20th January – Mini Blog

Hi All,

Just a quickie blog today as I have to get my backside up to Harrogate earlier than usual this year for BTME 2020. If you feel your ears popping a bit more than usual in the early part of this week it is because we have very high pressure at the earth’s surface.

It may also affect T.V and Radio signals as well. When I say very high pressure, my Netatmo is currently showing 1052.4 mb, which is the highest I’ve ever seen it register. Apparently the early part of this week will record the highest pressure we have measured since 1902 (which was 1053 mb !). That’s a big meteorological wow !

Somewhat hilariously The Daily Mail were warning that there may be a T.V blackout during ‘Dancing on Ice’, now wouldn’t that have been a god send 🙂 !!

Isn’t it nice to finally have a bit of proper winter weather ?

I was out at Pitsford reservoir, Northants before the sun came up on Saturday morning waiting for the Trout to wake up. Simply beautiful, very parky yes, nose tingling, affirmative, but utterly gorgeous, yes sir indeedy ! Did I catch ? Yep I certainly did 🙂

This weekend areas in the shade stayed frozen all day, there was ice on the puddles and we had two penetrating frosts on the bounce getting down to -4°C.  Nice to see a bit of winter finally, but will it last ?

General Weather Summary for w/c 20/01/20

Well this week will see high pressure stay in charge pretty much for the whole week but again as correctly predicted last week (I know I bang my own drum but somebody has to :)) we will see that high pressure push away in time for the weekend I am afraid. So the first part of the week looks dry, cold with some night frost and early morning fog. Day temperatures up to 6-10°C and night temperatures dipping down to close to freezing dependent on cloud cover in your location. The change comes about during Thursday when we will begin to see more in the way of cloud cover pushing down from the north together with the arrival of rain to the north-west of Scotland. This front of rain and wintry showers will mainly stay confined to that area making little progress south into Friday. On Friday morning we will see the wind direction change from southerly / south-easterly round to south westerly.  Dry through Friday for most areas though just duller and cloudier with no night frost. During the day we will see rain fronts amass over north-west Ireland pushing rain into Connacht, Northern Ireland and The Western Isles. Dry, cool with some sunshine and clouds on Friday for the most part. Through the course of Saturday we see more rain for the north-west of Ireland / west of Ireland and some of this will push inland on Saturday. That high pressure stubbornly refuses to relinquish its grip so away from the north-west of Ireland, Scotland and England, we look to stay dry, but noticeably milder and windier on Saturday. Sunday will see more rain across Ireland, Scotland and West Wales pushing into South Wales later in the day. Some of those showers may push inland later in the day.

Weather Outlook

So this time next week expect us to be back in a westerly air flow with strong to gale force winds and blustery showers.  Those showers are set to turn increasingly wintry across Scotland with blizzard conditions likely over higher ground. At this stage that cold air looks to extend down to The Pennines and no further south but we will see. Windy, dull and milder in the south with rain pushing through on Monday on a strong wind. Showers continuing through Tuesday into Wednesday before heavier rain arrives across Ireland and The South West through Thursday into Friday. It then looks like we have a transitory high pressure so that’ll dry things up a bit and push the rain further north before settling back into the same very wind, wet and mild (ish) weather pattern going into early February.

Agronomic Notes

Microdochium nivale disease pressure

The transition from high pressure to low pressure later in the week may bring with it some unwelcome Microdochium disease pressure across Ireland and the west of the U.K initially as that milder air pushes in and later into central and eastern areas. So before we see the wind ramp up and change direction at the end of the week we may see a peak of activity. At this stage I guess you may see activity around existing scars rather than new infection sites.

Leaf Dry Down

This winter one of the stand outs learns in my view has been the lower Microdochium nivale disease pressure during periods of low pressure i.e unsettled, wet, mild and windy vs. high pressure patterns characterised by low winds, mild night temperatures (sometimes) and heavy dews.

Now there are any number of reasons why this could be the case, but for sure one of the issues facing Microdochium nivale from a fungal development perspective is the rapidly alternating wet and dry conditions on the leaf surface.

Last week we had some wet and windy weather so I’ve downloaded the leaf moisture data and charted it against rainfall for the week. The results are below ;

The orange trace is the leaf moisture level as measured by a sensor vs. the blue columns which are rainfall. What you can see is that even during periods of rainfall, the leaf dried very quickly from its maximum leaf wetness level of 15 down to zero. 

In some cases it took less than an hour for the leaf to go from 100% maximum moisture level during a rain event to 25% moisture level because of the high wind speed associated with last week’s low pressure system.

Disease Triangle

Now imagine you are a fungus trying to develop across a leaf blade. You want stable conditions, in particular plant leaf moisture. In the above scenario we have wet, mild and windy conditions but what we don’t have is a consistently wetted up plant leaf.

Looking at the disease triangle above we can see that the one factor that doesn’t seem to be present during wet, mild and windy weather is a favourable environment for fungal mycelium development. We have moisture, we have temperature but it isn’t present in a consistent fashion.

Key to all of this is the strength of the wind because if it drops we will see dew development on the plant leaf at night and then Microdochium nivale can develop. So one of the most dangerous periods for us weather-wise is when we have low pressure system passing through and high pressure taking over or vice-versa. It also means sheltered areas with poor air flow are most at risk because they have lower wind levels, less leaf dry-down and heavier dew events.

That’s why taking scrub and volunteer trees out near greens to maximise light and air flow is a very necessary operation in this day and age, much as it irritates Joe Public and enviromentalists alike. So the option is leave them there and spray more pesticides to control disease…is that best practice I wonder ?

OK, time to pack my bags and ship out, looks like a very nice week for it, the Weathercheck link is available here

All the best.

Mark Hunt