Search the Community

I thought I would post a brief look at one aspect of Nov/Dec 2010, the record breaking cold spell that will remain a 'one-off' within all of our lives. Obviously we know what happened, but put simply, after the onslaught of very cold weather in the final week of November and first week of December, there was a brief rest-bite around the 10th to the14th; this milder spell was almost like the country surfacing for air before the cold air tightened its grip further; after this slightly milder period, the cold air dived back in across the UK from the North East until the close of the year. Okay, so the focus of what im trying to get at here is; This winter has been very very boring. I often check the GFS for signs of cold snowy weather, and i suspect many others do at this time of year, but even the charts past 192hrs+ haven't indicated much potential this year. So, what did the GFS charts hold for Nov/Dec 2010 7 days out? What did the GFS ensembles read 7 days out? Firstly, a brief look at the start of the cold spell: On 19th Nov, i took a screen grab of what the GFS was predicting for the coming Thursday 25th Nov (144hrs+). This 18z run really did start it all off- the cold weather plummeting down from Scandinavia was almost in the reliable time frame: So what happened? Well 5 days later i took a screen grab of the day (Thurs 25th) obviously this time it was a mere 24hrs away....it shows that the GFS was pretty accurate on its previous forecast... Focusing on the 10th Dec onwards, I took a couple more screen grabs from my phone while browsing the ensemble charts. The 850 temp ensembles (Using Cambridgeshire as the control point): On December the 9th the ensembles indicated a slight increase in temperatures (850's) between the 10th to the 14th, with a noticeable cold spell lasting to the 25th Dec. What is amazing here is that the mean (red line) was forecast to stay below -5 for over a week: I then took this screen grab 5 days later. As you can see, the consistency is still there, with the mean line still below -5 for the period: So, in summary: If cold weather is on the way, then i tend to look at the ensembles first. If the 850's 'mean line' is dropping away, and consistently (run after run) then i start to get interested. Obviously the operational and control charts are important, but the ensembles above clearly show the consistency and confidence of the GFS when something special may be on the way. Will that happen this winter? Paul