As I type this we are sitting at a shade under 10°C and it’s not even light yet. Uncanny really when you look at the temperatures that the continent is receiving with record low temperatures and snow as far south as Greece. Last week I said that currently we were dodging an Arctic bullet and you can clearly see why as this cold trough in the jet stream has sunk all the way south to Greece and Turkey whilst we sit protected under a peak of mild air.
Protected for the time-being but later this week (as forecast last week) we will briefly become part of an Arctic trough when it’ll become pretty chilly and some places will likely see snow. (Sorry Sue I know you don’t like Baltic 🙁 )
Don’t worry though because I think it’ll be short-lived, it’s the next potential trough that I’d be concerned about, more on that later…Here’s a snap shot of Thursday’s Unisys output and you can see the difference…A more northerly orientation in the wind direction and a cold air mass….
So how are we looking this week ?
Well as intimated above, Monday is starting off mild and wet for Ireland, Scotland and the north west of England. South and east of this it is pretty dull with a dense cloud mass over all of the U.K. Through the morning that rain will move south and east into Wales / The Midlands by mid-morning and then across the southern half of the U.K during the afternoon. As it does so it’ll leave behind showery weather for Ireland and Scotland with some sunny breaks between the rain especially for eastern Scotland and the north east of England. That rain will continue through this evening for north west Scotland and Northern England and will also turn more wintry in nature over higher ground. Temperatures will be mild though, high single figures, low double figures even depending on your cloud cover and wind direction which will vary between south westerly (for the south) and westerly for the north.
Overnight into Tuesday and we still see that rain lingering across south west Scotland and north west / northern England by dawn. Elsewhere across Ireland, Wales, central and southern U.K, it’ll be a pretty dull start to the day with only the eastern coastline of the U.K likely to see the sun to any degree. Through the day that rain will slowly fizzle out across Scotland but will linger most of the day across Northern England into dusk. Elsewhere a dull and dry day looks to be on the cards with a slightly cooler feel as the wind swings round to the north west. Temperatures still hovering around double figures though or high single figures in a strengthening north westerly wind.
Already we are mid-week and Wednesday seees a mixture of rain and wintry showers pushing into north west Ireland across Connacht and Donegal overnight and moving south and east, clearing by dawn hopefully to leave a dry day for Ireland with some spells of sunshine. For the U.K we see that mix of wintry showers into Scotland from first light and it’ll then drift southwards into north west England by late afternoon becoming more wintry in nature as it does so. South and east of this band of wintry showers we look to have a much brighter day on Wednesday and dry throughout the day with long spells of winter sunshine. It’ll be very windy though as those isobars pack together with the wind pushing in from the west / north west. This will keep the temperatures down in single figures for most places with Scotland feeling the chilliest as that cold air mass moves in.
Onto Thursday and this really is the change day as that cold air mass begins to make its presence felt. Overnight we have rain, sleet and snow on higher ground move into Donegal, Connacht and west Munster falling more as rain the further south you go. For Scotland and the north of England, that band of wintry showers is still in situ with maybe only the eastern coast missing the worst. Through Thursday morning those showers will push southwards into North and South Wales and the south west of England. It’ll be very much a west – east divide though because the east looks to have a dry but very cold Thursday. By the dusk we may just see those wintry showers extend down into The Midlands. For Ireland we will see that rain and wintry shower mix move south and east to cover most of the country by the close of Thursday falling mainly as rain I think at this stage. Temperature-wise it’ll feel really cold everywhere with low single figures the highest you’re likely to see. This is because we will have that strong westerly wind in situ so the wind chill will be significant, in reality feeling not much above freezing I’d say.
Closing out the week on Friday and we see that west – east split again with wintry showers into the north of Ireland, north west England and Scotland as the day begins. East and south of this it’ll be a bright and pretty cold start with a ground frost likely. As we move through the morning we will see those wintry showers clear Ireland but push in from the west coast across the north of Wales, north west England / Scotland and possibly The Midlands fizzling out by dusk. Most areas and especially eastern ones will miss any wintry showers completely and have a dry, bright but cold day with an even colder wind as it shifts to a more north westerly orientation.
So how is the weekend looking ?
Well Saturday looks wet for Ireland as a rain front pushes into the west at dawn and moves east across the country reaching Leinster I think by mid-morning latest. Some of that rain may fall as snow across The Wicklow hills and mountains (lucky you). For the U.K it’ll be a bright, dry but cold start with a ground frost likely to be widespread. By lunchtime that rain will push into the south west of England and Wales and move eastwards reaching The Midlands later in the day. Scotland and the north of England will follow a similar pattern to Ireland with rain, sleet and snow moving in from daybreak and pushing south and east through the morning. By dusk that rain will have moved south into The Midlands before it moves into the south east on Saturday night. Another chilly day in that gusty westerly wind with temperatures struggling above mid-single figures. Sunday looks a drier day for all of us after another batch of wintry showers clears north west / south west Scotland into The North Sea so dry cold and sunny with I’m sure another ground frost likely across all areas. During Sunday that westerly / north westerly wind will drop off and become lighter towards the afternoon so it’ll feel a little milder. Temperature-wise expect little change from mid-single figures across all areas.
So will this cold spell last or will our protective peak re-assert itself in time for Harrogate ?
