September 23rd, 2024

Hi All,

On Saturday afternoon, I was zipping around Leicestershire and Rutland's finest B-Roads on my restored 1989 Honda Hawk 650cc motorcycle, enjoying the dry roads and warm air when I glanced to the south and saw cumulonimbus clouds building into thunderclouds. I promptly turned around and blatted home, even though it was warm, dry and sunny, closing the garage door some 15 minutes before the first raindrop fell on the patio.

What has followed has been the most intense rainfall I can remember receiving in my home town with the streets quickly turning into rivers and sirens filling the afternoon air. Within 2 hours of the storm starting I recorded these stats on a nearby Davis Vantage Pro weather station ;

Not even 24 hours later we were looking at these stats ;

113mm over a 24-hour period, 4 1/2" of rainfall in old money, that's quite some storm.

The source of this extreme rainfall event turns out to be the exact same low pressure that a week previous had brought torrential rain, flooding and fatalities to Central Europe. In the week following it has moved westwards (which in itself is not normal behaviour because most low pressure systems move west - east) and reformed within the Bay of Biscay and gathered strength before moving across the southern half of the U.K. As it did so I believe it underwent 'cyclogenesis', this is the process where a low pressure system gathers strength / energy. The extreme rainfall across Central Europe is said to have been caused by a low pressure system picking up energy from The Black Sea and Mediterranean (which incidentally are sitting 3-4°C warmer than normal) enabling it to hold more moisture (remember for every 1°C increase in air temperature, it can hold 7% more moisture). I think the same happened last weekend, in that the low pressure picked up energy from the warm sea in The Bay of Biscay and that enabled it to carry more moisture and produce more intense rainfall. You can see the tracking of the low pressure below on the GIF from tropicaltidbits.com ;

Clicking onto the truly brilliant Copernicus.eu website and logging onto MyOceanPro you can select any point in the ocean and view the current sea temperature. So I selected the sea temperature off the west of Ireland, south west of Cornwall and Bay of Biscay to compare. The theory being if a low pressure originates in The Bay of Biscay it has the potential to pick up more energy, hold more moisture than one that vectors in from the west or south west Atlantic. Below are the results ;

So we can see the sea temperature in The Bay of Biscay is currently a balmy 19.08°C, significantly warmer than the south west and west ocean locations (16.22°C and 14.96°C respectively). So if a storm vectors in from The Bay of Biscay, it has the potential to carry more energy, more moisture and deposit it in an event now termed 'Extreme rainfall'.

Coming closer to home, I downloaded some data from my local Davis weather station to analyse how that rainfall fell last weekend because this is when it starts to become relevant to turf and actually infrastructure / facility management because both are affected.

Years ago I remember talking to a stadium manager about rainfall events and how his pitch coped. He quipped some massively high infiltration rate to me (not surprising when they're straight sand I suppose) and said his pitch can cope with extreme rainfall, no problem. He then smiled and said "But the city around us can't ! ". So the pitch could be as dry as a bone but all the streets and infrastructure around would be flooded.

The weather station I used records data over a 15-minute period and below are the 2 graphs of rainfall (in mm) falling over this timeframe vs. rain rate (in mm per hour) over the same timeframe for our storm event. (which is still ongoing as I watch the rain hammering down)

So we topped out with 25.9mm (an inch of rainfall) falling over a 15-minute period and reaching a rain rate of > 250mm per hour (10 inches per hour) at 17:30pm. During the 2 days, we had 5 successive peaks of rainfall that would have been classified as 'violent' falling at >50mm per hour. It is these peaks that cause the issue in terms of overwhelming infrastructure, washing out bunkers, flooding greens, tees, etc and generally affecting playability of a facility.

If you take onboard we were forecast 29mm of rain for Saturday and actually received 69mm, you can see it is very difficult (nigh on impossible) to accurately forecast such an event within current weather station models.

Future-proofing is therefore dependent on your facility being able to tolerate such events on a more frequent basis. Now if you look at the picture of Market Harborough High Street resembling a torrent, you could make the assumption that our infrastructure can't cope with such short-tern rainfall events and I think it would be an accurate one judging by the number of sand bags lining the shops in that street. Today though, it is workable and useable because we have invested in significant flood defences as a Town. Interesting.

GFS output for the next 7 days courtesy of tropicaltidbits.com

General Weather Situation - w/c 23rd September, 2024

So that's quite a pre-amble to my weatherblog, but hopefully an interesting one to boot.

Well, after a pretty dry end of August and start of September for many (not everybody obviously), this week may bring some long-awaited rainfall for many areas particularly the dry east of the country. (sorry to the seemingly never ending wet west).

