This time last year we were sitting looking at a trough in the jet stream that resulted in August 2014 being a cool wet month with frequent rain and low temperatures. This August so far has been a mixed bag, cool and wet for the west and north, but in central and southern regions we are dry once again however that may change this week with the formation of a low pressure system to the south of the U.K later in the week. If this forms as predicted it’ll be a case of role reversal with the south copping the rain and the north missing a lot of it…but we’ll see as continental rain is a fickle beast at times..What’s for sure is that August 2015 will see more troughs in the jet stream just like prior years so cooler and wetter is the prognosis going forward.
General Weather Situation
So for the start of Monday we have rain fronts pushing into the south west of Ireland, England and Wales and along the north west coast including Scotland. This is already giving heavy rain in these areas and this rain is set to move diagonally north-eastwards across the respective countries through the morning so a wet start to the week for Ireland, Wales, the south-west of England and the west coast. By late morning more rain will have pushed into the west of Scotland and moved into central Scotland. Further south the rain pushes inland but will principally affect a line northwards of and along the M5 up to The Wash so just skirting south of Birmingham. By late afternoon the rain will have cleared most of Ireland save for Donegal, but will be entrenched across all of Scotland and the north of England. The south east will sit dry for most of the day with just the risk of an odd shower pushing into the south of England. Temperatures will be variable, mid-high teens in the rain and low twenties in the south of the U.K. Winds will principally be from the south west / west and light to moderate in nature.
By Tuesday this rain will have cleared all but the far north-east of Scotland and northern Highlands to leave a dry picture over all of Ireland and the the U.K. Initially dull with heavy cloud cover in the north, this will break through the day to give some longer spells of sunshine and pleasant temperatures, high teens in Scotland and low twenties in the south. Winds will be lighter than Monday so a good spraying day for anyone considering it.
Overnight into Wednesday this is when things start to get a bit tricky to forecast because we have a continental low pressure forming in the Bay of Biscay and this will push moist air up into the south of England from mid-week onwards. Early Wednesday morning there’s a risk of some rain pushing into the south coast of the U.K and possible the far south east, but it’s one to watch closer to the time. For the rest of the U.K and Ireland we have another pleasant summers day with warm temperatures possibly pushing into the mid-twenties in the south and high teens for Ireland, the north west and Scotland. The wind will again be light but the warmer air in the south is due to a switch round in the wind to the east which heralds the arrival of the Bay of Biscay low pressure for Thursday.
So overnight into Thursday is when life gets interesting as that low pressure system pushes heavy rain into the south west of England and along the south coast. Now with warm air sitting over us and moisture pushing in, I think this is likely to mean some thundery outbreaks through Thursday as the two air masses meet. By the Thursday morning rush hour that rain looks to be pushing up to The Midlands with the heaviest bursts over Wales and the south west of England. Ireland should miss the worst of it but you never know with this type of rain event if it’ll swing westwards and push into south east Leinster / Munster. Further north away from this southern rain front, it’ll be dry and pleasant with warm hazy sunshine, your turn to have some nice weather whilst others have the rain 🙂 Throughout Thursday the rain is set to slowly push northwards and at this stage the heaviest rain is projected to be a band up from The Isle of Wight across Bristol and into South Wales. By Thursday evening some of that rain may just be into the east coast of Ireland and The Lake District / Borders, but all areas look to be getting more than a drop with 20mm+ threatened along the south coast.
What you’ll see if you’re using Weathercheck is that the daily projected amounts for Thursday and Friday will change almost hourly as we get closer to the rain event because they have more idea where the rain is actually going. Winds will again be easterly, perhaps with a sniff of north-easterly for a time so a cooler feel to Thursday with high teens the order of the day in the south of England. Ireland may finish damp along the eastern coasts as we move into Friday.
Overnight into Friday that rain won’t have left us as the low pressure system sits off the north east coast of England. So we expect another unsettled day for Friday with some heavy bands of rain swirling across the U.K, with rain right from the early hours for Scotland as well. Right is an image of how it looks for the start of Friday and you can clearly see the swirls of rain pushing anti-clockwise across the U.K. This rain will push north through the day reaching Scotland by and at this stage it looks like the west and east coasts will get the bulk of it as it does so. Ireland as you can see from the graphic should miss most of this rain but it all depends on where and how the low pressure tracks. By close of play Friday the rain is confined to a line stretching up the east coast from The Humber to The Shetlands. Again cooler in that easterly air flow so high teens the order of the day for Friday.
So how are we looking for the weekend ?
Well not too bad actually with Saturday looking a little cloudy and unsettled in the north west, particularly over Scotland where it’ll be dull and cool with low teens disappointing for August 🙁 Further south we look to have a reasonable day but like the north it’ll be on the cool side with only mid to high teens likely. It does look dry on the whole though with light westerly winds.
Sunday is looking a better day as high pressure asserts itself and pushes that low away. So a little more in the way of sunshine and temperature but only touching twenty degrees in the far south. To the west and north and over Ireland, expect high teens but crucially dry in light westerly winds.
