Last Thursday was yet another pivotal day in our ever-changing climate picture with excessive daily rainfall falling over a localised area of the UK.
How many times recently have you heard the forecasters say “A month worth of rain fell in a day” ?
Downloading the stats from a Doncaster-based weather station paints a depressing picture;
On its way to recording 92.46 mm for the day, the rain rate hit a maximum of 12.7 mm per hour at 6.34 pm (that’s 1/2″ an hour in old money) and didn’t rescind for another 3 hours or so.
That’s the straw that finally broke the camel’s back and the banks of the river Don.
Next week I’m doing a couple of talks at the Sportsturf Ireland Conference (should have them finished some time this week Damian 🙂 ) and in one of them I’ve looked back at daily rainfall and temperature data over the last 55 years and analysed that data statistically for signs of patterns/trends in the Irish weather. Surprisingly temperature trends weren’t consistent but rainfall trends were.
Last week’s excessive rainfall event (I won’t call it biblical) was forecast a good week before by the GFS (Global Forecasting System). I’ll qualify that statement in that GFS forecast a trough pattern to form and for a low pressure system to sit in it. When this happens the low pressure moves very slowly west to east and often pivots round on its own axis. This has the result of dumping rain and more rain over a localised area. You can see in the bottom trace for pressure on the graphic above that the low pressure was moving very slowly over Doncaster.
What we can’t forecast at the moment is exactly where that excessive rainfall event is going to take place. Over recent years, The South West and North West has been hit and now the north Midlands and the north of England. Here we got 14.8mm last Thursday, another very wet day but nothing like the above.
I can’t help thinking that there’s also other factors at play here. More houses and roads are being built in questionable flood plain areas as local government ticks the UK governments housing target box regardless of the consequences. More garden lawns are being turned into patio and plastic thereby increasing the run off rate and of course due our friends in London and austerity cuts, there’s been little or no investment into flood prevention measures (until after it happens of course then there’s money available).
A perfect storm indeed…
General Weather Situation
So as predicted we start this week with another low pressure system sitting over the UK & Ireland and that’s bringing general rain in a belt from the west of Scotland down to The South East. Ireland is seeing rain across Connacht and north Leinster work its way south and east as well. During Monday morning that rain is projected to push away from the south and east of England but at the same time more rain pushes into western Ireland and the west coast of England. In other words a dull, wet and cool day for some with a moderate to strong north-westerly / westerly wind. Away from the rain showers they’ll be some brief sunny intervals. Temperature-wise nothing to write home about at 5-7°C.
Onto Tuesday and overnight the centre of the low has pushed out into The North Sea off the north east coast. So this means most of the rain will be more north and east focused initially on Tuesday. Ireland looks to start and stay dry most of the day but they’ll be rain and wintry showers across Scotland particularly for central and north-eastern regions from the off. As we progress through the morning rain pushes into North Wales and this will then drop south and east into The Midlands and eastern / south-eastern counties. As we approach the early evening most of the rain across the UK will move out into The North Sea leaving a drier and cooler picture. Again a strong to gale force north-westerly / westerly wind will trim back the temperatures and take the last of the leaves off the trees at the same time. Similar temperatures to Monday with a high of 7°C.
Mid-week beckons and a dry start to the day for the UK and most of Ireland but of course this won’t be the case for long as a new rain front pushes in from The Atlantic. So the west of Ireland will see rain some of it heavy push in through the course of Wednesday morning moving across Ireland quickly. By mid-afternoon that rain will push into The South West and Wales as the low tracks south and east. Again another feature of a trough pattern in the jet stream is that low pressure systems often track further south. So by late afternoon we see heavy rain into Wales and The South West but further east and north including Scotland, Wednesday will be a drier day. Ireland will see that rain clear from the west through Wednesday afternoon to leave a dry end to the day for all areas except eastern Leinster possibly. Lighter winds for Wednesday and that means slightly milder but maybe only nudging 8°C maximum across the south of England.
Thursday sees that low pressure drop south into The Channel but its northern arm will pull in cool north-easterly / easterly winds as it does so and rain from the off for The Midlands, East Anglia, The South East and for Wales. The latter may fall as snow across The Black Mountains. Ireland and Scotland look to stay reasonably dry with just some rain moving down the eastern coastline of Ireland through Thursday morning. As we move into the afternoon we will see a continuation of showers, some of them heavy across the southern half of the UK, really anywhere from The Lakes south. Ireland and Scotland look to stay dry most of the day with maybe some wintry showers across the north-east of Scotland a possibility.
Closing out the week on Friday and that low has finally moved off to leave a pretty dry picture across all of the UK and Ireland. There may be a few showers down the north-east coast but winds will be light and they’ll be some sunshine as well so not a bad end to the week after a crap start it has to be said. No change in the temperature though with my lucky number seven being the order of the day across most of the UK.
The weekend of course won’t be so straight-forward with another low edging in off The Atlantic and bringing rain for west of Ireland from the off on Saturday. This rain will slowly edge eastwards through Saturday and we will also see further rain and wintry showers over elevation as we move into Saturday evening for the western coastline of the UK. By Sunday this low is projected to bring rain some of it very heavy for the east coast of Ireland, particularly around Dublin and Wicklow I’d say 🙁
They’ll also be further rain for the south coast and a line up to The Midlands and across to North Wales as that low swings up southerly winds as it passes through. Further north we will also see showers on Sunday throughout the day as that low pushes through but from The Lakes northward up to and including most of Scotland should be reasonably dry. Staying on the cool side for everyone with yes you guessed it, 7°C the most you can hope for.
