July 13th

Hi All,

Two pictures that kind of sum up the last week of weather…(thanks Ben / Lee)


So first we had a good drop of rain, here it was just over an inch in old money and so so welcome to crops and gardens alike unless you’re cutting hay that is. Not that it was too much of a problem with the latter because after a few days of drying winds, farmers round here were busy cutting hay and a good crop it looks too. As I was walking yesterday I was watching a farmer bailing hay, it looks so neat doesn’t it ?

Following the tractor weren’t Seagulls but Red Kite, hopeful of picking up a free meal, it just shows how nature adapts to our ways.


Some beautiful flat-bottomed clouds as well, I snapped this yesterday whilst on an early morning mountain bike. I don’t like stopping when I’m cycling but sometimes you just have to. These cloud formations are commonly known as ‘Mares’ Tails’ and signify high winds in the upper atmosphere. I always associated them with high pressure but the old sailors proverb “Mares’ tails and mackerel scales make lofty ships to carry low sails.” suggests otherwise. According to weather experts, these clouds are called cirrus uncinus (translated to curly hooks) and often suggest that rain may well be on the way (or that low pressure is advancing)

Just before I move onto this week’s weather I did note another proverb in the same article which intrigued me…..it goes something like….. “Mackerel skies, Mackerel skies, seldom long wet and seldom long dry”

Now again I’ve noted this on more than one occasion of late and I wonder how apt it is…Pretty appropriate I’d say…

So as we start the week, is this true, is the old proverb correct ?

Well pretty much yes….for some…

So here is the actual GFS output for today and I have to say if you look back at last week’s blog to the GFS projection for today, it is pretty much bang on. Fair play to the GFS algorithm 🙂


So we have high pressure currently influencing our weather and it was responsible for such a beautiful weekend. Not too hot, not too cool, not too bright, not too windy…just perfect in my books and accordingly I crammed in fly fishing, mountain biking, a lovely country walk and a cracking blat on my BMW R9T,  which even included two police bikers nodding approvingly to me (not that they would have nodded approvingly  5 minutes beforehand mind as I energetically applied myself to some of my favourite corners  :)….Onto the weather before I incriminate myself further…

General Weather Situation

So indeed yes we have a low pressure system edging into view north west of Ireland / Scotland and this will push some rain into Monday’s weather picture. So Monday starts dull for many as that low pushes cloud in ahead of it and rain as well into the west of Scotland, north west of England, North Wales and northern England. They’ll be some rain for Kerry as well, quite a dump actually. This rain will push south and east through the course of Monday morning, fizzling out as it does so. It may reach The Midlands later in the morning but doesn’t look to trouble areas south of The Wash until later in the day. Talking about later in the day we will see more rain pitch up across Scotland, The South West and Wales and this will push eastwards later this evening. The same is likely across Ireland as rain moves into eastern counties late in the day.  So a mixed day for some, sunshine and showers, cool in the west and north with temperatures in the mid-teens, warmer in the south and east with temperatures nudging up into the low twenties. Winds will be moderate from the west and picking up in the south through the day.

Onto Tuesday and the centre of that low is now sitting above Scotland so we should expect most of the cooler, wetter weather to have a northern rather than southern theme. A dry, if a bit dull, start for many but across The Irish Sea it won’t be long before rain arrives across the beautiful counties of Mayo and Sligo, where I plan to cast a line sometime in the near future. This rain will push east during the morning towards Leinster but further south across Kerry and Cork you should stay largely dry. A hop, skip and a jump back to the U.K (never the mainland you understand ?) and we have a pretty dry, dull and settled picture for Tuesday. There’s a chance later in the afternoon of that rain affecting the west and north west coast of Scotland, maybe a little further south as well across The Lakes but other than that we look dry. Again there’s a risk of some showers popping up along the south coast later in the day, but better to view your chosen rain radar for a handle on that. A feature of Tuesday will be a shift in the wind to a more northerly direction and that’ll take the edge of the temperatures, so mid teens for Ireland and Scotland and high teens, maybe low twenties down south.

Mid-week beckons and Wednesday sees that low moving away and high pressure trying to push in again from the south west of Ireland. Now as we know by now high pressure rotates clockwise and so the leading edge of a high like this will pull down northerly winds as it moves in. So continuing cool on Wednesday, cloudy but largely dry. There will be a continuation of those showers affecting the west coast of Scotland but nothing much more than this. Maybe later in the day some of those showers move inland across Scotland and North Wales / the north of England but nothing major. All in all, dull but dry and remaining on the cool side for July with mid-teens continuing across Ireland and Scotland and high teens for England and Wales. The wind will be light to moderate and from the north.

