August 10th

Hi All,

After a sustained period of heat last week, this week starts off with more of the same but a thundery breakdown and the possible appearance of a Bay of Biscay low pressure system could spell much-needed rainfall for the south of England and The Midlands. That rain really is much-needed and as we saw at the end of last week, the tinder dry nature of our countryside currently can result in fire rapidly spreading to affect heathland and golf courses alike. The  Chobham Common fire affected 150 acres on Friday and some golf courses local to it.

The combination of high temperature and humidity for the south of England and Wales this week is an unusual one and will take some managing.

I’ll look at this later in the blog but with Tempus in very much fugit-mode today, it’s onto the weather outlook for this week.

The forecast 7 days ago suggested a warm start to this week and then the chance of a breakdown later in the week and since last Monday we have seen the temperatures rise higher than was originally forecast. The reason is this pulse of hot air pushing up from southern Europe. It has moved slightly westwards to affect the U.K and consolidated at the same time. That’s where the forecast was a little out. (but not much as you’ll see from the images below)

You can see how the hot air peak has built over the week from the original forecast (right) to the current one (left). What is also just noticeable in today’s GFS output is a low pressure system sitting over North Africa amongst all that heat. It’s this that may bring us a thundery and humid breakdown later this week if it stays on track. So let’s see…

General Weather Situation

So as we start Monday we have a cool start to the day with plenty of cloud cover for the east of England and more central areas courtesy of that north east wind pushing haar in from The North Sea. There are also some thunderstorms over North Devon and Cornwall and some building already over France. Watch this space on those….Currently the projection is for those storms to consolidate over West Wales (fingers crossed Jim) through the course of the day and then these will track north and west across The Irish Sea into Ireland later this morning. Some rain also for The North West and Lakes. Now a big caveat here. Summer rainfall is the hardest to forecast so expect to see your daily forecasted rainfall totals jump up and down over the week. Summer storms can start from an updraft from heat generated by traffic on the roads.

On Friday I had a zip out into the worst of the traffic at the hottest point of the day for a work problem, so I chose my motorbike as the fastest thing likely to get me from A to B and to filter through the likely queues. The heat riding down the M11 was incredible. Even at **mph it was like a furnace and as soon as I turned off, it cooled down. The temperature was +4°C higher on the motorway than the surrounding area and that’s why we see storms tracking along them. Boy was I happy to get a cold shower at the end of the day. So with that slight digression we have rain for Wales, the South and North West of England, later pushing into eastern Ireland and the south of Scotland. For the rest of the U.K, it looks settled and dry but I wouldn’t be surprised to see more thundery showers pop up across the south of England today with France as the vector. Temperature-wise, into the thirties again today for the south of the U.K, low twenties for Scotland and high teens for Ireland ?(with more cloud cover and the possibility of rain). The wind will be from the north east.

Onto Tuesday and overnight that pulse of rain has cleared the north east and north of Ireland and pushed into the west of Scotland with some potentially very heavy bursts along the west coast and into central areas. This rain will track eastwards across Scotland so maybe Fife will pick up some on Tuesday. Further south we will see some showers break out along the south coast of England, nothing too heavy yet. Ireland looks to start dry if a little dull across central and eastern areas with the west picking up some pleasant sunshine. A mainly dry day for Wales and England save for some of those south coast showers pushing up into The Midlands through the day. Few and far between though at this stage. With lighter winds projected for Tuesday, we lose some of their cooling effect, so temperatures will rise to their highest of the week with mid-thirties likely down south and across the southern half of England. As we progress through the afternoon that heat will trigger some intense showers across central England and Wales so be on your look out. These showers will push northwards as that rain over Scotland becomes confined to the north east coastline. Dry for Ireland it looks like with temperatures picking up into the low twenties. The same for Scotland, warmer despite the rain so a humid day up there.

A hot night on Tuesday night to follow and onto Wednesday when it looks like we will do it all over again. That rain across England is now sitting across the north and north west and stretches up the east coast of Scotland. This rain will continue to affect the east coast of Scotland throughout the course of the day on Wednesday. Further south and west we look to have another hot day across the south of England but there is a subtle change taking place across southern Europe. Off our radar we will see a low pressure system edge up across Portugal and into The Bay of Biscay and it is this weather system that will start to feed in humid air to our weather through Wednesday. So during the course of the day as the temperatures rise into the thirties again we will see more in the way of thunderstorms kicking off through the course of the afternoon and evening. By dusk it looks like these showers will be consolidating across England, Wales and Scotland. Ireland on the other hand looks to enjoy another pleasantly warm summers day with temperatures in the low twenties again. Scotland will be similar despite the rain so hot and humid again here. Wednesday will see the wind swing round to the south and that again is significant as it will push that continental rain our way.

