Well that was a week and a half weather-wise and I know for Scotland it isn’t quite over yet in terms of recovering temperatures and a thaw. I ventured out into the countryside for a walk (climb) on Saturday and have never seen drifts like it, they were literally huge.
Amazing then that when the thaw started on Saturday night and through Sunday, such a large amount of snow disappeared so quickly. Now I’m not talking about these type of drifts, they’ll be hanging around for a while yet, but in general the snow in the fields went so fast. Part of this was because the real level in the fields was quite low as it had been pushed into drifts along the hedgerows. Part of it is because the snow had a very low moisture content so it didn’t pack down as hard, had more air spaces between the flakes and then when the air temperature increased, the melt occurred.
Snow to rain ratio
Usually you can work on 10mm of snow = 1mm of rain as a rough guide but this ratio can run as high as 50:1 with fine powder snow. In the latter, 300mm (12″) of powder snow can be equivalent to 6mm of rainfall.
The severe weather brought some unusual birds into the garden as well, not because they’re rare but because I don’t normally see them. Fieldfares took full advantage of the Apples I put out (I found putting them on skewers allowed me to slide them up above the snow as it fell saving them from being buried), Pied Wagtails and even a Treecreeper landed on my patio to feast on Mealworms, it must have been hard for them this spell of freezing weather.
One last point before I leave my anecdotal weather ramblings, yesterday it was a heady 5°C when I was fly fishing but it felt so warm compared to the earlier days freezing temperatures, I didn’t even need gloves on. Isn’t it amazing how quickly the human body adapts ? The Trout were a little picky though 🙂
So the thaw is well under way in most places south of the Scottish border but we aren’t totally out of the woods yet because the jet stream is still lying lower than normal and we are sitting in a cool temperature trough. The Unisys GIF above for today clearly demonstrates this. So a thaw yes, but a recovery to normal March conditions not. The same week last year we sat with maximum air temperatures between 10-15°C, this week we will be lucky if they just break double figures. The long-term prognosis is that we are to stay in this trough pattern until at least the middle of March and perhaps longer. In other SSW event years, we have seen the subsequent low temperature effects carry on for a number of weeks, so yes things will improve, but no we aren’t back to normal just yet.
General Weather Situation
I had some good feedback last week on my blog and its format, specifically this part (thanks Adam) where my friend and colleague said that he rarely reads this part of my blog because he can get that from a forecast, it’s the longer-term and agronomic notes part that is important for him. Now this part takes a good chunk of time so can I ask for some feedback if you agree or disagree with the above please as I’m always looking to save time 🙂
So onto this week and Monday sees a North-South divide in place with north-east Scotland still on the receiving end of wintry showers through this morning. There’s also a band of rain moving up the east Leinster / north-west England coastline through the morning. Elsewhere we look to be dull, dry and calm with a noted absence of wind. That’s the way we are set to stay through Monday save for a rain front that is due to affect The South West and south coast later this afternoon, pushing up into Central England and The Midlands through the evening. You can see the North-South divide in action today with a wintry 3°C for Scotland, 9-11°C for Central England and Wales and 6-7°C for Ireland.
Tuesday sees that overnight rain across the south of England pushing up through Wales, the north of England and The North East by morning rush hour. As it meets the cold air sitting still over Scotland it will turn to sleet and snow at elevation so winter is still knocking at the door for you guys I’m afraid. By lunchtime the rain has cleared The Midlands and will be affecting the north of England and still falling as wintry showers over Scotland. Ireland looks to have a dry day over most of the country save for some rain that’s into Kerry and will push north and east across into The Midlands through the day. By late afternoon we may just see that cloud cover break across Wales and the west to give a sunny end to the day. Temperature-wise very similar to Monday 3°C for Scotland, 9-11°C for southern England and Wales and 6-7°C for Ireland. Winds will be light to moderate south-westerly.
Wednesday sees a drier day on the whole but still unsettled with a risk of wintry showers over Donegal and the north of Ireland and the north-west of England / North Wales. Dull again with maybe a chance of seeing the sun down in Kerry but perhaps not for long as some wintry showers are due there during the morning. For the south, central areas and The Midlands, a dry, dull day, a little cooler than Monday or Tuesday but fine really when you consider where we came from. Through the afternoon we will see those wintry showers push up into Central Scotland and also some new rain fronts push into The South West and across South Munster / Leinster. A little cooler on Wednesday dropping a couple of degrees off the temperature for the day so 3°C for Scotland, 7 – 8°C for England and Wales and 6-7°C for Ireland.
