March 13th, 2023

Hi All,

Wow, what a topsy-turvy weather week we have just endured, heavy snow, heavy rain, a near 20°C temperature difference at one point between night temperatures in Scotland and England (-15°C vs. +5°C) and it isn't over yet !

Nature is confused for sure as I found out the other night when I decided to set up my night camera in readiness for late March when I normally start to see Hedgehogs visit my garden after the end of their winter hibernation. Imagine my surprise to pick up this little chap (or chapess) visiting in the wee hours for some food I'd put out. Bless his / her little cotton socks.....

After a bone dry February when we received 4.4 mm rainfall here in Market Harborough and 50 odd mm year to date at the end of it, we now sit at double that after heavy snow and rain added another 50 mm over a couple of days.

If ever there was an argument as to why your facility needs to be future proof, climate-wise in the areas of irrigation and drainage, the start of 2023 makes a compelling case !

Friday last week was perhaps the most bizarre weather day for awhile. I awoke to heavy and drifting snow, people struggling to drive through snow drifts on normally busy Leicestershire roads but 5 hours later, the roads were not only clear, they were bone dry and we were basked in blue skies. Bizarre, bizarre.

What we often forget about with snowfall in March is that the soil temperature is higher than in the middle of winter and so the thaw can and usually is rapid. That said, yesterday as I drove back from a nice walk around Rutland Water's peninsular, there was still snow in the hedgerows despite the air temperature topping 12°C.

So let's look at what's coming this week and next, as I watch the wind and rain batter the trees behind my house. As usual all GFS content is courtesy of www.tropicaltidbits.com.

General Weather Situation - w/c 13th March, 2023

So as we start this week, the jet stream is (as I suggested last week) sitting south of us and that has allowed and is allowing Atlantic low after low to push eastwards hence the high rainfall and wind speeds currently. You can see the strength of the wind on this windy.com graphic featured on Meteoblue's website @ www.meteoblue.com. Click on weather maps and wind animation.

So Monday starts off with low pressure crossing the country and pushing high winds and some heavy showers across Ireland, Scotland and the rest of the U.K. These showers will be around for all of Monday and your best bet is clicking on your favourite rain animation (I use net.weather.tv) to see where it is and where it is going. Across northern areas where the air is colder, that rain will turn to snow, particularly over elevation. That strong south westerly airstream is though responsible for mild air on Monday so temperatures will range from 10°C in Scotland to 13°C for Ireland, Wales and the south of England.

Tuesday brings a change as that mild air moves away due to a change in the wind from south westerly to north westerly. It'll be a drier day but there will still be showers around across the south of England, Ireland, the north west of England and Scotland. Much cooler than Monday with 5-9°C in that moderate to strong north westerly wind.

Onto mid-week and Wednesday sees a heavy rain front push into the south west of Ireland (blast) and move quickly north and east across the country. This rain will soon push across The Irish Sea into the south west of England and South Wales by lunchtime. Another change in the wind direction to southerly means that temperature will ping back up again, not quite to Monday's heights but into double figures. That rain will probably take till dusk to reach central parts of the U.K before moving into northern and eastern areas overnight. Again it'll turn wintry over The Lakes and Highlands.

Thursday sees that rain still straddling across the U.K, though it will have cleared Ireland. As we go through the day, the main front of rain moves north and east across the U.K, leaving behind showers across Ireland and the U.K. In common with the first half of the week, the winds will remain strong but now blowing from the south west again, so we go back to Monday's milder temperatures with 11-13°C the order of the day. As we head towards dusk, things start to dry out a little but for Scotland, they'll still be rain and wintry showers especially across the west and central areas.

Closing out the week on Friday and we have another low pressure system sitting off the south west of Ireland. This will bring rain across the south and south west of Ireland from the off. Across The Irish Sea we will still see that mix of rain and wintry showers across Scotland but England and Wales look largely dry until late in the day when we will see some showers across West Wales and the south of England. Some of that wintry rain, sleet, snow mix over Scotland may sink south into northern England at the same time. Mild again with 10-12°C.

