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Every month we issue a new seasonal weather prediction for the upcoming season. Full versions of these extended weather predictions include charts and figures and cover the Spring, Summer, Autumn and Winter periods. They are available on Amazon Kindle or PayPal. We also offer a weather subscription service that is offered to businesses and individuals that depend on the weather. The current seasonal weather prediction is detailed below ...
Re-analysis of our past forecasts with atmospheric temperature measurements indicates that our error margins are much too narrow, so we’ve adjusted the range of these possible outputs to +/- 1.5oC (4.8oF) to cover a much broader range of possible weather scenarios. The change also influences: Heating Degree Day data.
Seasonal Forecast for Winter 2011 - 2012 (Shortened)
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Valid from: 1st December until 29th February 2011
Issued: 30th November, 2011 (Final Edition)
Blocking Index: 7.3/10.0 (upper third on scale - According to our upper air flow blocking coding system)
During the course of November, major blocking patterns have been observed over north-west Europe, located between a two-way diverted jet stream. The increased southerly component of airflow relative to north has seen temperatures climb well above average for many parts of the UK and Ireland. In our previous forecast we anticipated the weather to swing into a more negative NAO phase, with an increased prevalence of cold weather blocking patterns. Although this cold transition has not yet been observed in November, a formation of a strong warm dipole either side of the North Atlantic indicates a change toward intense blocking features over the mid-Atlantic Ocean. The northerly placement of the polar jet stream in the vicinity of Greenland is beginning to spin-up deep and compact low pressure systems that have stormed into Scotland and Northern England. This north-westerly polar airflow is expected to dominate the scene for at least the first half of the winter period, with brief Arctic blasts bringing wintry showers to the north and the exposed coastlines. The long-range forecasts currently indicate that snowfall is likely in England during the middle of December, with a biting northerly wind-chill.
The current atmospheric signal also indicates that we are in an active period of cyclonic activity, although the tendency toward north-westerlies will bring a distinct chill factor and with temperatures typically around the long term average. Night time frosts are likely to be infrequent throughout the early part of the winter, due to high winds and increased cloud cover.
General Overview:
During the winter 2011-12 season, temperatures are likely to be close to average for much of the United Kingdom and Republic of Ireland with an anomaly of +0.2 ± 1.5oC (+0.4 ± 2.6oF). Much of this warm anomaly is due to a strong climate signal in the North-west Atlantic Ocean, whilst a cold dipole in the mid-Atlantic Ocean is indicative of a distant and strong blocking pattern with cold north-westerly winds. The energy required for heating a household or work-place is likely to be below average with an anomaly of -2 ± 13%, indicating less heating demand than during the inter-annual winter average spanning the years 1961 – 1990. Since land surface temperatures have slowly been increasing over the British Isles over the past few decades, this represents a cool winter (1 in 3) compared to the base period of 2005 to 2010. A combination of above average storminess and higher temperatures indicate close to average snow day events across much the UK and Ireland, with an anomaly of -1%. These calculations were achieved using the SnowCast predictions at Weather Logistics UK
The winter weather is likely to be experience near-average precipitation across all counties. Precipitation anomalies are likely to be around 104 ± 22% (with precipitation events +2% above average). Although there is a great deal of uncertainty at this stage, the North Atlantic Oscillation (NAO) is generally expected to be negative later in the season, giving rise to some severe cold at times. At present, the predictions are based on a cautious estimate of a slightly positive index of +0.5, based on NOAA data from the last two months and the trend toward Arctic weather by mid-December. Cold and wintry events are more likely to affect the exposed coasts of the UK and Scotland during the early season, as brisk periods of Arctic airflow take the bite. Easterly winds may develop later in the winter season, as the NAO tends to become more negative and if the mid-Atlantic cold anomaly in sea temperatures strengthens further.
In summary: Signals are currently in favour of a typical winter, with temperatures and rainfall close to average for many parts of the UK and the Republic of Ireland. There is a strong possibility of Arctic winds or easterly winds dominating the season throughout the British Isles, particularly over Eastern counties of England and Scotland if the long term weather swings to strongly negative NAO indices during the early to mid-season period.
Updates from last month …
Since our last forecast there has been an incremental rise in the NAO input from +0.3 to +0.5 that acts to strengthen the north-south trend of temperature and rainfall. The blocking index, based on the most likely positions and intensities of high pressures is similar, but with strong blocking patterns more likely to appear over the mid-Atlantic Ocean at 25oW. North Atlantic Ocean sea temperature anomalies have undergone a significant transition from last month, again confirming that blocking patterns in the mid-Atlantic are very likely. Due to the intensification of the jet stream at the southerly tip of Greenland a strong polar maritime theme will dominate the weather with frequent and heavy wintry showers in Northern England and Scotland. Stormy conditions are also expected for much of the United Kingdom as the weather systems converge downstream. The British Isles temperature anomaly has been decreased by 0.8oC to +0.2oC, aided by the tendency toward north-westerly airflow and falling SST anomalies in line with a well established La Nina. The weather is likely to remain changeable during the winter period, but with extreme periods of cold and snow likely at times as the winds swings toward the north in several sharp Arctic blasts. This is the final update of the winter and supersedes any previous seasonal forecasts.
Heating Degree Days (HDD) % Anomalies
Winter 2011 - 2012 Forecast
Heating Degree Days (HDD) % Anomalies
Winter Period December '11 to February '12
The heating degree data for you region can be found using the following links...
Aberdeen ; Belfast ; Birmingham ; Bristol ; Cardiff ; Durham ; Edinburgh ; Exeter ; Glasgow ; Leeds ; London ; Manchester ; Newcastle ; Norwich ; Nottingham ; Pembroke ; Sheffield ; Southampton ; Tenby ;Worked example for Aberdeen in Scotland (UK)
The figures linked above show the average daily maximum (red) and minimum (blue) temperatures with solid lines. The data is based on a 1961 - 1990 climatology of monthly temperatures from UK Meteorological Office data. Monthly data has been smoothed to indicate the gradual transition of annual temperatures for several UK towns and cities, reporting an error of ±0.5°C (0.9°F). The figure also indicates upper and lower bounds of HDD (CDD) anomalies by blue and red dashed lines. For example the average day and night temperature for Aberdeen on 1st January is +1.6°C (34.9°F). When the minimum and maximum temperatures are equal to the lower dashed blue and red lines respectively energy consumption for heating would be 20% greater than the climate average. In contrast, during a warmer interlude with a daily mean outdoor temperature of +4.4C, 20% less household heating would be require to reach a standard room temperature (HDD down -20%). For this day the daily maximum temperature would be on the upper red and blue dashed lines.
