Well a taste of summer is on the cards this week but unlike the tabloids I don’t think it’s going to last much past the end of the week I am afraid. The jet stream is projected to drop south by a long way and that means that cooler, wetter air will follow it down from the end of this week / weekend rather than a warm high filling underneath. It’s been a feature of this year that the jet stream has sat low, wether it’s related to El Nino I don’t know, but it’s certainly different from normal.
So how are we looking this week ?
Well we are set fair for sure but that doesn’t mean we’ll be entirely dry in all places because the heat is likely to set off some thundery downpours and these as we all know are difficult to predict.
So Monday looks to start off dry, sunny and fair for all of us but by mid-morning there’s a risk of some showers building up along the west coast of the U.K and across Leinster. In keeping with this type of weather it wouldn’t be a surprise to also see some thundery outbreaks heading across the channel into the south east / south coast of England as well. For most though a dry and warm day with temperatures picking up into the mid-twenties in the Costa Del South of England particularly. For Ireland and Scotland it’s likely to be a little cooler, but still in the low twenties I think. By late Monday afternoon we could see those showers merge into longer spells of rain for the south west of England, south east of Ireland and for Central Scotland / The HIghlands. Winds will be light and easterly.
For Tuesday we see a similar picture, fine, dry and very warm for most but again there’s a risk of showers building up through the morning for the south west of England, South Wales, the east and north east of Ireland and across Central Scotland. Some of these are likely to be thundery in nature as that heat builds and triggers thunderstorms. If anything Tuesday may be a degree or so up on Monday so mid-twenties again for the south of England, low twenties elsewhere, with a light easterly wind for all of us.
Wednesday sees a fine, dry start to the day but soon we will see some showers kicking off across Central Scotland and these are projected to sink south through the late morning into Northern England and by the afternoon, The Midlands. They will be quite widely dispersed though so you may easily end up missing them. Ireland and the west look to have a dry, sunny and warm day, maybe the threat of a shower across Leinster but otherwise looking fine and dandy. Again light easterly winds will be the order of the day.
Moving onto Thursday and again a lovely dry day in prospect for most. There’s a risk of more in the way of cloud, especially for eastern Scotland and the north east of England and this may be heavy enough for some drizzle. With this type of heat there’s always the chance of some showers building up, particularly along the west coast of the U.K, but on the whole we look dry. Maybe a little cooler for Thursday as we see more in the way of cloud across the U.K and Ireland but I’d still expect reasonably good temperatures into the low twenties for most of us.
Rounding out the week and now we start to see the weather on the turn because overnight into Friday, a rain front is due to make landfall across south west Kerry and move slowly up country through the morning so a potentially wetter day for Ireland to close the week. This rain will also feature across the north west of England / south west of Scotland through the morning and into the afternoon. Further south and east of this it should be a cloudier, but dry morning however those rain showers are projected to sink south through the afternoon / evening into The Midlands by dusk. So a cloudier and therefore cooler day on Friday with the wind on the turn to the south although it’ll be very light in nature.
You might have guessed that the weekend isn’t looking brilliant with the change in weather and that would be correct. We have a pronounced Atlantic low destined to influence our weather for the weekend and beyond so that means cooler, moist air pushed in on a south westerly wind with frequent rain. This rain will likely be heavier across Ireland, the west / north west of England and Scotland as it follows the normal diagonal projectory of an Atlantic low pressure system but I think everywhere will see some rain over Saturday and Sunday. There will be some sun around between the showers maybe more so on Sunday and more likely across the east, south and south east of England. Temperature-wise a little cooler than of late, so mid to high teens likely in a moderate south westerly wind.
As intimated above, we have an Atlantic low pressure dominating the weather next week and that means windier, wetter but staying mild throughout the first part of the week. So plenty of rain for the west and north, but I expect all areas to pick up moisture next week , especially in the early part of the week. As that low circulates round and slowly moves eastwards it’ll drag in a more northerly airstream (probably northwest) so that’ll cool things down to the mid-teens I think as we approach the end of next week. Thereafter it’s of course tricky to say but my gut feeling is that the jet stream will lift again and allow a warmer airstream to come into play w/c 20th June.
Above is a Meteoturf snap taken for a golf course in the south of England and since that’s where you’re likely to be bearing the brunt of the heat, this is where I will start.
Managing High Evapotranspiration (E.T)
Looking at the Meteoturf readout above, the projected E.T loss for the week is 31mm with some days topping 5 / 5.5mm per day of E.T loss. So what is likely to be going on in the grass plant during these high E.T conditions ? Well to answer that we need to also look at the projected Growth Potential for this week and we can see that it is approaching optimum growing conditions over a 7 day period with a total figure of 6.6 which means a daily average G.P of 0.94.
