Na­ture and Nur­ture

Cape Bre­ton Weather

The Victoria Standard - - Weather - BILL DANIELSON

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.

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