July 30th

Hi All,

Friday marked quite a transition  meteorologically-speaking, with some of the hottest temperatures I’ve seen on my weather station and car thermometer. At times we hit 36.5°C during Friday afternoon but the signs were already there that we were due a dramatic weather breakdown.

Returning from a mini-break in France, as we began our descent over northern France, I snapped this beautiful Anvil cloud or Cumulonimbus incus to give it its latin name. (Apparently the incus is an anvil-shaped bone in your middle ear, don’t you know, to further yours and my education this Monday morning :))

An anvil cloud originates from a thunderstorm and signifies the potential presence of hail, rain, thunder and some really strong updraft winds that my dad used to tell me are strong enough to break up a glider. Sure enough over the course of the weekend we saw some dramatic footage of hail, thunder and lightning, the arrival of rain and some pretty strong winds. Another thing I noticed from the plane was the thick band of smog / air pollution sitting over London, so those dissipating winds were welcome.

Of course again some areas got more than others with the east of the country, the north-west and Scotland getting dumped on. This radar image taken on Saturday evening shows the main pulse of rain moving across the east of the country though fortunately we saw a nice 10.5mm of rain over the last 3 days.

By Christ I think I wore out the rain radar link on my phone such was my desperation for some meaningful rainfall across Market Harborough. I caught myself repeating the words I hear so many times from you chaps…”The thing is here Mark, the rain just goes around us…..”

Yeah right…..

10mm odd is nowhere close to what we need but that and the lovely drop in temperature from the mid-thirties to the mid-teens had me scrambling to find another layer of clothing, such was the length of time since I needed it last…

So how are we set for this week, is that it rainfall-wise and is the heat that we know is set to build again looking long, medium or short-term ?

Image courtesy of NetWeather.tv

General Weather Situation

Well, it isn’t totally it for rainfall as we kick off Monday because this rain radar snap taken at 07.20 a.m. shows a raft of showers moving north-east across the U.K and Ireland. So definitely a day of sunshine and showers to kick off the week with the heaviest moving across the east and north-west of Ireland, north-west of England and East Anglia possibly. Winds will be moderate and from the south-west and temperatures will range from a high of 17°C over Ireland and Scotland to 23-24°C for southern England, in other words a nice day really.

Tuesday sees a new band of rain push into the west of Ireland but this one is much more likely to be north and west-orientated as we start to say goodbye to the low pressure that brought us such relief over the weekend. So rain likely from early doors in the west of Ireland but all the time the orientation of that rain is heading north and east into north-west Scotland by late morning. Further south we may just see some rain overnight and through the early hours for the far south-east of England but otherwise a dry, sunny day with varying amounts of cloud. The wind will be moderate and more westerly and temperatures similar to Monday.

Wednesday sees that low pressure still pushing in some thick cloud across mid / north Wales, the north-west and Ireland with some of it thick enough to generate light rain. We will also see some persistent rain across north-west Scotland, right from the off. Through the morning we will see temperatures rise as the cloud cover breaks but for Ireland the early afternoon will bring in some rain as well across the north, west and south. Elsewhere the cloud will build and keep the temperatures similar to the first part of the week, high teens across Scotland and Ireland and mid-twenties across the south of England.

Thursday sees that low pressure firmly pushed away to the north and this will allow heat to build from the continent so temperatures on the up with heat arriving in the shape of mid to high twenties across the south of England. It won’t be a totally dry day though because we will see a thick band of rain push over Ireland and into West Wales, The North West and Scotland through the morning with some locally heavy downpours likely. The demarcation line will be from The Severn Estuary to The Wash with thicker cloud and rain north of this and clear skies and higher temperatures to the south. Ireland looks to have a pretty grim day with thick cloud and rain throughout the day and the same for Scotland, The North West and Wales though South Wales may miss the worst of it. Much lighter winds on Thursday and more southerly in orientation turning northerly on Friday on their way to easterly for the weekend.

