:42   #14
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The NAO in May is considered to be a factor in predicting the Winter. This is because due to research, there seems to be a correlation between the setup in May and Winter. May is normally the quietest month in terms of westerlies or the jet stream during the year in Ireland. May 2017 had a negative NAO throughout the month as can be seen from NOAA's chart:



However, there was no tripole. If you don't know what a tripole is, here's an example of a tripole in May 2010. Of course, we all know what happened after that - the December to remember of 2010.



This was the SST anomaly chart for May 29th 2017 (it's updated every Monday). As you can see like I said, there is no tripole as the bands are as follows: Cold, cold, warm when you want Warm, cold, warm so we were very close to a tripole.



However, in May 2009, there was no tripole either. The Met Office predicted as a result for Winter 2009/10 to be a mild one. Of course, they laughably failed on this prediction and it was the coldest Winter since 1978/79. In May 2009, we weren't even close to a negative NAO or a tripole - then the Winter of 2009/10 had a record breaking negative NAO.

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04-08-2017, 14:47   #15
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It's not Winter but I thought I'd add it here. The CanSIPS model is showing very significant Northern Blocking for November 2017 and in turn, a negative NAO.

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