April 12th - A warm Easter and then dropping back to cooler and wetter maybe...

Hi All,

Oakham sewerage works probably doesn't come 'Top of the Pops' on most people's list(!) but last weekend I stood across the road from it and smiled. A flock of House Martins and Swallows were feeding on the wing above it and they were the first ones I've seen this year. They are late for sure this year and maybe down in numbers, but seeing them arrive again after flying all the way up from Africa signifies to me the start of better weather and gives me optimism. That said, I didn't linger long like :P

Last week, the GFS output for the end of this week hinted at the possibility of a nice temperature progression towards Easter and sure enough it has transpired to play out that way. Today you could feel the warmth in the wind. That's why I like using the GFS output, I find it pretty reliable bearing in mind it's 7-10 days out when I'm sort of trying to get a feel for weather patterns and their effect on grass agronomics.

If you look at the GFS output below you'll notice a number of things ;

First up this mild, warm interlude lasts through till Easter Monday before dropping into a cooler, more unsettled pattern from the north.

Secondly, by the end of next week / weekend we have a potential trough pattern forming which means it could be potentially very wet for some areas.

Lastly, as this low pressure moves away, it moves east to west when usually weather patterns move the other way i.e. they come from The Atlantic and push across the UK & Ireland into Europe. This one is projected to do the opposite so that means we have a very sluggish jet stream pattern and the likelihood of easterly winds.

GFS output courtesy of www.tropicaltidbits.com

This week's weather

Well this week's weather is set pretty fair, that is apart from today (Tuesday) when a rain front is currently progressing south to north across northern England and into Scotland. We will see some more rain moving into the south coast this afternoon and again moving south to north before fizzling out. Winds are from the south / south west veering more westerly by mid-week. With this warmer wind and exactly as predicted last week, we lose the colder nights and so pick up better day time temperatures as well, pushing up into the high teens and possibly twenty degrees. 😎

Wednesday is a bit of a mixed one because again we have some light showers and cloud moving south west to north east across the U.K and some light rain fronts across the north and north west of Ireland. Plenty of cloud cover around on Wednesday so that means temperatures will be mid to high teens and backed up by a south westerly wind veering westerly through the course of the day. Most of the showers will be south of The Humber with the odd one rolling across northern England. Ireland looks to have a very nice day with cloud clearing and plenty of sunshine though temperatures are still likely to be mid-teens.

Thursday sees an Atlantic front do its best to push into Ireland from the off but at this stage it looks like maybe some western coastal areas of Co. Clare and up to Connacht will be affected on and off during the day but it doesn't look to move much further inland because high pressure is building over the continent and the U.K. For England, Wales and Scotland, that wind drops on Thursday and we see more in the way of sunshine, so that means temperatures will push up into the high teens and possibly 20°C down south like :) . A lovely April day.

Closing out the week we have high pressure very much in charge but overnight we will see a rain front push into the west and north west of Ireland and this will hang around for the first part of Friday morning before fizzling out. So cloudy and dull but mild for Ireland with some rain across the west and drier to the east. Across The Irish Sea to the U.K and another lovely day with warm temperatures up in the high teens again, plenty of sunshine and light to moderate southerly winds.

The outlook for the Easter weekend is very nice with albeit cooler and a bit duller for Ireland but not bad all the same. For England, Wales and Scotland, we should see plenty of sunshine, especially on Sunday and nice temperatures up in the high teens I'd say. Can't fault it unless you want to go fly fishing :)

Weather Outlook

Well as intimated in the title to this week's blog, the spell of warmer and settled weather is not projected to last beyond the start of next week with a slow breakdown from the north / north west ushering in more cloud cover and rain. You can see the change in the projected GFS output for next Monday with cooler temperatures and two low pressure systems, one off the north west of Scotland, the other, the north west of Ireland.

