On Saturday morning I was walking down to town, an urgent appointment with a Flat White front and centre in my mind when I looked up to see these clouds in the sky. I smiled to myself and made a mental note to pack my waterproofs the next day when fishing....
They are Cirrus clouds and one of the most useful cloud formations you can observe. Think of them as the advanced guard of a warm front. A warm front that invariably brings rain. The direction of the Cirrus clouds also tells us which way the front is approaching from and even though that rain may be over a thousand miles away, seeing these clouds provides a 12-24 hour warning.
The mechanics of Cirrus cloud formation are really interesting as warm air approaches, it encounters cold, dense air at ground level and slides over the top in a wedge shape. The moist air at the leading edge of the approaching warm air rises and freezes into ice crystals and these form high altitude Cirrus clouds. (see above)
I learnt about Cirrus clouds from a fabulous book, I've mentioned it before but it really is a weather game changer because it answers some of the questions that we all have concerning the weather and yes you'll even find the answer to the greenkeepers oft repeated claim that....."the rain just goes around us here you know Mark" :) :)
So the next time you happen to glance upward and see Cirrus clouds, you'll know that rain is on the way. It was a nice drop overnight and continuing for the south east of England this morning as the front departs across The Channel. As predicted last week, this rain event marks out w/c 17th October as a wet and sometimes windy one as well.
General Weather Situation - w/c 17th October
From the animated GIF's above, you can see that this week features a lot of low pressure systems starting off with the one that brought us rain overnight. The start of this week though is probably going to be the driest and most settled part of the week because behind the warm front that we are currently experiencing is a cold front and this will bring a temporary period of cool, dry and bright weather following the departure of the rain on Monday. This cold, bright theme will continue into Tuesday with cold overnight temperatures for all. Unusually for this time of year we will see easterly / south easterly winds dominate from Tuesday onwards as the leading edge of a deep Atlantic low pulls in warm air from the continent.
So very mild during the day with temperatures in the mid to high teens, cool at night for the start of the week once the rain departs but this is really just clearing the stage for mid-week onwards.
The wind will ramp up from the east from Wednesday and this announces the arrival of that deep Atlantic low pressure that you'll see on the GIF above. As the low moves closer, the wind will swing round to the south and push mild air in with the rain. Another point to note is the position of the low pressure system, it's to the south west of the U.K and this means the associated rain will have a southern bias initially.
So we will see the first effects of that low pressure overnight Tuesday into Wednesday as rain pushes into the south west of Ireland and England. This rain front will push into Wales and affect largely westerly areas moving later into The Midlands and northern England. It won't reach Scotland till the early hours of Thursday morning by which time the south west and south of Ireland will be on the receiving end of more rain, some of it pretty heavy. Thursday sees more rain, some of it heavy, push up from the south coast across the southern half of England and this time it looks to have a more central and easterly orientation with Wales and the west of England missing the worst. Importantly (and slightly selfishly), The Midlands looks on target for appreciable rain.
Thursday night into Friday morning sees more rain across the south of Ireland and this will push into the south east of England and then move northwards. More rain will follow on behind for Ireland and the southern half of England with Scotland missing the worst (I think Thursday am will probably be Scotland's wettest day) The rain will clear through Friday evening to leave a mild night and possibly a cause for concern Microdochium nivale-wise ?
The outlook for the weekend is decidedly mixed with a new southern-bias, low pressure system waiting in the wings. Saturday will probably be the driest day but they'll still be rain around across the south coast of England, Wales and the east coast of Ireland through the day but the second front of rain will arrive later on Saturday night pushing rain across Ireland initially and then the southern half of the U.K incl. Wales during Sunday. Scotland seems to miss the worst of this. Sunday will be a cooler day everywhere because we will lose the southerly wind and it'll be replaced by a northerly.
Weather Outlook - w/c 24th October, 2022
With the jet stream lying in a southerly position, this will continue to provide carte blanche to Atlantic storm systems and so we can expect next week to continue the unsettled theme, albeit significantly cooler than this week. There may also be a sting in the tail to October agronomically-speaking, but more on that later. So next week will start cool and unsettled with the vestige of the weekend's low pressure system bringing some showers to the picture on Monday across the U.K & Ireland. Just like this week, Tuesday looks like being the driest day before we see another Atlantic low push rain accompanied by strong south westerly winds into Ireland on Tuesday night. This will cross The Irish Sea into the U.K to bring the same on Wednesday clearing through into Thursday which will be drier before another low pressure slips into the south of England on Friday. Now after this could be a cause for concern in my mind because I see a possible hiatus when warm, humid air could be pushed up across the U.K & Ireland accompanied by light winds. If I was still running my disease modelling, I'm sure this would be showing as a red flag. Now a lot can change between then and now but it's a warning.....
Some rain but still a long way to go in some areas of the U.K
The change to unsettled weather with rain crossing the U.K & Ireland is typical of autumn of course but as should remember, it follows one of our most prolonged droughts ever and we need surplus rainfall to correct it. The state of water reserves in this country is dire and in some areas we are so far down on rainfall it is a concern if the situation will correct itself before next spring. This matters for turf management because we need new seed to establish and develop roots. These roots must be deep enough into the soil profile to provide a degree of protection against future droughts. If the profile isn't wet, then the roots wont be able to penetrate more deeply and survive. Now of course part of this is down to the overseeding operation, obtaining that critical seed / soil contact and avoiding overseeding into areas of high surface organic matter without removing that barrier.
