Wednesday 16th October - another almost perfect day to swim those extra kilometres, whether you are training for an event, or general exercise infusing morning vitamin sea, or simply to search for sea life or capture that "money shot"... today was a great day for all of the above and so much more. Whales were spotted heading South to the Antarctic wilderness for the summer....
Water temp: 18.7 degrees
air temp at 7am: 11.3 degrees
conditions: ever so slight swell from the SSE (thats South South East), flat across the bay with a few little bumps as the SSE swell curved around the Bower, a light, with zephyrs of light, gentle breeze
vibe: happy for wonderful conditions & abundant sea life again (and funny fish face photos!)!
The talented mermaid Petra once again ensured that the daily talking point (or should I say chalking point) was displayed on the wall before 7am. The addition of swell (height and direction) and wind direction & speed are fabulous as the visual reference and provides us information to compare the to the sea state observed. Understanding that relationship will help educate all of us as to how to read the forecasts and determine what kind of swim to expect (well, as much as we can rely on forecasts!). I was lucky to learn to sail when I was young. I learned to look for signs on the water to measure wind speed in Knots (proxy for nautical miles per hour). Overseas, wind speed is measured and reported in Knots (or the Beaufort scale which is based in knots). In recent years, Australian news feeds have been reporting wind speed in Kilometres per hour. I thought the B&B community may be interested in a bit of history and the points of difference, as a small poll this morning (there werent many swimmers!) indicated that both measurements were pretty much equally referred to.
A few fun facts about the historical measurement of wind speed and the concept of a nautical mile & a "knot":
- 1450 Leon Battista invented the first instrument to measure wind speed - an anemometer (from the Greek word for wind, “anemos”), which measures wind velocity (number of revolutions over a set time) using a disk placed perpendicular to the wind. The familiar "spinning cup” anemometer (which is still used widely today) was invented in 1846, and the sonic anemometer was first developed in 1994 (modern aenometers can measure wind speed in km/h, knots and metres per second which is commonly used in scientific measurements such as the speed of light (light speed for star wars fans!) and sound.
- a "knot" refers to a historical (17th century) measurement of ship speed in the days of sailing ships where crew would throw a rope (full of knots evenly spaced) over the side and count the number of knots that passed over a period of time, ie per hour, so references to "knot" are "nautical miles per hour"
- A nautical mile is based on the circumference of planet Earth. If the Earth were to be cut in half at the equator, you could pick up one of the halves and look at the equator as a circle. That circle is divided into 360 degrees, and a degree into 60 minutes. A minute of arc on planet Earth is 1 nautical mile (approx 1.8km give or take).
- Therefore, the concept behind the nautical mile is that it takes into account the curvature of the earth. A measurement in Kilometres (or simple miles) generally refers to shorter land based distance measurements and more for "flat" surfaces (music to your ears if you are a "flat earther" ha ha).
- in the northern hemisphere in particular, "breeze" over oceans, lakes and water is measured using the "beaufort scale" - developed by Britain's Admiral Sir Francis Beaufort (1774-1857) in 1805 to help sailors estimate the winds via visual observations (from 1-12 where 12 is hurricane force!). Whilst we dont often refer to the beaufort scale in Australia, recognising the signs is useful information for when travelling overseas especially if you are planning a sailing trip and need to understand the local forecasts (http://www.bom.gov.au/marine/knowledge-centre/reference/wind.shtml).
Somewhere along the line, the term "knot" entered the vernacular to measure, report and forecast wind speed and boat speed as it took into account the curvature of the earth. Like sailing vessels and aeroplanes, wind also travels over the curvature of the earth. Therefore, knots (as opposed to simple km or miles per hour) are generally considered a more accurate way of predicting & measuring how a boat, plane or wind traverses the face of the earth.
In the mid 1970's, Australia started reporting wind speed in kilometres per hour for "land based" posittions as well as knots for nautical and aviation use. Quite a few people i spoke to today related to km per hour as they can compare reported wind speed to how fast their vehicle feels it is travelling, whereas those who prefer to refer to wind speed in knots look for signs on the water.
So, what does this mean for swimmers? The answer is, personal preference. A "quick reckoner" to convert km per hour to knots is to divide by 2 (its actually 1.8 - something - but 2 will give a proxy). As a general rule, swell east of SSE depending on wave height can be a little tricky, and breese from "onshore" direction (from NE or SE as is the prevailing sea breeze on the East Coast) can also exacerbate messiness and conditions (and in the case of NE, bringing the "blue peril!"). The forecast information today, indicated a sublime swim which it deinitely was!
At the end of the day, information about wave height and direction, and wind speed and direction is incredibly valuable, as we build up our own "knowledge bank" to help us "forecast" the type of condiions we may face and therefore determine whether to swim, or not to swim, or how far and where to swim (or to use flippers, wear a wetsuit or not!). So if you see km per hour on the temperature wall and you are a "knot" person, simply divide by 2 (or look for the signs!) and you will be equally happy :)
Of course, no matter the reported forecast, mother nature is always the boss and frequently frustrates sailors in particular by changing direction and speed, and even disappearing altogether (as happened to us last night in the Royal Sydney Yacht Squadron Tuesday twilight yacht race!).
As always, take care of each other, be kind, look out for and after each other and have a wonderful wednesday!
Jocelyn
A few reminders!
1) B&B talent quest finals are Tuesday 22nd October - still time to buy your tickets!
https://events.humanitix.com/bold-and-beautiful-s-got-talent?_gl=1%2A1sg0pt6%2A_gcl_aw%2AR0NMLjE3MjYyOTU1NzkuQ2p3S0NBand4WS0zQmhBdUVpd0F1N1k2czZ6UENjajhoZXhUNktwb3JQdzUtWkh5MjJRSVEyRHI3YXp2eXRGSndJNHJFSDZEZ0lsbWd4b0NQdUVRQXZEX0J3RQ..%2A_gcl_au%2ANzU5MTYwMTkwLjE3MjM2ODY4NTU.%2A_ga%2AMTI5Mjc0NDUzLjE3MjM2ODY4NTY.%2A_ga_LHKW5FR9N6%2AMTcyNjI5NTU3OC4xMy4xLjE3MjYyOTY3NDIuMjMuMC4w&fbclid=IwY2xjawF8Xr1leHRuA2FlbQIxMQABHZhOLHxtVyfD6C97s1jVj-1ToPTg8qs2rnR1TjFOrqf0I185zhZ96fkoBg_aem_I2EbWX1H9XzQlDROALPSRw
2) winter badges are still available, see Ian at the welcome desk with Cash or tap & go
3) Quite a few B&B swimmers have photos shortlisfed in the Northern Beaches Photo competition - take a look and vote for your favourite!
https://www.northernbeaches.nsw.gov.au/things-to-do/whats/council-event-program/ocean-festival/underwater-photo-competition-2024
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