For some of us this week we have some warm, dry and sunny weather and be jaysus it has been a long, long time coming.
Soils are still saturated mind from weeks of incessant rain so it won’t be an instant turnaround but it is heading in the right direction and accompanying those temperatures is significant evapotranspiration. 22mm of E.T is forecast for my location here in Market Harborough, Leicestershire. So effectively we will expect to see nearly an inch of rainfall evaporated from a grass sward this week (sorry for the mixed measurements) and that’s good news for sure in terms of drying up turf.
We have to be patient though and let Mother Nature do her job before we can take over.
I was out walking on Saturday and to have warm sun on my face was a true pleasure even if it was matched by wet boots and mud splattered trousers. I watched Buzzards climbing in the thermals and then fold their wings and plummet like a stone before pulling up just before the ground, only to do it all again 10 minutes later :). They seemed to be having a blast…
The air was full of Skylarks as well on some parts of my walk and the chatter of Swallows and Martins, newly arrived from Africa and gorging themselves on the huge Midge hatches taking place. Simple things please simple minds for sure and definitely the case this weekend that bigger fools on….(politically)
So onto this week’s weather and the crucial question, is this just a welcome blip for most places or something longer term remembering that April isn’t traditionally the greenkeeper / groundsmans friend when it comes to growing grass.
General Weather Situation
With a deep Atlantic low west of Ireland and high pressure over the U.K it isn’t going to be sunshine and warm winds for everyone for sure..
So Monday sees the last vestiges of Sunday’s rain push up north across North Wales, north-west England and western Scotland during the morning and fizzle away to leave a dry day just about everywhere. I say just about because that Atlantic low will make landfall across south-west Munster and Connacht early afternoon and will push rain across Ireland through the 2nd part of the day. Some of that rain will be heavy in coastal areas of Kerry, Sligo and Mayo. Away from this low pressure, the U.K looks to have a dry and dull day according to the forecast but looking out of the window right now, it is blue sky and so your temperatures will depend on cloud cover. I’d expect 11-13°C over Ireland and Scotland and something approaching 13-17°C across England and Wales if you see breaks in the cloud cover. A strong to moderate south-westerly wind will be in situ and that will only help in the drying game.
Onto Tuesday and that heavy rain over Ireland continues overnight and then edges west into Scotland by dawn bringing heavy rain to the west and south-west of Scotland. This same rain front pushes into Mid and North Wales and the north of England in time for the morning rush hour, edging slowly eastwards through the morning pushing cloud cover ahead of it. By mid-morning that rain will be into The South West, across Wales, the north of England and most of Scotland leaving behind a pale of thicker cloud over Ireland which will break slowly through the 2nd part of the day. Further south and east looks to start dry with clear skies across the south-east of England and bright sunshine greeting the day. As that rain front pushes eastwards through Tuesday it’ll push thick cloud ahead of it so you might start bright but it’s likely to cloud over from the north-west through the morning. At this stage that rain looks to halt over the western side of the country, so south and east of this you should stay dry. I also think The Midlands should miss most of that rain. Temperature-wise, a real split as you can imagine, 11°C for Ireland, Scotland and Wales, 14-16°C for central and southern regions, maybe higher.
Mid-week beckons and Wednesday promises a better day for those areas that picked up rain on Tuesday with thick cloud and light showers starting the day off for Ireland and the west coast of the U.K. Just in time for the morning rush hour, another rain front pushes into Kerry and south Munster but the majority of this rain will track northwards and quickly clear so by lunchtime it’ll be away out into The Atlantic. Closer to home and after some thicker cloud and light showers across the west coast of the U.K, the cloud will thin and break by lunchtime with the sun pushing through and temperatures really ramping up. For most areas, Wednesday will be the warmest day of the year so far. Scotland will see some thicker cloud and rain for the 2nd part of the day but this will clear through the evening to finish dry and sunny. With a strong to moderate south / south-easterly wind in situ, Wednesday will also be a significant drying day to boot with 13-16°C for Ireland and Scotland and I’d say 19-21°C for England and Wales.
Thursday sees the last vestiges of that rain clear the north west of Scotland and then for the rest of the day we will see cloud clear (where it is present) and the sun pushing through. I’d expect the south-east of England to start be clear from the onset and that means here you’ll likely to get the highest temperatures. With cloud clearing Ireland and Wales quickly as well, Thursday promises to be a cracker of a day with long spells of sunshine and rising temperatures. The wind will be very light and swing round to the north by close of play, not that it’ll be very noticeable though. So I’d say 16°C for Ireland and Scotland, rising to 23°C or even a smidge higher for the south-east of England. What a turnaround, factor 30 here we come.
Closing out the week on Friday and we see more in the way of cloud around for Scotland and the north of Ireland. Some of this cloud may be thick enough to give some light rain in coastal areas. Ireland looks to start cloudy with that cloud breaking through the morning whereas England and Wales will start with pretty clear skies and so another warm, dry and sunny day beckons. Similar temperatures to Thursday, maybe a degree or two down but I’d expect to hit the twenties again in the south of England, high teens for The Midlands and north of England and mid-teens for Ireland, with Scotland only low teens because of that thicker cloud cover. The wind will be north-westerly / westerly and light to moderate.