Friday sees a very similar picture with a thick front of cloud covering Ireland, Wales, The North West and Scotland. Again that cloud will be thick enough to bring some rain in places in the affected areas. Below this band of cloud we will see the sun break through and push temperatures up into the high twenties across The Midlands and south of England and East Anglia. As we progress through the afternoon, the thicker cloud layer will start to dissipate across the west and north to give more in the way of sunshine and better temperatures though Ireland may only clear in some north and western areas. Light westerly / north-westerly winds for the end of the week.

The upcoming weekend looks pretty nice really with high pressure in charge and warm, dry conditions and cloud cover burning off through both days. (I say nice, it’s not my nice, I like wind and rain for fishing 🙂 )

Temperatures up into the high twenties can be expected across the south of England but I reckon the warmest areas will be South Wales and The South West with the possibility of hitting thirty degrees here. This heat though comes with the threat of thunderstorms on both days as we approach late afternoon / early evening. Ireland will see some of this heat as well especially on Sunday with temperatures in the mid-twenties but they’ll be rain around as well, particularly across the west. Scotland will have a cooler side of the coin, still thoroughly pleasant though with some rain over the north and west on Sunday.

Weather Outlook

So with high temperatures forecast for this weekend, are we looking at another long dry spell across August or is the outlook less certain ?

Image courtesy of Unisys Weather

Above is the projection from Unisys Weather for next Thursday (10 days time) and as you can see we have a low pressure pushing down across the U.K bring cooler temps and no doubt rain as well. So looking to next week I think we will take the weekend heat into the start of next week but right from the off we may see the beginnings of a breakdown across the west of Ireland as the low pushes in. The settled conditions will probably persist further east through Tuesday but all the time we will see more unsettled conditions come into the west and move slowly eastwards so I expect by late Tuesday / early Wednesday we will see cooler temperatures and a more unsettled picture across the U.K and Ireland.

The usual caveat applies, that of the low winning the day vs. the resident high pressure so please don’t shout if I’m wrong. For the 2nd half of next week it looks like strong westerly winds and unsettled sunshine and shower conditions. Not great if you are on your summer holidays but I don’t think it’ll be a permanent switch with high pressure possibly following on from this.

Agronomic Notes

Ok, so we have had a really extended dry spell, my weather station recorded 57 days since the last meaningful rainfall fell across Leicestershire on the 30th May with only 1.8mm recorded in June and the same in July though that might have been because I hand-watered my rain gauge trying to keep my newly planted garden alive !!

The weekend didn’t just bring rain, it also brought humidity and that means we are likely to be seeing a peak in disease activity as we go through this week rcarrying over from the weekend.

You can see the effect on humidity and temperature on the stats from my Netatmo Weather Station below….

It’s likely that your turf could potentially show a number of pathogens over the coming days if it isn’t already. The good news is with warmer and drier conditions coming this week, we should see some of these disappear as quickly as they come, though as usual with everything in life, there will be exceptions.

It is likely that pathogens like Microdochium nivale may persist across the geographical areas that will experience thicker cloud, rainfall and high humidity through this week, so that’s Ireland, Wales, The North West and Scotland in particular. Where we see drier and more settled conditions I think it’ll fade as quick as it came in.

I think as we approach August and in some areas carry over humidity / rainfall we will see increased pressure from Dollar Spot as well.

Anthracnose Foliar Blight

One of the pathogens that is likely to be more visible is Anthracnose Foliar Blight which has had nearly two months to sit within the grass plant as a biotroph (resting state within the plant). I received a good few reports of activity over the last 3-4 weeks and I expect this will increase as the arrival of rain stimulates growth, especially on greens.

The appearance and growth of grass after summer rain is always far better than after irrigation, part due I think to the presence of nitrogen in stormy summer rain and part to the pH of the water, with many mains water supplies in the U.K and Ireland, high in pH and bicarbonate. Rain typically falls as a weak acid (Carbonic formed from a reaction between H2O and CO2) at a pH of 6.7, but can be much lower depending on its source.

