Winter Forecast 2010-2011- Average Winter, Dry, Mild End
Factors affecting winter forecast (period 1.12.11- 29.2.12)
• Enso state
• Solar activity
• QBO
• Yearly analogues
• Jet stream behaviour
• Long range model output (CFS, ECM LONG RANGE etc)
So here it is, the winter preliminary thoughts as promised; this particular has proven more tricky to put together than last year’s offering and so confidence is slightly reduced due to conflicting signals. During the past 6 months we have seen a reduction in the strength of the la Nina that was particularly prevalent during the latter half of winter 2010/2011, even so we remain in la Nina conditions- however predictions are for a weak la Nina rather than a moderate/strong offering. I consider this to be a good pointer to a colder than average winter across the UK.
However, less positive indicators include the awakening of the sun which has seen heightened activity over the last 12 months and a propensity of the jet stream to migrate further north than has been the case prior to the beginning of the year and post 2006.
Long range model output at this moment in time appears to support the notion of a dry winter period, this can be seen within long range forecasting models such as the ECM. Another theme appears with average temperatures being displayed across models such as the CFS. This suggests high pressure over or very close to UK shores.
Winter to start off colder than it ends- November into December looks to be the coldest period of the winter, much like 2010-2011, a much milder end to the winter seems likely with an early spring season.
December
Starting off cold or perhaps very cold with a propensity for high pressure around Iceland and southern Greenland with east to northeasterly winds being the dominant direction. As the month progresses, it remains cold with some very cold minima but with high levels of sunshine relative to the time of year. A dry month with rainfall around 70% of average or lower. Less in the way of snow as the month progresses with high pressure, originally across Iceland, slipping south to settle on top of the UK.
CET estimate: Below Average
January
The month starts off cold and dry with extensive night time frosts but predominantly dry. Day time temperatures will be on the cold side though will feel pleasant in the extensive sunny intervals where mist and fog clears. Throughout the month, high pressure will settle over or very close to the UK but with a southward trend and thus allowing an Atlantic feed into the north of Scotland and Ireland. This atlantic influence will increase temperatures and will begin to spread further south during the month as the jet stream powers up over the top of the high pressure cell. An average month in terms of temperature but possibly below in terms of precipitation.
CET estimate: Average
February
An above average month in terms of temperatures- synoptics akin to February 1998 though perhaps not as mild. High pressure slips away south with powerful jetstream to the north. Rain and drizzle commonplace across northern and western areas with the driest weather across the south and east. Limited frost potential.
CET estimate: Above average
These are my preliminary thoughts on winter 2011-2012, the final forecast will be released around the middle of November.
CreweCold
Crewe, Cheshire
55 metres above sea level