March 7th, 2022

All GFS output featured in this blog is with the kind permission of tropicaltidbits.com

Hi All,

Well what a difference a few days makes from a meteorological perspective. Last week when I typed his blog the orientation of the weather systems had lined us up for a week of cold northerlies but that flipped on its head over the weekend and the dominant wind direction will now be milder southerlies. That change has already started with the wind swinging round from a cold north easterly over the weekend to more of a south easterly today and southerly from tomorrow. That will push temperatures up into double figures and low teens this week.

No great shakes but better than we thought last week when we were looking at a total of 2GDD for this week and now it's 15 odd dependent on your location.

As usual there's a flipside to this scenario and it's the fact that the predicted low pressures will arrive earlier in the week than projected last week. So we are going mild and unsettled and personally I'll take that even though more rain isn't particularly welcome in some areas. It will be pretty windy though especially across the west.....

So let's see how we shape up for the rest of this week and have a glimpse at next...

General Weather Situation

You can see how close the first band of rain is out in The Atlantic from the image above lifted from Meteoblue's excellent output.

So Monday looks to be a mainly dry day for us all with the exception of a few isolated showers moving across The Fens and the north Midlands towards Wales, underlying the change in wind direction. For some areas this may be the only dry day of the week and perhaps the coolest as well with temperatures only sitting between 6-8°C across all of the U.K and Ireland, thanks to that cool south / easterly wind direction. With skies clearing there's likely to be a widespread ground frost away from the cloud cover in the west.

Overnight into Tuesday and by dawn that rain front pictured above is just tickling the feet of Kerry with some other showers sitting across Leinster. For the U.K, Tuesday looks a dry, bright, frosty start overall but it won't stay that way for long for everyone. Through the course of the morning that rain band will push into the south west of Ireland and track along the west coast bringing heavy rain to the south west and west of Ireland. We will also see some lighter showers develop across The South West. Some of the rain across Ireland will push into Wexford and Leinster and we will also see a band of showers appear from The South West all the way up through Wales and into The North West as we approach dusk. So a deteriorating weather picture in the west, dryness-wise but a much different one across central and eastern areas of the U.K with plenty of sunshine and slightly milder temperatures accompanied by a strengthening southerly wind. Nothing earth shattering but touching 10°C for most areas.

Overnight into Wednesday, that rain front again pushes heavy rain into Kerry and the western half of Ireland with some wintry showers thrown into the mix across Connacht. The top end of this rain band makes landfall across the west of Scotland around dawn and brings some heavy rain into The Western Isles. Away from this rain, Wales and England look to have a dry start to the day but during the morning that rain band pushes east across Ireland and The Irish Sea, arriving into Wales and The North West by mid-afternoon. Those southerly winds will really ramp up on Wednesday with gales force winds across Ireland in particular and strong winds across the U.K as well. Wednesday will definitely be the wettest day of the week for Ireland and Scotland, with 25mm plus forecast. Temperature-wise, we sit in a milder airstream so 11-12°C will be the norm but it's those winds coupled with the heavy rain for Ireland, Scotland and The North West that may be problematic. Overnight that rain band will push eastwards across the U.K and break up into heavy showers.

Moving onto Thursday and that band of heavy rain fizzles out towards the morning to give a dry and mild start to the day with a bit of sunshine for most. Out in The Atlantic we have another rain band pushing towards Ireland but at this stage it looks like high pressure building over the continent will keep this away till the early hours of Friday. Not a completely dry day with some showers over central and eastern areas of England but much better than Wednesday !with slightly lighter winds (though still strong across Ireland and the west) and temperatures again sitting around 11-12°C. The wind is still fixed from the south.

