SUMMARY – TEMPERATURE: For November-December-January above-average temperatures are more probable than below-average temperatures. Overall, the probability that the UK-average temperature for November-December-January will fall into the coldest of our five categories is between 10% and 15% and the probability that it will fall into the warmest of our five categories is between 30% and 35% (the 1981-2010 probability for each of these categories is 20%). CONTEXT: Sea surface temperatures in the tropical Central and Eastern Pacific have now fallen close to La Niña thresholds. Long-range prediction systems indicate this cooling is very likely to continue in the coming weeks, leading to a full La Niña event over the next few months. La Niña slightly increases the chances of blocking patterns over the North Atlantic and Europe in late autumn and early winter, leading to increased chances of colder-than-average conditions. The Quasi-Biennial Oscillation (QBO), an oscillation of the equatorial winds in the stratosphere, is in an easterly phase. The QBO is linked to conditions over Western Europe during late autumn and early winter through an influence on the phase of the North Atlantic Oscillation (NAO) at the surface. An easterly phase of the QBO tends to moderately increase the chances of a negative phase of the NAO, which in turn increases the chances of below-average temperatures. Sea surface temperatures in the North Atlantic are generally above average, consistent with the current high levels of warmth globally. West of the UK, however, temperatures are slightly below average. Nevertheless, warmth beneath the ocean surface, which is expected to have an increasing influence on surface conditions as the period progresses, favours higher-than-normal temperatures for the time of year. For November-December-January as a whole, long-range forecast systems generally show an increased chance of westerly air flow over the UK, although some show more likelihood of high-pressure patterns over the North Atlantic implying a greater likelihood of northerly or north-westerly winds. Overall, the outlook shows increased chances of above-average temperatures in the 3-month period (see figure T2). Despite this, the risk of colder-than-normal conditions remains a significant possibility, with some of the drivers of UK winter weather, such as La Niña and the QBO, favouring weather patterns associated with colder-than-normal weather.
Thought it worth pasting the full METO contingency forecast for November to January.
They come down on the warmer than average side but with a significant possibility of colder than normal.
Overall I would still go for an NAo+ winter.
Originally Posted by: roger63