October 31st

Hi All,

This image will probably strike a note with most greenkeepers as it depicts an active fungus and leaves. Both are very evident at the moment with the mild and humid weather creating significant Microdochium activity, as I predicted it might two weeks ago :(

It is not unusual nowadays to have very warm day and night temperatures in October, with temperatures peaking at 23.9°C in 2018 and 29.9°C in 2011, which I think was on the 1st day of October and the current record. I would also say in general, the end of October is typically very mild now. I think it is the most changed month temperature-wise in my lifetime.

Back in the day, Halloween and Bonfire night were usually accompanied by frosts, fog and cold weather, with air temperatures typically around 6°C. That is no longer the case anymore. Whether the jet stream characteristic has changed and / or the warming climate, it matters not because this is what we have to deal with from a turf management perspective. It's a plus / minus situation (eh Bernie :) )

About this time of year I begin to look for the first signs of colder weather, both out in The Atlantic and to the east and indeed there is the first signs of both so I don't think these milder air conditions will extend significantly into November, although we could pick up a mild period mid-month.

General Weather Situation w/c 31st October, 2022

As you'll see from the animated GIF's above courtesy of www.tropicaltidbits.com, we have a lot of activity on the weather front this week, with low pressure systems rattling in from The Atlantic and lots of packed isobars meaning it'll be windy as well. After today there is a subtle shift in the wind direction from south to south westerly which will mean we will lose that really mild, humid air. It'll still be mild, just not un-naturally so with temperature dropping to the lower teens during the day and high single figures at night.

In terms of rain events, we already have one on the go across Ireland as this clip from Netweather.tv shows. This rain front is set to cross The Irish Sea later today and bring rain, some of it heavy to the U.K, later on today and extending overnight. It'll also bring with it increasingly strong winds with Tuesday and Wednesday looking like the windiest days of the week. As this rain front clears on Tuesday, it'll leave behind a sunshine and blustery showers sort of Tuesday with the main concentration towards the west. No sooner has this low departed than another one is projected to push into the west of Ireland in the early hours of Wednesday morning and move eastwards again, bringing very heavy rain extending from The South West, through Wales, The North West to the west of Scotland by lunchtime Wednesday. This heavy band of rain will then push across the southern half of the U.K through the course of Wednesday, but they'll also be plenty of rain for the north west and Scotland.

Thursday and Friday will be drier days, but they'll still be plenty of showers, some of them heavy across western coasts of Ireland and the U.K. During these clearer spells of weather, we will see the temperature drop to just into double figures, so feeling much cooler than last week and more typical I'd say for early November.

That just leaves the weekend and here again we have another rain front projected to push into Ireland on Friday pm and then move across the U.K overnight into Saturday, so a wet and windy Saturday in on the cards till that rain clears from the west. That low pressure is sitting out in The Irish Sea so Sunday promises to be a pretty dull day with plenty of showers and longer spells of rain for Scotland and possibly the south east / East Anglia, Midlands during Sunday pm. Feeling cooler than of late with low double figure temperatures but that wind will still be predominantly south westerly, although it'll veer north westerly on Friday.

Weather Outlook w/c 7th November

So next week looks like starting off in pretty much the same style that this week finished off with. That is to say wet and windy weather pushing across Ireland and the U.K through the course of Monday and into Tuesday, leaving behind sunshine and showers on the Tuesday. A shift in the wind from westerly to north westerly will cool things down as we head towards mid-week. After which we could see high pressure push up to bring a period of settled conditions, most likely with fog and mist patches. The appearance of this high pressure peak will push rain north of the U.K, so only Scotland is likely to continue to pick up showers.

By the weekend after next (12-13/11/22), we could be in a classic Omega blocking pattern in the jet stream with high pressure sandwiched between cool and more unsettled weather to the west and east.

It's called an Omega block because the jet stream forms the shape of the Greek letter, Omega....Ω (see below)

Watch the Met Office's you tube video explaining this weather phenomenon here

With the high pressure sitting to the east, it may mean it could still pull up humid weather from France and the continent so I'd pick this out as a possible period of high disease pressure (more on that later)

To summarise, unsettled for the first part of next week, wet and windy but this will become increasingly more northerly as high pressure pushes up mid-week onwards and the weather settles down to cooler and foggy for a time before possibly milder air pushes up from the continent.

Agronomic Notes

So the main issue I want to discuss in this week's blog is the effect of the mild weather during September and October.

From a meteorological perspective we have had two warm air peak events caused by Omega blocking events.

Below, is the GFS output from last Friday, 28th October and you can clearly see warm finger of high pressure sandwiched between low pressure either side.

The result of this from a turf managers perspective is that warm and humid air is pushed up on a southerly wind and this causes mild overnight temperatures, long periods of dew / leaf wetness and perfect conditions for Microdochium nivale.

Below, is a graph showing relative minimum and maximum overnight (between 00:00 - 08:00) air temperature together with humidity plotted against the Smith Kerns Dollar Spot Probability Model (calculated on the usual rolling 5-day average).

You can clearly see a period at the beginning of September and another at the end of October when overnight temperatures and humidity were high. This in turn drives up the resultant Smith Kerns Probability to close on 40%. At this point we expect high Microdochium pressure and that's what we have been seeing judging by the facebook and Twitter posts of late :(

Overnight temperature / humidity - Sept 1st - Oct 31st, 2022 - Location - Sevenoaks

I have added in the maximum overnight temperatures from a data label perspective so you can see how mild it has been overnight.

If you bear in mind that Microdochium nivale as a fungus can grow from 0°C and hits optimum growth at 15°C, then it doesn't take a rocket scientist to understand why disease pressure is so high currently looking at those temperatures.

The other component driving this disease equation is leaf wetness.

Using data obtained from a Davis Leaf Wetness sensor (shown above) mounted to a normal Davis Vantage Pro, we can see from the graph below how these two periods of high overnight temperatures have coincided with long periods of sustained leaf wetness. This makes it very easy for the fungus to more across the leaf and from one grass blade to another.

It is a perfect storm I'm afraid, but hopefully with temperatures dropping back this week, we should see disease pressure do likewise.

With soil temperature closing mirroring air temperature trends and the arrival of frequent rain, it is no surprise that we have a very high level of worm activity currently. The only plus side is that with soil conditions still on the dry side in places, it is taking its time in some locations to penetrate the rootzone. Let's hope by the time it does, it'll be colder and they'll be less active :)

OK, that's all from me this week, have to prep for Saltex, remember if you are up at the show, please pop by and see Peter Palmer and I on the Prodata stand C097.

All the best.

Mark Hunt