Well quite a topsy-turvy type of weather we are having at the moment. (Try saying that after a few Tuborg)
A very warm end to March and then an Arctic blast which has brought snow flurries to many areas and an absolutely brutal windchill even in the middle of the day. Here’s a readout (sorry the axes are small type, can’t change that) from our Davis Vantage Pro2 weather station at Great Dunmow, Essex for yesterday, 6th April. It is sited on top of a hill so it picks up some pretty harsh windchill and E.T as well. The warmest it got from a windchill perspective was a sweltering 2°C and it was only above freezing from midday to 6 p.m. when a snow shower turned up and dropped the windchill to close on -3°C !
Cold and windy dries just as harshly as warm and windy and yesterday was the 3rd day in a row with > 3 mm of E.T.
Harsh weather indeed for winter, a bit ‘Day After Tomorrow’ for April !
Still nature carries on almost oblivious with those warm southerly winds from last week ushering up more summer migrants. Last weekend I saw more Swallows arriving, an Osprey and loads of Blackcaps and Chiffchaffs (summer Warblers). They just need the weather to play ball now and I worry about there chances of survival if this cold weather persists as indeed it well may. That said when I fly fished on Monday afternoon, there were plenty of buzzers (midges) hatching even though it was only 3°C. I retired after 2 hours not being able to feel my finger tips, but with 16 Trout caught and released to add to the tally and a smile on my face 🙂
Now I haven’t spoke much about Hedgehogs since Bertie the Badger decimated our local population a year ago, I kind of gave up with them because it was awful to witness the carnage first hand. Badgers have a particular way of killing Hedgehogs. They grab them by the face and literally bite it off, shaking them vigorously. No Badger fan am I.
So a few weeks ago I noticed an odd shaped dropping on the patio and that night I put out some Hedgehog food and sure enough, an old timer visited (I recognised him as Reggie the Hedgie 🙂 ).
I’ve since invested in a Wildlife camera (thanks Rob, Iain for the nudge) and sure enough I now have 3 Hedgepiglets visiting the garden with at least one resident.
That’s ace and it brings a smile to my face every evening. Nature always finds a way I think the quote was from Jurassic Park and invariably it does.
Onto the matter in hand, the Baltic blast (makes a change from Beast from the East) and the chances of it continuing…..
General Weather Situation
So as you can see from the GFS output from yesterday, the perpetrator responsible for this current very cold weather is a low pressure system sitting over northern Sweden / Finland. This is sending down a very cold Arctic airflow on strong northerly winds. So starting off Monday, we are quieter than yesterday when the winds reached gale force at times. We will also see far less of those wintry showers as well with currently a smattering over the west of Ireland, Central Scotland and The South West. Through the day we will see a continuation of those wintry showers across Connacht and down the west coast of Ireland into Kerry but elsewhere it looks like a clearer picture with those snow showers over Scotland becoming few and far between. Not quite as windy as yesterday but still bitterly cold after a hard frost (-3°C here). There will be some spells of wintry sunshine especially during the morning before more cloud builds in the afternoon everywhere. So mainly dry for the U.K & Ireland, away from those western coasts, remaining bitterly cold with more in the way of cloud cover in the afternoon raising temperatures a degree or two, with 7-9°C likely for England, Wales and Ireland and Scotland a degree or two down on that.
Overnight into Thursday we will carry that cloud cover over so that means less chance of a harsh frost and Thursday will also bring a change in the wind direction to westerly. This will raise the temperature nicely with double figures just likely across the south of England. Overnight a band of rain will push into Northern Ireland and the western half of Scotland so a wet start to Thursday here. Through the morning this rain will intensify and push south across The Borders into The Lakes falling as a mix of wintry showers and snow. The western half of Scotland will see this rain / snow over elevation mix in for the day and indeed during the afternoon it will push inland across Scotland and south into the north of England. For Ireland, England and Wales, we look to be dry here again, except for those persistent wintry showers across The North West. Later in the day we will also see some showers across northern Connact. Further south we look to be dry and cloudy but with a westerly wind in situ, those temperatures will rise to high single / low double figures across Ireland, Wales and England, buoyed on by a westerly wind, so it’ll feel much milder.
