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  • Writer's pictureMark Hunt

August 21st, 2023

Hi All,

Well I am back from another 'interesting' campervan holiday this summer when I experienced the full might of Storm Betty (I keep thinking of Frank Spencer and ooh Betty) that passed almost directly over the campsite I was staying in on the clifftops of St Davids, Pembrokeshire, West Wales with 60mph+ winds and torrential rain. Some people left prior to the storm, some people left during the storm as their tents, awnings collapsed and some (me) chose to ride it out. This was ultimately the wrong decision as by the morning we were minus one awning as the storm straps broke at the height of the wind, the awning poles broke, the storm pegs bent double and the awning collapsed in a reasonably orderly fashion and critically stayed put. No great shakes but lesson learnt.

I definitely underestimated the intensity of this storm but we had coped with 50mph winds earlier this year. As with most things weather-related, the outlook changed very quickly. It gathered intensity as it broke and the wind estimates where 10-15mph shy of the mark. The critical factor was a change in the wind direction during the storm, starting off with a SE wind (that brought chaos to the south east of Ireland) and then vectoring round to the SW during the night. This made it extremely hard to counter. Storm Betty was a sneaky one. I was out in the middle of the storm and its power was absolutely amazing, almost supernatural. In future I will check with Met Éireann as they provided the most accurate information in my view and of course, Ireland is the first country in the way of Atlantic storm systems before they reach the U.K.

Storm Betty was the 2nd summer storm we have experienced in August, this in itself is unusual.

Are there any more on the way I wonder, maybe is the answer to that one....

General Weather Situation

So we are well into August and this summer has been a bit of a meteorological rodeo ride, hottest June, near wettest July, coolest and stormiest August maybe ?

This week continues that rodeo ride being a week of two halves, the first, warm and sunny, the second, wet, cool and continuing windy with a pronounced northerly wind direction making it cool for the end of August.

So Monday - Thursday sees a mainly pleasant spell of summer weather with temperatures in the low to mid-twenties, a warm moderate westerly / south westerly wind and any rain confined to western coasts, except for Scotland which will see a cooler, more unsettled theme dominate most of this week. Plenty of sunshine for England, Wales and Ireland for the first half of the week. Wednesday night into Thursday morning sees heavier rain across the north west of Scotland, England and Wales and this will push into the north and north east later. Some of these showers will head further south across The Midlands on Thursday morning and will continue across the north west of Ireland and Scotland. The wind will start to move round to the north west during Thursday and that will begin to drop the temperature.

Friday sees that low pressure push down and bring rain to the west / south west of Ireland and this will quickly cross The Irish Sea into Wales, England and Scotland through the course of the day. Cooler on Friday as that wind pushes in from the north west and cloudier, duller for all areas with heavier rain to boot. This change in temperature and rainfall may also trigger some thunderstorms across central England during the afternoon. That rain should clear Ireland as it moves eastwards on Friday.

Unsurprisingly, the outlook for the weekend isn't particularly great with that wind direction swinging round to a northerly from Saturday and this will pull down showers and heavier spells of rain across Scotland, northern England extending down into The Midlands and south of England later in the day. Sunday looks potentially drier in the morning for England and Wales, but wet over Scotland later as a band of rain that will affect Ireland for the first half of Sunday crosses The Irish Sea. Cooler with temperatures in the mid-teens for most areas. Those showers will continue down the eastern and western coasts of Scotland, England and west coast of Wales later in the day. Bank holiday Monday looks slightly drier but remaining cool with that northerly wind now decreasing somewhat and still a tendency for showers to form across central and eastern areas during the day. Temperatures remaining in the 16-18°C range and disappointing for this time of year.

Weather Outlook

Storm Cillian maybe ?

Not wishing to scaremonger here but it could be that we see a 3rd summer storm hit the U.K & Ireland right at the end of August. Looking at the list of storm names, if it does transpire it will be called Storm Cillian (a nod and a wink to Cropcare there me thinks).

It is a feature of modern day storm systems that form within a trough pattern in the jet stream that they stay in situ for a number of days and continue revolving around the same area rather than moving through over 12-18 hours as used to be the case. I have pasted above a schematic of the GFS projections so you can see what I mean in terms of the longitudinal position of the low pressure vs. date. The consequence of the slow-moving habit is that we get a lot more rain in a storm event nowadays and the rain rate (in mm per hour) tends to be higher.

Now it may not pan out this way as we are talking 7-10 days ahead but if it does occur, it is the 1st time I have seen blue (cold air) on an Atlantic low pressure system since the winter. Hopefully it won't last as I am off to Pwllheli in early September :)

Agronomic Notes

August 2023 has been a really challenging month from a turf management perspective (to go with June and July of course).

