September 20th, 2021

Hi All

It has got a real feel of autumn in the air of late with some cooler, single figure night temperatures, and mist and fog lingering around in the hollows.

One of my favourite seasons I think….

Looking at my last two ‘weather outlooks’, they’ve been pretty wide of the mark and that’s because of the orientation of the jet stream.

Currently we are sitting in a pattern of undulating peaks and troughs with the occasional wet interlude. A subtle change in position and the whole forecast changes.

Take yesterday (Sunday) for example. As you can see in the image above taken from from Netweather’s R8 rain radar yesterday morning, we had a vertical line of slow-moving rain that crossed the U.K & Ireland through the day. This band of showers escalated in the afternoon and then halted over the east of England. Our Throws Farm Davis weather station recorded 42.2 mm falling between 3:00 pm and 11:15pm. The forecast was for 8 mm !!!!

I’m hoping this doesn’t transcend to this week as I’m away down to The Gower in a modern camper, my first camper trip for many years and a bit of a toe in the water. Talking of which I hope to be chasing the Bass again with my fly rod, can’t wait……Out fly fishing at the weekend and the farmer was combining a pretty tatty crop of winter wheat next to the reservoir. The water was littered with adult Crane Fly and the Trout were having a field day pardon the pun.

One of the consequences of this run of weather of late is the lack of wind and sunshine in some areas which has meant that as a country we have had to fire up a coal-fired power station because the output from solar and wind generation has been so poor. A reminder maybe that going forward we can’t afford to put all of our eggs in one particular energy basket, despite the fact that we live on an island. I’m amazed at the lack of development in tidal energy, I mean it’s an absolute given, every day, twice a day and we have some of the highest tidal changes in the world. All that energy going to waste.

Energy and energy generation is in the news at the moment with record prices for gas and a potential shortage of supply looming this winter unless we go back to older generation methods. This is having a big knock on effect with prices of goods including fertiliser and the like with the sad fact being that we rely on other countries for most of our fertiliser raw materials and this makes us vulnerable in times of volatility. We saw the same thing in 2009 / 2010. This blip I think will be longer-lasting and will have some profound implications for product availability going forward. Just like on disease management I think change is in the air when it comes to plant nutrition.

Onto the weather for this week…..

General Weather Situation

So Monday starts as a quiet day with many areas seeing their lowest temperatures of late after the skies cleared on Sunday night. (we got down to 8°C) That said we still have some heavy showers over East Anglia, a last vestige of yesterdays deluge for the east of England. These showers will dissipate during the morning but for everyone else, Monday looks a lovely autumn day. Plenty of sunshine and pleasant temperatures though a north wind will keep things this side of 20°C, as the leading edge of a high pressure ridge feeds this wind direction into the U.K. Cloud will move in later in the day.

Onto Tuesday and a repeat of the same sort of lovely autumn day with a cool start, heavy dew and then plenty of nice autumn sunshine and settled, dry conditions across the U.K & Ireland. Still that wind will be from the north west so that means pleasant but not hot conditions with temperatures typically in the high teens and low twenties. Now you can’t complain about that…

Now as you can see from the image above, we have high pressure out in the South Atlantic and low pressure in the North Atlantic and it is the latter that will start to shape the weather from mid-week onwards as a band of rain extending from that low pressure makes landfall across north west / west Scotland on Wednesday morning, Northern Ireland and north west of Ireland. South of this we have another quiet and settled start to the day with calm weather conditions and a little more cloud than earlier in the week as the wind direction swings round to the west and pulls cloud cover in, gaining in strength as it does so. This northern rain will sink slowly south and east into the south of Scotland and Midlands of Ireland, fizzling out in the latter as it does so. Similar temperatures to earlier in the week away from that rain front but a drop to mid-teens for areas under that thicker cloud and rain.

Overnight into Thursday and that northern rain sinks south and fizzles out over northern England however a new heavy rain front is projected to push into north west Scotland from early doors and this will bring heavy rain to all areas of Scotland from first light. Through the morning this rain will sink south into The Borders. Away from this northern rain front, we will see a windier day as that westerly wind freshens up and pulls more in the way of cloud in, dropping the temperature a little from earlier in the week. So a much duller day on Thursday and with a westerly veering north westerly wind, a cool one to boot. That rain across The Borders will fizzle out as it moves south during the 2nd half of the day. So wet for the north, dry and settled but duller / cooler for England, Wales and Ireland, with the west a bit sunnier and warmer.

Closing out the week on Friday and again we see more overnight rain for the north and north east of Scotland extend into the morning. Further south we see a similar day to Thursday but with a slightly gentler and milder feel as the wind drops a little and swings round to the west. A bit more in the way of sunshine to close out the week for Ireland, England and Wales and dry again so it looks like being a dry week all in all for most areas except Scotland. That morning rain will again fizzle out over Scotland as we head through into the afternoon, following a similar pattern to the rest of the week. Cool for Scotland with mid-teen temperatures likely, but warmer for England, Wales and Ireland with the best temperatures in the west I think (ha!)

So how does the weekend look ?

Well I’d say sunshine and showers judging by the projections above with the north of Ireland and Scotland set for some rainfall on Saturday during the morning. Some of this rainfall looks to be particularly heavy across the north west of Scotland as a new front of rain combines with an earlier one later on Saturday. Away from this rain I’d say we will be mild with plenty of cloud and a fresh to moderate westerly wind. Overnight on Saturday, rain pushes into the north /north west of Ireland and western Scotland and begins to sink south and east so by Sunday morning it’ll be crossing Ireland and Scotland, clearing the north and west as it does so. This band of rain will introduce some showers further south and west later on Sunday and some cooler temperatures as that cool air sinks south. So a mixed picture for the weekend.

