March 17th, 2025
- Mark Hunt
- Mar 17
- 6 min read
Hi All,
Well, we are already past the mid-point of March and in my mind winter still refuses to release its grip entirely on our weather, with continual night frosts and a biting wind chill from the north east. This week we will see that wind direction change round to south easterly / south and usher up so warmer air across the U.K & Ireland (Happy Saint Patrick's Day Ireland !!!) . Even Denmark's air temperature might hit double figures for a time 😎
The reason for this temperature change is that the high pressure system that has sat over us last week is now slinking off to the south east of the U.K and with the trailing edge of a high pulling up southerly air (clockwise rotation), that is the mechanism behind the change.
Whatever your sentiment, spring still to me feels like it is dragging its feet, even though the Chiffchaffs are starting to arrive and the first Osprey has reached Rutland Water. I was installing a weather station last week with my colleague on a ridge that was right in the firing line of that NE wind. It was a sultry 3.3°C, with a wind chill just this side of zero, positively Baltic and I can tell you spring felt a long way away. Even though temperatures will recover this week, I still think there's a question mark over the end of this month / early April with the potential effects of that SSW event potentially to play out (or not as the case may be)
The Met Office has released its summary of Winter 2024/5 taking into consideration that meteorological winter encompasses Dec / Jan / Feb. A nice clipped summary is available on the netweather.tv webpage here and it highlights how dull it was overall but particularly in December and that dreary February just gone.
Time to look forward me thinks....
General Weather Situation - w/c 17-03-2025
So for the 1st part of this week we continue in a similar pattern to last week, that is with a north easterly wind, showers pushing in off The North Sea and tracking NE - SW and sporadic sunny intervals, more of these to the west than the east. Temperatures will begrudgingly tip toe into double figures by mid-week, but night frosts will continue if the sky is clear overnight. Despite starting cold, Wednesday is the change day as that NE - SE - S wind directional change takes place and we will immediately feel the benefit in those temperatures as they climb into the teens for the U.K. Ireland and Denmark won't feel quite the same benefit but here temperatures will hit 10-11°C by Wed / Thur. Not great but a pleasant enough change as will be the wind direction.
As we approach the end of the week, we will see a BOB (Bay of Biscay )low pressure system push up on that southerly wind and introduce some rain to the equation. This will be in the form of showers from late Friday onwards overnight into Saturday. The south and south west of Ireland will also see some rain, some of it potentially heavy on Friday. Denmark will stay dry I think until Sunday afternoon / evening when a weak rain front will push up across Jutland, Funen and Zealand. So the weekend looks like being sunshine and showers with temperatures a little cooler than the end of the week, 11-12°C sort of territory with more in the way of showers I think on Sunday across the SE and Midlands initially before moving northwards. The increase in cloud cover from Thursday onwards should see us lose those overnight frosts and that's a big benefit growth-wise (more on that later)
Weather Outlook - 24-03-2025
Now next week potentially sees another wind change, this time to the NW as a more Atlantic theme to the weather is set to dominate. Winds from the north west tend to be cool and wet with plenty of cloud cover. Now the NW winds are a result of that low pressure system that sneaked up late last week. Denmark will be on the other end of that weather system, so that means southerly winds and rain will mark the start of next week here. As that low moves eastwards, Denmark will see that wind direction align with the U.K & Ireland from Tuesday onwards. So a cool, windy and unsettled start to next week me thinks but cool is still 10-12°C with cloud cover preventing overnight frost and that is a good thing. There is a suggestion of a strong Atlantic low pressure system to push across the north of Ireland into Scotland mid-week and bring some very wet and windy weather. One to keep an eye on as its storm track may change. As we progress through next week we see the wind swing to W and then SW to usher up more unsettled conditions but milder as well for the U.K, Ireland and Denmark. So the end of next week looks like being mild, unsettled and potentially better growing conditions than of late.
Agronomic Notes
I thought I'd carry on my yearly comparison of Growth-Degree-Days for the time being until spring decides to play ball. You can dress it up how you like but we are still tracking a long way back from previous years in terms of growth.
If you look at the 2025 light blue line, you can see how the line is flat for the last week or so. That means no cumulative GDD were added on a daily basis, so flat lines = no growth, upward gradient lines = periods of growth.
If you wanted to look at it another way, we could also express growth utilising the Growth Potential model which takes average day temperature and compares it with an optimum for cool season grasses (I use 18°C, the original model utilises 20°C).
I equate a daily Growth Potential of 0.4 as indicative of good spring growth where you'd expect to pick up significant clip in your box. Using this benchmark since January 1st, 2025, we have had 5 good growing days, last year by the same date we had had 15 days of good growth. So if you are waiting for seed to pop, for disease / wear scars to fill in, this is why.
Now the good news potentially is that we are moving into a period where we lose night frosts and the handbrake to growth is tentatively lifted from Thursday onwards. what's more, if next week pans out cool and unsettled, then we will still be seeing some positive growth potential. Ok, no great shakes but it'll probably be our most consistent growth period this year and that's to be welcomed. As you'd expect, further east looking across to Denmark, we will be cooler and not benefit from this until we see the SW airstream take over later next week I think. Ireland and Scotland should also see the growth pick up as well albeit at a slightly lower rate than the south of England.
Staying on a positive theme, some rain will be welcome as well because up until now we have been on the dry side and that in itself has been growth-limiting. As you can see from the yearly summary above, in March 2025 we have had more E.T than rain, which is quite unusual for March as a month, this is usually the form for April it has to be said.
Using the GFS projection above and bearing in mind we have had very little positive growth so far this year, it is vitally important to make sure you have some cool temperature nutrition in place (ammonium sulphate - potassium nitrate type) to take advantage of these short advantageous windows. Get it right and it'll tide you over to the next one arrives, get it wrong and you'll be staring at the same issues you had at the beginning of the month. All this whilst players expectations begin to rise as we approach Augusta and The Masters.
'Fail to plan, plan to fail' comes to mind.
All the best.
Mark Hunt
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