16th May, 2023

Hi All,

Apologies for the lateness of the blog but I was away installing yesterday so today I am playing catch up.

Looking at the GFS output for today from www.tropicaltidbits.com, you can see we are in a cold temperature trough pattern of weather currently. Feeling the nip in the air this morning is a constant reminder that we are still firmly in the spring phase of the year.

As I have commented upon before, May is very much a yo-yo month with night temperatures failing to stabilise till we approach the end of the month. That said we appear to be due for a significant change in our weather with warmer temperatures round the corner and a move from a trough to a peak pattern in the jet stream.

So if you were looking for some drier weather, your prayers may be answered.

General Weather Situation

So this weeks weather is broken down into two parts, with Monday through to and including Wednesday characterised by the leading edge of a high pressure system pulling down cooler northerly / north westerly winds and providing that nip in the air during the morning. There will be some rain around over Scotland on Tuesday and pushing showers south into northern England and The Midlands later in the day. That wind will swing southerly on Wednesday, first over Ireland and then later in the day over the U.K and that will set up the weather for the second part of the week. Mainly dry but we will see rain into the north west of Scotland for Wednesday afternoon and evening but this will become confined to the north west of Scotland by nightfall. Further south we look to have warm temperatures in the mid-teens for Ireland, Wales and England, a degree or two lower for Scotland with that cloud cover. Still the odd shower around but no consolidated rain front. As the wind changes through Wednesday into Thursday, we will see better temperatures climbing into the high teens and by the weekend touching 20°C across many areas. That wind direction won't be stable though and will swing round to a more northerly direction over the weekend in some areas (dependent on your position to the high pressure) but it won't affect temperatures too much. The outlook for this week is mainly dry. (haven't typed that for awhile)

So cooler on Tuesday and Wednesday first thing but temperatures will be on the rise and rainfall will become confined to the north west of Scotland with Ireland, England, Wales and most of Scotland, dry as we progress through the week. We will still keep some moderate wind strength though which means E.T levels will be on the rise as progress through the week into the weekend and that'll be something to keep an eye on. In addition, with plenty of moisture in the ground and temperatures picking up, we will see Growth Potentials heading towards and maybe above 0.8, meaning a growth flush will accompany this next phase of weather.

The outlook for the weekend looks very nice, more in the way of cloud cover over Scotland and Ireland, but dry with very pleasant temperatures and light winds. Further south we will see less cloud cover, more sunshine, particularly on Sunday and a freshening north easterly wind. Despite this, temperatures will be very good and nudging 20°C.

Weather Outlook

So for the first time in a long time we have a mainly dry end to the week / weekend. Will this dry theme continue ?

Above is the tropicaltidbits GIF for next Monday. Compare it with the one at the start of this blog and you can see we are transitioning from a trough to a peak pattern in the jet stream. In turn the jet stream position is moving further north and this will allow warmer temperatures to fill in below it. Looking further forward that peak pattern will fill with warmer and warmer air through next week pointing towards this scenario as we head towards the end of May.

Now as always there's plenty of uncertainty behind these projections and particularly the above where a high pressure peak effectively connects between Africa and southern Europe and the U.K / Ireland towards the end of May. If this happens it will funnel up warmer and warmer temperatures pushing up to the low to mid-twenties possibly.

What we are looking at is the mechanism behind our record high temperatures last year. I am not saying that's going to happen towards the 2nd part of next week but the mechanism where hot air builds over Africa and then is conducted northwards by the formation of a high pressure peak pattern is how our climate is subject to more and more hotter temperatures.

So putting some detail on it, we look to be moving to a mainly dry and settled pattern of weather next week with temperatures building from mid-week if that warm air peak connects to Africa and southern Europe. Predominantly south easterly winds as well will fan a quickly drying picture and although the peak in temperatures may be relatively short-lived, we look dry for the foreseeable sitting here typing this.

Agronomic Notes

So as our weather appears to be about to transition, we too have to transition our thinking from wet weather and cooler temperatures to warmer weather, drying down of the surfaces and of course dealing with the inevitable growth flush on heavier soil types particularly.

Growth Flush

The graph above highlights the upswing in projected daily Growth Potential for 4 locations in England, Wales, Scotland and Ireland. As you can see we are heading towards a daily G.P of > 0.8 for all of the locations as we progress through into next week so that means growth levels will really be pushing on.

If this graph doesn't scream PGR to you, then you'd do better off to un-subscribe and go and watch some paint dry somewhere. Seriously though on heavier soil types, particularly outfield areas will really bounce and with a better spray day forecast, you should have good opportunity to keep these areas in check providing of course you have the resource and budget available (not always a given I know).

One advantage of the anticipated growth flush is that it will also help the Poa annua seedhead flush along mightily, so yes you may see more seedheads for a time but the quicker it goes, the faster it is over and that's a blessing.

Above is a download from our Prodata Reports software package for a weather station near Sevenoaks, Kent and there's some key pointers that I have highlighted.

Smith Kerns Dollar Spot Probability Peak

First up, we have seen quite an impressive peak in disease activity over the last 7 days or do with the Smith Kerns (S-K probability) showing levels pushing up towards the mid-20's. High enough to kick into action Microdochium, Red Thread and other foliar pathogens. Fortunately for some of this period, the daily Growth Potential was also good so for some days it grew out as fast as it came in, however between the 11th of May and the 13th of May, the daily G.P dropped back a bit whilst the Smith Kerns remained > 20%, so I think they'll be some scarring out there as a consequence. With the projected growth flush, this should soon fade away with a bit of localised topdressing and overseeding.

An overseeding window opens for greens

Speaking of over-seeding, with a much warmer soil temperature around the corner, it will play into the hands of those looking to tip the balance on their greens towards more bentgrass with 'little and often' overseeding.

Higher E.T anticipated

Lastly, I'd draw your attention to the daily E.T levels I have highlighted in green on the 14th / 15th May because certainly for the 14th, the day and night temperature will be similar to what we are forecast for next week as the temperature uplifts.

So we recorded daily E.T levels of between 3.18 - 3.35 on this weather station on those dates. Looking forward, I'd expect the E.T to sit somewhere between 3.0 - 4.0 dependent on wind strength of course. 5 days of that weather and we will have already lost 15 - 20 mm of moisture from the ground and grass plant.

Now on heavy clay soil types that kind of news is a blessing, especially after the amount of rain we have had in April / May. For sandier soils the boot is on the other foot though and they will quickly dry down and put the plant under moisture stress if the forecast turns out to be correct and we have consecutive days of higher temperatures and E.T. One to keep an eye on with irrigation strategies looking forward for sure.

Ok, that's it for this week, enjoy the better temperatures if they turn out to arrive :)

All the best

Mark Hunt