15th April, 2024

Hi All,

Well we have reached the middle of April and as we know, it has been a roller coaster ride this spring. Last week I reported that the jet stream was edging northwards in the right direction and that trend is going to continue this week, so after an unsettled start, we have a good period of dry weather coming up with high pressure establishing this week. Hurrah. So if you're sitting listening to the rain batter the windows as I am typing this blog, despair not. Plus it is only a chilly 6°C outside !

Higher up in the atmosphere, meteorologists are reporting that the Polar Vortex has undergone a reversal (read about here) and is now spinning backwards. Typically this occurs following a Sudden Stratospheric Warming Event, which you may remember I documented in early March. The Polar Vortex normally flows westwards, but when it reverses, it flows eastwards and that effect can filter down to influence our weather in the same way. Looking at the long-term GFS projection courtesy of tropicaltidbits.com, we can see the normal west-east flow of weather systems halt and reverse towards the end of this month (10 days time). So there is a suggestion that the 2nd half of April and particularly the end of the month mayl drop into a cold run of easterlies. The danger is that the colder air mass to the east will displace the jet stream south again and create a trough pattern into which low pressure systems will move, more on that laer.

General Weather Situation

So today we have a wet one as heavy rain is moving diagonally eastwards (/) across Wales and The South West into The Midlands and southern England during this morning. This front is already clearing the north of England after crossing Northern Ireland and Leinster in the early hours of this morning. Further north, a raft of heavy showers is pushing into Scotland and The Borders. Urged on by a chilly north westerly wind, these showers will be wintry in nature over elevation. Further south, that westerly wind will be anything but mild and it'll feel chilly as temperatures struggle into double figures for all areas. As that main rain front crosses the southern half of the U.K, it'll be followed by sunshine and heavy showers. The same will be true across Ireland, but the showers will be confined to the north and east of the country. So a windy, cool and wet one for the start of the week.

Tuesday will be a drier day overall but there will still be blustery showers across Scotland and the north, particularly in the second half of the day. These will push south further later in the day. Ireland also looks drier, still with showers across the north and north east. Milder on Tuesday as we see more in the way of sunshine, despite a north westerly wind direction pushing those showers across the U.K and north of Ireland. Temperature-wise, cooler up north, with 8-9°C across Scotland, milder in the south and west with 12-13°C typical. Remaining very windy with that wind edging round to the north later in the day.

Wednesday sees a similar day with a raft of showers pushing down into northern Ireland and the north west of Ireland during the morning. These showers will move quickly on a brisk wind and push across The Irish Sea into West Wales and The South West later in the day. Further east we will see another sunshine and showers day, more across the east and north of the country, but everyone will see some showers I think. That wind will be north - north-north-west, so chillier again on Wednesday, with temperatures struggling into double figures, despite sunshine between the showers.

Thursday sees high pressure beginning to make itself felt with drier weather for the west and south. There will be rain across Scotland though but currently this is projected to push through in the morning and possibly down the east coast of England. Jury's out on that one. Winds will begin to drop back in intensity and slowly tip back towards the west. Temperature-wise, these will start to pick up, with the west (Ireland) warmer than the east (UK). So 12-14°C will be typical with the warmer temperatures to the west and south.

Closing out the week, the weather picture continues its improvement, with just some showers pushing down the north east and eastern side of the U.K, the only blot in the copybook. That wind picks up again from the north west, so more in the way of cloud cover on Friday and a stronger, brisk wind in situ. 12-14°C temperature-wise, maybe hitting 15-16°C down south and across Ireland. None too shoddy.

The outlook for the weekend is good, dry and warmer with 14-16°C likely and calm, settled conditions. The wind will be lighter on Saturday, picking up a bit on Sunday and remaining north westerly. That's nice and a pleasure to communicate 👍

Weather Outlook

The outlook is a bit of a concern for me because of the potential behaviour of the displaced cool air mass to the east of us. If the projections are correct, this air mass will move westerly next week and displace the high pressure system mid-way through next week. So the 1st half of the week looks calm, settled and mainly dry, cooler though with a change to a northerly wind direction, so temperatures 11-13°C will be typical. As we progress into the second half of this week, a trough pattern in the jet stream forms as that colder air mass displaces the high pressure. The wind swings round to the south / south east and a low pressure system emerges to the south west of the U.K. This will push rain into the south of the U.K and Ireland from Thursday onwards and being a trough pattern, this low pressure will then push rain further north into Friday and the weekend after next.

