From the outset this has been an incredibly difficult forecast to work through, with multiple variables this season that are outside expected parameters. In essence, it is a winter where wildcards are in abundance.
Temperatures - Front Loaded Cold
During December and January, there is a greater probability (60%-70%) of colder than average conditions as high pressure systems become situated in, around and particularly to the north of the UK. This points to an increased risk of cold air masses originating from the north or east affecting the UK. A lower likelihood outcome is that temperatures during this period will be close to average, but even so, relatively cold conditions can be expected at times, and especially so when compared with last December and January. There is the potential for a change to milder conditions later in the winter, but this is an uncertain development at the current time.
Rainfall - Dry First Half, Potentially Becoming Wetter Later
The overriding signal this winter is for a greater chance (>75%) of slightly drier than average conditions during the first half of the season. This is due to the expectation of frequent high pressure and 'blocking patterns'. This signal is in contrast to last winter, with December expected to be very different to the exceptionally wet and windy December of 2015. There may well be a recovery in precipitation totals to nearer average through February and the latter half of the winter in general, but given the time frame involved this is an uncertain development, with a lower likelihood (>25%) of drier conditions continuing throughout the winter period.
New - Forecast updates
Over the last two seasons, we have issued a full December, January and February synopsis and prediction across the Winter. And while the full forecast examines similar analogues and provides a commentary on the season, we acknowledge that during winter, and in particular a year with so many 'wildcards' it will be useful to provide a consistent evaluation of the atmosphere.
With this in mind, we plan to issue a regular summary mid-month to capture where the atmosphere may have moved, and whether this inflects upon the following months. We feel this will be of assistance in updating readers on what has or has not changed within the key assumptions of the forecast.