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  • Writer's pictureMark Hunt

April 17th, 2023

Hi All,

Well, our very untypical April continues with some really heavy rain at the end of last week. We recorded 18.2mm here in Market Harborough on Friday, with a rain rate of 6.6mm per hour which is reasonably gentle rainfall. There just was a lot of it !!

Plenty of flooding with the nearby River Welland at the top of its banks again. Quite different from this time last year when we had 19mm all month, already we are at 44mm and counting. Despite everything though we are only 25mm ahead of last year because of that very dry February 2023.

The Bluebells are just coming into flower on the Hambleton Peninsular at Rutland Water and they are about the same timing as last year. I'll be looking at 2023 vs. 2022 from a Growth-Degree-Day perspective later in this blog to see where we are. The woodlands are full of summer migrants and I also noted that our winter visitors, Fieldfare's and Redwings departed for Scandinavia earlier than usual after arriving later than usual the previous autumn. Nature is changing and adapting.

Last week I mentioned that I was going to have a play with Chat-gpt

( and it really is quite impressive, though entirely dependent on the type of question you ask it to explain. Firstly, I asked it to write a weather blog for the U.K & Ireland and it proceeded to do so for the whole year. Impressive but entirely useless with sentences like "From June, the weather will become warmer and more settled though they'll still be rain in the north"...ear shattering...If you ask it a more clipped question (I'd say fairer), it is much more accurate in its response.

What are Growth-Degree-Days ?

Growth Degree Days (GDD) is a measurement of accumulated heat over a certain period of time that is used to predict plant growth and development. GDD is calculated by taking the daily average temperature, subtracting a base temperature, and then summing the values over a period of time.

The base temperature is the minimum temperature at which a plant will grow, which varies depending on the species. For example, some plants have a base temperature of 0°C, while others may have a base temperature of 10°C or higher. If the daily average temperature is below the base temperature, then no growth occurs, and no GDD is accumulated for that day.

By tracking GDD, growers and farmers can predict when plants will reach certain stages of development, such as flowering or harvest, and make informed decisions about planting and management practices. GDD can also be used to compare plant growth and development across different regions and years.

It's important to note that GDD is just one factor that affects plant growth and development, and other factors such as moisture, sunlight, and nutrients also play a significant role. However, GDD can be a useful tool for predicting plant growth and development in a given region and can help optimize management practices for maximum yield and quality.

Interesting and impressive isn't it ? Particularly the line "The base temperature is the minimum temperature at which a plant will grow, which varies depending on the species"

I wonder how you square that with grass growth GDD models that use a base temperature of 0°C ? Well to me using a base temperature of 0°C is not a growth model, it is purely aligned to the frequency of PGR applications. Thanks Chat-gpt for the clarification.

OK, so I think it could be quite possible to write this blog with a number of clipped questions linked together using Chat-gpt. A bit unnerving that, I mean what would I do on Monday mornings ?????......Over to Chat-gpt again 😊

If you didn't work on Monday mornings Mark and weren't writing a weather blog, there are many different things you could do depending on your interests and priorities. Here are a few ideas:

  1. Get some exercise: Use the extra time in your morning to go for a run, attend a fitness class, or take a yoga session. Exercise is a great way to start the week and can help boost your mood and energy levels.

  2. Plan your week: Use the time to plan out your schedule for the week ahead. This can include setting goals, prioritizing tasks, and scheduling appointments or meetings.

  3. Meditate or practice mindfulness: Take a few moments to meditate or practice mindfulness. This can help reduce stress and anxiety and improve your overall well-being.

  4. Learn something new: Use the time to read a book, take an online course, or learn a new skill. This can help keep your mind sharp and increase your knowledge and expertise.

  5. Connect with friends or family: Use the time to catch up with friends or family members. This can be a great way to start the week on a positive note and maintain important relationships.

Ultimately, the choice is yours, and it's important to use the time in a way that makes you feel fulfilled and productive.

Wow !

