what direction will the hudson river be flowing on sunday morning?
July 8, 2005 10:01 AM   Subscribe

I'm doing the New York City Triathlon on Sunday morning and want to know if I'm swimming with, or against the current. Here's a link to the tide chart I referenced: http://www.columbia.edu/~tedb/tri/tideChart.html and the tool used to construct it: http://tbone.biol.sc.edu/tide/tideshow.cgi My guess is that folks starting earlier in the day will have the current against them, but that it will weaken as the tide changes. The swim starts at 99th street and goes to 79th Street. More on the event itself: http://www.nyctri.com/. Thanks for taking a look!
posted by teddyb109 to Sports, Hobbies, & Recreation (4 answers total)
Response by poster: I should add that the race begins at 6 am. My wave starts around 6:45am. The last wave of racers leaves at 9:30 am.
posted by teddyb109 at 10:02 AM on July 8, 2005

Mod note: hyperlinked your links
posted by jessamyn (staff) at 10:26 AM on July 8, 2005

Best answer: Actually, you're linking to a current (as in flow) chart, which is a little different than the tide charts you usually see in the paper. The chart you link to suggests the current will be downstream (that is towards 79th street from 99th street) until 10:15 a.m. That makes sense from a race organizer's perspective, as progress against maximal tidal currents in the Hudson can be (all but?) impossible.

If you look at a tide chart at the same station and date (the next station choice on the select a different site page,) you'll see low tide at 6:33 a.m., with the tide then rising for a while before the current turns. What's going on here?

This apparent paradox is because the Hudson has a net outflow to the ocean, so water can pile up even when the current is downstream -- it's just not downstream enough to get it all out.

Also understand that these times are dependent on, among other things, winter precipitation, recent rainfall, wind and pressure differences over the region, so there will be some variation this model isn't picking up. The Coast Guard might be able to give you a better prediction for two days out (I don't know but it might be worth a shot.)

The moral of the story: Tidal rivers are weird.
posted by Opposite George at 4:50 PM on July 8, 2005

Response by poster: Great Answer!!!! Thanks!!! This was a much more informative than the scoop we got at the race briefing today: there will be a stronger current downtown to start, but that it will get weaker as the day goes on. It also makes sense that then that the elite athletes will be starting their swim at 9:30. Again, many thanks. I'm eager to learn more about tides now. Until last week, I just thought the Hudson flowed down and out into the ocean...
posted by teddyb109 at 6:33 PM on July 8, 2005

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