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Dear Friends, October has fallen prey, yet again, to that persistent pattern, with low-pressure stubbornly dominating west and north-west of Scotland whilst high-pressure dominates over central and Eastern Europe and over the Azores: This regime' is occasionally interrupted by the wet, windy blast of some ex-hurricane that skirts the western coasts and brings horribly warm sticky air- totally inappropriate for October - to northern Britain as much as anything else! But it is the relentless prevalence of the High-Pressure over Europe and Low-Pressure South Of Iceland, and the persistent muggy, yucky and damp South or South-westerly Winds this Stubbornly Persistent Weather-Pattern brings that is the greatest cause of concern. These winds bring warm humid air up from the Azores, plenty of dankness and the wind and cloud-cover at night, not to mention the warmth of the airmasses, prevents anything like frost at night. The reasons for this pattern at this time of year are fairly obvious: The North Atlantic is just past it's warmest in October (so strong high-pressure seldom persists over it), whilst seasonal net radiative cooling over Central Europe encourages high-pressure to form there instead. The other main influence on the weather-patterns in mid and higher latitudes in October is the sharp seasonal cooling of the High-Arctic which quickly becomes very cold, though the Arctic cold is seldom extensive enough to help precipitate cold Arctic outbreaks these autumns it is sufficient to cause a big increase in the atmospheric temperature and pressure gradients between the Arctic and still-warm mid-latitude oceans so as to encourage some deep depressions to form. With high-pressure over Europe and the three-wave pattern of the upper Circumpolar Vortex these depressions have a tendency to linger south of Iceland whilst high-pressure dominates Europe. Another elemental reason why we have south-westerlies for much of the year, with the possible exception of late-spring is due to the fact that the Earth rotates. Easterly trade winds in low latitudes constantly impart westerly Atmospheric Angular Momentum to the atmosphere as a result of the winds blowing in a direction opposite to that in which the Earth rotates. This Westerly Atmospheric Angular Momentum does not dissappear as this would transgress the fundamental physical Law of Conservation of Angular Momentum, which stipulates that the total Angular Momentum of a rotating body must remain constant unless acted on by an outside force: Tidal influences from the Moon and Sun are so small as to have no meaningful impact on Westerly Atmospheric Angular Momentum that could really affect our weather. What goes up must, therefore, eventually come down and under current climatic conditions the excess Westerly Atmospheric Angular Momentum in stiff west and south-west winds that dominate in higher latitudes. Problem is, we are getting more of the south-westerly variety rather than north-west or even westerly winds that would be just as (if not more) effective at removing excess Westerly Atmospheric Angular Momentum from the global atmospheric circulation. For us who live in Scotland and the North of England, in particular the causes of the recent autumn weather-patterns are maybe a little academic, but the persistent mildness, damp air and the proliferation of bugs brought by the muggy October weather that results from persistent south-westerlies is starting to grate! It is utterly shocking that we should have to wait until November for the first air-frost! Even at my home in the North Pennines, at over 400 metres above sea-level, these are the extreme minima that I have recorded in October since 2010: 2010:-2C, 2011: 0C, 2012: -2C, 2013: 3C (!!), 2014: 0C, 2015: 0C, 2016: 0C, and the weather -pattern remains most unconducive to frost to the end of October 2017 (extreme low so far just 2C).