May 4th, 2021

Hi All,

Well as the wind clatters the house and some mean looking showers blow past the window we continue our transgression into winter, I mean spring or should that be summer ?

Took these pics from a broody Rutland at the weekend, some beautiful Bluebells and the first of the rain arriving over the weekend to be followed by a welcome deluge on Monday even if I shivered in my waders as I fished Eyebrook from the bank, up to my waist in cold water. I was chasing some remarkably obliging rising Trout whilst the Martins, Swallows and Swifts fed happily on the emerging buzzers (midges). I saw my first Daddy Longlegs as well.(one for Glenn and Pest tracker @

I did say pretty early in the month that April 2021 would shape up as one of the coldest on record and sure enough the media started churning out the stats towards the end of the month…the driest for…the coldest for….the frostiest for…blardy blah.

On our GDD stats shown above which I’ll delve into later in this blog, our default location at The Oxfordshire came in at 26 total GDD for the month.

That compares with 151 last year for April 2020, so I make that about 17% of last years growth or if your pint is half empty, 83% less growth than April 2020.

To put that in perspective April was colder than March and February this year !!!!!!

Our cumulative total for the year came in at 132 which is the 2nd coldest Spring we have recorded with only the long drawn out winter of 2013 coming in worse. That’s one cold spring and of course a dry one as well. At our Great Dunmow location we recorded zero rainfall for the month, that’s nothing, not a jot, not a drop, sweet naff all…And to cap it off, April came in as one of the highest E.T months I’ve measured at 91.64 mm of moisture lost from the soil and plant surface.

So if you’ve come through till now looking reasonable on your turf surfaces, fair play to you…

Without further ado let’s see what this week has in store for us…

General Weather Situation

So no surprise when you look at the low pressure system in the GFS output above that the start of this week is likely to be windy, cool and wet !

With a prevailing and chilly north westerly wind in situ we should expect the bulk of the rain to be north west-orientated today with Scotland, Northern Ireland and the north west / north of England / Wales in the initial firing line. As we progress through the morning towards lunchtime, we will see those bands of rain push further southwards into Wales, The Midlands and east of England. The same will happen across The Irish Sea with those showers moving down into Connacht through the day. It won’t be all rain, there will be some sunny intervals across the south but it will be chilly with that strong north westerly wind pegging back temperatures into high single / low double figures. Better to look at your rain radar today than my forecast to see whether you’re likely to pick up some of them heavy showers.

The one benefit of a low pressure is cloud cover preventing frosts so after a cool night (single figures), Wednesday looks to start brighter and drier for most areas save for some showers across the north west / east of Scotland, the west coast of Ireland and Wales. During the morning, cloud cover will build and some light rain will push into the north of Ireland down to The Midlands. Across The Irish Sea we will see the same, with rain pushing down through Wales into the south and also across Scotland as well. These showers will consolidate through the afternoon to some give some heavy bursts with some of them wintry over elevation. By the late afternoon the showers extend from Wales down to Kent, from the north west of Scotland to the north east of England and down the coast of Leinster. Still breezy with that north west wind in situ so similar temperatures to Tuesday with 9-11°C likely.

Thursday sees a north-south divide with heavy showers across Scotland pushing down through the day into the north of England, but further south it looks to be a better day with plenty of sunshine between the clouds. Still with that strong north westerly wind though so no great shakes when it comes to temperature. Ireland will see showers across the north and north east, but like the U.K, it should be drier further south. As we progress through the day those showers form into a solid rain front from Scotland down to the north of England. Overnight these will fizzle out as we go into Friday. So similar temperatures again for Thursday with 9-11°C the new norm for the start of this May.

Friday at last sees those winds relent and a generally nicer day with lighter northerly winds which will swing round through the day. A drier picture everywhere on Friday with plenty of sunshine and an absence of rain for most areas. I say most because later in the day there’s a risk of rain and wintry showers pushing into the north east of Scotland and extending down through The Borders into the north east of England. Generally though a nice day and with the lighter winds it’ll feel warmer with temperatures pushing up into the low teens (gosh, golly)

The weekend though…ahem….hmmm, cautiously shuffles feet….So the weekend will feature a new Atlantic low pressure system that will push into Ireland and the south of England through the course of the early part of Saturday bringing with it a band of very heavy rain across Ireland, the south of England, Wales and the like. This heavy rain will be accompanied by strong southerly winds so at least it’ll be warm rain 🙂 Probably only Scotland will miss the worst of this rain but we will also see some wintry showers in that mix, anywhere north of The Peak district as that mild air butts up against the incumbent cold air. So milder yes, but Saturday looks a real wash out with 9-10°C for Ireland / Scotland and 11-13°C for England / Wales.

Sunday is better (well it couldn’t be much worse!) initially with a drier start to the day for the southern half of the U.K, but they’ll be plenty of showers about for the north of England and snow for Scotland amongst that rain. Ireland will see showers from the off for the top half of the island. As we go through Sunday the low sinks back south pulling rain into all areas of the U.K & Ireland. It looks like a tying flies, working on the motorbike, DIY sort of weekend to me.

Weather Outlook

So as you can see from the GIF above, we start next week with that Atlantic low departing stage right to Scandinavia. And the good news is as it does so, high pressure looks to fill the void and bring some stability to the weather picture with some warmer temperatures from the middle of the week. Nothing balmy like, but better. So an unsettled start to next week, particularly for the north of the U.K, but really a threat of showers everywhere from Monday through to Wednesday. Then drying up as we approach mid-week and temperatures picking up as well before there’s a risk of some continental rain pushing in at the end of next week / weekend. Sort of sunshine and showers I’d say with a cooler end to the week as more cloud cover builds from the east.