Overnight into Thursday and we will see heavy showers across The South West, Wales and the north and western coast of England extending into Scotland. By late morning some of those showers will start to affect the eastern coast of Ireland and move further inland across central England. At this stage the heaviest rain is across the western side. By mid-afternoon we will see those showers consolidate into heavier spells of rain across central England and hopefully The Midlands with rain pushing west across The Irish Sea moving that eastern coast Irish rain further inland during the afternoon. Scotland looks to have a pretty wet one. By Thursday evening that rain continues to consolidate across all areas of the U.K and at least the eastern half of Ireland with some showers reaching the west coast. No surprise then that Thursday will have a much more humid feel to the weather although temperatures will be down into the high twenties across the south of England, high teens for Ireland and low twenties for Scotland. Winds will be light and swinging round through the day to westerlies.

Closing out a hot, humid week, overnight into Friday and we see potentially more rain for England and Wales, some of it heavy early doors. This rain will move westwards during the morning and push across Ireland as the low swings the rain westwards. So an improving forecast for England and Wales through Friday morning with the rain pushing up north and west across Ireland with Scotland seeing some light rain during the morning. As we move through the afternoon, we will see rain across Ireland, the north of England and Scotland with Wales and the southern half of England drier. Slightly cooler again on Friday with temperatures in the mid-twenties for England and Wales, low twenties for Scotland and high teens for Ireland.

With low pressure close at hand, this coming weekend is likely to be an unsettled affair and one where it’s probably better for you to look at the weather radar rather than my forecast, such is the variability of summer rainfall. At this stage Saturday doesn’t look too bad as that low pressure has spun off south west of the U.K but it isn’t finished with us yet. Saturday then should be mainly dry, some showers across Ireland, the west of Scotland and possibly England but at this stage they look few and far between. That low pressure system though is due to swing round again and we will see the first effect of that with rain, some of it heavy building over The South West later on Saturday. Overnight into Sunday this rain pushes up into South Wales and the east of Ireland. Later through Sunday the rain crosses Ireland and begins to push north and east into central England so a wetter end to the day here. Temperature-wise for the weekend, mid-twenties on Saturday dropping back to low twenties on Sunday as the wind swings round to the east. Scotland looks to have a nice weekend, with temperatures holding above 20°C into the mid-twenties by Sunday. Ireland, cooler yes, but pleasantly warm with a potentially drier day on Sunday.

The ‘behaviour’ of that low pressure system will really govern our weather this weekend if it slips west or east expect things to change rainfall-wise.

Weather Outlook

If you look at the GFS output above and compare it with the one that started this week you’ll immediately notice the absence of heat, so next week should be pleasantly warm rather than hot as per this week. Next week is a tricky one to forecast because early on in the week we have that low pressure dissipating in strength so we will probably start the week cooler with some showers on Monday and Tuesday, Now we have a strong Atlantic low pressure trying to push in but also another pulse of warmer air pushing up mid-week so at this stage it looks like warming up through next week before that low pressure finally pushes cooler and more unsettled conditions into Ireland at the end of next week and the U.K over the course of the weekend after next. Now as we have seen with warm air pulses, a lot can change so that low pressure may not arrive but my hunch is that it will because it is tracking in a low position relative to the U.K and therefore less likely to be pushed up and over the U.K and Ireland. We will see…

Agronomic Notes

Hot & Humid Turf Management

When you see a forecast like this on Weathercheck, you know it’s not a normal week from a turf management perspective !

As featured in last week’s blog we know that during days where the air temperature is exceeding 30°C , the soil temperature at 25mm depth is pretty much on a par with this, so our grass plant roots are getting cooked. That’s the first take home point and particularly where it comes to turf areas where we have an excess of organic matter. We saw this in the summer of 2018 on fine turf and on outfield areas. Organic matter heats up quicker than rootzone and since the grass plants roots tend to be concentrated in the surface region in an excess O.M scenario, they are adversely affected. It is a really tricky balancing act because if you over-compensate and over-water then you will cause further issues by reducing oxygen availability to the roots of the grass plant and potentially cause die-back. Warm water holds less oxygen, so a saturated warm rootzone, high in organic matter is not what you want this week.

This is where a good irrigation system, hand-watering and moisture meters come into their own.

The balance is to keep your turf hydrated but without over-watering and reducing soil oxygen levels.

 

Giving the plant the ability to breath from a roots perspective is also key and it is now when I think spring and summer vertidraining with compact machinery, narrow tines and no heave, really pays off.

A great shot (above) which I have used before courtesy of Mr Todd of Sevenoaks, thanks again Mark 🙂

Keeping nutrition sensible, prioritising biostimulant over nutrition applications and not over-regulating / stressing your turf with PGR’s / over-aggressive aeration should all be considerations this week…

This article from the USGA RECORD has some great tips, it’s a bit ‘American’, you know fans and all that stuff but it does how some good ‘does and don’ts’ for this type of week ….You can find it here

As I said last week, this won’t apply to everyone and with temperatures 10-15°C lower in Scotland and Ireland respectively, it isn’t a consideration for you thankfully 🙂

GDD – July Review

Didn’t get round to this last week, so here it is…

Monthly GDD Summary – July 2020, Thame, UK

So July 2020 came in towards the low end of a ‘typical July’ with a total of 330 GDD, that’s considerably down on last year and particularly on 2018, due to rainfall during the month,  but I think August will make up for that. If you’re working on a 6°C base (as I do) for GDD calculations and applying a PGR on greens every 130GDD or so, it means you’ll have needed 3 apps of PGR to keep them locked down during July.