Closing out the week on Friday and overnight that band of rain that briefly held sway out in The Atlantic has pushed across Ireland and into The South West and Wales by dawn. This band of rain across the U.K will extend up the western coast and into the west of Scotland. So a wet start for the east of Ireland but the west should see this rain front clear during the morning. The band of rain across the west of the U,.K will slowly move eastwards reaching central areas of England and Scotland by lunchtime. Ireland will see showers popping up across all areas with the heavier rain now across the south east and east coast. By dusk this band of rain reaches the east and south east of England clearing to showers across the west. Those winds will still push in strongly from the south but across Ireland their strength is projected to ease a little.

So a messy end to the week, how does the forthcoming weekend look in comparison ?

Well equally messy depending on where you're located....

On Saturday another low pushes rain across the south west of Ireland from the off. This band of rain will quickly move across The South West and push north and east through the course of the day into Wales during the afternoon and The North West. It'll clear Ireland as it does so. Sunday sees more rain across the south and east coast of Ireland with the west getting a bit of a break. The South West will see rain from the off and this will push north and east into central and northern areas though the day, clearing behind as it does so. The rain shouldn't reach Scotland will later in the day. That strong to moderate southerly wind is in situ for the whole weekend. So the weather word for the weekend is 'unsettled'

Weather Outlook

When you look at the GFS output above for next Monday, it is hardly surprising that we are set to experience wet and windy conditions over the weekend but for the start of next week that low pressure is already pushing away northwards with drier conditions forecast. If this transpires it'll be a welcome break from the rain and strong winds.

So much calmer conditions next week with gentler winds and it looks to me like through Tuesday we will see some nice temperatures possibly into the mid-teens. As we approach mid-week that high gets pushed eastwards a little so cloudier, wetter and cooler conditions are likely to push in from the north and west but at this stage it doesn't look like a complete breakdown though the north and west will pick up rain. By the end of next week we look set fair into a westerly wind so possibly sunshine and showers type weather with decent temperatures, certainly for the southern half of the U.K with cooler and unsettled weather in the north and north west.

Agronomic Notes

Last week I promised I'd get up to date with my monthly summary information and so here it is. I've changed the data format so we can see how the picture changes between the locations as the months of the year tick by (provided they do of course - ref Putin)

I thought this was more interesting that way both from a Growth Potential and rainfall perspective. Now I know some of you who normally send monthly data to me haven't been able to or I can't access it as it was sent to my old email address but if you want to still send me the info, email me on markh@weatherstations.co.uk

Monthly and Cumulative Growth Potential and Rainfall stats - U.K Locations

So the top graph is comparing the monthly growth potential for the various locations around the U.K (apart from South Wales as I have no data currently available) and the bottom graph looks at both monthly rainfall and total rainfall for the year to date (2022 cum). So the location that has had the highest cumulative G.P so far this year is Harlech in beautiful North Wales at 10.6 combined January and February vs. the lowest location which is Northampton (serves you right Rob 😂) at 5.8.

Rainfall-wise, we know from previous data that the two wettest areas tend to be The South West (so that's the Okehampton location) and Central Scotland. Now I know South / Mid-Wales wouldn't be far behind but I need to grab some reliable monthly data. So our highest cumulative y.td total is from Dumbarton at 450.5 mm for January and February. Now that isn't far off what some East England locations have for the whole year !!!

Remember also if its raining then it will also be cloudy so the amount of light reaching the grass plant is also going to be pretty low in a high rainfall location.

Talking about light intrigues me.....

One of my favourite sensors to fit to a Davis Vantage Pro2 weather station when I'm out in the field is this Apogee PAR light sensor. Firstly it looks cute and secondly it provides data on an area where I think our industry is lacking...

It measures PAR (Photosynthetically active radiation) which in plain language is the part of the light spectrum (wavelength) that the grass plant can utilise for photosynthesis. Typically it is held to be between 400 - 700 nm (nanometers) and consists of the blue, green, yellow and red part of the light spectrum (think Rainbows)

So the theory goes that if you add up the total amount of PAR light you get in a 24-hour period it gives you something called the DLI or Daily Light Interval. This is measured in mols per m2. I've talked about this before but I find it really interesting because it has a lot of connotations with respect to grass species.

