October 23rd, 2023

Hi All,

Storm Babet Dynamics

As the clear up from Storm Babet continues with over 100 flood warnings still in place, it is worth reflecting on why this storm was so damaging from a flooding perspective.

Image courtesy of tropicaltidbits.com

Firstly, it was a BOB, a Bay of Biscay low pressure that tracked from the south of the U.K and then moved north through central and eastern areas and finished up across the east of Scotland. See animated GIF above.

Secondly, It was slow-moving, occupying a trough pattern in the jet stream, which meant rather than cross Ireland and the U.K in 12-18 hours (as would be the case normally with in an Atlantic low pressure), it took 72 - 108 hours to clear the U.K.

Slow moving low pressure systems = heavy rainfall and rain rate totals.

Thirdly, the rain rate associated with this storm was particularly high I think over a concerted period.

Here's the stats from 3 locations across the U.K for the storm period ;

What you can see is not only were the rainfall totals of Storm Babet considerable, the rain rate was also classified as heavy to violent. It is a high rain rate that causes the issues because they overwhelm drainage systems, ditches, brooks and rivers and quickly turn them into a torrent.

Surprisingly, looking back it isn't very easy to access historical rain rates, so I can't comment on past rainfall events although my hunch is that peak and trough patterns in the jet stream are not a new phenomenon. My home towns wettest day was on July 1st, 1958 when 115mm fell over a 24-hour period. Although I wasn't alive at this time (nearly but not quite thanks), I would hazard a guess that this was a result of a summer trough pattern. What I think is happening now is that we are seeing more and more of these peak and trough patterns as the jet stream weakens and moves closer to the North Pole.

Content reproduced courtesy of Nature.com

I was reading some meteorological research papers over the weekend that have looked at the position and strength of the jet stream going back to the 1950's. One of them (above) was published by Nature and you can read it here. The conclusion of some of this research is that the position of the jet stream is changing, moving further north and it is weakening. Now currently it is inside the 'normal' variability associated with the jet stream, but there's an assertion that by 2060, it won't be. Since I'll be a slow release form of phosphorus by then, I find myself unable to verify this claim :)

A weakening of the jet stream dramatically increases the potential for trough and peak patterns forming, so called Omega and Diffluent Blocking Events and consequently, high rainfall events AND heatwaves, whether that be during the summer or periods of warm, humid weather late into the autumn / winter as we have seen recently.

This is the new norm.

This storm event was forecast, appeared as high rainfall totals 7 days before it arrived so we should have been prepared. The fact that we still saw flood defences overwhelmed and homes affected maybe points to a lack of investment and of course the building of houses on known flood areas, take note Keir Starmer with your plan to build millions more houses in the U.K. No doubt accompanied with the same woeful lack of infrastructure investment as the current administration.

Back to the weather, as I look at the next 7-10 day forecast, I can see another BOB or maybe two waiting in the wings.....

General Weather Situation - 23rd October, 2023

So looking at the coming week we have more rainfall on the way though pleasingly night temperatures have dropped to a more normal, low single figures for this time of year.

So for Monday we currently have rain moving across Ireland and that'll cross The Irish Sea into The South West and West Wales during the early afternoon. Some of that rain across Cork, Wexford and Leinster could potentially be heavy. They'll also be another rain front pushing into the south east of England later this afternoon. Mostly dry for Scotland and the north of England thankfully. During the afternoon, the bands of rain will move across England and up the east coast. After a cool misty start, temperatures will climb into the low to mid-teens.

Tuesday will see that slow-moving rain still affecting Leinster, the north and north east of England on Tuesday morning. Thankfully through the course of the day it'll push off eastwards into The North Sea leaving a vestige of showers behind. Later in the day more rain will push into The South West. Again reasonably dry for Scotland and most of Ireland thankfully. Slightly cooler on Tuesday with temperatures in the low double figures.

Overnight that rain across The South West will track along the south coast into The South East and that rain will still be in situ early on Wednesday morning. Elsewhere we will have a largely dry picture across the U.K & Ireland, save for some heavy showers across the north east of Scotland. Out in The Atlantic, a heavy rain front is lurking and this will push into the south west of Ireland by lunchtime on Wednesday. During the course of the day this rain will move slowly north and east across Ireland and into The South West and Wales during the evening. So wet eventually across the west but drier for central and eastern regions. Slightly cooler as the wind swings round to the north west with temperatures just climbing into low double figures.