If the projection is correct, the southern half of the U.K and Ireland will bear the brunt of the rainfall before it moves further north. Let's hope the outlook changes.

Agronomic Notes

So we have a possible hiatus in the run of wet weather that has extended since October, through March and into April. Quite unprecedented. The Met Office recently confirmed that the period of weather over the last 18 months is the wettest since records began over 200 years ago.

Of course it is difficult to extrapolate this into a longer-term trend, fueled by global warming, but if we are in for longer periods of rainfall over the autumn winter, it fundamentally challenges our ability to manage amenity turf in some scenarios. Namely golf courses and pitches on heavy soils with limited drainage capabilities. Without a doubt, drainage and irrigation are the 2 areas of focus, with the former in my mind, top of the list. After all, as one of my golf friends pointed out recently, you don't normally see golf courses closed because of a drought.

It isn't just the amount of rainfall, it has also been a very mild winter, with less frost days (due to the lack of winter high pressure systems) and consequently more growth.

That combination of rainfall and temperature has caused many headaches on wetter, heavier soils. I was looking at a Twitter picture today of a golf course near Oldham cutting fairways at 25mm just to try and get a cut in and on top of the burgeoning growth. Tough work.

The chart above shows average monthly air temperature in °C from Sept to April 10th covering the periods of '22-'23 and '23-'24 in Central England. Air temperature drives plant growth as we know when we convert his data into GDD and GP figures. The 1st part of the autumn was pretty unremarkable really with a cooler November than previous, but once we get to December, things change significantly. December was the change month in my mind both from a temperature and rainfall perspective. A near doubling of mean air temperature vs. the prior year, December was followed by a 'normal temperature' January, before we took another hike up in February, March and April to date.

So its clear to see the driver behind growth from these stats.

The chart above shows the same time period, just with rainfall. Now Central England is a drier part of the U.K vs. the west or the north for example. It is the trend though vs. prior year that is key. For Sept '22- April '23 period (up to 10-04), the total rainfall was 418mm, the same period for '23 - '24 was 562.8mm, that's nearly 35% more rain. In the previous year there were drying months (Jan / Feb '23), but this year the trend for high monthly rainfall has been unchecked. Undoubtedly, Dec '23 and Jan '24 caused the most damage in terms of flooding, waterlogged rootzones and the like.

This data isn't a worse case scenario though because there are areas (Neath, South Wales for one) that have received nearly 1,000mm (that's a metre) of rainfall already so far this year in a little over 3 months. As I said earlier, unprecedented.

If this indeed is a long-term trend then what's to be done ?

Well one of the agronomic practices we could try to factor in is a wall-to-wall PGR + iron late into the autumn, if and when a drier pattern of weather (to allow spraying) presents itself. This would button down growth, reduce the requirement for cutting (and therefore smearing of worm casts) and leave us sitting pretty from a maintenance perspective. Of course it is additional financial outlay, but it may become a necessity, as of course will functional drainage. The problem of course is where do you stop, particularly on heavier soils , greens, tees, approaches, fairways, semi's - cut rough ?

One of the lessons of this autumn winter is that the above rainfall patterns will have shown clearly what parts of your facility are affected the worse by standing water and poor soil drainage characteristics. These are the areas to focus on going forward. Take lots of photographs because memories are selective. The same is true growth-wise, some areas will have grown more than others or maybe it is a combination of the two, wetter areas of the course that grow more and can't be easily maintained.

One of the concerns in the back of my mind is what has been done to the soil structure overall by this relentless amount of rainfall. Migration of fines, compaction of the surface and a grass plant that has not had to look hard for nutrients and moisture all point towards a shallower root system. This is of course a threat when (yes when) the weather turns hotter and drier.

So we have a window this week and the 1st half of next week to get as much buttoned down as we can cutting-wise and if ground conditions allow (i.e. you are on a drier course), I think trying to carry out a vertidrain operation will prove beneficial in terms of maximising drainage, venting some hypoxic gases and giving the grass plant the ability to breath. I won't apologise for using this cracking picture (cheers Mark) again to demonstrate the benefit of deeper aeration, deeper roots and drought tolerance. Hopefully the area that wasn't vertidrained is clear to see 🤔

Now of course this is entirely dependent on ground conditions, working a wet soil will do more harm than good of course, but if the opportunity arises, I'd go for it !

OK, that's me for another week, enjoy the hiatus and high pressure once this cool and wet weather has pushed through.

All the best.

Mark Hunt