So our wet start to August continues with some significant rainfall over the U.K and Ireland over the last week. I got some interesting snippets emailed to me last week, the first stating that it is set to rain all through all of August (that one is from the Express and we know what they’re like accuracy-wise when it comes to weather :))
The second was that Shetland was sunnier than Cornwall in July and that’s due to the fact that the jet stream sunk a long way south and so did the low pressure systems bringing more rain further south. Lastly as a result of that trough pattern in the jet stream, Hampshire was one of the wettest places in July with 118% of its normal July rainfall. What’s the betting that the rain fell in 3-4 days rather than evenly across the month ?
This week we are set in that trough pattern and so we can expect some more rain, some of it may be very heavy. There is though just the merest hint of a change in the weather right at the 10-day mark with high pressure making an appearance next week but I don’t think it is set to last.
General Weather Situation
So we start the week on Monday with a rain front that has crossed the U.K and Ireland overnight just exiting across the east of the country. So currently we have some rain around across northern England and the north Midlands in a line drawn from the Severn Estuary up to The Wash. These showers will push up diagonally across northern England during Monday morning. We will also see further showers affecting The South West and the south coast of England. All of these shower fronts will move north east across the U.K during this morning. The same is true for Ireland with some showers over west Munster moving north east across the country during the morning with another band across Donegal. These shower bands will eventually stretch right up to the Scottish border however north of this looks mainly dry today. As these showers clear through the afternoon we should see some sunny intervals between them except for The South West where later in the afternoon we see the cloud build and more showers push in. This band of thicker cloud will push north and east across the southern half of the U.K later this evening. Quite a temperature difference today with Scotland and Ireland in the mid-teens and the south of England and Wales sitting in the high teens, perhaps just breaking into the twenties. Winds will be light to moderate and from the south west.
Onto Tuesday and last week I commented that we have a battle between an easterly low and an Atlantic high projected for the start of this week, well the easterly low wins. So it will be on Tuesday with wet weather pushing in from the east coming off The Wash and affecting East Anglia and The Midlands initially. This rain will consolidate and become heavier through the morning so not a nice day here. We will also see another rain front affecting Ireland that consolidates through the morning along with Wales and the north of Scotland as well. By early afternoon that low pressure is tilting and pushing rain across most of the southern half of the U.K and it extends into northern England as well pushing north into Scotland by mid-afternoon. So Tuesday looks like a pretty wet day for most of us and because the low pressure system is in a trough, it’ll be slow moving and therefore localised rainfall totals may be heavy. As we go through Tuesday afternoon, that rain over Ireland starts to fizzle out and you’ll have some sunny intervals here but across The Irish Sea that rain will sit stubbornly over the southern half of the U.K from northern England down to the south coast. Scotland looks to lose its showery rain pattern to finish the day dry. As predicted last week, a battle between a low and a high pressure yields a northerly wind direction and that’s what we will get on Tuesday so a much cooler feel to the weather for all of us with temperatures down in the low to mid-teens at best. Pretty crap for August.
Mid-week beckons and Wednesday starts off with that rain front over The South West and southern coast of England at dawn and it’s likely to add even more rain to Hampshire’s high total with some torrential rain likely in this area before it moves off into The Channel. This band of extremely heavy rain looks set to track very slowly eastwards along the south coast through the course of Wednesday so really affecting the area from the M25 / London southwards I’d say pushing into The South East later in the afternoon. Potentially very heavy rain here. The exact location of this rain band will I’m sure change as we progress through Monday and Tuesday so keep an eye on your forecast and rainfall totals, they may change significantly depending on the behaviour of this band of rain. North and west of this band of heavy rain it’ll be a dry day after that overnight rain clears so Ireland, Wales, Scotland and the remainder of England will have sunshine and broken cloud. Temperatures still low though for August with mid-teens the best we will do in that moderate to blustery northerly / north easterly wind. Ireland, Wales and Scotland though away from that cloud cover will be warmer with high teens likely.
Onto Thursday and a much better day for everyone as that rain finally exits into The Channel overnight. So a settled and much sunnier day on Thursday for all areas with some long spells of sunshine and lighter north easterly winds. High teens expected in that sunshine and may be we will just nudge into the twenties in some areas through the wind direction will keep temperatures down. Enjoy it while you can because overnight into Friday we see the next band of rain push into the west coast of Ireland.