The whole question of how we use A.I to 'improve our life' is a subject of fierce debate within society. At a very basic level it could allow someone to write / speak about a subject with no real retained knowledge base.

'Plus ça change plus c'est la même chose' or in English.....No change there then eh ????...

OK, onto the weather delivered by a non-A.I medium !

General Weather Situation - w/c 17-04-23

So this time last week, I promised you a pretty dry week and that's the way we are heading, however the Bay of Biscay (BOB) low pressure that looked to appear at the end of this week is still on track, so although it'll be dry, it won't stay that way for the southern half of the U.K particularly. This means the north and Scotland will definitely come out the driest and actually the warmest I think as we go through the week, with Ireland missing most of the rain. Let's put some detail on it ;

So the week is really divided into two parts, Monday to and including Wednesday and Thursday onwards......So for the first part of the week we have high pressure in charge which means all areas will be largely dry and settled after early morning rain over southern England has moved off into The Channel. One of the clues that our weather fate will be dictated by a BOB is the wind direction and that is easterly veering to north easterly and it'll be moderate to strong during the week So settled, dry conditions, the odd shower on western coasts and pleasant temperatures between 14-17°C, Monday is likely to be the warmest day of the week for some places. Plenty of cloud cover around, particularly to the west across Ireland and this will peg back the temperatures a little to the lower teens. As intimated earlier, Scotland will have a lovely week with good day and night temperatures and plenty of sunshine. Talking of sunshine, we will see more as the week progresses across the southern half of the U.K, but the presence of some cloud cover will keep night temperatures up above freezing and that means reasonably good growth levels.

As we move into Thursday then we see change on the cards as low pressure across Germany and The Netherlands begins to make its transition across The Channel and bring rainfall to the east of England initially on Thursday morning. This rain will consolidate and move westwards across the southern half of the U.K, reaching Wales by the evening. Away from this rain, Scotland and Ireland look to have a lovely day with lots of sunshine. Moving into Friday and with that easterly wind still blowing, the next phase of rainfall pushes into the east of England. This rain is projected to be more across the north of East Anglia through Lincolnshire and stretching up to The Scottish Borders. Again it'll move westwards across The Irish Sea and into the east of Ireland (Leinster) by lunchtime Friday. We will also see rain across the south east of England on Friday and The Midlands. By the close of Friday this rain will have crossed Ireland from Leinster into Connacht. It'll feel noticeably cooler in this rain with temperatures in the low double figures. It'll also move north into The Borders later on Friday.

The outlook for the weekend looks mixed, particularly across the southern half of the U.K. That is the rub with a BOB, it is the southern half of the U.K that is on the receiving end of the rainfall. So it will be on Saturday with rain, some of it heavy moving into the south east and pushing slowly northwards into The Midlands and up the east coast. We will also see rain across Scotland during Saturday. Ireland looks to miss most of this rain. Sunday looks slightly better, still with rain across the south east and east of England but also Scotland. This will move away during the morning to give a temporary drier period of weather before some more rain pushes into the south / south west of England and Ireland. This will push northwards through Sunday evening to give a wet end to the day. During the weekend, the winds will swing round to the west, north west and lessen in intensity. This means the rain we get will be slow moving and therefore totals are likely to be high.

Weather Outlook - w/c 24th April

So how does the last week of April look, a continuation of the unsettled conditions or something else ?

Well, if you look at the projected GFS output courtesy of, you can see we start next week with low pressure sitting just off the north west coast of Jutland. Knowing that low pressure rotates anti-clockwise in the northern Hemisphere, we can deduce that it will pull down cool north westerly winds to start next week, so I think temperatures will be on the lower than average side for the end of April, 10-12°C at a guess. So next week looks cool, particularly for eastern and north eastern coasts. Not the ideal bucket and spade week for Holkham I'd say. The previously-identified low pressure will pull rain down the eastern side of the U.K from Monday and this means the east will be wetter and the west will be better both rainfall and temperature-wise. As we get to the middle of next week, we lose those cool north westerly winds and they swing round to the south and south west, so better temperatures I think but.....Yes, more rain, this time for Ireland and then the U.K, with milder south westerly winds from late on Thursday, early on Friday onwards. We then look to move into a more unsettled period of weather, milder temperatures and plenty of rain as well.

