July 14th

Hi All,

Well another heatwave peak has passed and this time, it was also experienced by Ireland, Wales and Scotland. It was England's 3rd and I don't think it'll be the last of summer 2025. Last week we had a contradiction in forecasts with the GFS (and ECMWF) showing the heat would peak on Friday, whereas regional forecasts were saying it would build through the weekend and beyond. Well the GFS was accurate and the regional forecasts were not. I am glad for this because I attended the World Superbike races at Donington on Sunday and 26°C was bearable.

According to The Met Office, the last three years have been in the UK's top five warmest on record, with 2024 the fourth warmest year in records dating back to 1884. No doubt 2025 is well on the way to coming in as the warmest ever for the U.K. Looks like we will have to get used to this type of weather then, interspersed of course with periods of very wet weather as well. I guess it is common sense but if we are going to get short of water at some points and have excess water at others, we need to balance this equation by storing more of that excess when we can. More reservoirs need to built. It's not just water quantity that is at stake here, water quality is also a developing problem, particularly for wildlife. The warmer water gets, the less oxygen is dissolved in it making it harder for fish to breath. This summer we are seeing more fish kills in lakes and rivers, a whole food chain is at stake here. This weekend past, dangerously low dissolved oxygen levels were recorded on the River Trent near Newark.

So, we are mid-July and feasibly we have 6 more weeks before day length shortens and night length increases noticeably meaning heat and E.T has less time to build. The flipside of that coin is this is when duration of plant leaf wetness increases and pathogen activity increases notably, with Microdochium, Anthracnose and of course Dollar Spot causing the biggest concerns. It got me wondering, when do we hit peak E.T demand in a hot summer, when we are we losing the most amount of water to evaporation and respiration from a grass plant's perspective ? Remember that this would also coincide with when we lose the most water from our storage reservoirs, so that's something I am going to take a look at later.

So what's in store for us this week weather-wise ?

GFS projections for the next 7 days - tropicaltidbits.com

General Weather Situation - 14th July, 2025

So this week we start off pretty much as projected by the GFS outlook last Monday, namely with an Atlantic low pressure system trying to push in from the west (and already bringing rain for Ireland, The north / south west of England and Wales) and a cut-off low pressure system sitting over Denmark (again as predicted). The role of these cut-off low's in shaping our weather is I think very important. From my (amateur) perspective they seem to act as a bridge / link to Atlantic weather systems, keeping the warmer air further south and allowing Atlantic weather systems to push in from the west. And that is exactly what I expect to happen this week.

So for Monday we see rain for the west of Ireland and the U.K and this rain will spin northwards into Scotland during the day leaving a dry, bright and breezy day further south. As we move into Tuesday, the main rain front sitting over the west of Ireland begins to move eastwards over Ireland and across The Irish Sea into Wales during the morning. Both Wales and The North West look inline for heavy rain on Tuesday before it moves eastwards across northern England and The Midlands, finally into the east later in the day. Denmark looks to stay largely dry although that nearby cut-off low will push the odd showers across southern Jutland and Zealand. As this low pressure moves eastwards it'll leave behind a showery, cooler outlook for Ireland, the north of England and Scotland. Further south the temperature will be higher, sort of low to mid-twenties and accompanied by fresh / strong winds, so a high E.T week is in store.

As we approach the end of the week, the low pressure of earlier in the week forms a cut-off low across northern Germany and a new low pressure system begins to build to the north west of the U.K. This will begin to to introduce showers to the south west of Ireland on Friday morning and later the south west of England. Later on Friday we will see showers, potentially thundery build across the U.K, Ireland and also Denmark. This rain will carry across into Saturday for central and eastern parts of England and Wales with a heavy band of rain crossing Ireland at the same time. On Sunday morning we will see a heavier band of rain push into the south of the U.K and move northwards slowly through the day into northern England and Scotland. So it looks at this stage like a wet weekend is in store....haven't typed that for some time !

Weather Outlook - w/c 21st July, 2025

Now the GFS forecast for next week is an unpredictable one, with essentially two different outcomes for the end of next week. For that reason I am going to keep this narrative to 7-10 days and then we can see how it plays out as the week goes on.

So we start next week with low pressure sitting across the U.K, Ireland and Denmark. This will push cooler air and showers, mainly across the west on Monday before a heavier band of rain comes through on Tuesday (pushing into Denmark overnight into Wednesday). Thereafter it becomes harder to follow with a low pressure system coming in from The Atlantic at the same time as high pressure begins to build from the south. Currently it is pointing towards another heat plume / heatwave event at the end of July and it looks significant extending east into Denmark and Scandinavia.

