February 17th, 2025

Hi All,

Short blog this week but some good news from a temperature perspective as the Sudden Stratospheric warming event across The North Pole doesn't seem to be affecting our current / near-term weather prognosis.

Indeed quite the opposite as from mid-week we look to pick up a pronounced change in our wind direction from the current easterly to a much milder southerly. After what seems like months of cold, this is going to feel a lot like spring has arrived !

That's great news as the weekend just gone was a pretty miserable one, especially Saturday with its incessant drizzle / sleet and cold. I sort solace with another round of Danish baking, with some more Rugbrød and Tebirkes (which this time retained their integrity !!)

You can see the difference in these two images taken from Meteoblue below ;

Images courtesy of meteoblue.com

With that warm weather out to the west of us, it will be Ireland, The South West, Wales and western coasts that will feel the most immediate benefit temperature-wise but central and eastern areas will notice the difference as well. Unfortunately this milder air won't push enough eastwards to provide a taste of spring for my Danish counterparts, but it will probably bring an end to the run of hard frosts that they have endured.

Animated GIF courtesy of tropicaltidbits.com w/c 17-02-25

General Weather Situation - w/c 17th February, 2025

So this week we start off with pretty much normal service for February so far with cool temperatures after a hard frost overnight. Some sunshine though so let's not knock it. The wind will be south easterly and the outlook is dry for all areas, except Ireland and Scotland, where we will see rain pushing into the west later this afternoon. This rain will vector north and east across Northern Ireland into Scotland where it'll butt up against the resident mass of cold air and fall as snow overnight into Tuesday, Tuesday looks to be a re-run of Monday with rain pushing across Ireland during the day and this time crossing The Irish Sea into Wales overnight into Wednesday. This rain will push easterly but fizzle out as it does so on Wednesday. Still that south easterly wind in situ.

Wednesday carries on this wet, westerly theme with more rain crossing Ireland, heavier this time and pushing across into the west coast of the U.K later on Wednesday and then across central and eastern areas of The U.K on Thursday as showers. It'll feel much milder across Ireland with temperatures pushing into the teens. Further east across The North Sea, we have a stable situation with that cold air mass in situ across Denmark, some sunshine during the day and frosty at night until we reach the end of the week when temperatures are projected to nudge up a little towards 5-7°C.

By Thursday that wind has pivoted round to the south across the U.K and this will raise temperatures in the south first but pervading northwards, so Thursday looks mild and a sunshine and showers type of day and temperatures around 13°C. That southerly wind will pick up strength through Thursday and Friday with gale force gusts in the south. More rain for Ireland on Thursday as it pushes into the south west and vectors north easterly across The Irish Sea into the west of Scotland. Closing out the week we are mild, sunshine and showers type of weather with a very strong and mild, southerly wind. Night temperatures will stay up later in the week as the wind and cloud cover prevails.

The outlook for the weekend looks sort of mixed, a shade cooler as the wind swings round to the south west. There will be a band of rain crossing the U.K overnight Friday into Saturday and that'll take awhile to clear the south east of England on Saturday. So west and central areas will be drier. We aren't finished with the rain though as another Atlantic front pushes into Ireland later on Saturday night and crosses The Irish Sea into The North West, Scotland and Wales. This rain looks to pivot round and push south easterly into central areas during Sunday. Temperatures will be down a little, sort of 9-11°C territory, but still a pleasant uplift from of late. Denmark looks manly dry, some showers across Jylland on Saturday but the main rain front will arrive late on Sunday with some heavy rain likely.

Animated GIF courtesy of tropicaltidbits.com w/c 24-02-25

Weather Outlook - w/c 24th February, 2025

Well the outlook for next is wet, windy and remaining mild for the first part of the week before the wind pivots north westerly and drops the temperatures a little. Next Tuesday it looks like a southerly-biased low pressure system will pass across the southern half of the U.K bringing heavy rain, with more rain on Wednesday into Thursday and a cooler, north westerly wind. This same pattern will hold for Denmark with heavier rain on Tuesday and more showers / heavier rain during the rest of the week. It'll remain windy with that wind direction changing as low pressure systems pass across the U.K & Ireland. As it stands I think we will continue into March with a wet and windy framework to the weather.

Agronomic Notes

Last week I discussed the miserable situation from a GDD perspective in January and February 2025 to date, but all that is projected to change with the non-appearance of a SSW influence on the jet stream and milder temperatures pushing in from the west from mid-week. I have projected the likely effect on GDD (6°C base) on the graph above in red, I think you can see the trend quite clearly !!!!!!

So that's going to mean a significant uplift in air AND soil temperature because we are having rain as well as milder temperatures. Mild rain changes the soil temperature very quickly, so I'd expect you to see an uplift in growth from diddly squat to something pleasant to behold.

Long overdue because the combination of low light levels and low temperature so far this year has left many places struggling from a sward density perspective, particularly on surfaces with Lolium perenne and Agrostis sp. The sudden uplift in day and night temperatures may bring some concerns from a disease perspective, especially on Thursday night into Friday but I am hoping the combination of strong winds and rain will keep this at bay (Above a certain wind speed it is difficult for mycelium to grow on the plant leaf). That growth uplift should provide the start of some recovery from some winter disease scarring as well.

Early Season aeration and recovery

So bearing in mind the above graph and the almost flat-lined growth aspect we have endured since the start of January 2025, you'd probably expect (as I did) that clubs who aerated early (Mid-January onwards) would be staring at some pretty limited recovery.

So it was with mild surprise that I received the following time frame of images taken after hollow core / topdress aeration in the 3rd week of January, from a Bent / Poa golf course in Kent. My thanks to Ben for sharing.

When you consider the evident recovery has taken place with a total GDD figure of 7.1 / Growth Potential of 3.4, it is quite amazing to me. I would add the caveat that shade isn't a great issue on this course but even then the amount of natural sunlight / PAR dove-tailed with the lack of temperature, I think it shows that even in the worst combination for the grass plant, early aeration has a place.

When you consider that we are in line for 23.5 GDD or thereabouts over the next 11 days, you could well envisage that by the time this particular course goes into March, they'll be practically fully-recovered and ready for the new season. Hence the rationale for getting it done early. I'd add the caveat that I fully appreciate in some areas that getting kit out to do this has been impossible because of ground conditions.

How come we see this recovery when the actual models for growth, whether that be GDD or G.P suggest a very different result ?

I can't fully explain it, some of it I know will be down to consolidation of the surface closing up the core holes but I also think some tillering-type growth has taken place as well. You'd imagine with more temperature, they'd be more upright growth, but maybe when temperature is limited we see more lateral tillering-type growth ? Not sure myself as I'd have expected the plant to grow more upright towards the light. Either way I remember seeing the same effect in the cold winters of 2013 and 2010/11 as well, that is recovery when you wouldn't expect it.

OK, that's it for this week, all the best and enjoy the feel of some milder air, a portent of things to come maybe ?

Mark Hunt