Mark Hunt’s Weather Assessment 24th May – 1st June 2010
Well, as predicted the high temperatures and warmth arrived last week and now we're sitting in a very warm airstream but, as you've probably seen, this is due to come to an end soon with cooler air asserting itself from the North in the form of a weak low pressure which will bring showers to Scotland and the North of England. I expect temperatures to be around mid-teens during the day, so 13°C down on what we're currently getting with more cloud cover and, therefore, a low risk of night frost (hopefully) and this weather pattern will stay pretty much settled for Ireland and England.
By now everyone wants to know when it's going to rain as areas have quickly moved to being drought-stressed with the high daily evapo-transpiration, but this is a tricky one due to the type and behaviour of the weather systems that are on the way. Basically, we have two low pressure systems coming. One on the continent (first) and one coming in from the Atlantic (next week) and both could potentially bring rain though, as we have consistently seen this year, Atlantic low's are very unreliable in terms of rainfall. Continental low pressure systems are more reliable in terms of bringing rain to the East of the country. I'd say there is an increasing chance of rain as we move towards the end of the week, with a high probability at present for a wet weekend and early part of next week, but at this stage we'll just have to wait and see.
This unreliability of rainfall is due to the jet stream folding in on itself and this pushes the rain either north or south of the U.K. and, if you believe the weather scientists, this will be a more frequent occurrence in the future because of the suggested relationship between Sunspot activity and the Jet Stream. Indeed this change in pattern of the Jet Stream has been identified as the reason why the last few winters have been colder and, if they are right, this will be the pattern for the near future as sunspot activity declines.
(See for a brief summary http://www.newscientist.com/article/mg20627564.800-quiet-sun-puts-europe-on-ice.html )
Agronomically, the temperature transition from the week previous when we were getting regular night frosts to last week’s 15°C night temperatures was quite a big step and this has kicked greens growth off, promoting a major perennial Poa seedhead flush and quite a bit of disease activity, namely Fusarium.
In some cases this is being grown out as quickly as it forms, but if a plant growth regulator has already been applied, it will make it more difficult to remove the mycelium by cutting and a fungicide treatment may become necessary unfortunately. Obviously in sandy or lighter soil areas, drought stress is kicking in with the very high localised temperatures (I recorded 35.5°C in my back garden over the weekend), so in these areas I would hold off on any physical work and delay a plant growth regulator hit until temperatures have settled down and hopefully we have some rain.
I'll update this on Wednesday if the rainfall pattern looks any clearer.
Mark Hunt
Technical Director
Headland Amenity Ltd
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