February 10th, 2025
February as a month is usually a dull and cold one with easterly winds a common feature and 2025 is no exception. The February of 2024 definitely was the exception, more on that later. Looking at the weather patterns on the latest GFS projections and how the jet stream is behaving had me reaching for the search engine and keying in 'Sudden Stratospheric Warming'. (SSW)
Sure enough, we have one ongoing currently above The North Pole with a rare splitting of the Polar Vortex. This signals very cold weather for Canada and North America but not necessarily for us.
That said January has (and I think February may) record temperatures colder than the 1991-2020 long-term average. SSW events don't always impact on the weather across the U.K and Europe but they can do. (Note - in 2024 we had 3 SSW events but one of our mildest starts to the year so it doesn't always follow)
Below is a super video from The Met Office explaining what happens during a SSW and what effect it can have and why.
Read about Sudden Stratospheric Warming and how it may affect our weather at The Met Office here
So those current easterlies that are in place may well become more a feature of February 2025's weather picture and certainly we can see on the GFS, a stalled jet stream with an Omega Blocking Event in place. The risk is with cold air to the east of us this can then allow colder air to dominate later in the month. It is worth saying that in some years when we have had a SSW event, we just see a blocking event that eventually peters out to allow the more normal westerly airflow to dominate without a cold snap, but as the narrator above comments, it does increase the chance of this occurring as the jet stream drops south and weakens. One to keep an eye on me thinks.
Thankfully February is also a shorter month and to me it is one where we just have to grin and bear with, knowing that March is around the corner. Nature is the same I think though I was very surprised to pick up a young Hedgehog feeding at night (I put some food out as I had a hunch we had a nocturnal visitor) because usually they are hibernating until the middle of March. I suspect this one is unwell and may be destined for the local Wildlife hospital.
When the weather is rubbish, I turn to baking to keep in a happy mode and so to my quest to make Rye bread Danish-style. Happy to say my third ryebread starter came up trumps and over the weekend I managed to bake my first ever loaves of Rugbrød. Not perfect by any means, that'll come as I apply myself to the art, but I now have the basis for some Winter Smørrebrød (Danish Open Sandwiches).
Rye as a plant is more winter hardy than wheat and so tends to be grown in the north of the northern hemisphere and being naturally high in fibre, it's a healthy addition. For this reason, this type of bread is a feature of the Scandinavian and Icelandic diet. Indeed in Iceland, they use the natural thermal nature of the earth to keep their bread starters at the right temperature prior to baking, placing them in little pits covered with slate to house them, how smart is that ?
General Weather Situation - w/c 10-02-2025
Last week,we picked up a southerly low pressure that funnelled rain / sleet across the south and south east of England and this week I think we will see the same phenomenon occurring right from the get go on Monday as rain and sleet push in from the east across the southern half of the U.K. A low-lying, southerly low pressure means that the wind direction will continue in an easterly / south easterly direction and it will feel in a mix of rain, mizzle, sleet and maybe snow during the week to the southern part of the U.K. At the same time as we have this southerly low pressure doing its work, we also have an Atlantic low pressure trying to impose from the west and that'll feel in rain to the west / Ireland on an ever-so slightly milder airstream later in the week, most likely from Thursday onwards. Away from these incursions, it'll be cold and dull as that easterly wind picks up cloud and Haar from The North Sea and pushes it inland. Sometimes that mix of low-lying cloud will be thick enough to fall as drizzle and rain across eastern areas and the east Midlands.
That cold airstream means night frosts will be a common feature of this week dependent on cloud cover.
From Thursday onwards that wind tilts more to the south east for us all and that could pull in a little more in the way of sunshine but it'll still feel parky with the effect of wind chill. As we get into the weekend I think we settle down to cold and dry, except for Ireland where that Atlantic low will continue to push rain across western and southern areas. For Denmark though, that southerly low sneaks up the Dutch coast later in the week and that could introduce some wintry showers to Jylland and to Sealand at the end of the week, cold and dry before that I think with a biting south easterly wind.
Beyond this week is I think not worth documenting yet because of the SSW event and how that may yet determine the weather later this month. For what it is worth, the GFS is currently predicting a cold air mass from The Atlantic to impact the UK & Ireland towards the end of February.
Agronomic Notes
Bearing in mind my previous reference to how 2025 has started off as a cold one, I thought I'd chart out the GDD-to-date from my default location @ The Oxfordshire, UK.
For clarification purposes, I'd like to point out I use 6°C as the base unit for this calculation rather than 0°C as is utilised in the U.S. I often get asked why ?
Well to me it is an entirely logical. 6°C as a specific air temperature is where we begin to see shoot growth and since GDD is a growth model (there is a clue in the name) and I am primarily concerned with comparing the potential for the grass plant to grow year-on-year, the model should be indicative of this. I understand there's a counter argument to this with the use of 0°C as a base from a product basis but if we have a positive GDD reading I want that to be indicative of the potential of the grass plant to grow. In some ways, using Growth Potential as a measure of potential growth is more accurate still and supersedes the use of GDD.
So above is the graph of cumulative GDD for this year vs. 2024/2023 and 2022.
You can see just how cold we have been so far this year tracking way lower than we have for a number of years. This is the benefit of measuring GDD because it gives you a good yardstick and an actual measurement rather than just saying "Well it has been cold so we haven't had much growth this year so far". It also allows you to see the difference year-on-year and how in previous years (last year for instance) we were way ahead from a growth perspective. 2025 has started very much like 2013 and if the month pans out as I suspect it will, by the end of February we will be looking at one of our lowest GDD totals for the y-t-d since the early 2000's.
Since GDD is measurement involving the maximum and minimum daily air temperature, it follows that a low GDD total means a cool / cold start to the year.
At odds with the global rhetoric / reporting of our constantly warming planet, but that's entirely logical because our climate is affected by the jet stream and as I have said many times before, it is the behaviour of the jet stream that governs our weather. With more blocking events predicted as a consequence of a warming North Pole, the potential for warm air, but also cold air blocking events is always there. Watch this space for the rest of February to see if we get the latter.
All the best.
Mark Hunt
Good luck with Hedgehog......... and will be interesting to see how this pans out... was 2013 warm and dry later on? looking at getting bee supers on.. could do with a bit more warmth soon..