Sometimes when I am writing this blog, I find it frustratingly difficult to try and summarise all of the different weather and turf management scenarios you experience. It is difficult therefore to remain 'relevant'......

This week I have taken a data snap shot from the south west of England for August 2023 using an agronomic report generated by our very own Prodata Reporting System.

The reason I have chosen the south west is because I think it has been on the receiving end of the worst conditions this summer and because I think it is also representative of Wales (certainly south and west) and Ireland as well.

One thing I have found very unusual this August was the high humidity and the associated dew formation. Last week despite staying on the cliff tops right by the sea I noted heavy dew formation overnight and extending into the morning. On the data snip, you can see how the maximum humidity is well into the high 90's, which is very advantageous for fungal development.

So first up when we look at the agronomic data snip obtained from a golf course near Bristol, we can see the associated mean high humidity through the month of August with 15 out of the 21 days so far >=85%. Normally in August we have higher E.T levels so dew evaporates quickly after sunrise, not this August. If you look at the chart above, you can see a total rainfall for the month of 62.6mm vs. a total E.T figure of 39.57mm, in other words, we have had more rainfall than we have lost by evaporation. This is unusual for the summer and for August.

Extended periods of plant leaf wetness coupled with high air temperature spell only one thing....disease. All of the diseases below are significantly encouraged by high humidity and plant leaf wetness. They are joined by Leaf Spot and Anthracnose.

Looking at Smiths Kerns Dollar Spot probability readings for this month and we can see they peaked at 47% on the 12th of August but have stayed > 40% for long periods. Normally a reading > 20% is a calling card for some diseases and I'm sure we are seeing plenty of activity on sites affected by this pathogen (along with Red Thread and Microdochium nivale). In short, August 2023 has been a very high disease pressure month.

Another disease that is increasingly an issue is Take All. (fungal mycelium above)

With a cool, wet spring and summer interlude, this pathogen is in its element and of course with more bentgrass around (it's natural but not only host as it will affect Poa annua), it has a ready host species. Difficult to control once you see it as well and with less effective fungal options and no doubt, more resistance to the few active ingredients we have left, you can understand why we are seeing it more and more. Building a good input of manganese into your nutrition regime is key, particularly in calcareous, alkaline sands (Ireland) where availability is diminished due to high pH. Little but often is far better than heavy and infrequent.

Trying to think of positives, if we look at the next column (highlighted in green), we can see that the daily Growth Potential has been nearly optimum for a good chunk of August.

Now of course, high growth rates and rainfall are unwelcome bed fellows and that means potential issues trying to keep on top of growth on fairways and rough, if you are indeed able to get machinery out there and a cut in the first place. This isn't a given.

There are also however many benefits to this.

First up, we can get very good recovery, be it from disease and / or aeration because a growing number of golf courses are choosing (correctly in my view) to get their main aeration done in August / September. If we are overseeding, the good soil temperature means seed germination is super-quick and so we can recover damaged areas by pre-chitting seed in damp topdressing and then dimple seeding into the affected area.

I have written elsewhere but not only is this a great time of year to get good recovery, I think late summer aeration is going to become more and more critical in helping our industry to manage the effects of peak and trough patterns in the jet stream.

Be that helping to move excess water away, venting anaerobic soils due to waterlogging and of course stimulating new root development for those periods when we are tested from a temperature and E.T perspective. In short, there are so many benefits to being able to aerate mid-August to mid-September and there are an increasing number of negatives to putting this off till later in the autumn.

On the subject of waterlogging, although 62.6mm of rain so far this month isn't an excessive amount from a volume perspective, (though it is for August) look at the HOW this rain has fallen in mm per hour shown in the rain rate column.


  • Light rain - less than 2.5 mm/h (<0.1”/hr)

  • Moderate rain - rain rate of fall is 2.6 to 7.5 mm/h (0.1 to 0.3”/hr)

  • Heavy rain - rain rate is greater than 7.6 to 50 mm/h (0.3 to 2”/hr)

  • Violent rain: - rain rates greater than >50 mm/hr (>2 in/hr)


Five times this month, the rain rate has been recorded as heavy - violent rainfall. This is the type of rain that washes out bunkers and pathways, overwhelms inadequate drainage and generally makes greenkeeping and groundsmanship a real challenge, day in and day out.

Hopefully I have covered some relevant points that strike a chord :)

Till next week, all the best.

Mark Hunt

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Sven Livesey
Sven Livesey
23 aug. 2023

Hi Mark

I'm really enjoying these emails and so happy I signed up. There sure is plenty of data to get my head around.

Keep up the great work.


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