Closing out a very short week forecasting-wise, Friday sees that band of rain drift southwards overnight into northern England and Wales and it joins a much more unsettled picture for the U.K & Ireland, with showers from the off, some of them wintry over elevation for the north and south of Ireland, Central Scotland and North Wales. During the morning we will see those showers drifting further south into The Midlands, South Wales and across The Irish Sea, the rain across the north will drift south as well. A pretty dull affair is Friday with plenty of cloud around across all areas. During the afternoon, we will see those showers consolidate over northern Scotland, The Borders and north of England. At the same time that band of rain across the north Midlands will drift southwards into southern and eastern England. The same pattern occurs for Ireland with rain drifting south into central and eastern areas through the course of the afternoon. No great shakes temperature-wise, with 6-9°C the norm, but for southern England we may just see some low double figures again. During the day that westerly wind swings back to a more northerly bias, setting up a cold weekend I’m afraid.
So as hinted the outlook for the weekend is unsettled with Saturday starting reasonably bright but showers soon develop. Probably most notable across East Anglia, the south and north of England, with some snow amongst it from the far south from the word go. Plenty of showers developing through the course of Saturday afternoon as well for all areas after a drier, bright morning for Scotland and Ireland. The wind will be back into the north east so that means a higher likelihood of wintry showers pushing in off The North Sea and a return to some pretty low windchill figures. Can’t wait as I’ll be sitting in a boat pursuing Trout :). Temperature-wise, 7-9°C I think will be the norm across all areas but it’ll feel much cooler with that wind direction. Sunday looks a much brighter affair but with that persistently cold, north easterly wind, you can still expect wintry showers down the east coast of England and possibly for Ireland as well. A bit colder on Sunday despite the brightness, so 6-8°C again I think.
As you can see from the GFS image above for the start of next week we have a complicated weather situation on our hands with that cold airstream still pulling down from northern Scandinavia.
So is the weather going to warm up ?…..well in a nutshell, a little, but no sign of significant warmth in the next 7-10 days from the forecasts I’m looking at, unless something changes radically. Next week looks to return us to sharp frosts, some snow showers for Northern Ireland, Scotland and the north west and this moisture will gradually sink south through Tuesday and Wednesday into Wales and the southern half of the U.K. Winds will be lighter in general mid-week, so I don’t expect such a windchill as we have experienced of late and typically I’d say 8-10°C will be the norm, but colder in the north. As we progress through the second half of the week, those wintry showers become less frequent and confined to coastal areas and with lighter winds we will see temperatures pick up towards the 10-12°C range with less risk of night frost. So not a huge amount of warmth around, a little moisture and some night frosts. April 2021 to me already looks like going down as one of the coldest in recent years and I bet we run towards the end of the month and then suddenly we are into summer in May with nothing in-between..
So since this is the first blog of the month, I will start with looking back at last month…
GDD – March 2021 – Thame location, U.K
So as we can see from the stats, March 2021 came in with a total GDD of 52, which would put it towards the low end of ‘normal’. Those statistics are deceptive though as the vast majority of those GDD came in the last 5 days as you can see from the daily GDD output above. Up until then we had very little daily GDD, to be precise the last 5 days of March contributed 31 out of a total of 52GDD, so all in all, March was a poor growth month and April is if anything starting off rather worse.
Cumulative GDD-wise, we are up to 106GDD by the end of March 2021 and again this total places the start of the year sort of mid-pack, nothing special I’d say and a long way away from what we would think of as a good spring from a growth perspective. Compared to last year we were 20GDD behind at the end of March and falling further behind by the day as we go into April.
On this day last year at this location we were enjoying 19°C and our cumulative GDD from Jan 1st was up to 171.5GDD.
Today at the same location, it’s currently 4.9°C, with a windchill temperature of 1.2°C and the cumulative GDD is 109.2.
Last year, the cumulative GDD reached 109 on 7th March, so currently we are tracking a month behind last year !….How do you like them apples ?
U.K Locations – March 2021 – Growth Potential and Rainfall
So here’s how we stack up and again you can see the value of using Growth Potential rather than GDD. Bearing in mind the maximum value for March with 31 days x 1.0 optimum G.P = 31, the values above indicate that the growth varies from 18 – 23% of optimum dependent on location. The 2 lowest G.P figures come from the Great Dunmow and Sevenoaks locations in the south east of England and the highest G.P figure comes from Devon and this graphically illustrates how easterly winds shaped the weather and growth patterns during March 2021. The further away you were from the east coast, the better. The same is true for Ireland as we will see shortly. Rainfall-wise, a dry month which is continuing into April with the North Wales location coming in the wettest. In general the rainfall was pretty evenly spread but York came in as the driest location last month.
