The first blog of December, time flies as we head to the shortest day and then Christmas of course..So how is that meteorological battle shaping up that I mentioned last week ? Well it’s really interesting and it highlights my thoughts about long-range forecasting and the like. Last week I gave a talk at the GCSAI Educational Conference, held at Croke Park, Dublin. It was a good day, thanks for everyone that stayed to hear my talk and for the feedback 🙂 One of the questions related to my comment that a forecast longer than 10 days had a very high degree of doubt behind it (I think I said it was crap actually…tut tut) and this week’s weather just highlights that.
As I’ve looked at the forecast for the end of this week, it’s gone from -4°C and snowing to +6°C, by the weekend, and anywhere in-between and this is due to the uncertainty whether a peak or trough event would get the nod. So if we have this degree of uncertainty at 7 days, how can anyone give an accurate prognosis on the weather months ahead ? I believe they can’t. My feel is that the cold trough will not exert itself longer than a couple of days maximum and milder, westerly winds will push this onto the continent leaving us mild into December, not cold.
By the way if you’re ever over Dublin way and need something to do before hopping off to the airport, I can recommend the tour at Croke Park, (last but one stop on the Aercoach to Dublin Airport) it’s fascinating, the history behind the venue, (doesn’t reflect well on the English, but we all should know about it), the venue itself (Particularly now knowing the lengths that Stuart Wilson (Head Groundsman and co-speaker at GCSAI) has to go to, to keep grass on it) and the atmosphere that they re-create for an all-Ireland GAA final, must be immense in real life and now on my things-to-do-list of life ! 🙂
So on to the weather…
General Weather Situation
Monday looks to be a quite day, settled, dry and dull on the main part, save for a slim chance of sunshine on the south and east coasts of England. The wind will be light and changeable in direction, with temperatures peaking at around 7-8°C.
Tuesday follows a similar pattern with a dull, settled day for most of us, light winds and similar temperatures to Monday. Depending on cloud cover, I expect us to just miss a frost as well. Later in the day, a rain front pushes into the north-west of Scotland and drifts slowly south, affecting Donnegal and Connacht by dusk. Winds here will be strong and from the north-west as a cold low passes over the tip of the U.K.
Overnight into Wednesday, this rain band sinks slowly south (/) across Ireland and the north of England, but as it does so, it weakens, so further south Wednesday should be dry, with a chance of seeing the sun and again a frost-free start to the day. Winds will begin to freshen from the north-west and that’ll make it feel a little nippier than earlier in the week.
Thursday is a change day and it’ll be windy to very windy, with the winds pushing in from the west / north-west as a cold low pushes into Scotland early doors and brings wintry showers to the north-west. By mid-morning, the rain is into central Scotland and Donnegal, falling as snow on higher ground, pushed along by very strong winds. That rain / sleet / snow is projected to reach into North-Wales / Northern England by dusk and it’ll be heavy in places, with localised flooding predicted. It’ll be a cold night for many because of those winds and any remaining moisture will fall as snow across Scotland and Donnegal in particular, with the odd snow shower pushing further south.
Friday is a very cold day with an Arctic blast pushing cold air down on mainly north / north-west winds, though these will be lighter than Thursday’s. It will be bright and sunny though over much of the U.K and Ireland. This is the weather that was initially projected to stay with us for early December, but I believe it won’t, as milder air pushes in from the north-west / west.
The weekend is looking ok at the moment, save for some rain early doors on Saturday over the north of England and Scotland. Further south it’ll be windy, but much milder feeling than Thursday / Friday as a high pushes warmer air over us. It will be dull though in the main for Saturday, perhaps a chance of some hazy sunshine later in the day. Sunday looks a little cooler, with those winds dropping away, so a ground frost is expected to start the day.
If everything pans out as I think it will, next week we see a transition to westerly / south westerly winds and so milder, but unfortunately wetter. There’s some real humdingers of low pressure systems out in the Atlantic at the moment and this wind flow will bring these over the U.K and Ireland at some point, so I think we’ll start off mild and dry, except for Ireland, next week, where I can see some rain coming in. It’ll remain mild all week, but there’s a strong possibility of rain most of the week, with heavier rain towards the end of next week, pushed along by some strong, south-westerly winds.
As it’s the start of the month, then growth-degree-days (GDD) is on the menu 🙂
I used these as a discussion topic last week at the GCSAI and when you number crunch weather data using GDD’s, it really highlights differences in the weather. These differences give us quantifiable data, i.e where growth is vs. the same stage last year, how warm it’s been in the autumn, e.t.c, so I’m convinced they’ll be of use to us going forward. Crucially we can also predict over 7 days how GDD’s are going to look and act accordingly, rather than sticking a finger in the wind and hoping… I intend to cover this topic during my talk at Harrogate as part of the educational conference and use some real data from around the U.K to highlight points.
So if anyone from Kent, Scotland, East of England, North-West of England has some weather station data they’d like to furnish me with, that would be very helpful. All I need is daily minimum and maximum air temperatures and maybe rainfall. Drop me an email to firstname.lastname@example.org please (cheers in advance)
Monthly and Cumulative GDD Totals
You can download these in pdf form here
When you look at the monthly chart for this year, it shows a GDD total of 43.5, which compares well with 2012 and 2010, but look at 2011 when we had a warm, peak jet stream pattern in place. The monthly total figure is 122.5, so that means we had 3 times the growth potential in November 2011, than we had in other years, that’s the beauty of GDD, it makes things definitive. So what you might say ?, well I bet you spent a lot more money on diesel that month than you did in other November’s because there would have been a lot more growth, how did you quantify that when you were reviewing your budget at the time ?….
October / November Summary
You can see the up and down nature of October and early November as we moved from a warm peak to a cold trough and back again. Each time you see high peaks, this will reflect strong growth, but also strong disease activity. As we move into November you can see how growth and disease pressure dropped off by the middle of the month and this is important because I always maintain that it’s the October to mid-November period which is critical in Fusarium control. During this period we have high potential for scarring and it’s here that fungicide applications, type, frequency are key.
End of November Growth Spike
That said you can also see at the end of November we picked up some growth and this is what I predicted would happen last week from forward forecasting data courtesy of Meteoblue. You can definitely see some growth on higher-height of cut areas for sure…This shows how GDD is not just a cumulative or historical tool, it’s also useful for looking ahead. Surprisingly I have had some feedback of increased disease activity associated with just these 3 days of milder temperatures, even though we were dry.
Why is my turf area still so wet ?
A number of you have commented to me how wet everywhere is still, despite the relatively dry month that November was (after that first week of course !). When I crunched the rainfall vs. E.T figures for October and November from Sean at The Oxfordshire, it’s not hard to see why !…The graph below shows daily rainfall and E.T. It’s not the detail that’s important, it’s the fact that the rainfall spikes in October and early November were high (though other areas were much higher I know), but the E.T rates are so low by comparison…
If you look at a cumulative comparison for October and November, you can see that we’ve been running in surplus soil moisture since the beginning of October and that very little change in this has taken place since mid-November, which although it didn’t rain much, it didn’t dry out much either because the daily E.T figures are only 0.2-0.3mm.
Now obviously this is a simplistic model because it assumes all moisture is retained in the soil, rather than being run off through drainage, but the key take home message is we’ve had more rainfall than E.T over the last 2 months and a clear lack of drying days…
Ok that’s it, next week will be the 9th and that puts my forecasting up to the week before Christmas, a critical time to make turf tonic and protective fungicide applications, particularly if we’ve been wet and mild in the meantime..
All the best, wrap up well for Thursday and Friday…