November 23rd

 

Hi All,

A stiff frost here today with the temperature dropping to -1.5°C at dawn, everything is white out there and looking lovely.It is a strange time for our industry, being in lockdown (aside from Wales of course) and preparing for the day when we will emerge out of the other side. For sure I think the demand for golf will be extremely here during December and over the winter which will create plenty of pressure in terms of short daylight hours, compressed tee times and keeping surfaces open / playable.

2020 will go down as one very strange year but with the announcement of the 3rd vaccine results this morning I’d hope that at some point next year we will return to a level of ‘normality’, whatever that is. It is interesting that a process that normally takes 10 years has been condensed down to the same time frame but in months with Covid-19, interesting and slightly worrying. I mean that time frame was either necessary or a function of bureaucratic red tape, time itself will be the best judge 🙂

Weather-wise we remain very unpredictable past the 5-7 day mark, the scenario is literally changing every day, so there’s little confidence in it from a forecasting perspective. We have high continental pressure currently slugging it out with Atlantic low pressure systems and currently the former is winning and looks to hold until some point next week, but like I say, it’s very unpredictable.

General Weather Situation

So we start the day with most places dry, cold and across the U.K, frosty. For Ireland though we already see showers / heavy rain pushing across Galway, Connacht and the north west and these will move eastwards through the morning. This rain front is on a north easterly trajectory so it’ll push up into the west of Scotland by lunchtime and then slowly move inland across western Scotland / south western Scotland this afternoon. At the same time it’ll push inland across Ireland but I think the east will stay dry. Further south we look to enjoy a pretty dry day across England and Wales save for some rain late in the day for The Lake District. Staying on the cool side despite a moderate south westerly wind strength with temperatures looking to hit around 9°C, with Ireland a degree or two higher.

Onto Tuesday and that band of rain is still butted up against the continental high pressure system straddling the west of Ireland up to the west of Scotland at dawn. Through the morning this band of rain will begin to push eastwards across Ireland, Scotland and the north west of England. And there it stays for the remainder of the afternoon, clearing Ireland from the west through the afternoon / evening but otherwise not making a bunch of progress eastwards but it will move from west to east across Scotland p.m. tomorrow. So for Wales and England, another dry day beckons without the risk of a frost Monday into Tuesday as more cloud cover will hold temperatures up. As strengthening south westerly wind will give us a milder airflow and so temperatures are likely to break into double figures (10 – 11°C everywhere) for Tuesday with plenty of sunshine across central and eastern areas.

Mid-week and overnight that weakened rain front has pushed across The Irish Sea into Wales and The South West. This rain will slowly move eastwards across the southern half of the U.K, weakening as it does so for a time before consolidating across the south east and east of England. Ireland and Scotland will see some showers on western coasts but a much drier day than earlier in the week on Wednesday. A big change in the wind on Wednesday as it flips around 180° from south west to north east and that’ll both increase cloud cover but also drop the temperature back down to high single figures.

That north east wind continues on Thursday but does lighten off a little through the morning but as we know with this wind direction we get plenty of cloud pushing in off The North Sea. So expect Thursday to be a dull, dry affair just about everywhere with a bracing north easterly wind and any signs of sunshine limited to the north east of Scotland, Ireland and the west coast of the U.K. As we go through the day we may just see that cloud break further south across eastern coasts as the winds die back appreciably. A much colder day on Thursday though with temperatures lucky to hit much above 5-6°C, maybe a little higher if you see the sunshine.

Closing out the week on Friday and another cool one with similar temperatures to Thursday. A lighter, changing wind as well so that’ll allow more in the way of sunshine to break through. For Ireland and Scotland, we see a rain front from The Atlantic push in to western coasts but make little progress inland. There is likely to be some rain around across the south / Midlands through the course of Friday but more likely to the east and across East Anglia later in the day. Through the late afternoon / evening that rain front over Ireland pushes east and introduces heavier rain to the north west of Scotland at the same time. Similar temperatures to Thursday 5-6°C

So onto the weekend and a complicated forecast I’d say as initially low pressure pushes rain across Ireland on Saturday but as this butts up against high pressure it pushes north and east into the west of Scotland. With high pressure remaining over England and Wales, we will be mainly dry but the proximity of the low will feed some showers into the system over the weekend. So a little milder on Saturday as the wind turns southerly but through the course of the weekend it’ll swing round to northerly so don’t expect much change out of 6-8°C. More showers around on Sunday with a band of rain moving south and east through the day across England and Wales, whilst Ireland and Scotland will see more in the way of sunshine and less chance of showers. Now this is a complicated weather picture looking at the proximity of low pressure and high pressure so I expect this to change as we go through the week. Tricky to say which one will win the day beyond the weekend but here goes…

Weather Outlook

Jet Stream – 30/11/20 – Courtesy of netweather.tv

Jet Stream – 05/12/20 – Courtesy of netweather.tv

The two images above show where we are projected to be at the start and end of next week jet stream-wise.

You can see why it is so tricky to pull together a forecast for the weekend and start of next week as the jet stream is weak, fractionated and therefore unpredictable. By the end of next week though you can see that it reforms into a strong transatlantic pattern and that means a more predictable weather picture.