So I guess this is the part most people focus on when I write about the weather, the outlook for the next week. i know the question I get asked the most currently is not surprisingly when is it going to stop raining ?.
Well to me next week does look a bit drier, not completely dry but drier and colder I think with a potential for a trough pattern to extend across from Russia and Scandinavia. So that means more frosts and perhaps snow towards the end of the month. Now I know I’m sitting here on the 11th of November and projecting forward but it does look pretty cold with a pronounced northerly / easterly bias to the weather. In the winter north and east in my book mean cold winds and an increasing risk of snowfall. (and Waxwings…yeah :))
Here’s the GFS output for November 27th…
Now it is just a hunch at the moment but this type of pattern doesn’t appear that often and it would tally with nature.
So next week looks to start off pretty much as a repeat of the end of this week. That is to say with a southerly biased low pressure moving through and bringing rain for the southern half of the UK and Ireland on Tuesday after a reasonably quiet Monday. So unsettled through Tuesday and Wednesday but then we start to see a drier picture, still with showers around coming in off The North Sea on a north / east airflow. So a cooler, drier end to the week still with some showers across Scotland and north-eastern coasts but less in the way of heavy rain events after the one early in the week. After that we will see…
Now I know your minds are most likely preoccupied with water-logged courses / pitches, washed out bunkers for the ‘nth time’ and the inability to start / continue winter projects but I thought it timely to update the autumn so far from some of the locations we are forecasting disease pressure.
As you can see we had a spike prior to the weekend from the forecasting perspective but there’s another factor coming into play here that probably would negate this spike from a practical perspective, more on this below…
So the good news and let’s face it we need some good news is that we have decreasing disease pressure as an outlook on all sites monitored. Now in sheltered locations there was a recent smaller spike prior to the weekend but of course we must take into account ground conditions in the growth of Microdochium nivale. What I mean by this is that a wet, cold surface isn’t actually the ideal environment for Microdochium nivale and for this reason we can expect low disease pressure when we have saturated ground conditions from a spore germination and mycelium growth perspective.
There’s further good news in terms of spray longevity with the now normal 14-day or so longevity for a spray applied in early October. As with last year, the 2nd half of October was cooler and actually as reported last week one of our coolest. So a spray applied mid-October is still likely to be working well in the grass plant and with a low disease pressure forecast there’s no need to scramble looking for a spray day this week (even if you are able to get a tractor out on your golf course!)
The graphic below shows estimated fungicide longevity for a Northampton location (Ta Rob)
Grass growth dip equals problems for areas under wear pressure…
That tail off of growth over the last 14 days or so has meant that surfaces that are receiving wear are not able to regenerate sufficiently with virtually no growth at the end of October and over the last 5 days (and little on the horizon either).
This means golf greens, tees and winter season pitches will be on the back foot especially when you dovetail that in with the information I posted last week showing reduced solar radiation for October and now November. It’s been estimated that roughly 45% of Solar Radiation reaching the earth is in the correct wavelength for photosynthetic plants to utilise as light energy. So with declining heat energy from the sun comes much lower available light levels for the grass plant, reducing photosynthesis and therefore growth potential. So it isn’t just temperature that is growth-regulating currently, light is also an issue.
Now some grass species (famously Poa annua) are able to grow well at low light levels but others like Bentgrass and Ryegrass are less able to and so we see these species being out-competed by Poa annua currently.
Ryegrass, I think is especially sensitive to low light levels and tends to show senescence on older leaves as a result. These break down on the surface and encourage algae growth and sward thinning as a result. So don’t be surprised to see thinner ryegrass areas at the moment because of lower temperatures and light levels….I’d also expect to see more in the way of algae and moss around because of the above and prolonged surface wetness. Bad news when we no longer have very effective methods for treatment 🙁
October 2019 in the UK & Ireland actually went against the global trend for warmest October’s by being one of our coolest since we started monitoring GDD back in 2010. OK, that isn’t a long time, but it’s enough time to show that we aren’t seeing the same trend in globally rising temperatures as the rest of the world in some months of the year
What we measured as a cooler October agreed with The Copernicus Program which monitors global and European temperature trends. (see below)
This doesn’t mean global warming isn’t happening here but its effects (I think) are likely to be different for the UK and Ireland because of our location in terms of longitude and latitude on the planet and the fact that we lie slap bang in the path of the sub-polar jet stream.
Let us remember, eighteen of the 19 warmest years on record have occurred since 2001, with 2016 the hottest since monitoring began 169 years ago. The current decade is set to be the planet’s warmest on record, according to the UK’s Met Office, who expect 2019 to “amongst the warmest of years”. Well let’s see but I’m reckoning on different.
The above graphic also highlights that some of the biggest temperature anomalies are taking place at the poles and again I think in the case of The Arctic this is because of the phenomenon of Rossby Wave formation in the jet stream. These undulating waves form peak and trough patterns in the jet stream and can pull cooler air further south and push warmer air further north. Currently Russia is experiencing a mild and wet autumn compared to usual and that is directly as a result of the sub-polar jet stream pushing warmer air than normal further north….
OK that’s me done for another week, most likely they’ll be no blog next week as I’m away in Germany and Ireland doing talks unless I can grab some airport time courtesy of Ryanair 🙁
All the best.