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Writer's pictureMark Hunt

14th October, 2024

Hi All,


Well, it has been an interesting October so far, with some unusually (it used to be normal) cold and frosty weather for some of us. Clear skies last week gave many advantageous views of The Northern Lights as the sun's cycle continued at its 11-year peak in activity.


Now as someone who has slept through two successive, premium viewing opportunities on the North Norfolk coast (a great dark sky area) whilst in the campervan I know how irritating it is to see lots of beautiful images the next morning. My apologies therefore in advance.

Last week, my Aurora Watch app buzzed a red alert at 10pm and I nearly ignored it but looking outside I thought hmm maybe worth a punt. As we drove out I could see the sky had a pinky hue and sure enough sat on a hillside at Cranoe, surrounded by hooting owls, we watched a beautiful spectacle. Cracking....

The next day I was ensconced on the banks of the River Trent when I noticed a bird to my right flying along the river. It flew straight past me and I knew it was a Hoopoe. I then proceeded to bore my mate fishing just up the bank with my Hoopoe imitation call until my efforts were cut short by a well-aimed ball of groundbait. What a sight though and they are turning up all over the place. Along with that, they are incredibly tolerant to humans.

So what is going on with the weather ?


General Weather Situation


Well, our old friend the jet stream is up to its usual tricks with some real undulations allowing high and low pressure systems to do their stuff. This week the weather picture is a complicated and busy one with high pressure positioning itself to the east and for a time pulling up very warm and humid air from the south. Whilst this is going on, an Atlantic low pressure is feeding in rain in from the west, so not surprisingly the outlook is wet and warm, with a particularly mild day, mid-week, with temperatures likely to touch 20°C. That mid-week temperature peak will bring with it the potential for some pretty aggressive disease activity I think dependent on how the wind behaves overnight. One to watch.


From a rainfall perspective, we see overnight rain clearing the southern half of the U.K during Monday morning and providing a brief, dry hiatus for Monday into Tuesday. For Ireland though, Tuesday morning brings rain, some of it heavy into the south of the country before this spreads north and eastwards into the south west and west of the U.K later that on Tuesday evening. This rain looks heavy for the The South West and Wales initially before pushing up into The North West. The bulk of this rain will affect the western half of the U.K on Tuesday but on Wednesday as the rain clears Ireland, another rain front pushes into the west again and extends northwards across Wales into The North West and Scotland during Wednesday morning. It then moves eastwards across all areas during the day to give a very wet and very muggy mid-week day because this rain coincides with those warm southerly winds.


Thursday sees a mainly dry day with some rain across the west of Ireland and in the far south east of England before that high pressure nudges eastwards and allows low pressure to push a heavy rain front into Ireland on Friday morning, before this moves eastwards to affect the west of the U.K and later central and eastern areas. This rain again looks heavy.


The outlook for the weekend doesn't look too bad, except for Ireland and Scotland, which will see another Atlantic weather front push across on Saturday night, continuing across into western Scotland overnight into Sunday.


Temperature-wise, mild and muggy this week with day time temperatures in the mid-teens before climbing mid-week and then dropping back. No risk of frost this week with Wednesday night in particular looking very mild with temperatures not looking to drop below the mid-teens.


Wind-wise just about everything thrown into the hat this week with south east and south dominating dependent on your location of course.


After a topsy-turvy weather week this week, how are things set for next week ?


Weather Outlook


Well, if you are hoping for dry weather, the prospects don't look great, particularly across the south of Ireland and England with a Bay of Biscay low pressure system sitting just between Ireland and the south west coast of England for the 1st half of next week. So this appears to suggest unsettled conditions across the south next week with potentially more heavy rain. Further west and north, a strong, south westerly airstream will push cooler and unsettled conditions across Ireland into the north and west of the U.K. That low pressure will pull up more mild and humid air from the south east, so I can already see a potential disease peak spanning the 1st half of next week.