That said I do wonder whether a plant going under heat stress means that any rebound effect is negated by the inability of the grass plant to actually rebound’ because of the effects of that stress ?

Anybody measuring clip yields seeing a rebound effect even when applying PGR on a 14-day basis ?

Y.T.D we are well up there though and only just behind 2018 from a total GDD to the end of July perspective. Warmest year to date maybe 2020?

Monthly GDD & Rainfall Summary – UK

Quite an ‘even stevens’ sort of GDD readout across the board and very similar rainfall totals, particularly across The Midlands. You can see the west side of the country picked up the most rainfall extending all the way up from Devon to North Wales. This is to be expected with the Atlantic low pressure weather pattern that prevailed during July. It’s going to be a very different set of stats for August me thinks…

Monthly GDD & Rainfall Summary – Ireland

When I was collating these results I had a ‘double take’ episode when it came to Valentia’s rainfall nearly matching its GDD !

The end of July was a particularly wet period for both Ireland and Scotland but to receive 54.5 mm in one day as Valentia did on the 29th of July, that takes some beating.

I feel very sorry for anyone down there on their summer hols at that particularly week. It might have been a ‘tent in the skip’ ending to a holiday as I have witnessed before whilst staying on a cliff top campsite in St Davids, Pembrokeshire !

Image courtesy of NetWeather.tv V8 radar

That said my stepbro has just rang me up from North Devon to say it’s absolutely p*****g down and could I give him some weather advice. I told him to drive towards Cornwall for 30 mins and then he will be through the rain and have a lovely day. Looking at the line of very heavy thunderstorms stretching up from Plymouth, through Pembrokeshire into Wales and Ireland, some of those locations are getting a clattering.

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When you compare the U.K and Irish / Scottish data from a GDD and rainfall perspective you can see how turf management will be so different and particularly when it comes to summer stress (a rare event in Ireland) and disease activity. With a wetter climate, Ireland and to that end, Scotland tend to pick up earlier Microdochium pressure than England / Wales and I think more than their fair share of Anthracnose as well due to extended periods of plant leaf wetness.

On the other side of the coin you have the south / south east of England / Midlands, which is hot, dry and arid and ‘looking forward’ to 4 x 30°C plus days in a row. The south west of England has a foot in both camps, they tend to get more moisture down there and they get the temperature, so it is no wonder that diseases like Dollar Spot are an issue for Devon, Cornwall and the west country in general.

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E.T Loss = Plant Stress = Anthracnose

When you look at the above stats and an average daily E.T loss for this site of 5.12 mm, you can understand why the grass plant is a tad up against it. Elevated levels of plant stress are a calling card for Anthracnose and other stress-related disease. As covered in a previous blog, we have already had 2 clear signals for spore germination and plant infection this year. It’s no surprise then that I’ve had a lot of feedback on this disease recently. The problem with Anthracnose is the way it works in the plant and the way it manifests itself from a turf appearance perspective. Once you start to see the familiar bright yellow basal leaf followed by subsequent die-back, it is very difficult to arrest the situation because it’s already done its damage. I know some organisations suggest treatment with a fungicide but primarily all you are achieving is a ‘ring fencing’ exercise rather than any curative process. The affected plant won’t suddenly better, it is on its way out, period. As a disease it also looks different on a day-to-day basis, sometimes it looks to be getting better, sometimes progressively worse. Rubbing some rootzone into the affected areas with some seed is a good policy (rootzone rather than sand as it holds more moisture and nutrients).

Summer 2020 will I think prove to be a bad Anthracnose summer and particularly if we pick up rainfall and temperature this week like The South West, Wales and Ireland are already doing…

Soil moisture deficit / surplus – 2020 vs. 2018

No summer blog could be complete without this little gem 🙂

In July, I predicted that summer 2018 and 2020 would be pretty even stevens by early August but that was before the run of high E.T days hit us, so the chart looks very different now…

Looking back at my old data, in summer 2018, we hit -299 mm at the end of August / early September and here we are on the 10th of August and we are already at -320 mm odd, so officially we are drier than the summer of 2018. Comparing the same date we were approximately -260 mm in 2018, so we are 60mm drier in 2020 and still moving the wrong way. No wonder rivers look so dry and the ground is so hot and tinder-like 🙁

That rain couldn’t come soon enough..

Fingers crossed by the time I start next week’s blog we are in a better situation and have had some rain 🙂

All the best…

Mark Hunt