This blog post is going to be about analogue #2 I have created for Winter 2018-19 and this one is on El Niño Modoki events. I did an Autumn counterpart to this for Autumn 2018 just the other day where I explained exactly what an El Niño Modoki is but I have to assume that some people did not read that post (or for those that are in need of a reminder) and thus, I have to explain what El Niño Modoki is again.
If you did not know what a classic El Niño is, it's when warming occurs in the eastern part of the equatorial Pacific i.e. El Niño Southern Oscillation (ENSO) regions 1+2. The below diagram shows you the ENSO regions of the equatorial Pacific. The warming has to involve sea surface temperature anomalies of at least +0.5°C above average over five tri-monthly periods (an example of a tri-monthly period being Jan-Feb-Mar).
Most of the time, this warming occurs in ENSO regions 1+2 but sometimes, you can have another type of El Niño. This type of El Niño is a "central based" El Niño or in Japanese, El Niño Modoki. With this type of El Niño, the warming is focused on the central part of the Equatorial Pacific i.e. ENSO region 3.4 (see diagram above). The diagram below compares the circulation of the classic El Niño and El Niño Modoki.
The long range models are forecasting an El Niño Modoki event to occur for 2018-19 but be aware that they can be very wrong. You don't need to go back far at all to find them wrong on this. Last year (2017) for example up to July, the models were showing an El Niño event to occur in the equatorial Pacific and it was looking likely that was going to happen due to the sea surface temperature anomalies but there is the Spring predictability barrier which makes ENSO forecasting extremely difficult and next to near impossible. As a result of these model forecasts, I have decided that the next Winter 2018-19 analogue I will look at here is Winters during El Niño Modoki events.
The 500mb height reanalysis from NOAA of El Niño Modoki Winters shows an area of above average heights just to the north and west of the UK into Scandinavia and ridging over us with below average heights to the southeast of Europe. There looks to be some sort of easterly flow but not a severe one at that and just really anticyclonic. The way the high is aligned suggests that there would be a lot of frosty conditions but perhaps not much snow as the pressure is high.
Do the individual Winters follow what the overall reanalysis shows? Let's see, shall we?
1979-80: December was a very wet and mostly mild month though cooler up to the north with variable sunshine. It was still a drier December generally than 1978. January was a mostly dry and cool but sunny month with wetter conditions in the northeast of the UK and Ireland. February was a very dull, wet and mild month. Absolutely nothing like the overall reanalysis.
1986-87: December was very wet especially in Scotland and mild. It was among Scotland's wettest Decembers on record. January provided a huge change to December with a bitterly cold month setting in with one of the coldest spells ever recorded in the UK and Ireland being recorded mid-month thanks to a Beast from the East event with upper air (850hPa) temperatures widely being between -15 to -21°C on the 12th and 13th. The severe cold air resulted in huge lake effect snow. It was the last January up to 2018 when writing this blog post with a CET below 1.0°C. February was a fairly cool, dry and quiet month. March continued the Winter though with many snowfalls.
1990-91: December was fairly cold and unsettled with a notable snowstorm for some on the weekend of the 8th/9th. After a stormy start, January became very settled and anticyclonic with rather cold conditions for some but for others, it was a mild month. The first half of February was extremely cold with heavy snowfalls. Like January 1987, this was as a result of a Beast from the East event with 850hPa temperatures widely below -15°C on the 6th into the 7th. The second half of February was rather milder at times and more unsettled.
1991-92: A very anticyclonic but mild Winter with barely anything going on. One of the driest but also dullest Decembers on record. January started off fairly unsettled but then became anticyclonic with a meteorological drought (at least 15 consecutive days with 0.2mm of rain or less) setting up for the second time that season after late November/early December. February was a more unsettled month overall but still dull and mild. It was one of the dullest and driest Winters on record. There was little to no snow for the majority of places. This takes the cake for the most boring Winter I have studied.
1992-93: This was part of the warm Junes analogue so I'll post its summary here again. December started off fairly unsettled but as the month went on, it became much colder and even some ice days were recorded. The weather tended to be just quiet and frosty with a lack of snowfall. January in contrast was very zonal with the deepest and most intense storm to be recorded in the North Atlantic ever took place. This storm on the 10th January had a minimum pressure of 914mb leading to blizzards over Scotland in hurricane force winds. February was just very mild, dry and dull with not a lot going on at all.
1994-95: Exceptionally wet with each of the months being wetter than average. It was the wettest Winter on record for some before 2013-14 and 2015-16 including the majority of Ireland. December featured some unseasonable and record breakingly mild nights. This was following the warmest November on record too and we had to wait 'til March to get a taste of Winter and it was quite a snowy March at that.
2002-03: A very dull and rather wet December continued its wet weather into the first few days of January with some notable flooding over England and Wales but otherwise, the Winter then on became very sunny and mostly dry. At times, it turned severely frosty especially in mid-February with an easterly flow. The 26 January was an exceptional mild day though. Out of all the Winters here, I think 2002-03 fits the reanalysis the best.
2004-05: This was part of the warm Junes analogue so I'll post its summary here again. A mainly mild Winter overall but not exceptionally so with a notably snowy Christmas Day (which was the highlight of the season really for the majority). It was the Whitest Christmas in the last 50 or so years in terms of the number of stations reporting falling snow. The end of February and start of March brought persistent easterly winds over the countries but accumulations were small and limited leaving enthusiasts in a lot of disappointment. Only parts of the east of the UK including Kent, southeastern Scotland and northeastern England had some significant accumulations.
2009-10: This was part of the warm Junes analogue so I'll post its summary here again. The coldest Winter since 1978-79 with the longest cold spell from mid-December to mid-January since 1963. During this period, there were lots of snowfalls, especially in early January with accumulations surpassing 30cm widely. Daytime temperatures did not get above freezing on several days, especially the 7th/8th January when virtually the whole of the UK and Ireland was under severe frost and or deep snow cover. Since records began in 1910, it was the coldest Winter on record in northern Scotland. It was the coldest January since 1987. February was the coldest since 1991 though its snowfalls were rather light and cold wasn't that severe. March was the coldest since 2001 with some blizzards taking place on March 29-31. The month was full of air frost due to an anticyclone giving away to lots of sun during much of March. April and May continued to record some air frost too and it was the longest "Winter" in that case since 1996. It was also a very cold Winter over much of Europe and parts of north America thanks to a record breaking negative North Atlantic Oscillation (NAO).
Following on from the warm Junes analogue, 2009/10, 2004/05 and 1992/93 have appeared again. If you do not know how analogues work, I pick a topic like warm Junes and look at the seasons that followed them or took place during the event. At the end of the analogue season, I bring them all together and put the most common years that appeared in the analogues into one overall analogue for the season and each individual month. For a year to qualify in this category, it must at least appear in 5 of the analogues. These years; 2009/10, 2004/05 and 1992/93, are the most common years to appear in the analogues so far but as we go over more analogues, maybe these will change and become less common or vice versa. Stay tuned for our long season of analogues. I will say that El Niño Modoki combined with other factors like low solar activity make for an epic combination for cold Winters.
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