So mild and muggy for the 1st half of next week, especially across the south of the U.K and Ireland, with rain likely as well. As we reach Thursday next week, the Atlantic airstream pushes cooler and more unsettled conditions from Ireland further eastwards, so we will see stronger south westerly winds and cooler, less muggy conditions dominate from Thursday onwards. As we reach the end of the week, a high pressure system in The Atlantic will orientate those winds round to the north west, so a cooler end to next week than the start. Unfortunately the 2nd half of next week looks like we will see more rain into Scotland, accompanied by high winds and this will push down into all areas later next week. This Atlantic high pressure will bring warmer and drier conditions to Ireland and the west at the end of next week / weekend.


All animated GFS output provided courtesy of tropicaltidbits.com




Agronomic Notes


Well, September provided to be a rocky ride when it came to both Dollar Spot and Microdochium nivale with 2 significant peaks in the 1st and 3rd weeks of the month. In those peaks, overnight temperatures were high enough not only to promote Microdochium activity but also Clarireedia (Dollar Spot). On the flipside of that disease activity coin, we also had very good levels of Growth Potential which meant although we saw disease activity, some of the damage potential was negated by mycelium removal by cutting and natural growth providing recovery. Fast forward to the middle of October and the situation is different in a number of ways.


Firstly, growth levels have dropped off significantly with the arrival of what are now unseasonable early ground frosts last week, so daily G.P levels have dropped right back. In addition the overnight temperatures are generally no longer high enough to promote Dollar Spot activity, leaving Microdochium as Greenkeeper enemy no.1. Having said that, Wednesday night may just upset that particular applecart as projected overnight temperatures may be high enough for activity of both pathogens.


As we approach the 2nd half of the month of October, we know we start to lose daily G.P as air temperatures drop. We also lose photosynthetic potential as well because daily PAR (photosynthetic active radiation) levels show a marked dip in around a week's time, so the DLI (Daily Light Interval) level will also drop. Indeed this month we have already seen DLI levels drop below the sufficiency range for Lolium perenne as well as Agrostis sp.


You can see the 2 September peaks in Smith Kerns in the chart above and how it also coincided with a growth peak (dotted black boxes). Fast forward to the last few days though and we can see how the Smith Kerns is still around the 20% mark (or higher) which means a high probability of Microdochium, but the daily G.P has dropped right back to less than 0.2 (in other words, 20% of optimum growth). Now it has dropped off to zero over the last day or so because the average temperature was below 10°C, but don't be fooled. This is the issue with relying on Smith Kerns only as a disease prediction model, it doesn't work for Microdochium once the daily average temperature starts to dip below 10°C. I expect though for the Smith Kerns to shoot right up again this week.


This is why we start to see an increase in scarring potential on fine turf surfaces as we approach the end of October. Conditions are conducive for aggressive disease development but not always conducive for grass plant growth, so the balance tips in favour of fungal growth and away from grass growth.


Looking towards the next 7-10 days.....


So we have a clearly identifiable peak mid-week with high pressure vectoring up humid and warm southerly winds dovetailed in with rain leaving the grass plant leaf wet.


For England, Wales and Ireland, day time temperatures for Tuesday - Thursday will range from 17-20°C and overnight temperatures from 12-14°C and this suggests to me very high Microdochium pressure with perhaps a chance of Dollar Spot resurgence as well, maybe for the last time this year (but who knows). Looking further ahead to the weekend and beyond, I can see this disease pressure continuing from Sunday into next week, particularly for the south east and eastern side of the country as here it is closer to the continental high pressure system. Scotland will be mild but temperatures won't hit the same dizzy heights, more like mid-teens during the day and 11-12°C overnight before cooling off.


With the heavy rain forecast this week it is difficult to see a good spray window prior to the mid-week peak (Tuesday ?) but maybe afterwards. Of course those milder conditions will also raise the daily G.P again, so we will see a growth peak from grass as well as Microdochium I believe, but I think the balance will still be in favour of the fungus.


A tricky one to manage, good luck.


All the best.


Mark Hunt














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