One to keep an eye on for sure....

Image courtesy of Roadracingworld.com

Agronomic Notes

So I was pondering, whilst watching Turkish rider Toprak Razgatioglu perform unfeasible feats of heavy braking into the Melbourne Loop at Donington. Every lap looked his last but that's how this chap rides, if you've never heard of him, you will, he's brill. Anyway back to the pondering......This summer is a hot and dry one, following on from a warm and very dry spring. We know we passed into a soil moisture deficit situation very early in 2025, the 3rd week of April and since then it has been a steady slide downhill, save for a temporary blip with some rainfall at the end of May and June.

I am sure people will be looking at their water situation with nervous glances, depleted by high temperatures and evaporation. Hosepipe bans have already come into force in the north of England with more sure to follow (as I type this Thames Water has just announced their hosepipe ban). Our industry is an important one, Wimbledon, the Test Series (which I am listening to avidly), The Open, all major events high up in the public spotlight and psyche, not to mention all the amateur events up and down the country, from golf to bowling greens and everywhere in-between. We depend on water for our grass but that source of irrigation is not for our preserve only. It is an intensely competitive situation with industry, agriculture and of course the domestic market all well up the pecking order vs the amenity industry.

Now we have this debate every time we have a period of hot and dry weather and then when it starts to rain again, it is forgotten, pushed quietly aside till the next time. It is coming though, the day of reckoning when we need to justify why we need to irrigate our turf and how much irrigation water we are applying. On the latter point, if we aren't measuring E.T in our situation, how do we justify / measure how much irrigation we are applying. How do we manage that situation and how do we communicate effectively as an industry with one voice across all areas ? Now I fully appreciate a lot of work is going into this already, these aren't questions that haven't been asked before and that's because it is a priority. I believe it is the biggest challenge we face currently.

Monthly E.T rates in mm - The Oxfordshire, Thame, U.K - 2018, 2022 & 2025

Knowing we have this challenge and currently are facing an extended period of dry and hot weather, when do we reach peak E.T ?

So I looked at 3 years, 2018, 2022 and 2025 and graphed out the total moisture loss by E.T through the year. I picked 2018 and 2022 because we have significant heat and drought during those respective summers.

The graph shows firstly how 2025 is our sternest test in recent years with a higher monthly E.T moisture loss than either of the 2 previous hot summers. The pattern suggests that July is the point where we reach 'peak E.T'.

Interestingly in 2018, we lost 59mm in the first 13 days of the July at this location. In 2025, in the first 13 days of July, we have lost.....59mm !!

So as we move towards August we can hope (I said hope, particularly bearing in mind we might start the month with a heatwave) that we will have passed peak E.T in July and that next month will offer less of a test. Still high E.T though potentially, with August 2018 indicating 97mm was lost and 2022, 108mm. By the time we reach September we can expect the monthly E.T loss to reduce by approximately 50% as the nights draw out. Remember September is only 6 weeks away.

Daily E.T loss in mm - July 2025 - Multiple locations

Whilst I was writing this blog I took a break to chat to a superintendent working out in Cyprus. We looked at some of the data and I was amazed at the difference between the U.K. Just 4mm of rain since April by the way but the E.T rate was nearly double some of the locations in the U.K. Bentgrass greens BTW.

Acervuli spore-producing structures of Anthracnose (Colletotrichum cereale)

Anthracnose trigger event

The most recent heatwave spread heat further west and north than the previous two this summer and in so doing they clicked past the threshold for Anthracnose fungal spore germination and growth across Ireland, Wales and Scotland (as well as England). We can look nervously towards next month because in my books as I have always said 'A' is for August and Anthracnose.

On the flipside to that concern, I am increasingly heartened to see how well greens are holding up this summer. I guess one of the consequences of more warmer summers according to The Met Office is that we all get more practice with managing our turf during hot and dry periods

In addition, the tools we have to do the job in terms of PGR's, surfactants, biostimulants, pigments and the like grow ever more effective. It is not just down to products of course, our work with data, clipping yield, growth potential and ratio are also contributing in matching nitrogen and PGR applications to growth and plant health. I think we are more in control and that is a credit to the industry.

We are adapting to our changing climate.

All the best for the coming week.

Mark Hunt