June 5th, 2023

Hi All,

Welcome to the first weather blog of June and sitting here typing it in my office, it's bloody cold you know for the start of June !!!

As readers of my blog will know I'm an avid naturalist, a trait handed down to me by my parents and a love of fishing that puts nature front and centre.

Last week, I had cause to smile a number of times whilst experiencing nature. On Friday, I was installing a new Davis weather station over at Shifnal Golf Club (great to catch up Chris) and as I unloaded my car, my attention was drawn to a male Chaffinch sitting on my car. It was fascinated by its reflection in the car roof and proceeded to peck the crap out of it.

It made me laugh because many years ago I was on a camping holiday with my family and we were staying by a lake near Dolgellau (Wales). Every morning from sunrise, Male Chaffinches used to peck at the gleaming hub caps of my Dad's Austin Maxi and keep us all awake. They are fiercely territorial birds so when they see another male Chaffinch, they are up and at it, even if it turns out to be their own reflection !!!!!

Then on Saturday I was on a mammoth (for me) 50 mile plus mountain bike ride that took in Leicestershire and Rutland. Cycling around Rutland Water my path was crossed by 2 Weasels chasing each other along the cycle path and quite oblivious to me. They are rarely seen but as they ran they were chattering away and I just laughed, so lovely to see.

Image courtesy of the BBC's article that you can find here

Finally, there came the news that a species of Butterfly (The Black-Veined White) that has been extinct in the U.K since 1926 has popped up in the south east of England, flitting around the hedgerows. There's a theory that they have been released rather than are naturally occurring but to me I think it's great news and hopefully they manage to prevail. Speaking of Butterflies prevailing, there is more and more evidence of the importance of our gardens to Butterfly (and Moth) species. Butterfly Conservation circulated some research to that effect carried out by the BTO. You can read about it here

Let us hope that those Butterflies can endure cool winds or head westwards for awhile whilst these cold north easterlies prevail.

Living in the centre of England in beautiful Leicestershire, we tend to be on the receiving end when the wind is in the north or north east when it comes to temperature and cloud cover. This year has been really strange weather-wise because our wind direction has been so fixed for so long.

If you look at the climatic summary courtesy of Prodata's Davis weather station reporting software (PRP) , I have highlighted the dominant wind direction for this weather station located near Milton Keynes.

You can see how often the wind direction has been northerly or north easterly. In fact that trend to a north easterly wind started on the 12th of May and will continue through this week so it'll be a solid month of the same wind direction. That isn't normal for an Island climate.

That is why in central and easterly locations the temperature this week will barely hit the high teens, 16-17°C. Whereas if I look westwards to Newport in Wales, you can add 4-8°C on top of that this week as the east-west weather divide continues. (Hope you have your factor 50 on Jim !)

The 12th of May was pretty much when we had the last meaningful rain in central and eastern areas (though some places picked up the odd mm last week) and I think this dry spell will continue this week but there may just be some rain creeping into the forecast.

General Weather Situation - w/c 5th June, 2023

So this week we continue that dominant north easterly wind and therefore the continuation of the east-west divide in terms of sunshine and temperature across the U.K and Ireland.

So the east and central areas of the U.K and Ireland are looking at 16-17°C day time temperatures and (unusually) a continuation of some pretty cool nights with single figure temperatures typically sitting at 7-9°C. The west will be by contrast much sunnier and warmer and therefore temperatures around 20-21°C will be typical. Across the west of Ireland, you can expect even warmer temperatures with 22-24°C typical. That is warm for June across the west. Scotland will follow that pattern as well and continue dry with 20-21°C typical during the day and single figures at night.

As commented upon above, the strong to moderate north easterly wind will continue this week and into the weekend with a more easterly wind direction across Ireland and Scotland.

Now we have a change over the weekend and it is due to the formation of that widely-predicted Bay of Biscay low pressure system shown in the above GFS projection from www.tropicaltidbits.com. That low pressure will cause two main processes to take place. First up it will pull warmer air from the continent so as we progress through the weekend it will get noticeably warmer with mid to high 20's likely on Sunday for some locations.

Now with the proximity of low pressure out to the south west of Ireland, it will begin to feed in more humid air into the weather picture and that could mean some thunderstorm development. Now predicting where and when summer thunderstorms will form is almost like looking for an honest man in parliament. It is difficult. Currently the projections are for storms to develop across the east of Ireland on Sunday morning and these will push across Ireland during Sunday. Some of these thunderstorms will also creep into The South West.

As we move through Sunday, temperatures will build and those storms will head across Ireland. Now currently they are projected to form on Sunday but it wouldn't surprise me to see some thunder around on Saturday as well across the southern half of the U.K. This low pressure will stay out west but another one is set to form across France and The Netherlands and that sets up an interesting dynamic for next week.

Weather Outlook - 12th June, 2023

Now the effect of that low pressure will be extremely difficult to predict but I think it'll begin to introduce moisture into the equation from the end of the weekend. With high temperatures and rising humidity it is likely this moisture will be very stormy in nature and hit and miss, in that some places will get it, others won't. I think we will also loose that strong north easterly wind as well so for me that's a good thing as I have had enough of being buffeted around in the boat whilst fishing !!!!