Thursday dawns and we carry on that dull, cool feel to the weather with that high pressure continuing to pull in cool north / north westerly winds. As with the rest of the week, any brightness will be along eastern coasts. So during Thursday morning we see a continuation of the showers proliferating along the north west coast of Scotland. During the course of Thursday some of these will push more inland into Central Scotland. Further south and west we remain dull and on the cool side but during the morning that cloud will break to give some sunshine across central and eastern England with the west staying cloudy. So another largely dry day, dull but with more sunshine. That north west wind theme for the week continues and that means similar temperatures to Wednesday, mid to high teens depending on where you lay your hat.

Friday sees a new Atlantic low try to exert itself and so that high pressure doesn’t appear to dominate (as first projected to). This low will push bands of rain into the north and west of Scotland and Ireland early doors on Friday. This rain will then try to push south and east but at this stage is projected to fizzle out. So it looks dry and dull again for England and Wales on Friday. Later in the day we may see some showers push in across the north west of the U.K and also for the south west coast of Ireland. Further south the cloud cover is expected to break up a little and that’ll up the temperatures significantly so we may be talking low to mid-twenties across the south of England to end the week. That rise in temperatures will also be felt across Scotland and Ireland despite the cloud cover with temperatures nudging up into the high teens. Not a bad end to the week that.

So with low pressure north west of the U.K and high pressure to the south west, how does the weekend look ?

Saturday sees that low push rain across the west of Scotland and the north of England / Ireland. Some of this rain may push into Wales and The Midlands. It’s a north-south divide on Saturday because further south, high pressure will hold the reins and that means temperatures will push up into the low to mid-twenties again. Later on Saturday that rain will fizzle out and the cloud cover will break to give some sunshine over central and southern England. The same is true for Ireland, with the north and west dull with rain, but further south you should see some pleasant spells of sunshine after any early rain moves off. Further north that rain continues across the north west of Scotland and intensifies as it does so. Winds will be more westerly on Saturday. Sunday looks to be drier from the off and maybe a little brighter with lighter winds. That rain will continue to harass the north west coast of Scotland but elsewhere it looks dry and warm, particularly across the south of England with temperatures in the low to mid-twenties again.

Weather Outlook

So above is the projection for next Monday using the GFS (Global forecasting System) output.

As you can see we continue the weather theme we embarked upon early in June with high pressure and low pressure both influencing our weather, Mackerel skies and all that…

So the outlook for next week at this stage is for that high pressure to nudge north and eastwards and dominate most of next week’s weather. That means dry and settled with any rain likely in the north and east but principally we will be warm but not hot so I think low twenties, maybe a bit higher further south. Later in the week the projection is for low pressure to move this high onto the continent and push cooler, fresher weather with rain in from next Thursday onwards. This could point to an unsettled weekend.  So not bad really and if we continue this pattern I will be a happy camper 🙂

Agronomic Notes

Something I wanted to do last week but ran out of time (story of my life) was to compare at low E.T day with a high E.T day to show you what the actual drivers are because it might surprise you (as it did me)

Now just as a quick refresher we know the grass plant and the rootzone loses water to the atmosphere due to a number of factors, not least solar radiation, atmospheric pressure, air temperature and humidity.

This loss of moisture is estimated / calculated using a very complex formula known as the Penman-Montieth calculation and the calculated E.T value is used by many turf managers to estimate how much of this theoretical water loss they need to replace. I say ‘many’ but that isn’t strictly true because to get an actual calculated E.T loss from your site you need a weather station ideally and not many people have one unfortunately. We also know that the calculation for managed turfgrass over-estimates the water loss because if we replace 100% of E.T, we end up with the equivalent of a paddy field !

Typically a golf course superintendent may replace 50-60% of calculated E.T loss through irrigation and he may or she may then monitor the effectiveness of this strategy by using a moisture meter.  The subject area I want to talk about today is just what makes a high E.T day ?

So the the day I was doing some data downloading from a weather station and I expected to see quite a high E.T figure for the day, but I was wrong, it was much lower than I expected.

Conversely this morning I was looking at some data from a weather station for yesterday and I was pretty surprised at how high the E.T loss was.

So first up I’ve charted out the two respective days side-by-side…Here they are below ;

So  I am comparing the 8th of July with the 12th of July, the former had an E.T loss of 1.79 mm for the day (which would be regarded as pretty low for the summer) vs. the latter which had an E.T loss of 5.79 mm (this would be regarded as pretty high)

Looking at the two days on the graph above, you can see the temperatures aren’t really that different, the 8th had high teens and on the 12th the temperature just nudged into the twenties, no great shakes there. Certainly not hot days by any means. Then we look at the wind,it was 9.7 km/h on the 8th and 8 km/h on the 12th, so it was windier on the lower E.T day. So far, so perplexing, because the temperatures aren’t that far apart, the wind speed is higher on the lower E.T day but the fact is that over three times more water is lost on the 12th than the 8th. How so ?

Well the biggest driver to E.T loss between these two days was the humidity.