I am indebted (again) to Rob Hay at Northampton County for providing me with a couple of images. The first (above) illustrates this point perfectly. It shows an area overseeded with Fescue after solid tining through the surface organic matter layer after the drought of 2018. The picture was taken at the end of summer 2022 and the live grass in a block pattern is that sown back in 2018. The grass in-between has stressed severely because of the effects of high heat on surface organic matter. So point no.1 is the importance of seed / soil contact when overseeding and if you have an area of high organic matter you should think about how (mechanically) you're going to give the new seedling a chance to survive. Removing that organic matter level removes the impediment to root development for the new seed and improves viability going forward.
The other part of the successful overseeding equation comes courtesy of Mother Nature and that is our reliance on autumn and winter rainfall to redress the soil moisture deficit from the summer.
Below is a snapshot across the U.K using some of the Davis weather station data I have access to (so if an area is missing and you have a Davis weather station which reports rainfall AND E.T, please drop me a line on firstname.lastname@example.org).
You can see for October, some areas are in moisture surplus and so they have started the road back towards rectification of this summer's drought. Worryingly, some are still in deficit this month.
The pattern is that for the west and north of the U.K and Ireland, the rectification process towards low water reserves is well on the way. Interestingly for the south of England this is also the case although the rainfall surplus is more modest. For The Midlands and east of England, the situation is more of a concern with these areas still showing a deficit between the amount of moisture falling as rainfall and the amount removed by evapotranspiration in October.
With this week promising more rain for the south, east and Midland areas it will be interesting to repeat this graphic this time next week. Let us hope we have some surplus to report in the areas that are remaining dry.
Going back to my original point, in these areas where we are still dry, any newly planted seed will be on the back foot because although it can establish with the moisture that we have received so far, this has only wetted the top 10-15mm of the soil profile. Deeper down we are still powder dry....
Not wishing to end this part of my blog on a negative, the chart above (thanks Rob again !!) shows that where we are now and where we were in 2018 (after another warm, dry summer) is pretty much identical for the location plotted above (Northampton). Mother Nature retrieved that situation for us then, so lets hope she does so again.
Now we are well into October, we are approaching the time when this disease can become problematic. Now I think despite the loss of some excellent active ingredients over recent years, we are well-placed to combat this disease.
Well firstly with more successful Bentgrass and Fescue overseeding taking place over recent years, we have more heterogeneity across a sward, that is to say we have a mixture of grass species present rather than just Poa annua. With more species present which have a better natural resistance to this troublesome fungal species, we see a lower incidence or more precisely, less scar damage. The image above shows Poa annua growing amongst creeping Bentgrass and you can clearly see where the Microdochium is occurring.
This is a key component of a successful IPM strategy, it is the bedrock I think to mitigating the effects of M.nivale.
The snag point comes when you have localised climatic effects that prevent this type of scenario being reached. One of those is shade. Unfortunately or perhaps fortunately for those in a high shade-affected environment, Poa annua has a low DLI requirement vs. any species of Bentgrass and so will out-compete it in a shade environment. This is great for grass cover but not so good for vulnerability to Microdochium and it remains one of the trickiest situations to manage in my mind without reliance on repeated pesticidal applications.
Of course pesticides and their usage in public areas is a hot topic, not least because of the E.U's announcement of a proposal to reduce the use and risk of pesticides in public areas with a proposed complete ban in sensitive areas which of course includes golf courses. You can read an interesting article about this here
Now we aren't of course in the E.U any longer but for chemical companies serving this industry, it represents a challenge because if they are developing an active ingredient for sale within the E.U and the U.K, they will lose one of the market places potentially. The situation is already complicated because after Brexit those same companies have to register a pesticide in the U.K and in the E.U. That's an additional cost and another layer of bureaucracy to deal with.
You can already see the impact of this in the U.K pesticide market vs. Ireland for example, with no registration as of yet for Chipco Signature Stressgard and only a partial one for Ascernity here in the U.K, whereas across The Irish Sea they have both been registered (I think) since 2021. So if the E.U go ahead with this proposed ban or restriction, it will likely have an effect on the U.K I think in terms of product availability.
The flipside of this coin though is that there are countries like France and Holland who already have significant pesticidal restrictions in place and here they are managing by improving their non-pesticidal IPM programs. It isn't a black and white solution but then again, neither are the newer pesticides that we have available due to their lower A.I content. The challenge is whether we can further improve our IPM programs in the face of potentially higher disease pressure due to climate change. Be that higher levels of plant stress encouraging more of the stress-related pathogens like Anthracnose or plant parasitic nematodes or more humid and milder conditions later into the autumn encouraging more severe Microdochium.
On that last point, we need to keep a pertinent eye on the weather patterns at the end of this month. Above is the projected GFS output for the 29th of October and we can see humid and warm air pushing up into the southern half of the U.K. If this proves to be a reliable forecast signal, it will bring with it some high disease pressure.
Watch this space...
OK, that's it for this week, all the best.