June 10th, 2024

Hi All,

Staring out of the window this morning with the temperature not yet in double figures and the rain lashing down, one could be forgiven for thinking summer will never arrive in earnest. The weather has once again reverted to type with a cool trough pattern pulling down cold winds and rain when a week ago the GFS output suggested something slightly different. Ho hum......

My oldest Stepson was asking me this weekend how the weather forecast was looking for Glastonbury at the end of June and I just sighed and shrugged my shoulders. My best advice was take a good coat, an umbrella, your wellies, a T Shirt, suncream and shorts.......that said I think if you are looking for summer to start, the end of this month might just be looking favourable. Not because of a projection for high pressure that won't arrive again but because of how the temperature south of us is building and ushering a reluctant jet stream higher.

The image above from tropicaltidbits.com is of course more than two weeks away and so we could easily dismiss it as very likely to change, but just from a common sense perspective, we know heat is building in southern Europe and at some point it is going to affect our weather pushing up in a high pressure peak pattern. My bet is towards the end of this month and start of July, so let's see.

It's strange because looking back at May '24 from a GDD (and therefore temperature) perspective as I will do later in this blog, it came in as one of our highest numbers since I have started logging data in 2005. It is almost temperature by stealth because I wouldn't necessarily associate May 2024 with record heat and warmth. Odd that. Looking at the current temperature projections for the rest of June, even if a heatwave arrives at the end of the month, I can't see this following the pattern of record warmth months, indeed June 2024 will most likely pan out as one of the coolest.

General Weather Situation - w/c 10th June, 2024

So we start this week with a trough pattern in place, cold low pressure sitting over Scandinavia and high pressure trying to push up from The Azores. Now the first thing you should notice is the wind direction, northerly, so that sets the tone for temperatures as we approach mid-June, it'll remain chilly for this time of year.

So for today we have rain associated with the nearby low pressure moving off east today, clearing East Anglia by the afternoon. This will leave behind a mass of showers for the eastern side of the U.K, extending down from Scotland all the way to Kent. For Ireland and the west of the U.K, it'll already be brightening up and these sunny spells will extend eastwards but they'll only reach as far as the showers across the east of the country. So a sunshine and showers day for most, drier across the west and wetter and cooler across the east. Temperature-wise, we are looking at mid-teens for most after another single figure night, pinned down by the cooler wind direction.

Tuesday sees a drier day for most though we will still see showers pushing down the east coast of Scotland and England during the day, urged on by that cool wind direction. Dry for Ireland and the west / central areas but with that cool, north west wind in situ keeping those temperatures in the mid-teens for everywhere. Possibly cooler on eastern coasts.

Wednesday looks like the driest day of the week with those showers across the east pushing away and the wind turning more westerly. Dry and bright for all areas but still not really warm and mid-teens remaining the order of the day, with chilly single figure nights.

By Thursday we see a significant change as overnight, a rain front has pushed into the west of Ireland bringing heavy rainfall for some areas. By dawn it is projected to cover all but the far east of Ireland and it'll make short work of The Irish Sea, moving into The South West and western coast of the U.K by mid-morning. So a wet start for the west, dry for the east, but that rain will be heading your way. By lunchtime it'll

be clearing the west of Ireland and straddle the length of the U.K clearing the west by dusk. So a wet day for most, the only difference will be when you get the rain with it not arriving in the east till late evening. It will feel marginally milder despite the rain as the wind will shift round to the south.

The end of the week will finish off with a raft of showers across Ireland and the west of the U.K pushing easterly and southerly through the day. It'll be a windy one with strong southerly winds and a sunshine and showers outlook for most. Ireland will see more in the way of rain later in the day as those showers consolidate across the south and south west in the 2nd part of the day. No change with those temperatures though it'll feel a little milder at night with the change in the wind direction and more cloud cover.

The outlook for the weekend looks pretty mixed with some showers and heavier bands of rain moving across the U.K & Ireland on Saturday and Sunday. Currently they look to track up from the south west of Ireland and England pushing across Wales to reach all areas by midday. Carrying on the theme for the week, we have mid-teen temperatures, light winds on Saturday from the south and east, gaining in strength on Sunday.

Weather Outlook - 17th June, 2024

If you look at the animated GIF from tropicaltidbits, next week starts off with a trough pattern in place and low pressure sitting across Ireland. That low pressure system will stay across to the west of the U.K tracking northwards for the 1st half of the week, before moving westwards (so against the normal flow of pressure systems) and return again by the end of the week. This is the ying and yang of trough systems, they stay in place for a good length of time, we should be used to it by now. So cool and unsettled is the forecast for the week but by the end of the weekend, a ridge of high pressure is projected to build. To be honest it looks pretty wet most days next week, with rain pushing in from the west across Ireland into the west of the U.K before moving east from Monday. The wind will change through the week, initially southerly, turning westerly and finally north westerly, so I don't expect much change from the temperature range we have had this week, maybe a degree or two higher in the day and staying mild at night with the cloud cover, so probably 11-12°C night time and 16-18°C during the day. The weather might just hold for The Summer Solstice on the 20th of June.