Now there is some information about the minimum DLI requirement of a grass species but it is limited.

Creeping Bentgrass is held to have a DLI of 30 mols per m2. That in itself is interesting because we don't usually come anywhere near that during the winter here in the U.K & Ireland so we can presume that this particularly grass species would have a sub-optimal photosynthetic rate for a period of the year. Less photosynthesis means less energy produced and so less growth. Chuck a load of wear into the equation and you have trouble if the amount of wear exceeds the amount of growth / re-growth.

Now lets say we have another grass species like Poa annua which from anecdotal evidence sits at the bottom of the DLI league table meaning that it can grow at low DLI levels. Not only that but it adapts to its surroundings, so each generation is finely honed to its environment. Let's say Poa annua can grow at a DLI of 6.0 for example. If this is accurate then during the parts of the year when the DLI is naturally low (late autumn - winter when day length is short and light levels are traditionally lower), it has a competitive advantage.

This doesn't just have significance in golf, it has lots of relevance in sports pitches, particularly those where the last thing the stadium designer thought about (or maybe never did at all) was how the grass was going to grow in near permanent shade. Now of course this has led to an industry in itself, that of lighting rigs and artificially raising the DLI to the point where the grass plant can photosynthesise. It isn't rocket science, horticultural growers have been doing this for years. It is expensive though (not that footie has ever had to worry about money of course)

And in domestic lawncare.......For example, my back lawn is a bloody disaster from the beginning of November to the end of February. It is completely in shade and the only wear it receives are the myriad of Blackbirds and the like that appear on it when I put out food .

I remarked to my significant other when we first looked at the house with a view to moving......"The house is lovely but it is in a really crap place to grow grass" . Strangely the estate agent had forgotten to mention this :)

Of course I do everything to get a good stand of grass, I've overseeded Lolium and Festuca species and though they look good from April to September, once the light goes then so does the lawn because Lolium has a minimum DLI of 11 mols per m2 and obviously my garden doesn't get anywhere close to that. No surprise then that Ferns love it when their DLI requirement is down at 4 mols per m2 (But they don't stripe up well 😂)

During this year I hope to present some DLI data that may give some clues as to how light affects our surfaces, our sward composition, etc....Just think you spend an arm and a leg on grass seed but we don't even know whether it is suitable for the environment we're applying it into, simply because we don't have the knowledge or the data at a cultivar / grass species level. For instance I'd love to see some Browntop Bent DLI data......

Wow....that was a big digression from monthly rainfall and Growth Potential stats. My mum used to be famous for what I called her 'tangential conversations' and clearly I've picked up some of her gene pool (no bad thing)

I'll finish off by looking at the same stats for Ireland and to thank Aine for relaying these over to me in her usual diligent fashion 👏

Monthly and Cumulative Growth Potential and Rainfall stats - Irish Locations

Well no great shakes here because we know that Valentia is the wettest location usually over a year from the ones we measure though Claremorris in the lovely (when it isn't raining) Co. Mayo is running it close this year. The eastern coast of Ireland featuring Johnstown Castle and Dublin are the driest at nearly 50% of the previous locations.

Growth Potential-wise, Valentia is streets ahead and interestingly though it similar to Claremorris for rainfall, the more northerly location of the latter has a significant effect on the growth potential coming in at nearly 50% of the Co. Kerry location. If you compare the cumulative G.P figures for the Irish locations with the ones from the U.K, you'll see they're pretty similar and in some cases higher because Ireland tends to have milder, wetter winters compared to the U.K or parts of it anyway. I'd expect the latter to begin to pull away in March and April but this is wholly dependent on what Mother Nature serves us up in the weeks and months to come....

Ok, that's it for another week and thanks to everyone for following my new blog in its new location. Remember if you want to sign up then just click here to take you to the subscribers form or go to weatherblog.co.uk 👍

All the best.

Mark Hunt