Well the longest day has passed us by and it is all downhill now to winter from a time perspective. On balance after enduring 4 x 30°C days in a row last week I don’t think I’m a fan of summer anymore. Especially not when it brings out the worst in peoples behaviour. (we had 100 youths in the park behind me generally behaving anti-socially all last week culminating with an iron bar fight at some ungodly hour in the morning…….which was nice)
Now sleep and me don’t go together at the best of times but last week was a p.i.t.a. Waking up on Saturday morning and having to put an extra layer on before heading out to fly fish was just nice and that suits me.
It probably suits the grass and crops alike a bit better as well.
This photo of a Winter Barley field I took whilst out on a pleasant yomp yesterday kind of sums up the coming week from a weather perspective.
Dull, gloomy, windy and occasionally wet but I’ll take that any day over last week.
It’s not difficult to pick out the source of the wind when you look at the GFS reading for today, courtesy of Tropical Tidbits.
It’s the kind of weather pattern that wouldn’t look out of place in October or November, so let’s see how our week stacks up.
General Weather Situation
So we start off Monday with as you can probably guess an unsettled weather picture. With low pressure sitting north and west of us it shouldn’t come as a surprise that that’s where the bulk of the rain is going to be today. Really anywhere from The Wash northwards I’d say looking at the current radar with the north and north west likely to pick up the brunt of it again after enduring a wet weekend. So currently we see rain over Northern Ireland, a rake of showers across The Irish Midlands and heavier rain straddling a line drawn up from North Wales across the north of England and into The North East. There’s also a heavy looking rain front over the west of Scotland. All of this rain will by and large track north eastwards through this morning and be followed by showers across the north and west of Ireland, England and Scotland. Further south and east of this rain, it looks to be largely dry, dull and windy with the odd sunny interval and of course it’ll feel cool with temperatures in the mid to high teens. The wind will be strong and from the west. Quite a temperature differential across the U.K with the south maybe nudging 20°C and Scotland under heavier skies and rain barely making the teens all day 🙁
Overnight into Tuesday, most of that rain fizzles out but there will still be rain across Central Scotland. The low pressure system is projected to run out of puff on Tuesday / Wednesday but it’ll still be windy and we will see rain push across Ireland from the off on Tuesday and into the south of England. At this stage it looks like the bulk of the rain will run along The South Coast with some across the north of England and Scotland. In-between we look to stay largely dry, cloudy with some sunny intervals, but still with a brisk to moderate wind, maybe a little down on Mondays in terms of strength. Tricky ultimately to determine where and when those rain fronts will and won’t affect, so I suggest cranking up the radar tomorrow morning and assuming any rain you’ll see will be on a west-east trajectory.Temperature-wise, similar to Monday though Scotland will edge up into the mid to high teens after that chilly start to the week.
Mid-week beckons and more unsettled weather to kick off July with as we will see showers across Ireland, Wales, the north west of England and Scotland. There’s a suggestion that although these showers will be more westerly-focussed, as they were earlier in the week, they may push more eastwards through the course of the day so later we may see more consolidated rain push into The Midlands and Central / Eastern England. Lighter winds on Wednesday as that low begins to run out of puff so feeling a little more pleasant if you aren’t under the rain. That rain over Ireland incidentally looks to be more easterly-focussed from Cork up the east coast to Dublin, with the west looking drier. Similar temperatures to the rest of the week, high teens the order of the day in this ‘sunshine and showers’ April type of week.
Thursday looks to start a lot drier with just some rain early doors across the east / south-east coast of England. Enjoy it though because there’s a very ominous looking dump of it appearing on Meteoblue’s weather chart out in The Atlantic. So on the whole a drier day on Thursday with just a threat of some showers along the south coast of England, Wales and The North West, nothing too heavy by the looks of it. Some of these showers may push inland through the 2nd half of the day. With light winds it’ll feel pleasant in the high teens sort of temperatures projected across all of the U.K and Ireland, but enjoy it because it’s only a temporary respite from more wind and rain at the end of the week. Definitely the driest and most pleasant day of the week.
So we close out the week on Friday with that front of heavy rain making landfall across the west of Ireland around midnight. By dawn this rain will be across Ireland and into the west of Scotland and it’ll be heavy in places. During the morning this rain front will push into the north west of England and Wales clearing Ireland temporarily as it does so but there’s more to come here. Away from this impending rain, the east and south of the U.K will stay dry and pleasantly warm with temperatures nudging into the high teens / low twenties. The imminent arrival of more unsettled weather will be signified though by the strong westerly winds. During the 2nd half of Friday, that westerly rain will push into more central areas though the east will remain dry throughout. So a pretty wet day for Ireland, Wales, Scotland and the north of England, drier across central and eastern parts.
