June 1st, 2021

Hi All,

Love this time of year when everything is bursting with growth. The hedgerows in particular are full of Hawthorn blossom and the verges high with Keck (Cow Parsley). In our world, The Buttercup is not a welcome plant but stuff a lovely meadow full of them and flowering clover and it looks and smells beautiful. We had some perfect Bank Holiday weather, lots of sunshine and warmth once the east coast Haar had burnt off. After the trauma of the last 18 months and confinement it just felt so good to get out for a lovely walk, have a crafty Cinnamon swirl and Flat White at the Scandi Cafe in Uppingham (so good) and then do some more walking to work it off. Ace.

I don’t know whether it is the effect of Mother Nature’s PGR in April followed by plenty of warmth (?) and rainfall in May, but everything looks in good order from a countryside and garden perspective.

Jump to our side of the fence and I saw the E.T shave 5.5mm per day yesterday at our site in Great Dunmow and with temperatures topping 25°C in the U.K (warmest place was in Scotland I think), then I’ll look later if this serves up a bonafide Anthracnose trigger for the summer ahead or not….Onto the week ahead and will that Bay of Biscay low pressure make an appearance or will high pressure carry on winning the day ?

You may remember last week I posted a lovely picture (cheers Adam) of a Mammatus cloud formation. Well some of my colleagues (Pete and Pete like) suggested they could see all sorts of images in those formations, most of which I can’t repeat here for the sake of common decency. It probably says more about my colleagues warped imagination than it does the weather so I thought I’d put another of Adam’s cloud images up to sort of clear the air and raise the tone of this blog….Hang on….That looks like a pair of…..

General Weather Situation

So for Tuesday we have a beautiful start to the day already with any overnight cloud burning off as I type which suggests that this one will be a hot one. Of course this is the U.K & Ireland so it’s not going to be like this everywhere and across The Irish Sea we have a band of heavy rain moving northwards up the west coast and pushing inland a tad as well so a wet start here. Well this rain will continue to trouble the west of Ireland and later some showers will push inland as well. So a hot one for England, Wales and Scotland with temperatures in the low to mid-twenties and a balmy easterly wind. For Ireland a nice day for the east with temperatures in the high teens but more cloudy with rain for the western half of the country and a degree or two down here.

Onto Wednesday and we see that Bay of Biscay low pressure sneaking up into the south west of England so rain still for the south west of Ireland but maybe drier for the west initially. Through the morning we will see rain push into The South West and the western / southern coast of Ireland and push north covering the southern half of the country by midday. The rain across The South West will push northwards into Wales and further eastwards along the south coast and M4 corridor. Away from this southerly band of rain we look to have another beautiful day with plenty of sunshine and likely the warmest of the week as well. By Wednesday tea time that low pressure continues to push rain northwards across Ireland and the south of the U.K into the South Midlands and South East. I am guessing with the heat and moisture it’ll trigger a few thunderstorms. Similar temperatures to Tuesday but maybe across the south of England we may hit 26°C.  The wind will moderate and from the south east so a bruising E.T day again. (from the south west for Ireland)

Thursday sees that low pressure off the coast of Ireland’s lovely Co. Sligo so we will continue to see a cooler and more unsettled outlook for the south and west of Ireland with plenty of showers initially although they’ll soon fade. Plenty of cloud for the west side of the U.K, so cooler here but across the east we will see more in the way of sunshine and warm temperatures. Some showers early doors for the south west of Scotland. During the afternoon, the combination of high humidity and temperature is likely to trigger off some showers across the southern half of the U.K. Watch them build on your radar. So Ireland looks to have a largely dry but dull day, except for the west with 18-19°C. Similar temperatures for the west of the U.K, but across the south and south east, up into the mid-twenties again. Late on Thursday night those showers consolidate to form a longer spell of rain for some areas across the south which will extend up to The Borders.

Overnight into Friday and this band of rain will push northwards and trigger some heavy downpours and by dawn it’ll sit across the east of the U.K. For Ireland, Friday will bring a largely sunny start after the dullness of Thursday but they’ll be rain in the west across Galway and Sligo initially before more rain moves into the south west in time for lunch. A hop, skip and a jump across The Irish Sea and Friday morning sees that slow moving band of rain across the eastern side of the U.K, with sunshine and cooler temperatures behind it across Wales and the western half of the U.K. A change round in the wind to westerly means a much cooler day on Friday with 18-19°C typical. Plenty of sunshine for the western half of the U.K through the second part of Friday, but duller across the east with that rain not threatening to clear the south east corner of England till the evening. Ireland sees the reverse with rain and cloud across the west vs. sunshine and pleasant temperatures across the south and east. A brisk south westerly wind for Ireland on Friday with a moderately westerly for the U.K.

So how does the weekend look ?

For Ireland we see a continuation of that unsettled theme with plenty of cloud on Saturday and rain for the east I’d say, whereas Sunday looks the drier of the two with more sunshine in the east as that rain front clears. For the U.K, it looks a dry (ish) weekend, dull in central areas on both days with more in the way of sunshine for the east and west. Scotland will see some showers across the south and north west on Saturday and later in the day these will consolidate into longer spells of rain overnight into Sunday. During the course of Sunday these showers will push eastwards across most areas of Scotland. Light winds on Saturday from the west gaining a bit of strength to southerly for Sunday. Temperatures in the high teens / low twenties for the southern half of the U.K, mid to high teens for Ireland and Scotland. Not bad, all in all but……..