Agronomic Notes

So as it’s the first blog of the month I’ll try and make sense of one mean April….

April 2021 – GDD Stats – The Oxfordshire, Thame, U.K

OK, I’ve already posted this one up top but for the sake of completeness, here it is again. 26 total GDD ranks it last by a good way with even April 2013 coming in considerably better (if I remember back to then, the weather changed mid-month). So half as warm as March 2021, 2/3 as warm as February and only just a bit warmer than January, how bizarre is that. We know the reason, a slow, low inertia jet stream allowed north and particularly easterly winds to dominate.

You can see this very plainly when you look at the readout from the Davis Vantage Pro 2 at our Great Dunmow location….

So I’ve highlighted the days when the wind had either a northerly or easterly component in April 2021.

As you can see there were only 4 days out of the 30 in total when this wasn’t the case with the dominant wind direction being ENE. Quite convincing I think….

Back to the GDD and let’s look at how we stack up Y.T.D at the Thame location….

So a whopping 132 total GDD at the end of April which puts us as the second coldest spring since 2010 with only 2013 being colder. The schematics of the weather was different though because by mid-April 2013, we were warming up, but this year we were getting colder. It’s amazing that 2021 is the first year I can remember where we have actually got colder the further into spring we have gone….

So let’s have a look from our regional data locations ;

U.K locations – Monthly G.P and Rainfall – April 2021

So the first thing to comment on from a G.P perspective is that the total optimum G.P for the month of April is 30 (30 days x 1.0 optimum G.P).

You can see most of the figures were in the region of 3.5 – 4.0 for the total monthly G.P which means April 2021 represented 13% of optimum growth with Harlech the highest figure of our locations. My Market Harborough figure is biased because of the siting of the Netatmo (I think so it got more of the sunshine that we had). So a very poor growth month with precious little difference if you were in Sevenoaks or Fife with the eastern and central side of the country picking up the coldest weather courtesy of the wind direction I discussed above. We also know that April 2021 was one of the frostiest on record due to the clear skies and wind direction with an average of 13 frosts for the U.K, but many locations recorded more than 20 grass frosts.

Moisture-wise, across the board it was dry with the easterly locations not surprisingly coming in extremely dry (well you can’t get much drier than 0 mm !!!). I have to mention Northampton which picked up 19mm of rain on the 28th of April and we got 0.8 mm just a few miles away. God was I so jealous, I mean it just missed us, went round us, copyright every single greenkeeper / groundsman in the U.K and Ireland up until yesterday 🙂

Seriously though one hell of a dry month and accompanied by some exceptionally high E.T for this time of year. The chart below is from our Great Dunmow location which sits on top of a hill and so catches the wind and of course it is also located across the east of the country so it copped the full force of evapotranspiration during last month. Now I think anything over 2.5 mm daily E.T and you need to start thinking about replacement of E.T with irrigation on a daily basis. Typically replacing 60% of total daily E.T loss will keep the turf healthy, so superintendents go lower, some higher depending on species mix and site dynamics. If we pick 60% as a norm, then the total E.T loss for April from this site was 91.64 mm, which means you’d have needed to apply 55 mm odd of irrigation just to keep the plant from going under stress. That’s a lot of water for April.

Daily E.T loss in mm – April 2021 – Great Dunmow

Let’s see how the stats stack up for Ireland ?

Well they tell a very similar story with the eastern locations like Dublin and Wexford showing the lowest total monthly G.P and the south west and westerly locations coming in with higher G.P, not that a total of 9 – 9.6 is anything to shout about. So across the north and east we typically saw only 18.7% of optimum growth vs. the west where we saw 32%, so better across the warmer west but still not good growth stats. Rainfall-wise, a very similar picture to the U.K with an extremely dry month and to see figures of 30.5 mm for Valentia and 29.6 mm for Claremorris in the lovely Co. Mayo (my fav) is I think exceptional. Cold and dry then for Ireland as well and a hard growth month for sure.

They say pictures tell a thousand words so here’s a graphic summary of the situation in Ireland using the Dublin location stats…

So we can see where Dublin was ahead of last year at the end of March, it has slipped behind by the end of April, some 9 days, not as much as the U.K, but a hard month nonetheless. You can also see from the daily stats that when there was sufficient temperature for a small amount of growth, there was no rainfall, so growth was both temperature and moisture limited during the month.

Here is how the same stats look for the U.K using The Oxfordshire location ;

An even more growth and moisture-limited scenario here with lower growth levels on a daily basis and even less rainfall days.

So in summary April 2021 was a p.i.t.a of a month because we had ;

  1. Poor growth potential
  2. A high frequency of frosts
  3. Little rainfall
  4. High evapotranspiration

There now…..

Looking ahead….

So this week with its sunshine and showers outlook and high wind speeds means if you want to fertilise you need to reach for a granular really and this will likely carry through to next week. One word of caution though, the milder air stream at the weekend will no doubt kick a bit of Microdochium activity into play because we will ‘enjoy’ some warmer night temperatures overnight Friday and Saturday. Now of course we will pick up a nice growth response from this milder air so it’ll be a case of the grass growing as fast as the Microdochium hopefully if you have your nutrition stars aligned correctly and you haven’t applied a PGR too early like. As I type this I can’t see any boom point in the next 7-10 days so that means no sudden increase in seedhead development though the rain will kick off a flush of more annual biotype seedheads before we hit the main perennial seedhead flush presumably sometime later this month.

OK that’s me for this week, next week we will talk PGR’s, roots and stress (grass and personal for being someone who works in the industry this spring !)

All the best.


Mark Hunt