With Friday’s arrival of more wind and rain, it should come as no surprise that the weekend may turn out to to be a re-run of the last one, that is windy and unsettled. Saturday sees that rain cross Ireland but initially remain westerly and northerly-orientated, but through the day that rain will push east and south into pretty much all areas during the day, clearing Ireland as it does so. It looks at this stage like the south and south east of England will miss most of it unfortunately but it is summer rainfall so it can and probably will change by the weekend. Sunday sees heavier rain overnight across Wales and central areas of the U.K and this looks to straddle the south and east of England by dawn. Some of this rain looks pretty heavy. As the low passes across the southern half of the U.K, the trailing edge will drag down northerly winds so Ireland and the west of the U.K will feel noticeably chillier on Sunday as the wind swings round from south westerly to north westerly. Scotland looks to miss the worst of the rain which looks to stay southerly-orientated through most of Sunday. There may be some sunny intervals as it clears but it’ll feel chilly for early July. Hopefully a park clearer.
Above you can see our projected GFS situation at the start of next week with the cool low that brought us an unsettled weekend heading off to Scandinavia.
The weather projection for next week is really determined not by what we see above but by what is following through from The Atlantic. At this stage it is projected to be low pressure that’s just visible on the left hand side of the image. This low will push in unsettled weather strong winds and rain from the west through the course of Monday with rain expected for Ireland before this crosses The Irish Sea and pulls wetter weather through the 2nd half of Monday and Tuesday for the southern half of the U.K. Scotland and the north will miss the worst as it stands now. Wednesday looks to remain unsettled with showers before a new low arrives for Thursday. This one is projected to track further north and so it’ll be the north and west that gets the rainfall and stronger winds whilst the south stays relatively dry and pleasant. After that it really is mystic meg stuff. Will the alternating peak and trough pattern continue or will one dominate ?
Soil Moisture Deficit and E.T
Last week’s high temperatures accompanied by moderate to strong winds made life tricky from a turf management perspective.
As predicted, daily moisture loss by E.T topped 6 mm at some locations and it wasn’t till the weekend that we picked up some rainfall. (for some)
It is easy to forget when I talk about soil moisture deficit that across The Irish Sea and Scotland, last week they had low pressure in charge so E.T stress wasn’t actually much of an issue.
Here’s how the week looked across 4 different locations from 22/6 – 28/6 ;
Location Rainfall E.T Soil moisture deficit / surplus
Sevenoaks, Kent 2.6 mm 33.11 mm – 30.51 mm
Thame, Oxon 5.8 mm 36.85 mm – 31.05 mm
Northampton, Northants 9.8 mm 35.46 mm – 25.66 mm
Blessington, Co. Wicklow 9.2 mm 16.20 mm – 7.00 mm
The highest E.T measured was at The Oxfordshire on 26th June, with a figure of 6.6 mm, below is how the day broke down from a temperature and E.T perspective ;
I assumed (incorrectly) that the E.T would be at its highest when the air temperature was likewise but as you can see from the graph above, the E.T peaked at 14:00 and the air temperature at 17:00. The reason why the E.T peaked earlier was due to the wind which was 7-8 kmh up until 14:00, but then dropped away reducing the water loss from the canopy. I forgot to chart humidity which peaked at 06:00 in the morning at 78% but by the time we reached the peak E.T / temperature was down below 50%. Having low humidity actually helps the plant to maintain its osmotic balance because it is able to lose moisture to the atmosphere in order to cool itself (think stepping out of a shower on a hot day and feeling your body temperature drop as water is evaporated off your skin). In certain locations around the globe, they experience higher temperatures and higher humidity and here it is much harder for the grass plant to cool itself because it can’t lose moisture to the atmosphere because it is already saturated or close to it anyway.
The shower analogy also relates to another turf maintenance practice during periods of high E.T and that is syringing, that is applying small amounts of irrigation to the turf canopy in order to cool it. I was reading an interesting article on syringing in GCM the other day (you can view it here) that concluded that the temperature reduction was pretty short-lived (10-20 mins only) and if it was windy it was relatively inefficient. In addition, syringing also increased soil moisture levels in the surface which at certain times of year may be detrimental from a disease / agronomic perspective.