So Easter Monday looks a duller and cooler affair for the north with rain moving in but further south England, Wales and the southern half of Ireland may hang onto the sunnier, milder weather for one more day before that rain and cloud over Scotland pushes south through Tuesday. Wednesday will be a bit of a hiatus with some showers around but largely dry and then we see another Atlantic low pressure pitch up and bring rain to Ireland before pushing eastwards across The Irish Sea towards the south of England. A southerly low pressure means the trailing edge will pull an easterly wind direction in for Thursday / Friday before things settle down ago. So I think the outlook is cooler and unsettled next week but crucially with low pressure in the picture, we will have more cloud cover and that'll keep night temperatures up and maintain growth.

Agronomic Notes

How much of a growth flush have we got coming ?

Well considering that we were running around with a daily growth potential figure of 0.2 - 0.25 up until yesterday, we will be picking up growth nicely this week into the 0.6-0.7 sort of region depending on your location, so it'll be both noticeable and largely appreciated I think even with 2 x 4-day weeks on the bounce.

Here's how it pans out from a growth potential perspective based on 4 locations around the U.K & Ireland over the coming 14 days using projected day and night temperatures ;

You can see Scotland is a bit behind the curve this week and drops off a bit quicker after Easter whilst England and Wales stay reasonably good. Ireland lags a little behind and drops back to a similar level as Scotland next week as they are closer to the low pressure systems.

So a nice week or so of reasonably mild and warm temperatures, cooler for Ireland and Scotland. This is really just what the doctor ordered to move things on, get some additional recovery and build some sward density.

Seed germination window on the horizon...

With an increase in day and temperatures we can see a reciprocal increase in soil temperature. Up until the last few days it has been 2-2.5°C lower than 'normal' for this time of year (for the 2nd year running that is) due to the number of night frosts and their severity.

I took data from a Terros 12 soil moisture, temperature sensor fitted to a Davis Vantage Pro weather station equipped with an EM Node. This one is located on a golf course down in Sevenoaks, Kent.

The sensor is positioned horizontally in the soil profile at 100mm depth and readings for soil moisture, temperature and E.C (conductivity) are uploaded to the cloud over the cellular network every 15 minutes (in this case). Here's how April looks from a soil temperature perspective ;

As a matter of interest I renovated my back lawn in the first week of February and I overseeded with a straight rye mix. The lawn is in permanent shade all winter and the sun doesn't start to clear the trees behind my house till early March. It took 7 weeks for this seed to pop but now it is moving along nicely.

Talking about seed (flawless link alert 👍), our old friend Poa annua is going to get a move on in the next week as a bit of moisture this week combined with temperature will push its growth along. I found some seedheads on a Poa annua var. reptans biotype today although the majority was on the annual biotype.

If you want to see where your Poa annua is at seedhead-wise, pull some plants and strip back the leaves. You may well soon observe the seedhead sitting 'in the boot' as the Americans call it...(see below)

My guideline figure is 180GDD cumulative from Jan 1st using a 6°C base but I'm sure other biotypes (Scottish and Irish in particular) behave differently GDD-wise.

I have plotted the cumulative GDD for 5 different locations across the U.K & Ireland since January 1st to see where they are in relation to the main Poa annua seedhead flush. I used projected forecast maximum and minimum air temperature data from Meteoblue for the next 10-14 days because they're rarely off by much.

The results are quite surprising ;

From the above we can see that locations in Kent, Thame and Dublin are pretty much dear as dammit heading towards the same cumulative GDD or will be when you take into account the projected data. It suggests the main seedhead flush will start around the 17th - 18th April for these locations. Next up is Claremorris in the beautiful Co. Mayo, (my fav), it is running around 10 days behind Dublin GDD-wise and then we have Glasgow, which is around 14 days behind the southern U.K locations or will be approaching the end of April. So an early seedhead flush for some locations and others will be the 1st week of May which is (sigh) about 'normal'.....

OK, that's me done for another week, off to make a nice Thai curry and chill.

Have a nice Easter

Mark Hunt