On the 8th, it was a humid day and so at the point in the day when most water was lost (13:00 on both days), it was 90% humidity, which means the air was pretty saturated with water vapour.

Look across to the 12th of July and at the same time (13:00) we can see that the humidity was only 45 % . This means there was a relatively low amount of water vapour in the atmosphere. Now imagine that humidity acts like a sponge. If it is already wet (saturated which means the humidity would be high) it has a relatively poor ability to soak up more water whereas if it is dry then it can soak up much more. This is how humidity affects E.T.

The more saturated the atmosphere, the lower the potential for water to be lost from the soil and grass plant. We see this ourselves when we sweat, a process akin to the grass plant losing moisture in order to cool its surfaces. In dry, warm climates we sweat a lot and it is evaporated from our body in order to cool it. In warm, humid environments, sweating does not act as an efficient cooling mechanism because moisture cannot be lost from the skin surface to the atmosphere because it is already saturated. The same occurs with the grass plant and means on hot, humid days, it is not able to effectively cool itself and it also means if you syringe turf, you’ll get very little benefit because that applied irrigation will not evaporate (and therefore cool) the grass plant.

So the big learn from my perspective is the part humidity plays in terms of E.T and therefore irrigation requirement. Sometimes I look at the forecast data and fail to recognise that a drop in humidity will mean a much higher E.T loss potentially and therefore a higher potential irrigation requirement. Now E.T loss isn’t all about humidity but it is a major driver. Look again at the examples above, similar temperatures and wind speeds but very different humidity levels and consequently E.T loss.

Food for thought maybe ?

Dollar Spot (Clarireedia homeocarpa) 

The first thing the eagle-eyed amongst you may have noticed is a change in the latin name for this disease, It used to be called Sclerotinia homeocarpa. Now there has been much debate about this disease and its taxonomy and this debate has gone on for the last 83 years or so since the pathogen was first linked to a turfgrass disease.  Plant pathologists are it has to be said, a really sad bunch (I can hear Kate E expressing her displeasure almost as I type but I know she’ll be smiling as well 🙂 ). The fact that they get so hooked up on this when all the course manager wants to know is “What is it and how do I get rid of it ???”

Well life isn’t that simple with this disease 🙂

Take where we see it occurring as an instance…..

In the U.K & Ireland, we may (may) see the odd Dollar Spot lesion on a golf green, popping up at the same time most years and on the same greens, but we very rarely (unless you tell me different) see it cause a widespread issue on greens. The fact that a Dollar Spot lesion looks very similar to an un-repaired pitchmark means that most golfers won’t draw attention to it either 🙂

On the continent, latterly in Scandinavia, France, Germany, Austria, Switzerland, Spain, Italy and lets not forget Portugal, it can be a very aggressive disease of greens as well as tees, approaches and fairways.

If I see it here, it usually appears in June, July, as the odd few lesions on say, an approach area or a tee, it then fades away and is often forgotten about. Come September and the arrival of cooler (and longer) nights, we see a higher incidence of dew and so extended periods of plant leaf wetness. This plays straight into the hands of C.homeocarpa and often where we saw a few lesions in July, we see a very aggressive attack with the arrival of autumn. You can read all about the science here.

In this article you’ll see it suggests there are 4 species within the Clarireedia homeocarpa clade, two of which only occur in the U.K – C. homeocarpa and C. bennetti (thought that was an Italian motorcycle), whereas the other two are more widespread worldwide. (C.jacksonii and C.montiethiana)

So what I think we are seeing in the U.K and describing as Dollar Spot is likely  C.homeocarpa and C.bennetti and as such they primarily affect Fescue species, but also Ryegrass.

The other two species attack multiple plant hosts and I think it is these we see on the continent and elsewhere. Just a theory, I’m sure someone will put me right here (eh Kate ? 🙂 )

Now in the U.S, they have a brilliant predictive disease model for Dollar Spot called the Smith Kern’s model, some of you I know already use it for Dollar Spot and for Microdochium to a certain extent as a predictive model. Not surprising really when you take into account it is based on humidity and air temperature. In the U.S they have a guideline where if the model returns a 20% or higher probability, it suggests applying a preventative fungicide. Over here we aren’t likely to do that anyway and to the case in point, we most likely aren’t dealing with the same Dollar Spot species. So I’ve been inputting data into the Smith Kerns model spreadsheet (from a Meteoblue forecast or from archived weather station data) and most times we need a probability of > 60% before we see actual symptoms. On some courses it needs to be > 70%.

So as a matter of interest and to try and manage this disease if you see it on your site, you might like to download the model spreadsheet and enter your respective min and max air temperatures / humidities and see how it equates to experience, i.e if you see Dollar Spot as an issue.

You can read all about it and download the respective article here


OK that’s me for now, it’s been an interesting day already but time to stretch my legs out of this office chair and have a cuppa before addressing (you guessed it) that bloody in tray 🙁

All the best..

Mark Hunt