The weather map for this week is of course dominated initially by rainfall from that low pressure system which will affect the start of the week with very heavy rainfall. Now currently the pattern of the rainfall is across the southern half of the U.K, from The Humber estuary south. Ireland will pick up some of this rain but it looks marginalised to the south and south west. So a very wet Monday for the south of England, drier for Ireland and Scotland with temperatures in the mid-teens and pretty typical for the time of year. They'll be a bit of respite for the south on Tuesday with rain developing over Scotland and particularly the east but on Wednesday and Thursday we have two successive heavy rain fronts crossing the south of Ireland and pushing across The South West and into central and northern England. The rainfall associated with these fronts will be heavy and falling on recently flooded ground. That said, the ground has easily been able to absorb the current rainfall.

We see a further change as move into Thursday with a trough pattern in the jet stream developing into which a low pressure will develop and in turn drag down a northerly airflow, so much cooler air temperatures at the end of the week with 11-12°C typical. The flipside is that as that cool air pushes down we will push that rain away and have drier, cooler conditions from Friday lunchtime onwards. As we move into the weekend a temporary ridge of high pressure will build and continue the drier outlook into Saturday and Sunday with 12-13°C, sunny with broken cloud and a change in wind direction to westerly and then southerly.

Weather Outlook - w/c 30th September, 2024

Now if you interrogate the GIF from tropicaltidbits.com above you can see that the weekend's weather is but temporary respite before we look to have another pretty gnarly low pressure system push into Ireland late on Sunday and then across to the U.K. This low pressure will introduce some very windy weather for the start of next week, with tightly-packed isobars making themselves felt through Sunday night into Monday and Tuesday before the low moves away. Of course not only will it bring some windy weather, but they'll be plenty of rain associated with the low pressure system and especially because it's tracking in from the south (warmer sea temperatures again). Most of the rainfall will again be over the southern half of the U.K, with Scotland currently missing the worst.

From mid-week onwards we look to pick up some warmer and drier weather with a strong to moderate south westerly wind, so some good drying conditions leading into next weekend.

That's how it looks currently.....

Agronomic Notes

This week we have seen some pretty humid, muggy air with overnight temperatures very similar to daytime temperatures and aside from the issues related to the extreme rainfall I have already detailed, it brings with it high disease pressure.

Looking at the weather station data I have access to, the overnight temperature has been 14-16°C dependent on location. This type of temperature is high enough for the growth of Dollar Spot disease as well of course as Microdochium, our 2 main protagonists for this time of year. Alongside this, the humidity and moisture will also see summer Anthracnose-affected areas 'flare up' again as the fungus morphs from its usual form (Foliar Blight) into more of a Basal Rot scenario.

Above I have graphed out 2 x Smith Kerns readings from a shaded and open location in England. You can see a similar trend with a peak observed in early September before the cooler weather of mid-September dropped disease pressure significantly. As we approached last weekend, the arrival of moisture / humidity with warm overnight temperatures has increased disease pressure significantly, whether we are dealing with a shaded or open location (though they differ in terms of intensity).

I expect this pressure to continue through Monday up to and including Wednesday night before that change to a northerly airstream will drop overnight temperatures and disease pressure significantly. This drop in intensity should maintain through the weekend as the night temperature stays in single figures.

Growth-wise we can expect a similar pattern with good G.P at the start of this week dropping away significantly as we pass mid-week. In theory this is good because we should grow out disease as quickly as it comes in, however I feel with the current conditions, disease development will out-strip grass growth and more importantly the control aspect afforded by a fungicide. Put simply, the disease will grow at a faster rate than it is controlled by a fungicide application leading to the oft-repeated assertion that the fungicide application 'isn't working'. In reality, it is working but climatic conditions are such that they are promoting fungal development faster than the fungicide itself can control / restrict population growth.

I have always thought the term 'fungicide' is mis-placed because 'cide' relates to killing (derived from Middle French and 'cida' from latin apparently pnar pnar) but in reality the term is more accurately fungiostat. Meaning that the application of the product is (hopefully) controlling the growth of the fungal population at a more significant rate than the fungal population is multiplying.

Imagine it as a sort of see saw effect ;

Fortunate as we are to have new active ingredients on the market in the U.K & Ireland, the fact is that the dose rate and effectiveness of those A.I's is not the same as had 5, 10 or even 20 years ago. That said I can remember having the same conversation with end-users to explain the above scenario when we had Chlorothalonil and Iprodione, with their associated very high application rates.

Now obviously with your IPM program, you are doing lots of things to tip the balance away from high fungal growth, whether that be cultivar overseeding, dew control and / or organic matter control. Even then we have to accept that there will be certain periods of the year when the cards are stacked in favour of fungal growth. Not just that, but a climate with warming oceans and higher humidity is more likely to stack those cards up, more often.

It is just something we have to live with and adapt to.

All the best.

Mark Hunt