As it looks at this stage we will indeed see the Atlantic blocking high that has been a close weather companion to the U.K and Ireland now for the last three months drift back in and push that colder air mass north and east of us. So next week looks like starting off a little milder with a south westerly wind in situ and that’s the way it stays but there will be subtle changes. It looks to be dry though over most of the U.K and Ireland through the early part of next week. As we go through the week that high will be pushed down so that means more unsettled weather for the north of Scotland and Ireland later in the week as another trough of cold air sits north and west of us. It’s this trough that I’ll be keeping an eye on because it’ll begin to squeeze that high pressure away from the U.K and Ireland and that could allow that colder air to dominate as we get to the weekend after next. I’ve got a sneaky feeling that we will see a colder end to this month and then a pretty cold February but we’ll see…..
Harrogate Weather Forecasting
First off for all of you travelling to Harrogate over next weekend and the week after, please feel free to use this Meteoblue weatherlink for Harrogate. You can see the forecast by clicking here
2017 Growth-Degree-Day and Growth Potential Spreadsheet
A little later than usual for that I apologise but please find the new spreadsheet onto which you can enter your daily maximum and minimum temperatures (and rainfall of course) and it’ll automatically convert these to Growth-Degree-Day and Growth Potential readings.
It’s worth pointing out that I use 6°C as a base for my GDD calculations and 18°C for the optimum temperature (To) for cool season growth in the G.P calculation.
For the sake of clarity the reasons are these ;
- GDD Calculation – In the U.S they use 0 as the base temperature for their calculations so if we had a day of 6°C day temp and 0°C, they would calculate that to be 6-0 / 2 = 3 growth degree days. Now to my way of thinking if we have that kind of day we’d be seeing no above-ground growth and by using 6°C as a base instead we’d be calculating 6-6 / 2 =0 growth degree days. Since GDD is meant to be a growth model I think it should be returning a 0 figure when we aren’t getting actual growth rather than a positive figure as it does if you have 0°C as a base. I’m sure there are counter-arguments either way but at the end of the day I think there’s some logic to my use of a 6°C base rather than simply an NIH-based argument. (Not invented here 🙂 )
- Growth Potential – Using 18°C for the optimum temperature (To) instead of 20°C I think is more relevant to our situation and tends to predict stress on Poa annua more accurately. I’ve run it by the oracle of Growth Potential – Micah Woods and he confirmed that in some other areas they do the same (Canada I think was mentioned). I’m doing the Growth Potential class at the forthcoming GCSAA Educational Seminars so I hope to come back with some more information to impart in this area 🙂
You can download the spreadsheet here
The beginning of January, it’s unseasonably mild isn’t it ?…well no it isn’t…..
I was chatting to a chap on Saturday at Rutland Water who was saying how unseasonably mild it was for the beginning of January and I said it wasn’t (politely of course). In my mind it’s the norm now for the first part of January to be mild.
So I thought I’d go back as far as I’ve been collating weather data from The Oxfordshire. Turns out we started in 2005 which means it’s now 12 years since I first started sending Sean irritating texts / emails asking for his weather data. To his credit he has never once told me to sling my hook but I suspect it was close sometimes 🙂
So here’s the first 14 days of January’s maximum air temperature going back every year to 2005 and I’ve split it into 3 graphs because it’s too confusing in one…
If I pick an arbituary day like the 10th of January we can see that over the last 13 years the following applies ;
Maximum air temperature on the 10th January ≥ 8°C = 12 Years out of the last 13.
Maximum air temperature on the 10th January ≥ 10°C = 6 Years out of the last 13.
So I think that’s reasonably comprehensive proof that the beginning of January is now traditionally mild and that’s why I think that January aeration (provided ground conditions in terms of rainfall or frost allow it) is more relevant now than it was back in the old days. If you look at the above data we have only had 2 years out of the last 13 when we have been properly cold at the beginning of January, those years were 2009 and 2010.
So gearing up for a mild first part of January from a nutrition and aeration perspective should I think be on the radar. What we can’t predict with more accuracy though is if it’ll be a dry or wet start to the year and I fully accept that can put the handbrake on early year aeration more than anything.
Microdochium nivale activity
I suspect when you have night temperatures of close on 10°C and a saturated atmosphere courtesy of Friday’s rainfall of close to 95%, it is inevitiable that we will see more disease activity on existing scarred areas. Leaf wetness really is key to fungal development and so my advice would be always to dewy the most-susceptible greens for Microdochium first when we are talking about dew removal.
As I showed last week it really has been an exceptional year for Microdochium activity going right back to September so that’s 5 months now when we have had mild peaks of air temperature coinciding with leaf wetness which has pushed the disease on. There is however clear evidence that it is currently October and November that are most critical for establishing a disease population or more precisely stopping a disease population establishing.
If you are clean or reasonably clear of scars by the end of December I think you’re much less likely to get a new outbreak after that. I have some cracking trials running currently which feature some of the heaviest disease pressure I’ve ever seen and bear that last statement out perfectly. I will share that data on this blog when the trials are complete or if you want a sneak preview come and have a chat at Harrogate 🙂
Ok that’s all for this week, all the best, wrap up well at the end of the week and count the days down till spring. You can already feel it is getting lighter in the evenings I think.