A little weather caveat though…..The GFS output has rain pushing in on Sunday from the continent and affecting the west of the country later whereas currently Meteoblue does not. Now we know continental rainfall is very unpredictable so it may or may not appear and Meteoblue’s forecast may change during the course of this week. Watch this space…

GFS Projected 070621

Weather Outlook

So above is the GFS projection for next Monday, the 7th June with low pressure over the continent and an Atlantic high pressure sitting off Ireland. So first off I think this combination will generate a more northerly airstream next week which means we will be cooler. Continental low pressure systems are unpredictable as stated above and countless times in this blog whenever I need to duck behind a caveat but at this stage it looks like next week may start unsettled bringing rain in from The North Sea on a north easterly wind for the southern half of England and Wales on Monday. This pattern continues through to mid-week but specifically looks to be more south east / easterly-orientated with the west and north enjoying much better weather and temperatures as they’re closer to the high pressure system. That low pressure retreats down into Switzerland (sorry Bernie, Tobias) through the latter part of the week allowing high pressure to settle down the weather. I don’t think it’ll be hot, just pleasant. At the end of next week that low continental low pressure pushes back north again to possibly bring rain to the east of the U.K and at the same time we see an Atlantic low pressure pop up to bring rain into the west for the weekend after next. If this occurs and the two low pressure systems merge then we will see a more cooler and unsettled spell of weather for a time.

The above forecast is very much dependent on the behaviour of that low pressure for both the start and end of next week in terms of pulling in cooler air and moisture so let’s see what the craic is closer to the time.

Agronomic Notes

Next week I’ll do a proper May 2021 review when all the stats have come in from across the U.K & Ireland (thanks as always guys and gals for sending in) but for now I thought I’d pick some U.K locations and summarise 2021 so far…..

So above is the story of our year weather-wise with a cool, wet January giving way to not a bad February (from a rainfall perspective) with as it happened to turn out, more growth than we had in April in all locations apart from Harlech. That makes sense because being in the north of Wales it was one of the areas insulated from the cool, dry easterlies that were such a hallmark of April 2021.

April 2021 will go down as a really tough month for some where they needed recovery, for others having done their work during lockdown it wasn’t so bad. Record-breaking cold and dry sums up April 2021 with lots of frost, more than a sprinkling of snow and next to no rainfall.  It didn’t stay that way for long though because May 2021 featured low pressure after low pressure and despite the change in wind direction it wasn’t the warmest of months. Looking at our default location, Thame, it came in with 12.52 total monthly G.P / 139.5 total monthly GDD.

If we look at the total monthly GDD graphic (below), we can see that 139.5 total GDD makes May 2021, the second coolest we have recorded and likely the wettest in some locations.

It is strange though because although May 2021 was a wet and cool month, it was also a very windy one and so it featured considerable E.T.

Rainfall vs. E.T – May 2021 – Great Dunmow location

You can clearly see when high pressure took over at the end of May, how the rainfall stopped and the E.T ramped up, hitting a highest figure of 5.46 mm on the last day of May, that’s going some….

Now I know some areas of Ireland, Scotland and Wales have had the reverse in May, far more rainfall and far less E.T, but that’s the rub, we live under a diverse weather pattern, here in the U.K & Ireland. One man’s (or women’s) drought stress is another’s flooding. The graph above shows just how quickly things can change…..

So how quickly does 5 mm + of E.T dry down a rootzone ?

Well here’s the soil moisture content as measured by a Soil Scout sensor at 25 mm depth during the 31st of May when this site experienced 5.46 mm of E.T….

Soil moisture levels at 25mm depth – 31st May, 2021 – Great Dunmow location – Soil Scout Sensor

So the E.T started at 07:00 am to a minimal level but soon increased through the morning as the wind and temperature climbed markedly.

This particular site was irrigated at around 08:00 am with 4.0 mm of irrigation water and you can see the increase in volumetric moisture content (vmc) soon after.

From irrigating at 08:00 to 22:00, the site experienced 5.40 mm of E.T and the soil moisture dropped from a high of 19.7% to 13.7% over the same time period.

Interestingly the last time point that E.T was measured was 22:00 pm !

So for every 1 mm of E.T, the rootzone lost 1.1 % of vmc at 25 mm depth.

Now every site behaves differently from an E.T, soil type, vmc at depth, etc but it is interesting to note the dry down rate on a high E.T day when 72% of E.T was replaced by irrigation.

Anthracnose trigger ?

Now we know from past experiences that as soon as the air temperature > 25°C for 48-72 hrs, the spores of this fungi germinate. They then need humidity to grow on the plant and assume a biotrophic (resting) state within the leaf itself. The recent weather over the weekend and this week will tick the first box for spore germination but it really depends upon that continental rainfall and whether it appears or not, for the fungus to be able to develop on the leaf thereafter. I’d say we will have a better idea next Monday as to whether we have experienced a potential trigger or not.

OK, I have to fly now as tempus fugit and all that….

All the best for the coming week.

Mark Hunt