Weather Outlook

So next week (and lets try to be more accurate this week eh ?) sees a cooler temperature picture across the U.K as the jet stream shifts further southwards. Now this is really key to how we see out September because if the jet stream does drop south then it opens the flood gates (in more ones than one) to a more westerly airstream and in particular Atlantic low pressure systems. Looking across The Atlantic a bit you can see the first of these big low pressure systems waiting in the wings…

So it’s a bit of a two step jaunt really for next week’s weather to fall into place…

First up, the position of the jet stream needs to take a subtle step southwards and following on from that, the Atlantic low needs to intensify and bring us our first prop

er autumn storm.So my take on next week is that the week will start quietly again (bit like this week) but they’ll be some rain across the north of the U.K even though high pressure is doing its utmost to stem the presence of that Atlantic low mentioned above. As we go through to Tuesday, still quiet so that means coolish temperatures, dew and varying amounts of sunshine. The second part of Tuesday will see rain and strong southerly winds push into Ireland as that low pressure makes landfall.

On the subject of storms, The Met Office’s list of 2021 storms is shown below with a projected 6-10 Atlantic storms in the pipeline for autumn / winter 2021….

So if this one occurs it’ll be called Storm Ana…..I particularly like the 2nd one on the list….Storm Bill….no Storm Mark though I see…..I digress…

So we are looking at this storm making landfall in Ireland sometime next Tuesday and then tracking north and east across the north of Ireland and into Scotland. This means that the bulk of the wind and in particular, the rain, will be north and west-orientated. As it stands now, next Wednesday looks the wettest day from our an England and Wales perspective, with Scotland on the receiving end from late Tuesday onwards. It’ll be extremely windy everywhere with some of these winds capable of damage and I expect more rain at the end of next week for the southern half of the U.K as that low loops rain around it….

Now remember this needs that first process to drop into place so lets see if that occurs….

Agronomic Notes

Last week represented some of the highest disease pressure I’ve noted since Paul and I put together our Microdochium nivale disease prediction algorithm. That pressure wasn’t just confined to Microdochium though as most peoples Smith Kern Predictors were also > 50%, so we saw loads of Dollar Spot as well across the board. Some on courses with a history of this disease, others a first.

September as I mentioned at the beginning of the blog has been an unusual month because of the lack of sunshine and wind so E.T rates or more specifically leaf dry down rates have been really poor / slow. This has meant extended periods of leaf wetness and coupled with warm evening temperatures, they provide a perfect recipe for foliar diseases…

Here’s how our Microdochium disease prediction looks for September so far, for a location in the south of England, Berkshire sort of way…..

As you can see the ‘fun’ begins on the 9th, 10th and 11th of September with some sustained disease pressure > 80% and pushing up to > 95% during that period. This sort of started the disease ball rolling so you may have noted visible disease at this point. Pressure backed off a bit for a few days thereafter but then built again on the 14th and 15th with a number of consecutive hours of high pressure. That’s what you are looking for in a disease model, not just the extent of the pressure but the number of hours of consecutively high pressure that allows the disease to move from mycelial development to sporulation. It’s a bit like looking at root systems (you know those crap adverts), length is less important than mass.

The actual climatic drivers behind this pressure were a lack of wind, consequential low E.T, high humidity and in particular, high evening temperatures that carried into the first part of the night before dropping which ultimately led to dew development. You can see this clearly on the output below from a Birmingham location….

The area dotted shows continual leaf wetness, low to mid-teens temperature and humidity > 90% and that’s what drove both Microdochium nivale and Clarireedia homeocarpa (Dollar Spot to you and me) pressure last week. So if you’re sitting there at the start of this week and you have scarring, you won’t be alone I can tell you. Looking on the positive side, Dollar Spot in our neck of the woods responds well to being grown out with nitrogen applications and although we will start to lose some GDD / G.P as that cooler Atlantic low pressure makes its presence felt, we will still have good conditions for growth going into the back end of September as you’d expect. So I’d look to push growth in areas affected by Dollar Spot and try to avoid acidifying fertilisers to achieve this (and that includes iron forms) because we know C. homeocarpa prefers an acidic pH range when we look at growth of the fungi. This is quite the opposite of Microdochium nivale which doesn’t. It’s logical then that agronomic treatment should be different 🙂

Last week’s pressure was so high that it easily overwhelmed recent fungicide applications but looking at the main driver, it was leaf wetness and here we can combat this relatively cost-effectively. OK I know, you have to have a ‘heads up’ and an obliging spray window but I think as disease prediction models develop, this will come.

Imagine how less aggressive last weeks disease would have been if the leaf was drier ?

Now I know someone comment that they removed the dew mechanically during that period and still got disease but look at the graph above. Most of the extended periods of plant leaf wetness occurred at night with moisture building during some evenings as soon as the sun went down. So you have a wet, saturated leaf by 19:30 pm and then you’re in the following morning removing dew some 10-12 hours later. Well those 10-12 hours are what a dew dispersal surfactant will take care of and believe me as we go forward, they’ll become more and more important in both fine turf and outfield disease management. The good news is that they can be cost-effective and so will not break the bank going forward.

The start of the storm season….

I guess one of the less welcome consequences of the commencement of the autumn storm season if indeed it does take place next week is leaves and worm casts. Not much I can say to remedy either of these other than the management plans you already have in place but I’d reiterate a comment from a previous blog and maybe think about a late PGR + iron application trial on some of your worst-affected fairways. Less cutting = less smearing.

OK that’s it for this week, next week’s blog may be on a Tuesday dependent on my Welsh camper trip and how it goes 🙂

All the best.

Mark Hunt