So how does the weekend look ?

Well, Saturday is a bit of a mixed day with plenty of rain hanging around across Scotland, the north of England, Wales and across Ireland. Maybe more of this will be from The Midlands north than across the south but it'll still be a showery / wet day in places. The same with Ireland, wetter across the northern and eastern part of the country than the south and south west (for a change eh ?). These showers tend to fizzle out from the south during the second half of the day. Remaining mild with 10-12°C again. Sunday looks a drier day for the U.K, but for Ireland, yet another rain front makes landfall across Kerry around Midday and then moves north and east. This moves into The South West during Sunday afternoon and heads north and east during the evening and into Monday. Sunday will feel cooler as the wind swings round from the south west on Saturday to the north west on Sunday, so those temperatures take a tumble back down into single figures with 7-9°C typical.

Weather Outlook - w/c March 20th, 2023

There's that song title going round my head from C+C Music Factory as I begin to type this and look at the GFS...."Things that make you go hmmm"

So what's making me go hmmm ?

Well, next week looks to me to start cool and unsettled with that chilly north easterly wind in situ. Sunshine and blustery showers type of weather I'd say but cool and dull with it. Later on Monday, rain pushes into Ireland and across The Irish Sea into the west of the U.K, but doesn't make much more progress on Tuesday sitting across the west, whilst central and eastern areas stay dry. Then the wind changes from north east to south west and that trigger pushes the rain across the U.K accompanied by milder air pushed up on south westerlies through Wednesday and Thursday next week. High pressure then tries to interject but we may continue showery, especially across Ireland and the west. With a low out to the west and a high to the east, this could....could funnel southerly winds and increasingly warm daytime temperatures across the U.K meaning we may end March warm, dry and sunny with a high pressure blocking pattern in place. Whilst you may welcome this from a growth perspective, let's hope it doesn't lead to a dry, stressy April.

Grass Agronomics

Cold temperature overseeding

I read an interesting article over the weekend on LinkedIn regarding research on cold temperature seeding of Bentgrass and subsequent vigour and establishment. You can read about it here. The research covered both Browntop and Creeping Bent varieties and focussed on how both species had demonstrated germination at temperatures down to 6°C soil temperature. Cold seeding is the process where Bentgrass is seeded during cold periods of the year and then germinates and establishes as soil temperatures pick up to give a head start in the spring.

It is an interesting concept and not dissimilar to the rationale behind dormant feeding of turf were you apply a granular fertiliser in say early January and it just ticks away supplying nutrient as and when conditions allow. I am a big believer in the latter concept, especially if the product is organic / slow release in nature and so ties into microbial activity for its release.

You could see a situation where you combined the two concepts to maximise sward density and transition away from a Poa-dominated sward perhaps ?

Now it is worth pointing out the more than significant point that the research was carried out in pot trials and as far as I can see without the usual wear and tear factor we experience in winter golf (couldn't tell from the article so happy to stand corrected)

This could have a significant effect on seedling mortality and therefore the potential feasibility of this process.

To look at this concept in more detail I thought I'd look at last winter's soil temperatures graphing out data using a soil temperature probe hooked up to a Davis Vantage Pro weather station. Caveat-allowing that November 2022 was unusually mild of course. It is also very likely that the soil temperature at the seeding depth is higher than the graphs I am showing below because the article looked at this area as well and found that shallower depth seeding of Bentgrass was more successful than deeper. At shallower soil depths, soil temperature more closely follows air temperature and is more reactive both in terms of increasing as mild air comes in but also decreasing under the influence of colder air / frost.

It is also worth mentioning that soil type plays an important role here because lighter (sandier) soils (as used in the research) tend to be more reactive in terms of soil temperature because they contain more air (or they should do anyway !). Heavier soils are less reactive due to the fact they tend to contain less air and consequently more water. Gases (for example, air) are more reactive than liquids (for example, water) as a general rule of physics. The soil type is sandy at both locations i have graphed below so are likely to be higher than a heavier soil type.

