Dry September is a farmer’s friend

Combining in the fields
Combining in the fields

Who hath not see thee oft amid

Thy store?

Sometimes whoever seeks abroad

May find

Thee sitting careless on a

Granary floor,

Thy hair soft-lifted by the

Winnowing wind;

Or on a half-reaped furrow

Sound asleep,

Drowsed with the fume of poppies

While thy hook

Spares the next swath and all

Its twined flowers . . . . .

The immortality of John Keats’ classical picture dedicated to the old style harvesting days of September lives on with its colourful threads of reality into this September of the 21st century.

The “winnowing wind” of the modern harvest field, the next swath (the cutting by the combine harvester) may well be “fumed” with the dust, dirt and grime of summer’s deluged weeks.

My principal recollection in this respect concerned the times of smaller combines with smaller threshing drums.

These used to become clogged up with rogue weeds in the cornfield.

The pungent aromas of meddlesome chickweed and cat-mint, perhaps a sad reflection upon the fact that weed killing standards were probably far less efficient in the late 50s and early 1960s than they are today.

Strange though it may seem, the passage of time has not clouded the glorious entry of September 1964.

This proved to be quite a unique affair in the farming scene.

With perfection, its first light brought the realism of “mists and mellow fruitfulness,” as a pale moonlit fog clothed the countryside amid the first real tang of autumn’s atmosphere.

Later, in the brilliance of cloudless afternoons.

When fresh heathery breezes blew from the unpolluted outlines of the Hambleton Hills across the Vale of York, it seemed that the long warm summer was still in its fullest rapture, without a grain of harvest to gather.

The corn fields looked golden, but empty with the arid ground like concrete waiting for the plough.

There is a certain piece of wisdom about the weather at this time of the year.

When people used to claim that September rests upon summer’s laurels, - scarcely appropriate this year when summer failed to qualify for any laurels whatsoever!

However, there exists a definite tendency towards redemption in September’s nature, when the meteorological wrongs of summer are righted through the benign days, sometimes weeks in early autumn.

If we take a look at the series of Septembers since the millennium, seven out of the 12 years (eight if we can count 2012) have produced lengthy rainless spells, the longest being 20 rainless days in 2002, between 10 – 30.

The year 2004 produced 10 days, 1 – 10, 2007, 11 days, 2 – 13, with 12 days in both 2008 and 2009, 17-29 and 9 – 21 respectively.

The meteorological events leading up to this September’s critical harvesting break to ideal drying conditions were particularly interesting with regard to what was happening over the North Atlantic, with a depression situated about four hundred miles to the west of Ireland.

Another feature, positioned just north of the Azores, was a tropical storm, identified on the synoptic charts as “Kirk”, having a small, but intense circulation drawing warm, tropical air into its centre.

This storm was ultimately drawn into the circulation of the Atlantic depression further north, allowing its central core of extra – tropical air to inject more energy into the Atlantic depression.

Inevitably, this process caused the low pressure to deepen and intensify considerably as it tracked north – north-eastwards towards Iceland, reaching that area with a pressure centre of 965 millibars by the start of September.

At the same time, pressure rose steadily to the south-west of the British Isles, following the removal of Kirk, with a large high pressure of 1028 millibars.

The subsequent difference of pressure between the high to the south west and the low just east of Iceland caused steep pressure “gradient” establishing a good blast of drying Westerlies across the country.

This type of weather situation becomes the answer to every farmer’s prayer following a summer like 2012, creating the most favourable compromise of sunshine and excellent drying conditions across our region when we are on the boundary of a large established anticyclone to the south.

With low pressure hundreds of miles to the north, the weakening fronts become nothing more than high cloud formations of cirrus, looking as though they are stippled against the sky.

The very gentle upper air movements form a unique delicacy of formations of these clouds which have given us some of the most classical sunrises and sunsets during the opening days of the month.

Another feature, unique to our own micro-climate, is the “humidity shadow” a refined form of the characteristic rain-shadow effect.

This occurs when descending air currents around a high pressure system are dried by compression towards the surface.

Coupling this effect with the leeward down-slope of the Pennines in light westerly winds, the atmospheric humidity levels fall quite dramatically on sunny afternoons.

They even provide a helpful element of dryness long into the evenings, when the farmers experience September’s mild dewless nights.

This allows the modern combine harvesters to drone across the fields gathering grain long after sunset.