Irish Locations – March 2021 – Growth Potential and Rainfall
An interesting set of stats from over The Irish Sea.
On the whole the growth levels are very similar to the U.K locations, varying from 18-25% of optimum (total monthly G.P = 31).
Again following the same pattern, the eastern locations tended to show lower levels of growth because that easterly wind lost temperature travelling over The Irish Sea and so blew cool on eastern coasts.
The east and south east of Ireland locations also showed lower monthly rainfall with Dublin and Killiney coming in at 29.4 and 18 mm respectively. So cold and dry in the east, a little milder and obviously wetter across on the south west, but effectively the U.K and Ireland showed very similar stats for March 2021.
How are we faring vs. 2020 growth-wise ?
Well if we compare 2021 with 2020 we get two very different pictures dependent on which side of The Irish Sea you are sitting.
So first up looking at our base location of Thame, Oxfordshire and comparing the cumulative Growth Potential from Jan 1st – March 31st for 2021 and 2020 we find the following ;
So you can clearly see how good 2020 was from a growth perspective. It got out of the traps fast in January and never looked back with an almost straight line through to the end of March, perfect and such a pity we were locked down for some of it. We reached the same cumulative G.P figure on March 14th, 2020 that we reached at the end of March in 2021, so we were already 17 days behind last year at the end of March and this gap has grown with practically zero G.P in April 2021 vs. good growth last year. As commented on above, we are a month behind looking at 7th April, 2021 vs. 7th April 2020, from a pure cumulative growth perspective.
So 2021 is a slow starter from a growth perspective and I think we will continue to slip behind as we go through this month with no significant warmth on the way.
The picture across The Irish Sea is very different and I was quite surprised when I saw the shape of the cumulative G.P curves because I thought an eastern location would be behind last year as well. As you can see from the graph above, 2020 did track ahead of 2021 until around the end of February and then the two curves have been very similar through March with 2021 ending up 5 days ahead of the same cumulative G.P point last year. It’ll be interesting to repeat both locations at the end of April as I suspect Ireland is following the same pattern as the U.K in April, cold and dry.
We are drying out very fast…
April has started off very dry and very cold with some significant windchill. The air of late has been unusually dry with a low relative humidity and this has caused significant drying of the turf surface.
Now in the wetter north and north westerly locations, this is probably a god send, but in the drier east and south, surfaces have dried down massively over the last 4-5 days.
Consider these stats for April from our Great Dunmow, Essex location.
So you can see, no rainfall recorded over the first 7 days of April and a total E.T figure of 17.2mm. If you look at the last few days you can see the mean relative humidity (RH mean) numbers have been low, with a figure of 56% recorded on the 5th April. The resulting E.T figure was 3.56 mm for the same day, the highest figure we have recorded so far this year. Why is this ?
Well when the air is drier, it has a lower moisture content (and hence a lower relative humidity figure) and therefore moisture can readily evaporate into the atmosphere, so we see high E.T values. So of late the cold, dry wind has removed a lot of moisture from the soil, whereas if that air was more humid and therefore had a higher moisture content, then less moisture would be able to evaporate from the soil into the air.
So just because it’s cold at the moment doesn’t mean moisture loss is any less significant than if it was warmer. With the low temperatures, the grass plant is dormant, so it isn’t growing and utilising moisture but it will be drying out due to the wind so we may start to see cold air desiccation later this week, particularly in the east and south east. With the high wind speeds at the moment, even contemplating irrigation is pretty pointless because you just won’t wet up the surface of the profile significantly. Better to wait to the wind drops and we pick up some milder air or more likely some showers Friday and Saturday.
OK that’s it for now, this has been a long, protracted blog and it is late, so my apologies. It hasn’t been helped by a mis-functioning mouse which has been flying all around my computer screen of its own accord and making work difficult and me feel sick just watching it. I can assure you it’ll soon be heading for the wall behind my desk at great speed 🙂
All the best, wrap up well.