So how does the weekend look, are we hanging onto that high pressure ?
Well the weekend will be mixed as we still have rain fronts trying to push in from The Atlantic so expect to see more in the way of cloud and showers of rain across Ireland and the west of the U.K, probably more so for the 1st part of Sunday I’d say than Saturday. Lot’s of sunshine as well so temperatures will stay up in the high teens I think, maybe touching 20°C down south. With moist air fronts pushing into a column of warmer air, there may be an increasing risk of some thunder and lightning as well. With thicker cloud over Scotland I think the temperatures will remain cooler here so just breaking into the teens possibly.
The above image is the prediction for the jet stream position come this time next week and hopefully you can see that it is sitting in a more traditional position with a westerly air flow, an Azores high pressure below it and an Icelandic low pressure above it. This is where it should be and so I think next week we are set for a sunshine and showers, April scenario. So initially on Monday we will start a little unsettled with rain across the west and as we progress to Tuesday we see low pressure push in westerly, mild winds and more showers. I think the tendency will be for more cloud cover and rain across the north of Ireland with some heavier rain on Tuesday and Wednesday for these areas. Unlike past rain though, this will whistle through on a westerly wind so that’s the key difference between last month and this month, no dwelling low pressures sitting in a big deep trough next week 🙂 Further south I think it’ll be sunshine and showers with good growing conditions, high teen temperatures and mild nights, all in all good I’d say. Maybe a little cooler at the end of the week as the wind swings a bit more north-westerly.
Ok it doesn’t need me to tell you this week that we have a significant growth spike coming for the areas that are set to receive the highest temperatures. You can see how it relates to the rest of the year in the graph below using data from my Netatmo Weather Station, I’ve added in the rest of April from temperature projections.
So on the 12th April, 2018 we were ticking along with scarcely any growth here and a G.P of 0.1 and 7 days later the projected G.P is 0.94, that’s some growth spike and traditionally the type of growth we have seen in the first week of May over the last 2-3 years and not the middle of April.
We know that the Sudden Stratospheric Warming event that took place in mid-February has brought us a very cold (and wet) start to the year but it is uncanny when you compare it with 2013 that the effect of this SSW ceased practically on the same date. In 2013 we started to get strong growth on the 13th of April and in 2018, it was the 14th April, weird.
So this growth spike brings with it both welcome and unwelcome consequences.
Firstly, we must remember that there are lots of sites which are still sitting saturated and so trying to keep on top of this will be very tricky without causing more mess than just a lot of clippings. Patience is the key here on all sides. We will obviously get a reduction in greens speed regardless of nutrition because the plant is growing 8-9 times faster than it was a week ago. On the flip side, newly seeded areas, areas that have received high levels of winter wear, scars from Microdochium nivale last autumn and of course, aerated surfaces will heal up so much quicker now and that’s a welcome bonus.
Remember I said in one of my recent blogs I put some Fescue / Rye seed down in mid-February hoping for an early spring and had seen nothing. The transformation in 3 days has been incredible, bare areas are filling in and newly-germinated seed is popping. So that means divot recovery or if you are able to undertake the work, overseeding thin areas will pay its way from now onwards.
For some areas in the north I would temper the description of a growth spike to just growth because up there it has been practically non-existent up until the middle of April. Happily despite your projected lower temperatures this week, you are still going to see some good growth and some drying days.
A week ago as we were just starting to see some growth I remarked that it wouldn’t be long before we started to see the annual biotype of Poa annua pop up its head. Now I know the annual biotype will produce seed in any calendar month of the year but traditionally for me it starts to really push along when the cumulative GDD hits the 100 mark, with the perennial biotype following on behind some 80-100 GDD days later. So for my location here we hit 100GDD tomorrow and sure enough I can see plenty of annual biotype Poa seedheads.
The question is when will the seedhead flush start for the perennial Poa annua biotype ?
What never ceases to amaze me is the fact that whatever type of winter we have we end up reaching a very similar time for the perennial biotype seedhead flush, typically the first week of May.
For my location I have projected forward the potential GDD count for the rest of April. Now there’s going to be siginficant variation with actual because of the inaccuracy of weather forecasting past 7 days temperature-wise.
So by the end of April we will be hitting a projected cumulative GDD of 170 in Market Harborough and just as importantly stacking on 30GDD a week. So ‘if’, and it’s a big ‘if’ at this stage, we carry on like this we will see the start of the perennial biotype seedhead flush at the end of this month / first week of May.
Looking back at data from our Northampton location makes interesting reading (Ta Rob) when we take into account SSW events vs. the date we hit a cumulative GDD total of 180….
So I’d say the smart money on the first week of May for the main Poa annua seedhead flush 🙂
Last week’s climbing day and night-time temperatures coupled with high humidity resulted in a good amount of disease appearing and not just on existing scars carried over from last autumn / winter. Last week saw significant new disease ingression and so we can deduce from this that the infection cycle has gone full circle and that last week represented high enough temperatures to initiate new infection activity from new disease populations rather than existing disease populations. A fortunate consequence of the growth spike though will be that this and any existing disease should be happily grown out without having to apply a fungicide.
Ok that’s it for this week, enjoy the sun if it is heading your way and don’t forget the sun cream…
All the best….