With this pattern of weather in April, it has me thinking that we will get to May and then the tap will be turned off you know that kind of thing. We will see.

Agronomic Notes

Well quite a bit to talk about this week as we push past the middle of April.

So first up let's look at where we are set GDD-wise as we progress through April. Well the first thing is that the 2022 and 2023 GDD plots are set to move very close together as we come to the last week of April. On April 16th, 2022, we were on 171 GDD and in 2023, we were on 174 GDD, so practically dead on. It'll be interesting because I have an image of the Bluebells at Rutland Water taken on 22-04-2-22 and I hope to take a picture on the same date and compare. If the GDD plots are right, the two pictures should look very similar !

What is the relevance of this ?

Well if you look back to your PGR timings last year then you should be pretty similar for this month if you are basing them on GDD, though that does of course depend on how your 2023 GDD are shaping up vs. 2022. The above is just for one location, Thame, Oxford. If we look at the commencement of the Poa annua seedhead flush, last year we hit the 180GDD threshold on 17th April, 2022 and this year on the 18th April.

See what I mean about how similar we are year-on-year ?

How has growth been in April and how does it look till the end of the month ?

Well here I am switching to Growth Potential because I feel it more accurately shows actual growth.

So the red line shows consistent spring growth (I use 0.4 G.P) as my guide. Well we haven't had massive growth flushes in April but we have seen a clear peak around the 9th and 10th of April and unfortunately this coincided with heavy rain, hence the issue with trying to get higher-height-of-cut areas under control at the start of this month and of course over Easter when we had two short (4-day) weeks labour and resource-wise.

Weather Window

You can see we have another peak this week on the 16th and 17th, but this time it coincides with dry weather until Thursday, so my suggestion would be to prioritise getting such areas cut asap but also to look at PGR applications because you will have good spray uptake and getting a spray on thereafter will be difficult.

Just saying so don't shoot the messenger 😉

E.T is rising......

As the days stretch out and the evenings are noticeably lighter, one parameter that begins to predictably climb is E.T. Above you can see how it has tracked over March and April to date at our default location. Now that's nothing major, nothing close to applying stress on the grass plant but it will mean more of the rain we receive is lost through evaporation and therefore areas will dry out quicker. That's a bonus for when we get more rain at the end of the week, it won't sit around for ages. Even in a cool, wet week, we should evaporate 10mm ish at this time of year so that's good news for all your sodden areas after the end of last week's rainfall.

If you compare the 3 graphs, the Irish and Scottish locations have received better E.T levels of late than the central English one. (Thame)

April to date the rainfall vs. E.T readings for the 3 locations above are ;

Rainfall E.T Difference

Thame 38.4 mm 35.05 mm 3.35 mm

Shannon 33.6 mm 31.75 mm 1.85 mm

Dumbarton 95 mm 28.6 mm 66.4 mm

You can see why Scotland needs and deserves the weather break this week !

I'll leave it to chat-gpt to sign off this blog 😉

  1. Thank you for reading - This is a simple and polite way to end your blog post. It shows your appreciation for your readers and their time.

  2. Until next time - This sign off suggests that you'll be back with more content soon, and it's a great way to keep your readers engaged and anticipating your next post.

  3. Stay tuned - Similar to "until next time," this sign off also creates a sense of anticipation for future content.

  4. Best regards - This is a more formal way to end a blog post, and it's appropriate if your content is more professional or business-focused.

  5. Cheers - This is a casual sign off that can work well for a more lighthearted or informal blog post.

Ultimately, the sign off you choose will depend on the style and tone of your blog, as well as your personal preferences. Just make sure to keep it consistent with your overall brand voice and tone.

All the best 😊

Mark Hunt

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