"Released on 2nd December 2018 this is the official Winter 2018/19 Forecast from GWV!
We being by bringing together the GWV Winter forecast methodology - SST anomalies, ENSO, Solar activity, Autumn pattern matching, etc. - To see which years have come out as the closest match to 2018.
Using a spreadsheet covering every year from 1850 and 2017 and our bespoke "total score" system we see that the beat matches from 2018 were: 1984, 1975, 1968, 1953, 1995, 1983, 1976, 1911, 1937 and 1913 which comes out as the number one match to 2018 with a score of 6.5.
So the relevant Winter 2018/19 analogues are 1984/85, 1975/76, 1968/69,19 53/54, 1995/96, 1983/84, 1976/77, 1911/12, 1937/38 and 1913/14.
We have a variety of individual outcomes from these top ten analogues but putting them together we see a very clear signal. In December we favour a blocking area of high pressure centered to the north-east of the UK with below average heights over and slightly to the south of the country. This indicates the risk of colder conditions at times during December but probably not an especially cold month overall as the blocking signal is quite weak.
In January we see a massive strengthening of the blocking signal which covers most of Greenland. A trough to the south of the UK would leave us in cold northerly or easterly winds and these cold blocking signals continue into February as well - Based on these analogues you would expect both January and February to be colder than average months.
In March the blocking signal weakens quite a lot and with below average heights to the south-west of the UK a milder, wetter month would probably be expected in March.
The top ten scoring Winters overall come out with a significant blocking and would be expected to be colder than average Winters on average (of course some of these Winters would deviate from that signal.
The top ten scoring Winters favour colder and drier than average conditions overall. December is forecast to be close to average but January and February are forecast to be slightly colder than average in the UK with much of northern Europe forecast to have a cold or very cold Winter. We do increasingly see a pattern of drier than average conditions across the north of Europe and wetter than average conditions through southern Europe and that is particularly the case in January and February as we start to pick up a southerly tracking jet stream.
If we narrow things down to the top seven scoring Winters we see very similar patterns with the only real difference being that February slightly favours a reduction of the northern blocking signal and has average temperatures for the UK rather than colder than average as we see in the top ten.
Overall our top ten Winter analogues do seem to be suggesting a slightly colder than average for the UK for Winter 2018/19 but one work of caution is what happens if we narrow things down to just the top two scoring years (which for the Winters are 1937/1938 and 1913/1914) because we then see a dramatic change as we flip to a much milder Winter outcome with only December possibly proving to be colder while January and February come out as much more Atlantic-driven and therefore milder westerly months.
So what is the GWV Winter 2018/19 Forecats?
Combining our methodology analogues with the NAO forecast, taking into account Eurasian snow cover and the warm sea surface temperature anomaly in the north-east pacific as well as everything else we've been looking at this season along with the long range seasonal models the GWV Winter 2018/19 forecast is as follows:
We predict a slightly colder than average winter is likely this year for the UK. Temperature anomalies are forecast to be 0.5C to 1,0C below the 81-10 average. A drier than average Winter is also expected overall as well, however we think milder and wetter interludes are likely to occur (which is why we aren't going fr a very cold Winter) and in those milder/wetter periods significant rain is likely to occur!
We think December could come out around or slightly milder than average while January and February are likely to be colder than average. Our analogues are clearly showing January to be the coldest month of the Winter but ENSO and QBO data suggests February is likely to be the coldest months. Either way both January and February should come our below the 81-10 average although probably not that significantly as milder westerly episodes will still occur as the blocking high's come and go and then come back again.
In a very changeable but cold Winter pattern snow is likely to occur with above average frequency although as stated a drier than average Winter seems probable overall.
All three Winter months should contain at least one appreciably colder than average episode but the cold risks probably grow as the Winter progresses. One way we'll know early on if the forecast is on track will be if December has at least one northerly or easterly outbreak - While we don't expect any cold weather to last long in December we will be looking for a cold interval in December to tell us that the forecast is performing OK. Cold outbreaks should then become more frequent during January and February.
A very cold or severe Winter can't be ruled out but we think with Atlantic SST's not favourable to a cold Winter, the warm SST's in the north-eastern Pacific and the transition from the east to the westerly phase of the QBO there should be enough energy within the jet stream to bring periods of moderation with milder/wetter westerly winds.
Equally a mild or very mild Winter can't be discounted particularly with 1937 and 1913 proving to be such close analogues for 2018.
We don't see any "fence-sitting" about this Winter - We think it will either cold or mild to very mild. We've favoured slightly colder than average for our forecast as what we think is the most likely outcome but if this forecast fails it will do so spectacularly!
Much of northern and central Europe is expected to have a cold or possibly even very cold Winter while south-east Europe could be relatively mild. Southern Europe may start off quite dry and mild but we're expecting January and February to be increasingly unsettled and cold through the Mediterranean. This leaves western Europe looking slightly colder than average but with some moderation at times.
Overall a very interesting Winter with loads to keep an eye one.
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https://www.gavsweathervids.com/winter- ... recast.php