So Friday starts with a change in the wind direction from northerly to westerly and that’ll push rain across Ireland from dawn. This rain will also push into the north west / west of Scotland in time for the morning rush hour. The rest of the U.K looks to start dry and indeed in some places most of the day will be dry with hazy sunshine and cloud. During the afternoon, that rain front begins to clear the west of Ireland but it’ll push across most of Scotland and into the north west of England reaching Wales by the evening rush hour. As it does so it’ll also push thicker cloud in front of it and this will finally introduce some showers to more central areas overnight on Friday. With a change in wind direction it’ll feel warmer with high teens / low twenties likely before that cloud pushes in later in the day. Cooler across Ireland and Scotland where you’ll see more of the cloud and rain during Friday so I’d expect mid to high teens here.
So how does the outlook for the weekend look ?
Well mixed is probably the best description with Saturday looking to be an unsettled day with rain pushing across Ireland during Saturday morning and this will move west into Wales and central England for the second part of the day. North of this rain band over The Borders and Scotland I think you’ll have a better day after showers and thicker clear in the morning. Sunday looks to be a much better day as high pressure nudges that rain away so plenty of dry weather around on Sunday I think.
So next week we have high and low pressure slugging it out once again over the U.K and Ireland and as you’d expect the outlook will be mixed depending on which one is in the ascendency. So I think we will see an unsettled start to the week, next week with rain pushing through on Monday and Tuesday coming in from the north west and heading southwards. All the time I think the rain bias is more north and west. By mid-week, high pressure pushes in and that looks to dry us out nicely with warmer temperatures and more settled conditions through Wednesday into Thursday. After that it’s tricky to call, but if I was a betting man (and I’m not aside from Paddy Power and White Christmas) I’d say that we’ll see a new Atlantic low pressure push in to bring wind and rain by the end of next week unfortunately.
July GDD- Thame Location
Ok first off we look at July’s GDD information from our resident location at Thame, Oxfordshire.
So July racked up 374 growth-degree-days which puts it on a par with last year at this location and cooler than other July’s, notably 2014, 2013 and 2011. The total for the year though just keeps going buoyed by the heat earlier in the spring and during May and June.
So we are still looking at our warmest year to date, a full 25% warmer, as measured by GDD compared to 2016 and that is a significant increase that brings many consequences to turfgrass management.
GDD and Rainfall – July 2017 – U.K Locations
For this month’s UK summary, I thought I’d add a few more locations in to try and reflect more accurately where the rain fell during July and to pick out the southern and eastern bias that a low-situated, trough pattern can bring to the weather.
Here’s the U.K stats….
So some interesting variability here and firstly you can see quite wide differentiation in GDD with both Scottish locations , Fife and Irvine down at 263.5 and 280.7 respectively. Although they were cool, the rainfall totals are a good bit lower than some of the more southerly locations.
Coming down country, Portsmouth stands out with 445.9 GDD for the month of July, along with 83.1mm of rain, but you can see the variabilty in rainfall with Okehampton picking up 147mm of rain and Norwich, 141.5mm !
In july there were plenty of times when the rain tracked eastwards and so East Anglia picked up more than its fair share of the moisture, quite strange really for that to happen.
What is also clear is that heavy rainfall didn’t fall evenly across a month…Here’s the monthly rainfall pattern for the two highest rainfall locations we have looked at in the U.K during July..
You can see that the first part of July was pretty dry except for some storm events when Norwich picked up 45mm in one day and a further 20mm for both locations on the 10th and 11th of July. The change from peak pattern to trough pattern in the jet stream is clear to see with cooler, wetter weather arriving from the 18th July onwards and prevailing for the rest of the month and into August as we know..
GDD and Rainfall – July 2017 – Irish Locations
Onto Ireland now and it’s a familar picture in terms of west / east divide with Valentia and Claremorris coming out highest compared to the eastern side of the country from a rainfall perspective…
GDD-wise again we see a west / east divide with the eastern locations of Dublin, Wexford and Cork highest and the most north west location (we monitor), Claremorris, Co. Mayo, the lowest.
I was on holiday once on Achill Island, Co. Mayo, and whilst I watched the wind and rain laying siege to the campsite in August, I commented to the campsite manager, (an unexpressive old chap), “Nice Day” , he looked up and said…”You don’t come to Achill for the weather boy” and duly returned to his paper…I considered myself told….Still love Co. Mayo though 🙂
July from an agronomic perspective..
