Nature and Nurture
Cape Breton Weather
Have you wondered how much of “you” is a result of your genetic makeup, straight from your parents, and how much is due to the environment in which you were raised? Child development experts love exploring the question, known as the “nature vs. nurture” problem.
We can ask the same question about our local weather: how much is determined by the atmosphere’s large-scale nature – its jet streams, fronts and storms? And what part is due to the nurturing and shaping Cape Breton Island imprints on the weather that arrives on our doorstep?
September 23 offered a nice example of nature and nurture at work. Weatherwise, it was a delightful early autumn day, featuring a broad, uniform flow of southwesterly winds which bathed Cape Breton in summer-like warmth. “Uniformity” was the basic nature of the weather that day. However, temperatures varied considerably across Cape Breton. At Roberta, the mercury peaked at 26.7 degrees, while Grand Étang only managed to reach 18.4. We can thank Cape Breton’s topography and its maritime setting for these variations, and others on the accompanying map. Let’s see how these differences came about.
A band of warmest readings (shown in red numbers) ran from Port Hawkesbury (at 25.6) to Roberta and Loch Lomond (25.2). In this warm corridor, the southwesterly breezes from Nova Scotia’s mainland threaded between the cooler waters of the Bras d'or Lake and Cape Breton's Atlantic south coast. These locales enjoyed the large-scale weather pattern unmodified by Cape Breton. All nature, no nurture.
Locales downwind (northeast) from the Bras d’or, comprising mostly of Cape Breton County, were slightly cooler than in the warm corridor. Traversing the cooler Bras d’or waters, the air temperature dropped a degree of two, leaving CBRM high temperatures in the 24’s. Mostly nature, a smidgen of nurture (cooling) by our great inland sea.
Meanwhile, the same warm, southwesterly wind flow resulted in markedly lower temperatures (in blue) in Inverness County north of Port Hawkesbury. The reason? Cape Breton’s cool offshore waters took the edge off the warmth, producing lower air temperatures at Grand Étang (18.4) and Cheticamp (22.2). The effect even extended inland to Hayes River (22.8) and Northeast Margaree (23.4.), amplified a bit by the cooling that air undergoes as it moves uphill. So, a mix of nature and nurture.
Cape Breton’s most active nurturing that day involved the air reaching coastal Victoria County from Smelt Brook (25.1) and Ingonish (25.5) to North Shore (25.8), and points between. Approaching Inverness county, the southwesterly air flow was cooled, same as the Cheticamp air; then, rising to the top of the Highlands, it was cooled further (down to 20.3 at North Mountain). Next came dramatic warming as it descended the highlands, reaching Atlantic shore communities at temperatures over 25 degrees. Three times in quick succession, Cape Breton altered the air destined for coastal Victoria County! Curious that after all that nurturing, the temperatures ended up the same as the unadulterated ones south of the Bras d'or.
On other days, Cape Breton’s impact can be vastly more forceful than these examples. Think of Les Suétes winds, of the towering snowbanks in the Highlands, of Unama'ki – “Land of the fogs.” These cases are more like “tough love” than nurturing. But it’s also a delight to see our island’s influence at work on the weather, even on the quietest sunny days.
Daily high temperatures on September 23, 2017. Red = 25 C or greater; Yellow = 23.0-24.9 C; Blue = less than 23.0 C. Data from Jonathan Buffett’s weather network and Environment Canada.