I’ve already had a number of reports of a growth flush on greens after the rainfall and what we may see associated with it, is an increase in Anthracnose Foliar Blight activity. This occurs because the newly stimulated grass plant tries to grow with a compromised shoot and root system and cannot uptake sufficient water and nutrient through damaged structures. The grass plants photosynthetic capacity is also affected with Foliar Blight.

So if you are looking at something like the above, what’s the best way forward ?

First off we should consider if applying a fungicide will benefit us ?

In my humble opinion I think the only benefit of applying a fungicide with active Anthracnose Foliar Blight is to ring-fence the currently healthy plants. I say this because we need to understand that the stage of disease present in the affected plants is already far too late to be corrected by a fungicide application. Once you see the above symptoms on turf, you’d also see blackening on the base, crown and leaves (sometimes) of the affected plants if you looked closer.

The blackening is attributable to structures called Acervuli, which are the fruiting bodies for this pathogen and produce asexual spores. These spores are raised aloft so-to-speak on hair-like structures called Setae and are then transported away from the affected plant to begin the cycle again.

So in plain English when we see symptoms of this disease on the turf surface it has already gone through its whole life cycle and that’s why fungicidal applications won’t correct the visible symptoms. There is therefore no effective chemical curative control of Anthracnose, whatever the rep that comes down your driveway says. Everything has to be aimed at preventing this occurring in the first place.

Another feature of this disease that I have noticed is its ability to look like it is increasing even when you have applied a fungicide and have ticked all of the BMP boxes. This is I think because within your grass sward they’ll be plants not yet showing leaf symptoms but with the pathogen present and so they’re already on their way to checking out.

So what’s to be done ?

Well I think the best course of action is to carry out renovation and introduce new seed to the affected areas to try and regain sward integrity. I know some people state that they ‘like’ Anthracnose because it takes out Poa annua but the same people should be mindful that unless you establish another grass species in the voids created by this disease, the only thing you’ll be staring at in the late autumn is the ultra-invasive, clumpy, annual Poa biotype, which is arguably a worse grass plant than the perennial Poa it replaced 🙁

Nutrition-wise you should still be aiming for the Rutgers baseline levels of 3.6% N and 2.0% K but often a light-rate, granular fertiliser accompanying the renovation and overseeding does no harm at all in pulling the surface together and creating an integrated sward.

Remember also that all the research shows that acidifying nutrient-sources tend to favour Anthracnose development and that more basic fertilisers like potassium nitrate do not, the exact opposite to Microdochium nivale. So for this reason think about your choice of granular fertiliser if you decide to go down that path.

If you’ve managed to come through 2 months of stress with surfaces that are currently unblemished, then you are due a pat on the back, but remember summer isn’t over yet 🙂

Ok, that’s it for this week, next week’s blog will cover my usual monthly summary for our hottest July on record and it will be the last for a few weeks as I depart for my Alaskan fix of all things wilderness, no Wifi and no phone network 🙂

All the best.

Mark Hunt

 

2 thoughts on “July 30th

    1. mark.hunt Post author

      Hi Micah,

      Yes I believe that’s true but I think the pH of rainwater isn’t just dependent on this reaction with nitrogen and sulphur dioxide also implicated. When I’ve measured the pH of rain and its contents (chemically), it is typically just under neutral (6.5-6.7) so that would suggest that the reaction of CO2 and H2O isn’t always at equilibrium and possibly there is only partial dissociation ? Also I’ve noted that when we have low pressure systems that circulate over the U.K landmass as opposed to moving across it in a west-east direction I’ve seen the pH of the rain drop the more time it spends over land. Presumably this is because it picks up more S and N pollutants which lower the pH further ? What do you think ?

      Reply

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