Another tricky one to forecast because of the battle between high and low pressure. Monday looks like being the quietest day of the week with light winds and cool temperatures, but crucially dry for most areas with just a risk of some light rain crossing the west and south of the U.K. By Tuesday we have another intense Atlantic low pressure system set to swing in though there’s some disagreement in the models as to how this may manifest itself in terms of how far south it comes. Presently it looks like the low will begin to affect Ireland and the west coastline of the U.K on Tuesday with increasing winds and rain before it pushes across eastwards to bring more rain and wind to the U.K as a whole. As always with an Atlantic low it’ll be the west and north that receive the majority of wind and rain so an unsettled week on the cards after Monday. For the south and south east it should be drier on the whole but staying on the cool side everywhere as that low pressure systems forms another trough in the jet stream, par for the course now for August it seems. So I’d expect mid-teens in the rain-affected areas and up to twenty in the south and south east next week.
It’s sometimes tricky to write this blog knowing that say the north and west have endured a pretty wet last two weeks whereas the central and south of England has been dry and warm with some pretty high E.T figures over the last few days. Saturday hit 26.5°C here in The Midlands and was still low twenties going into the evening. One size hat doesn’t fit all in for sure but I hope you can bear with me this week when I try to cram you all into the same one ! 🙂
Anthracnose Basal Rot Alert
Looking at the diverse weather patterns we have had this summer (heat early in July, wet end to July, wet for the north and west in August and dry for central and southern areas of the U.K) I think we are likely to see more in the way of Anthracnose Basal Rot this year rather than the Foliar Blight. With this in mind it is key that good aeration practices are adhered to in order to keep surface drainage functioning and allow the rootzone to breath. Oxygen is key to turfgrass growth and there is simply no substitute to punching holes in surfaces that allow growth-limiting gases like hydrogen sulphide to escape and for this to be replaced with oxygen. Remember call it ‘venting’ rather than aerating to keep the masses happy 🙂
With heavy rainfall it is very easy for areas to be hypoxic (oxygen limited) and this in turn will reduce the ability of the grass plant to grow so having a rootzone that can cope with rainfall and ensuring you have light channels (ideally filled with sand) through the surface organic matter layer is crucial. Grasses that are growing in a low oxygen environment don’t often show symptoms till it’s too late. Fertilising alone could actually make the situation worse as the grass plant tries to take up more oxygen in order to support the growth initiated by the fertiliser application but is unable to do so because there are insufficient levels in the rootzone. So my first advice whether you’ve had wet weather and have a dry week this week or are dry and expecting rain this week is aerate and topdress to keep the surface functioning.
Cool Weather Nutrition
The second issue is more nutritionally-orientated. Looking at this week and next we can see that temperatures will be cooler than normal for August, although I would argue that this is now the norm for August with the peak of temperature occurring in July. If you have Weathercheck you can clearly see the predicted drop off in growth as the cooler temperatures are set to arrive in both the GDD and G.P graphs shown below ;
So if we do indeed go cool and wet then liquid fertilisers will not give the longevity nor the speed of response, especially if they are summer-orientated analysis with high urea and / or a slow release content. So you have two options depending on how your turf is looking ;
- If you have good sward integrity and just want to keep things ticking then I’d look to use a light rate liquid that is more orientated towards lower temperature-available N forms like ammonium sulphate and potassium nitrate. As a guide I’d want at 50% of my nitrogen to be derived from this type of nutrient source in water-soluble or liquid form. You’ll want to use iron as well with that application because the cooler air and high rainfall levels will take the colour away quite quickly and my advice would be to apply from Tuesday onwards in the south before the rain arrives and get it into the plant whilst we still have good conditions for uptake.
- If you need to push on some growth, recover sward density, etc, often an issue on non-irrigated areas, then I’d be looking to apply a light rate granular product with at least 25% of the nitrogen from ammonium and nitrate sources so you get a good response during the cooler temperatures.
The last issue will be notable I think in the north and west and due to appear once we have rainfall in the central and south areas and that is Etiolated growth.
I noted some newly-published research earlier this year from the USGA because it’s an issue in the U.S on Bentgrass and Poa swards so they are throwing some money at it to try and understand what’s causing it. ($70,000 over 3 years is significant I think !)
Last year when I wrote about this subject I suggested that I’d seen and had feedback along the lines that PGR applications of Trinexapac-ethyl (TE) made the phenomenon worse. I received a number of comments that didn’t agree with this observation and in fact suggested that turf showed less etiolation when under the effects of TE than when not. Now it’s interesting because the latest work from the USGA carried out at North Carolina University which you can download here suggests that the effect is indeed exaggerated by applications of TE and their advice is to reduce the frequency of applications of TE if you are affected by the symptom. They also have the luxury of being able to use different classes of PGR’s that affect Gibberellic acid production at different points in the pathway to still gain regulation without the potential side effect of encouraging Etiolated Growth. All well and good ? Well no, because I still don’t think we have the answer and for sure I’ve seen Etiolated Growth on areas of turf that have received no PGR application. Their summary is that more work is required to isolate the bacteria or fungi that stimulates GA production in grass plants affected by Etiolation.
So if you’re seeing this issue please feel free to drop me a comment either related to TE applications or anything else that you’ve seen that either appears to encourage or better still decrease the severity of the effect.
Ok that’s it for now, have a good week, keep an eye on that rainfall because believe me it will change from today’s forecast !
All the best.