Thursday starts dry for most areas except the north of England where we will see a re-occurrence of wintry showers and rain dependent on elevation and a consolidated rain front across The South West. The latter will quickly gather up its heels and sally forth into Central England, Wales and The Midlands through the morning with some rain also crossing Ireland from The South West. Still some wintry showers affecting the north-east of England but Scotland for once looks drier and sunny. At this stage that band of rain over England is due to only progress up to Nottingham sort of way so a wet day down south and forThe Midlands on Thursday. Ireland will see those showers cross through the day but you’ll also get a glimpse of the sun across the south-east of Munster. Similar temperatures to Wednesday but with a changing wind dynamic switching to more northerly for a brief time as we end the day.
We close out the week on Friday with a settled, dry picture across the U.K and Ireland save for some wintry showers crossing Scotland from The South West and also some snow showers across Donegal. Dull again as is the theme for this week but by the afternoon we should see that cloud break over Ireland, the north of England and The Midlands. Staying dry for pretty much the whole day with similar temperatures to the rest of the week but enjoy it because we have a deep low on the way 🙁
So you’ve probably guessed it already but the outlook for the weekend is most definitely unsettled with a deep low pressure pushing up from south west of the U.K. (Because the jet stream is low) Now of course timing is everything and it might not reach us till Sunday so if I wanted to try and get a dry day out there then Saturday would be my pick but it’s by no means guaranteed ! A clear sign that it’s heading your way will be the wind direction changing from south-westerly to south-easterly though temperatures will be up around high single figures so not bad. With the low coming up from the south it won’t likely reach Scotland till later on Sunday but I expect it to be pretty entrenched over Ireland and the southern half of England by Saturday tea time. Much windier at the weekend as well with winds easterly for the U.K and a chiller northerly for Ireland.
Ok so is the jet stream likely to take a hike north back to its usual place or will we stay in our cool trough ? So first off I consult my oracle – Metman James 🙂
As you can see from the above, the highly negative North Atlantic Oscillation (NAO) that followed the SSW (it’s all acronyms you know), we are slowly pulling back towards normal but as intimated in last week’s blog it won’t be until the middle of the month that we start to pick up a westerly airflow and a return to more typical March temperatures. Even then I can’t see us losing the cooler trough pattern in the jet stream. So my feeling is that we will continue cool and unsettled with a high chance of a re-occurring low pressure systems with a southerly orientation i.e they come in from the English Channel as opposed to The Atlantic.
So next week I think will start unsettled following that deep low pressure system that arrives at the weekend with frequent rain showers across the U.K and Ireland and a strong north-westerly wind. Now the North-South Divide is likely to continue so I expect Scotland to have more in the way of northerlies and wintry showers I’m afraid. Once that low has rattled through I expect a quieter time on Tuesday and Wednesday as we are between low pressure systems before the arrival of a new low pressure system into the south of the U.K on Thursday. This means a change back to strong easterly winds (likely to stay on the cool side then) and more rain for the end of next week. Now there’s not a lot of agreement in the models as we speak although on Jame’s GIF above you can see a dip in the NAO on Thursday 15th which will be that low pressure system I’m on about above.
If I really mystic meg it, I think we will be into a westerly airstream around about the 17th March and that’s when we will see a true return to March’s normal temperatures and critically better night temperatures, always the hand brake to growth.
Ok so since it’s the first blog of March I’ll take this opportunity to play ‘Spot the GDD in February’ 🙂
February GDD – U.K Location – Thame
So we can see that pretty much nothing went on at this location during February 2018 with nearly the joint coldest February we have recorded in line with 2010, but not as low as 2013.
I looked back at the SSW event in 2009/ 2010 and although it occurred earlier in the winter, we also experienced an SSW around February 9th, 2010 which is about 10 days earlier than the date of the SSW we experienced in 2018. You can see a great animation of the 2010 SSW here
So where am I going with this SSW analogy ?
Well looking back at the weather data from this location in 2010, it took 5 weeks from when the SSW occurred for the wind direction to swing back to westerly and temperatures to rise to their March normal. Interestingly this occurred on March 15th, 2010.
This suggests that it took the jet stream 5 weeks to swing back to normal after a negative NAO back in 2010.
Our SSW event occurred on Feb 17th so if we apply the same logic then 2nd-3rd week of March is a similar outcome. We also experienced SSW events in 2013 which saw extended cold weather right through till the end of March with heavy snowfall on the 25th March, 2013.
During late winter 2016, we also experienced an SSW and looking back at my data, that took 4 weeks to right itself, so we can tentatively conclude that on average it takes 4-5 weeks after an SSW event for things (NAO, Jet Stream, etc) to right themselves but as 2013 showed us, this isn’t always a cert.
What we need to see for certain to know we are on our way back to spring is for the NAO to return to positive and cold air to re-assume its place over the North Pole. Last week The North Pole wasn’t even freezing and was some +35°C warmer than normal due to warm air being pushed over the top of the blocking high pressure system.