I know I’ve talked about this before but it doesn’t hurt to re-visit a theme (aside from the weather on Achill Island that is…).
When we get these peaks in rainfall during the summer of 20mm plus in a day, it can test the most free-draining rootzone. Especially when you consider the fact that more often than not at times the rainfall rate can get up to 200mm an hour, even if just for 5-10 minutes.
For this reason it is implicitly important that we have all the dots joined from a rootzone perspective..
I’ve talked before about the merits of summer vertidraining with small tines and no heave (to minimise disruption) and although the above model assumes a functional drainage layer (which I admit sometimes isn’t present 🙁 ), it can only help shift water off the surface and down deep into the rootzone when we have high daily rainfall. This is key to maintaining good soil oxygen levels, for microbial activity and for plant health.
But you have to have all the dots joined…
The first significant barrier to water movement from the surface down is obviously the organic matter layer on the surface. Now this doesn’t have to be a deep layer to cause an issue. If the level of topdressing is insufficient and the organic matter layer is tight, then 8mm of tight, compact surface fibre is quite capable of perching water on the surface, no matter what the rootzone quality below it.
Assuming you have your surface matter layer well-integrated with topdressing, the next barrier to movement is the infiltration characteristics of layers L2 and ultimately L3. So if you’re moving the water from the surface efficiently and these layers aren’t conducive to water movement (because of poor sand quality maybe or high levels of silt / clay) then what you’ll see is that after a rainfall event the water will ‘back up’ to the surface.
Lastly we have our functional drainage layer which if present and effective (and that’s a big ‘if’) will move water away from the rootzone. So aeration in my mind is all about joining the dots, varying the depths and moving that water away from the surface wherever possible.
That’s why if you’re looking into how your rootzone is performing it is best to sample it in sections, I routinely use 50mm depths, so you sample the top 50mm, 50-100mm, 100-150mm and so on and get them analysed seperately from a physical analysis perspective. If you just take a sample from 0-150mm and send it away for analysis, the readings you’ll get back will be averaged over the depth of the sample and this may ‘hide’ the presence of a badly-performing layer…
Here is an actual example of this from a poorly-performing golf green where we took an initial analysis over 150mm depth and then when the results didn’t pick up anything obvious, we split the sample into 50mm sections..
In this case, the topdressing being utilised was too fine and this was capping the surface. Even though the Superintendent was aerating regularly from 0-100mm to move water from the surface, the green sat wet and stubbornly refused to dry down. The answer was in the bottom 100-150mm of the roozone where there existed a layer of silt, fine and very fine sand and this was acting as a barrier to water movement down the profile. So aerating above and moving water through was just backing up water from the bottom and actually increasing the ability of the greens to sit wet.
Aside from playability and keeping greens / sportsfields open for play, there is of course a disease parameter here that has to be considered. Microdochium, Anthracnose, Dollar and Leaf Spot all like wet, humid conditions in order for their mycelium to develop across a plant leaf and to move from plant to plant. The dryer the surface, the harder it is for them to develop, it’s as simple as that.
That’s why as we continue our cool, wet summer we need to prioritise aeration wherever possible amongst all that your fixture list throws at you. I appreciate fully it is easy for me to sit in my office and put this blog together and it is much harder to make this argument to the powers-that-be and / or have the resource to enable you to do the work when you want to. (And that’s without the weather intervening and spoiling the day)
I’m afraid with a mix of alternating high and low pressure systems in mid-summer, we will continue with our high humidity theme through August for the next 10 days and that means more disease pressure from the types of fungus that prefer these conditions, namely Superficial Fairy Ring, Microdochium, Dollar and Leaf and I believe Anthracnose.
Sorry to be the pervayer of bad news….
The flipside is that our Growth Potential outlook for the next 7 days is very good because of the optimum night and day temperatures for cool season grasses (not too hot you see), so that means we should be able to grow out foliar pathogens like Microdochium nivale as quickly as they invade a green.
One last point though concerning these cooler conditions, it will pay to mix up your nitrogen sources and include some ammonium and nitrate N with your normal summer N source (along with iron) . This is because slow release N sources like methylene urea and to an extent, urea, rely on microbial conversion for their release and with cooler temperatures this will inevitiably slow down N availability…
Ok next week I’m off to do some serious walking in the beautiful Cevenne area of France but if my shakey hotel Wifi is working, I’ll put together a mini blog to keep you posted.
All the best…