So Monday looks to start off with high pressure pushing in off The Atlantic but its hold will be temporary as we have a deep low pressure across Iceland that is pushing south and this makes its presence felt as we go through into Tuesday. So I think a quiet start to the week on Monday but with an increasingly windier and wetter picture in the north and west from Tuesday onwards. As we go through into mid-week, next week we keep that milder westerly wind but as high pressure tries again to reassert itself, this spins the wind round to a more north westerly aspect so feeling cooler for the 2nd half of the week. A brief hiatus on Friday before the way is cleared for a really cold, deep, low pressure to push in next weekend. I wouldn’t be surprised if this doesn’t have a wintry aspect associated with it, albeit temporarily. So rainfall-wise I think we will start off mostly dry on Monday except for the north west of Scotland but from Tuesday we will see rain push south and east across the U.K & Ireland and this will continue to Friday when we will have a brief hiatus before more widespread rain for the weekend. Ending on a note of caution, there is a very intense low pressure system following on behind these fronts and this may hit the south of England in the earlier part of the week after. Now it’s a long way away from a weather forecasting perspective but if it stays on track it’ll be very windy and very wet w/c 7th December. I’ll keep you posted on this one.

Agronomic Notes

At first sight the forecast of a cool week with light winds might not seem like a recipe for Microdochium nivale pressure but the reality is that this week will continue the pattern of November 2020 representing a tough month to keep surfaces clean.

Here’s the prognosis for sheltered greens across 3 different geographical locations for the week ahead….

It is true that with cool temperatures Microdochium will not be at its most aggressive but as a fungal pathogen that can grow from 0°C, having air temperatures in the 4-8°C region at night is not an issue for it growth-wise. The driver to disease pressure this week will be dew formation on the leaf because with high pressure and the lighter winds associated with it, dew formation is a lot more likely. Add to that mix, the presence of an Atlantic low pressure that will feed into moisture / humidity into the weather picture and we have a real witches brew I am afraid.  This presents a headache I know for the clubs that are reduced to very low staffing numbers of the furlough scheme in terms of resource to manage dew removal. An additional issue that we know from previous autumn / winter periods is that dew will reform after removal in the morning if the conditions are conducive for it to do so.  It is during these type of periods that disease pressure really ramps up. Last week we saw this cycle of dew formation, frost and dew re-formation on many areas of the U.K & Ireland.

Of course if the plant leaf is wet overnight with dew then we will see the formation of frost on the grass plant leaf at the coolest part of the night (normally the run up to dawn just before sunrise)

Many people think that frost is good because it ‘kills’ Microdochium, well it doesn’t and in fact some people argue that having cycles of dew-frost-dew is more likely to push on the disease activity rather than suppress it. It is an interesting debate and I for one have observed more aggressive Microdochium coming out of frost. Maybe it is because we move straight from frost formation on the leaf to dew formation as the sun thaws the ice on the plant leaf surface ?

You can see the dynamic in the graph below showing dew formation over a period of days last week….

On the 19th of November, you can see the plant leaf started to pick up moisture from 18:30 reaching near full leaf surface saturation from a dew perspective at 02:00. During the night the air temperature dropped closed to freezing leading to ice formation on the leaf from 02:45 before the frost began to melt from 07:15 onwards as the sun rose. The leaf then stayed wet until mid-morning when increasing winds dried the leaf down. During the afternoon of the 20th, there were two brief rain showers which wetted up the leaf fully from 15:30 and it stayed this way right through to 03:15 the following morning when the winds were strong enough to dry down the leaf again. Over the course of this two day period the plant leaf was wet for 24 hours (including the frost period) and most of it at night when manual dew dispersal wouldn’t have been implemented (unless you are really keen that is !). So when I look at the coming week I see a similar pattern emerging of heavy dew, some frost later in the week possibly and then reverting to a wet leaf again as the frost comes out.

Fungicide longevity as described by Growth Potential 

One of the changes I think over the last few years in our industry is the acceptance of the role of GDD and G.P in the performance of nutrition, PGR’s and pesticides. Whether that be uptake windows as denoted by rising GDD / G.P or the frequency of application as denoted by a cumulative GDD / G.P period. Ultimately I think going forward we will end up adopting Growth Potential as the model for this area of application because it is based on an optimum temperature for growth and therefore importantly has the ability to decrease when we get temperatures which are above-optimum for plant growth. This is particularly important when it comes to managing Poa-dominated swards because we know there are periods of the summer when Poa annua growth decreases with increasing air temperature. For the last few years I’ve worked on a cumulative growth potential of 10.0 or thereabouts for fungicide longevity but appreciate that there are a multitude of variables associated with this parameter, not least plant nutritional status, grass species and of course the effectiveness of the fungicide in general when it comes to suppressing the population of Microdochium.

Last week I was monitoring the performance of some trials with respect to fungicide longevity and in particular, cumulative growth potential. I took a set of pictures 3 days apart, the first set at a cumulative G.P of 8.0 and the second at a cumulative G.P of just over 9.0. You can clearly see how the disease progressed aggressively as the fungicide grew out of the grass plant and the protection provided decreased.

Now to be fair this represents an extreme example of fungicide longevity because the control applied would only have been rated as moderate and there was very heavy dew formation driving the disease on. No dew control had been applied to the plots with the dew just being removed manually. It just goes to show though that G.P = 10.0 isn’t I feel far off the mark when it comes to practical longevity and the role that dew formation plays in Microdochium nivale development.

OK, my apologies for talking about disease (again) this week, but I’m afraid it’s very much front and centre at the moment 🙁

All the best

Mark Hunt