Overnight into Thursday that band of rain has crossed Wales and will affect central and northern areas from the off. We will also see more rain across the north of Ireland and south west. That rain will push eastwards across Ireland and the U.K through the course of Thursday and it'll also affect the north east of Scotland. Slightly milder as the wind will swing to the south west through the day but of course this is entirely dependent on your location. As my dad used to say..."Back to the wind, low is on the left"....a clever man indeed. So wet and breezy is the forecast for Thursday.

Closing out the week on Friday that low pressure system is tracking across the U.K so heavier showers and consolidated fronts of rain will be frequent. It is easier to turn on your rain radar app on Friday morning once your phone has recognised your tired 'fissog', rather than me forecast it here and now on a Monday morning. Remaining mid (ish) with a strengthening south westerly wind.

The outlook for the weekend is I think a cause for concern as we have 2 low pressure systems affecting the U.K & Ireland as the GIF above for Sunday morning from tropicaltidbits shows. I think Saturday will be showery with heavier rain across North Wales, northern England and southern Scotland. Sunday is the problem day as I see it with these two low pressure systems. So that could possibly suggest a very wet day for south and central areas of the U.K and Ireland. Heavy bands of rain will cross Wales and England and track northwards into Scotland with potentially more heavy rain for the north east of Scotland. Falling onto sodden ground with already high water levels is a recipe for more flooding I am afraid :(

Weather Outlook - w/c 30th October, 2023

Above is the projected GIF for next Monday courtesy of tropicaltidbits.com. As you can see low pressure is still the name of the game and with it sitting out in The North Sea, its trailing edge will pull down north winds, so I think we start next week cooler and unsettled, however it won't stay cool for long. During the first part of next week, a ridge of high pressure looks to push up from the south introducing much milder weather however out to the north west a very deep depression will build in The Atlantic and this will feed in rain to the picture most of next week I am afraid. The upshot is we will become sandwiched between the two as the week progresses which means it'll become very windy and it'll be pretty wet as well, especially from mid-week onwards. Later next week we will see cooler, but still unsettled weather push down from the north. Hang onto your hats.

Agronomic Notes

It is difficult I find to pen some useful agronomic advice when the reality for most people maintaining turf currently is that just getting machines out of the sheds is an effort.

And you know they'll still be some IQ-challenged members / players asking why the course / pitches are wet ?

In addition, draining bunkers, replacing wash outs, only for them to be washed out again can be mind-numbingly depressing. Spray days will be confined to this week I think judging by the forecast for a windier and wet scenario next week. Hold Fast.

Reproduced courtesy of USGA Record

I did happen on some interesting content from the USGA Record publication with a really informative Podcast by Dr Roch Gaussoin on organic matter testing (thanks to Dave and John for jogging my memory on this one). Although there's some discussion about American Football at the beginning, that aside it's a good listen, you can find it here

I have long talked about organic matter levels as key to many aspects of greens performance, notably grass species composition, water movement (a rather current topic), success of overseeding operations, plan stress and of course disease. With the type of rainfall rates I have detailed above becoming more and more the norm for us in the U.K & Ireland, moving water through the profile quickly is pretty important, no ?

Of course controlling surface organic matter levels and integrating with sand is all well and good but if your deeper rootzone has poor infiltration characteristics, all you will essentially do is make your greens wetter, quicker, as water fast tracks through the surface to the impermeable layer below and creates a perched water table. That is why deep aeration and efficient drainage goes hand in hand with surface organic matter management. You have to join the dots aeration-wise to get a successful outcome.

Cue Powerpoint slide copy from one of my presentations last year.....

On that note, I remember soil sampling a series of well-built USGA-spec greens and noted how the soil augur always got to around 10cm (4 inches) before encountering resistance. It turned out that the greens had never been vertidrained, but consistently worked in the top 10cm, thereby creating a pan. Once the Superintendent started vertidraining, the greens just turned around, especially from a root development perspective. Better roots = better nutrient uptake and plant moisture management, the fundamental basis for a healthier plant 24/7, 365 days of the year, IMHO.

Now conditions for aeration aren't optimum at present and in reality you'll do more harm than good even if you could get a machine out of the sheds, but the above is to really serve to highlight why aeration of all types is fundamentally necessary to keep you course or pitches playable. It isn't something to be pushed to the outer reaches of the playing calendar because it suits the management, committee or membership. That option is long gone if you want to keep surfaces playable nowadays.

OK, that is me for another week.

All the best.

Mark Hunt