Agronomic Notes

So 1st up, let's look at May GDD as a month from our default location, The Oxfordshire, Thame, U.K

May 2024 came in at 243.5 for the month which places in second only to 2017 in terms of highest GDD readings for May. As commented earlier it didn't feel like an especially warm month to me but when you see this level of GDD, you know it represents significant grass growth. The equivalent Growth Potential figure for this location was 22.63. So that's about 73% of optimum growth (22.63 / 31 x 1.0) and of course with accompanying rainfall, this meant that the theoretical growth corresponded to actual growth as areas didn't go under moisture stress at any point.

The cumulative GDD for this year till the end of May came in at 547.1, comfortably ahead still of any other year I have recorded and beating the stand out year of 2017 from a growth perspective.

If you compare cumulative GDD to the end of May 2024 vs. 2023, we have experienced 31.7% more GDD in the 1st five months of the year this year vs. last year. No wonder growth has been so difficult to keep on top of on heavy soil sites this year.

So if you had complaints about poor green speed, long rough, bunker edges , etc there's your reason.

I have collated some monthly total G.P figures from the U.K & Ireland below so you can see some of the variability this collection of countries provides us with !

Remember that the theoretical maximum monthly Growth Potential for May is 31, that is 31 days of G.P=1 every day.

Monthly Growth Potential Totals - Around and about the U.K & Ireland, 2024

Location	Country	Total Monthly G.P	% of maximum
Limerick	Ireland	20.4	65.8%
Sligo	Ireland	19.9	64.2%
Bray	Ireland	19.67	63.5%
Dumbarton	Scotland	23.1	74.5%
Fife	Scotland	16.44	53%
Okehampton	England	26.3	84.8%
Winchester	England	21.9	70.6%
Sevenoaks	England	21.4	69.0%
Pinner	England	23.82	76.8%
Milton Keynes	England	22.56	72.7%
Bury St Edmunds	England	22.74	73.4%
Lincoln	England	23.38	75.4%
Scarborough	England	19.94	64.3%

Some big geographical variation above.

One of the biggest surprises (though it shouldn't really be a surprise anymore as Scotland often comes in with a warmer May than further south) was Dumbarton at 23.1, significantly higher than a lot of English and Irish locations thanks to a particularly warm period of weather between 10th May - 18th May. Looking closer to home, Devon came in with the highest monthly total G.P, as it has done consistently in the past and this represented nearly 85% of optimum growth. I hope you have sharp mower blades, plenty of staff and PGR Pete !!!😎

The practical relevance of these figures from a turfgrass management perspective....

Well 1st up let's look at PGR longevity. If we are talking Trinexapac-ethyl then it is pretty much around the 13-14 day mark in a high monthly G.P scenario before the PGR is grown out and we experience the rebound effect. This in itself isn't unheard of, just one for the notebook. Also the level of growth on higher-height-of-cut grass will have required a higher application rate to control it just because moisture availability has not been a limiting factor.

If PGR's have been working through the system quite quickly, then you can apply that same rationale to fungicides and nutrition. It will grow out faster because the plant is able to utilise it with near optimum growth and moisture availability, so don't expect your feeds to last quite as long, dropping off maybe a few days short of 'normal'

Application efficiency from a liquid / foliar nutrition perspective would have been subject to significant leaching losses judging by the 'fruity' rain rates I have highlighted on the Prodata Reports output shown above for a golf club in the Milton Keynes area of England.

Those two hits of rain on the 21st and 22nd of May accounted for 56mm of rain between them falling at some very heavy rain rates, so no wonder we experienced flooding and saturated ground conditions, particularly on heavy soil types.

Normally May is the 1st month of the year when E.T rates exceed rainfall, in other words, the amount of rain that falls from the sky is exceeded by the amount evaporated by the combination of wind, temperature, humidity and solar radiation.

Sometimes we see this in April in a dry spring, but May is normally a banker month for more E.T than rainfall. This May at this location they experienced 93mm of rainfall vs. 71.96mm of E.T, so it didn't follow the norm from this perspective. As a matter of interest, their current June figures for rainfall and E.T are 5.6mm vs. 23.98mm respectively, so the balance has reset somewhat (may be different by the end of next week though)

For Scotland and England, that warm weather in the 1st half of the month definitely met the criteria for an early Anthracnose trigger, but as yet we haven't experienced significant plant stress for a sustained period. Ireland came pretty close as well on the 19th and 20th of May temperature-wise, so it will be interesting to see how this pans out later into the summer from a Foliar Blight perspective. As I have pointed out in earlier blogs, the Smith Kerns has been running pretty much around the 20% mark most of the month, so we say constant Microdochium pressure though this was balanced out nicely by good growth. A wet late spring / early summer period also marks this year out for significant Take All pressure because this pathogen likes to do its damage during the cool, wet part of the season, only showing later when the plant experiences drought stress and cannot uptake enough moisture through its damaged root system. This disease was on the way out with the emergence of effective fungicide chemistries in the recent past but the practice of bentgrass overseeding (it doesn't only affect Bentgrass but it is its preferred host most of the time) and wetter springs have seen a re-emergence of late and this year promises a continuation of that trend. It can only be dealt with preventatively mind.

OK, that's me for this week.

All the best.

Mark Hunt