Just for fun, here is every high and low tide for San Francisco Bay in 2016. Red dots are the high tides; blue dots are the low tides. (click to enlarge)
I found it interesting that the highest low tide of the year is lower than the lowest high tide of the year. There’s a certain narrow range of water levels — about 3.1-3.4 feet — which sees neither high tides nor low tides. Perhaps there’s some obvious reason for this, known to oceanographers, but it was news to me! I’m also curious if the non-overlap of high and low tides is true everywhere?
Here in San Francisco, the common sauna wisdom is that we just experienced one of the warmest winters in recent memory. The Dolphin Club’s Polar Bear Challenge was hardly challenging, and the South End’s “Dreaded 9th” of February swim was hardly dreaded.
Just how warm was it, though? I crunched the numbers from the NDBC, because, well, why not.
Here we see the last 15+ months of data from the Crissy Field station (FTPC1) inside San Francisco Bay, plotted in solid black. The dashed green, red, and blue lines show the long-term average, maxima, and minima for each day of the year, summarized over the eight years of available data from that station.
From July 2014 until just the past few days (early April 2015), Bay waters have been hovering 2-3 degrees (F) above the all-time highs (going back to 2006), and about 5 degrees above the long-term averages.
Eight years isn’t much data, unfortunately. Can we do better?
A bit: Lightstation 46026 – about two-thirds of the way out to the Farallones – has data going back to 1982.…
(tl; dr — 10 years of English Channel weather data, in a single CSV file. And some fun charts.)
Weather can turn on a dime in the English Channel, and the dreams (and finances) of English Channel swimmers often turn on the weather.
The most important source of information about that weather is a 156-foot lightvessel called Sandettie, which serves as both a floating lighthouse and a weather station. Here’s a nice photo.
Sandettie collects a variety of important meteorological data – air and sea temperatures, wind speed and direction, wave height and period, humidity, and barometric pressure. These data are then fed back to the UK Met Office, who publish the most recent 24 hours’ of observations on their website.
Anything before the last 24 hours are what the Met Office call “chargeable data” — at the rate of £6800per 10 years, per two elements (e.g., air temp & sea temp). According to the today’s exchange rate, that converts to no less than $11,575 USD.
LOL! (And yes, I actually requested a quote from the Met Office.)
Just sayin’: In the US, quality-controlled meteorological data are available from NOAA’s National Data Buoy Center — for free.…
SWOLF (“swim golf”) is a drill that measures swimming efficiency. A SWOLF score is your time (in seconds) on one lap of the pool, added to the number of strokes you took. Lower scores = Higher efficiency. SWOLF is a fuzzy, indirect measure of efficiency, because stroke count doesn’t necessarily reflect effort. In my view, the most precise definition of SWOLF is that it identifies the most efficient stroke count for a given level of effort.
I originally wrote about SWOLF in April 2012, and the post has become – by a wide margin – the most widely-read in the history of this blog. In a subsequent post a month later – “Stroke Count Games” – I described how SWOLF doesn’t quite capture the most efficient stroke count. At least for me, using stroke cycles (number of strokes divided by two) produces better results.
I wondered if this was true for other swimmers, so I asked any interested readers to send me their own data, using a test set of 8×100. Three readers sent me their results.…
Marathon swimmers talk a lot about rules – what should and shouldn’t be allowed during a swim – but as far as I know, there has never been any systematic study of what marathon swimmers actually think, as a matter of public opinion.
Google has a fun tool that lets you visualize trends in search queries submitted by its users. Google is often the first place people go to find out more about a given topic, so it’s a powerful measure of the public’s “interest” in that topic. Below are a few Google Trends graphs related to open water swimming.
Is open water swimming “growing”?
Interest in open water swimming is highly cyclical, with summer peaks and winter troughs. (Obviously.)
Two big “spikes” corresponding to the Olympic Games in 2008 and 2012.
Aside from the seasonal cycles and Olympic spikes, the peaks and troughs do seem to rising slightly over time.
What about two sub-genres of open water swimming: marathon swimming and triathlon swimming?
As expected, triathlon swimming is consistently bigger than marathon swimming. One exception: the surge of interest associated with the London Olympic 10K marathon swim.
What about the Triple Crown events: English Channel, Catalina Channel, and the Manhattan Island Marathon Swim?