We can see that although a hot week is forecasted, it is not going to be hot enough to put the plant under sustained stress because if it was we’d see the Growth Potential decrease as the daily temperature becomes too high for grass growth. So as long as moisture is available we are going to see a potential for a growth flush this week.
Now let’s look at that statement “As long as moisture is available”
In some areas we have had dry conditions for a while now, particularly the north of England and Scotland so growth is likely to be moisture-limited especially in an outfield scenario which is unlikely to receive irrigation in most cases. So realistically the limiting factor to outfield growth will be soil moisture levels and where these are low I’d expect the grass plant to shut down this week in order to conserve internal moisture levels. Where soil moisture levels are good then grass growth will be intially high but I expect as the E.T ramps up during the week it will start to decline as surface moisture is lost.
What kind of steps can we take to help the grass plant during this short period of high temperature ?
Cut and Roll….
Well one of the increasingly popular ways of decreasing stress on fine turf in particular is to miss a day cutting and just roll instead. If your nutrition and PGR use is correct then this shouldn’t be an issue because the plant should just be ticking along at present growth-wise and so missing a day cutting should not result in a negative. Rolling has been shown to be a positive in this situation in terms of decreasing stress but there are other benefits as well.
If your greens surface is firmer then it means you will have a better correlation between your bench set cutting height and your actual cutting height. If you have a softer turf surface with a higher organic matter content it’s safe to assume that your actual height of cut will be significantly lower than your bench set because the mower will be sinking into the surface.
In my books rolling is a great tool in the toolbox for hot conditions because not only does it allow you to save a cut and therefore put the plant under less stress but it also allows you to effectively cut higher. If your surface is firm with good organic matter control and plenty of dressing incorporated through the organic matter then you shouldn’t need to drop your height down markedly to get good green speed when you cut and roll. There’s a good (but slightly old article here on the subject of rolling Poa annua and Bentgrass Greens)
‘Little but Often’ PGR usage with nutrition…
The latest research has clearly shown that it is application frequency rather than rate of PGR’s that is key to maintaining a regulated turf. Growth-Degree-Day work in the U.S (Download “Avoiding the rebound” here) has pointed to the fact that during warm conditions, the longevity of a PGR application is decreased regardless of the application rate. I have looked at our temperature ranges in the U.K and Ireland and during the hotter periods of the summer we can expect a PGR application to only last 12-14 days maximum. That means that fortnightly applications of PGR and nutrition are optimum for keeping grass growth consistent. Stretching it out to three weeks will result in a drop off of greens performance and enhanced plant stress.
Reducing Plant Stress
I have already talked about the use of rolling as a means to reduce the level of stress the grass plant is under (fine turf obviously) and keeping nutrition and PGR usage on a ‘little, but often’ basis, but what else can we do ? Well obviously irrigation will come into play but how much should we irrigate ? Now that is a very contentious question but my rule of thumb has been to try and replace 50% of E.T loss through sprinkler irrigation and then use hand watering to take care of any localised dry spots (humps, ridges, areas affected by sand splash).
I came to this conclusion back in 2006 when I conducted some wetting agent trials and wanted to put the plots under stress. Initially I replaced 100% of daily E.T loss with irrigation and the only stress that the plots were subject to was flooding !!! (far, far too much water). Gradually I reduced the irrigation load and arrived at the 50% figure which kept the turf healthy.
Nowadays we have moisture meters which allow you to see first hand what is going on at a set depth in your profile but it’s worth pointing out that it is of course the surface that dries out quickest and most moisture meters will only measure at the depth of the probe (so you can’t put it half in and expect to get an accurate reading). It is likely therefore that when you are doing moisture readings the surface is running at a lower moisture content than what you are seeing on your moisture meter. So use them wisely this week to highlight and manage hotspots.
One of the key points I noticed way back in 2006 during that hot summer was how well the combination of soil surfactant and biostimulant worked in terms of reducing plant stress with more consistent growth and colour than plots just treated with a surfactant. The kind of week we have coming up is tailor made for this approach.
On a final point I’m often asked where you can go to look at lightning strikes and since this type of storm may be a feature of this week I thought I’d remind you of the link. The Met Office run a system called ATD Lightning Detection and you can access it by clicking on the link below. It’s updated very 15 minutes and to me it’s very useful in terms of looking for storms around your facility and which direction they’re heading. As I type this I can already see a storm sitting out in the sea off the beautiful St David’s City in Pembrokeshire and it’s probably giving the Puffins a fright or two on Ramsey Island 🙂
You can access the ATD Lightning Detector on the Netweather site on the link below ;
Ok that’s it for this week, all the best and enjoy the sunshine.