So a more showery weather picture next week, still warm, humid I think with lighter winds and temperatures remaining in the low 20's, but with a less marked east-west weather picture. I'm not going to even try and forecast who will get the moisture when but I think the west will pick up more in the early part of the week and the south, east and north later in the week. We will see, I do hope we get some rain though as it'll be a month since the last.

Agronomic Notes

Over the last two blogs I have talked about the turnaround in rainfall and E.T that took place from the 12th of May and has seen us dry up significantly.

Now this weather trait means many things to many people. Those sitting on heavy soils will have welcomed the chance for things to dry down and to be able to get on top of rough growth now that its growth rate has become moisture-limited.

To those sitting on sandier soils, it has presented more of a challenge as the wet spring allowed areas to regrow after the punishment that was last summer. Here I am thinking about the central and particularly the eastern side of the U.K which tends to miss rain from Atlantic low pressure systems and southerly-biased BOB events. Here the soils tend to retain less moisture and so are at the mercy of water supplied by either irrigation and / or rainfall. Since the 12th of May, these areas would have lost 50-75mm of moisture by evapotranspiration and therefore are well into experiencing drought stress.

Looking at our default location at The Oxfordshire, Thame, you can quite clearly see how rainfall vs. ET has shaped up since the beginning of May. Initially the soil had a surplus as the wet start to May continued April's wet rainfall pattern. Once we got to the 13th, things changed and that moisture surplus soon turned to a deficit by the 16th of May. Some change....

By close of play yesterday, that deficit had grown to -75mm or 3" in old money.

It is interesting that we have experienced this dry run of weather earlier than usual in the year after a wet spring. Rob Hay from Northampton County GC asked me recently if this was related to the SSW event we had earlier in the year because the last one occurred in 2018 and that year we also ran into a dry spell that started in May. Well who knows but it is a possibility. Hopefully we won't repeat 2018's dry summer though because after a brief wet spell at the beginning of June, we didn't get appreciable rain then till the middle of August !

GDD Comparison - May 2023 - The Oxfordshire, Thame, U.K

Looking back at May, 2023 from our default location, we can see we came in at 194.9 total GDD for the month. Now that's towards the low side for the month of May and quite a way below our other hot, dry years ;

May 2018 - 236.5

May 2020 - 215.5

May 2022 - 220.2

May 2023 - 194.9

The reason for that is the dominant northerly (north easterly) wind direction that I highlighted earlier. This has capped night time temperatures in particular and whereas normally we would see night temperatures up in the mid-teens during May, this year they have sat ay 5-8°C. Since GDD is calculated on the average temperature from the minimum and maximum for the day, this is why May 2023 has come in lower than 'normal' (whatever that is !!)

For the year we are at a cumulative GDD of 415.5, which again is sort of mid-pack when we are comparing years GDD-wise. Not far off 2018 though eh Rob 🤨

Next week I hope to do the round the U.K and Ireland round up looking back at May, 2023 but already I can tell from the stats that it was a very dry month for us all and especially up in Scotland and across The Irish Sea. The west of Ireland in particular.

Humidity = disease

Now if we do end up picking up some thundery showers and elevated humidity from the coming weekend you can bet your bottom dollar that it will initiate some of the diseases we usually associate with summer. That is to say Fairy Rings, Take All, Dollar Spot, Waitea Patch and Red Thread to name but a few. In my experience we tend to see the first Dollar Spot around this time but it isn't the main outbreak which tends to occur later in the summer towards the end of August / beginning of September when night temperatures begin to fall and approach the dewpoint temperature and dew forms,

With high E.T levels lately and a dry wind, disease issues have been few and far between except maybe for plant parasitic nematodes, the symptoms of which tend to become more prevalent as the grass plant goes under stress. With low humidity, plant leaf wetness periods have been few and far between and although that's a bonus as there's been less need for dew removal, it also helps in terms of discouraging disease development.

Below is a graph from a Davis leaf moisture sensor (image above) fitted to a Davis Vantage Pro2 weather station near Sevenoaks, Kent. It measures moisture on a scale of 0 (dry) to 15 (fully saturated) and anything above a reading of 8 represents dew formation in my books.

Now early on in May we had rainfall and dew formation so you can see some extended periods of plant leaf wetness. Once we get to the 13th of May, we see very few periods when the plant leaf has been wet for any length of time. In fact you can count the periods of dew formation on one hand.

Since dew is one of the main drivers of plant disease and especially foliar pathogens like Microdochium, Dollar Spot and Red Thread to name but a few, it is why we have seen very little plant disease around recently. Now if we pick up thundery showers and a period of sustained humidity that may change.

Possible Anthracnose Trigger.....

One area I'll be looking at carefully over this coming weekend and beyond is the rise in temperature and humidity to see if it is high enough to represent a trigger for Anthracnose.

As a reminder we tend to need 2-3 days of successive maximum air temperatures >=25°C, followed by (and that's critical) extended periods of plant leaf wetness. If your site has a history of Anthracnose and we hit those parameters, it might be worth thinking about a preventative fungicide application to try and break the cycle of spore germination and infection.

Ok, that's me for this week. Next week's blog may or may not be on a Monday as I am in to Nottingham hospital for my annual shoulder procedure. Nothing major but sometimes I do tend to feel a little second hand :)

All the best.

Mark Hunt