Cumulatively speaking 2018 already represents a cold start to the year at this location when we compare it with 2017.
In 2017, we reached a cumulative GDD of 36 on the 3rd of February, this year we reached it on the 28th February so that’s a good 3 1/2 weeks behind last year already and I expect this gap to grow because in March 2017 we piled on the GDD.
In this week last year we recorded 26.5 total GDD at this location, this week I think we will be lucky enough to record 5-6 maybe, see what I mean about not being back to normal ?
What to expect in the coming week ?
Well depending on your location you may already have gone through a phase of rapid thawing yesterday when the air temperature increased and we had mild air temperature rainfall. This is always a difficult time on a golf course or sports pitch because the upper region of the rootzone thaws first and deeper down it is still frozen solid. Initially when only the extreme upper layer (10mm) thaws you can get a very unstable surface with the upper layer shearing off from the frozen lower layer.
Once the thaw has extended deeper into the profile then you gain stability and I believe less risk of surface shearing. The problem is the surface looks thawed and so Joe Public will want to get out there and play but if you have slopes / mounds etc there is a pronounced health & safety risk until the thaw sets in deeper into the profile.
Looking at the temperature profiles across the U.K and Ireland I would have expected most of England, Wales and Ireland to have gone through this thawing cycle yesterday but areas like The Lakes and the entirety of Scotland will still be frozen and receiving more snow turning to rain through this week so possibly your pain is yet to come I’m afraid 🙁
Microdochium activity – How low can you go ?
The other month I was fortunate enough to share the floor with Kate Entwistle at the BIGGA Turf Managers Conference when we gave a presentation on Microdochium nivale. Kate’s task was to briefly and I mean briefly (because I didn’t give her much time:) ) to give a microbial perspective on this disease (and Anthracnose as well). True to form, Kate did this with time to spare (Cheers me dears) and in her part of the talk she covered the temperature range in which Microdochium is active. Although its favoured growth temperature is around 20°C, it’s main temperature range for infection is 0 – 15°C, but it is capable of completing its life cyle down to -5C.
So I took some soil temperature readings under the snow canopy last week and the average was 1.6°C, in other words not frozen even though we went into the snow cover rock hard.
So it is no surprise to see images like this of an old disease scar plug with new activity present emerging from the snow cover. This clearly suggests that disease development continued under the insulating effects of snow cover. Whilst we can expect to see cases like this with new activity around an existing disease scar, I’d be interested to know if anyone sees new infection during the same period, so please send me your feedback.
Things to do….
Now obviously if you’re reading this still staring out the window at snow drifts or a flooded surface, you can disregard the next paragraph. It’s a fact though that some regions of the country will dry quickly after this thaw and therefore some of you will be able to get out.
First off we have a pretty wetted-up moss plant so now is the time to hit it with an approved High Fe Mosskiller if you were thinking of applying it in the spring. It’s probably too early still for the chemical Mosskiller’s (Mogeton and the like) until we can clearly see the other side of this post-SSW weather event and so are guaranteed good grass growth. Species like Silver Thread Moss have to be fully wetted-up prior to application to gain any kind of benefit so the next couple of weeks could be an ideal time for treatment if a growth window presents itself.
Secondly, if you are planning aeration or carried it out just before the SSW event then you’ll be looking for some growth and recovery. Now obviously it’s staying cool with only a small amount of growth but for me this week would be ideal to apply either a liquid tonic when the air is warming or a granular feed if you need to promote more in the way of growth for longer because we have good levels of soil moisture and some rain throughout the week to enable granule breakdown and then recovery.
It goes without saying that your N sources in your chosen products should be immediately-available if you are looking for a plant response, so that’s ammonium sulphate, nitrate and / or potassium nitrate at this time of year rather than something like urea which isn’t immediately-available to the grass plant.
Urea requires the presence of an enzyme to catalyse the conversion from unavailable nitrogen to available nitrogen and since that enzyme will be in short supply in a cold soil, don’t expect anything to happen quickly with urea applied to the soil in the spring. With low soil and air temperatures giving low Growth Potential / GDD, there’s no point in applying lots of N in either form because it won’t be utilised so small N inputs are key, 4 – 6kg / N / Ha as a foliar / liquid or 12- 15kg / N / ha as a granular.
I like to split my N forms at this time of year between the immediately-available and the slowly-available, be that urea or organic N, so you get a quick response and then some longevity as well as the more longer-term N is released. Horses for courses though.
Ok that’s it for this week, remember to let me know what you think are the key parts of this blog for you and if you’ve seen any disease activity after the thaw, new or old.
All the best.