So, here's how the soil temperature profile looks at our default Thame location in Oxfordshire ;

As mentioned above, Winter 2022 / 2013 was unusually mild during the first half of November and mid-February particularly, but I wouldn't bet against this pattern of weather repeating itself as warmer air peaks later (and earlier) in the year are I think increasing in frequency.

So we can see there were some clear periods during the winter (mid-Dec to mid-Jan for example) when we could have achieved Bentgrass (and other species) seed germination.

I thought I'd repeat this exercise using data from Central Scotland.

Now there are obviously less periods of the winter in Scotland when it was mild enough for Bentgrass overseeding, but nevertheless, these periods do exist even up north like :)

For example, during February this year and right up until the end of November last year. Now you'd imagine that they'd be a higher rate of seedling mortality in a harsher winter and under winter play levels so the proof of the pudding is definitely in the eating as far as this concept goes. One area that I would highlight as a potential challenge to cold seeding is the now more common phenomenon of a dry April, whether that be cold / dry or warm / dry. This to me would present potentially significant mortality for newly-established seedlings unless they have irrigation and / or have developed a sufficiently robust root system to survive periods of low rainfall / high E.T.

We also have to think about light availability because we know some species of bentgrass requires high DLI levels to grow. You could debate whether seedlings have a lower light requirement because they have a lower surface area of leaf to sustain but on the flipside they also need to create more growth in terms of root and shoot to survive so maybe not ?

There's a big gap in turfgrass research when it comes to DLI, minimum light requirement, etc that I'd love to see filled some day or maybe it is just a gap in my knowledge. (more than likely)

Like most things, there are pros and cons and it is really up to you, the end user in your situation to judge whether it may or may not work. Why not trial a couple of greens to see ? Away from bentgrass, early season seeding during dormant conditions definitely has merit. For example, I renovated and overseeded my back (very shady lawn) in mid-Feb when it was dry, with a straight rye mix and all that seed has popped over the last week (so it took 3 weeks to germinate).

Reacting to our changing climate strategically

So you can see how as our climate changes, we also change our approach.

Remember this image from mid-February ?

You could easily contemplate aerating and possibly overseeding (in general, not specifically just with bentgrass) in January / February and using the milder temperatures thereafter for recovery (if and when we get them). In my mind this could equate to better surfaces, quicker in the spring. OK, you can legitimately argue that a dormant granular fertiliser application wouldn't have achieved much unless it was applied in the first half of January when we had sufficient rainfall to break it down but whereas milder winter interludes are common place now, a bone-dry February is a real meteorological oddity and I'd take a bet it will be a number of years before repeating (but perhaps not the 90 years since the last one eh ?)

The effect of the Sudden Stratospheric Warming Event on Growth-Degree-Days

At the end of February, I talked about the potential occurrence of a SSW event and its negative effect on air temperature and consequently GDD. I highlighted how in other years, colder than normal March temperatures caused by a SSW event had kept the GDD down to 55-60, (in total calculated with a 6°C base temperature) so I thought I'd take a look at March so far and use the weather outlook as well in my calculations.

Well, a quick snapshot on Prodata Reports (our new agronomic software linked to a Davis Weather Station) shows a number of locations around the U.K & Ireland are currently sitting at around 9-12 GDD total for the month. Extrapolating towards the end of the month using max and min air temperatures shows maybe another 40-45 GDD up until the 26th of March so we won't be far off other years when a SSW event took place. Another tick in the weather event predictability box me thinks from Captain Smug.

OK, that's me for another week, I'm off to get packed, run the gauntlet of Ryanair and head back to the west of the Emerald Isle for the first time in 5 years to do some weather station installations. Looks like I need to pack some pretty effective waterproofs from the forecast !!! :)

All the best.

Mark Hunt