Wait here I think we have been here before…(did you see what I did there 🙂 )
One such disease that’s been very much in evidence of late has been Waitea Patch. Its appearance is particularly linked to high soil moisture levels in the turf surface. Waitea Patch is a Rhizoctonia species (Rhizoctonia circinata var. circinata) and one of the clues concerning its appearance is given in its latin name i.e. circinata, which translates unsurprisingly to rounded or circular. It tends to form ‘nice’ circular yellow patches on greens, these may merge into combined patches and even heart-shaped double rings (ah bless). Often it can be confused with Superficial Fairy Ring but the patches tend to be more regular, circular shaped, they don’t tend to be associated with a mushroom smell, if you cut a section out of the affected area and smelt it, and the patches don’t tend to be sunken, depressed ( as no organic matter breakdown takes place)
Sometimes, well most times this is all you see, it comes and goes with a low likelihood of turf loss. That said if it occurs at a time of high E.T loss, you can see turf damage in a similar scenario to Superficial Fairy Ring, though for different reasons. Waitea Patch loves moisture and so its presence is encouraged by surface organic matter (SOM) that holds more moisture but it doesn’t need excessive SOM to become prevalent. High levels of soil moisture either / or due to over-irrigation / hand-watering and / or heavy rainfall in combination with high air temperature > 25°C are the key drivers. If you look at the run of weather we have had of late with periods of high temperature followed by rainfall, some it localised and heavy, you can understand why it is more prevalent this year than most. Poa annua tends to be worst-affected as a grass species but it has been reported on bentgrass in other countries. Control-wise, dealing with the cause rather than the symptom is the best and cheapest option, that is, lowering soil moisture content. Now if we are in a run of wet weather that isn’t a particularly realistic scenario I know :).
Interestingly when it first appeared over here (July 22nd, 2011 according to my records) I carried out some fungicide trial work and ‘most products’ I applied at that time worked really well. Of course most of those ‘most products’ aren’t available anymore but I am duty bound in terms of writing a reasonably impartial blog to observe that the only product still remaining that did work is Azoxystrobin. Also interesting was that we didn’t have particularly high temperatures leading up to its appearance but we did have exceptional daily rainfall events, so maybe it doesn’t need as high temperature to appear as the State-side variants ?
This year continues to be ‘not a Poa year’
Now some of you may read that title and rejoice, particularly if you are maintaining a sward where you are trying to minimise Poa annua or maybe encourage one or more of the so called ‘finer grasses’. I don’t subscribe to that particular philosophy myself because I believe all grasses have a place and all grasses have baggage, it just depends on which one or more species suits ‘your place’ and how you are equipped to ‘manage the baggage’ that comes with it or them. Whatever your MO, this year has been a hard one for Poa annua and I’ve had a number of end-users comment on this fact even compared to 2018 when we had those really hot temperatures and sustained high E.T / lack of rainfall.
The reason why it has been and remains a hard year for Poa comes in the timing of the stress event.
If we look back at 2018, using the rainfall / E.T / Soil moisture deficit graph above we can see that the main stress period really started at the end of May, though there was a blip before that. If we look at 2020, we can see we entered soil moisture deficit at the end of March but the continual downward trend really started at the end of April.
Bearing in mind most years Poa annua starts to seed at the end of April, beginning of May and does so for 4-6 weeks, we can see that in 2018, Poa annua was just about through its seedhead period before the stress really started to kick in. In 2020, the stress period started just at the point Poa annua was beginning to produce seedheads and that’s why 2020 has been and continues to be a difficult one for people managing Poa annua greens.
I’ve shown this on the graph below.
Given the fact that Poa annua has been producing seedheads from early May and experiencing stress at the same time, it is a fair assumption that periods of high E.T like we experienced last week will both prolong the seedhead production period and result in a weak Poa annua plant.
This combination may present us with a disease problem. Here I am pointing the finger towards Anthracnose and after a weak ‘signal’ at the end of May, the high temperatures followed by rainfall last weekend (for some) and this week respectively, must surely constitute a very strong signal for this disease. Now we know this doesn’t always mean that we see significant disease pressure but bearing in mind how early the stress started on Poa this year and how strong the most recent signal has been (air temperatures > 25°C for 4 successive days followed by rainfall and humidity in some locations), I think it is likely we will see a high incidence of Anthracnose this year. That said we also need a period of prolonged plant leaf wetness (heavy dew) to facilitate fungal growth and that has been a bit ‘hit and miss’ over the weekend. It’s going to be an interesting one to observe.
OK, Tempus fugit and all that, I must fly….
All the best.