How are you monitoring tides and currents?

gnome4766gnome4766 Member
edited February 2013 in General Discussion
What methods are people using to monitor their local tidal behaviour. I know of many resources that informs you of the high and low tide. But what about more in depth analysis such as directions of currents, depths, temps are these resources available?

Comments

  • evmoevmo San FranciscoAdmin
    edited February 2013
    SCCOOS for currents and bathymetry.
    NOAA for nautical charts (depth).
    NOAA NDBC or TempBreak for water temp.

    But I live in SoCal. There is a lot of regional variation in data availability.
  • loneswimmerloneswimmer Admin
    edited February 2013
    For many areas such as the continental US, tidal ranges are much smaller than what we a re used to in Ireland or the UK. Tidal range in Ireland averages 5.5 to 6 metres, UK is up to about 7 metres excluding tidal bores.
    My sources:

    * My trusty annual printed tide tables for Ireland. Make sure to check the offsets from the main stations.
    * Sailors & fishermen.
    * There's a very detailed tidal map computer prediction of the currents around Ireland from the Marine Institute that seems to confirm other sources.
    * Tidal maps from South West Cruising Club that are invaluable.
    * Marine charts are the single best (but expensive) information source. And usually th eonly source for offshore.
    * The annual sailing almanac can be useful for ports and harbours.
    * David Walsh (a kayaker, not the well-known journalist who chased Lance Armstrong for 15) wrote a book called Oilean about kayaking around Ireland that was very useful.
    * I trust my own experience for the South East. I think it really helps to understand how the tides split around Ireland and the general flows. (Also I think most swimmers don't believe me when I tell them about tidal lag, the difference between high & low water, and slack tide, which not always the same.

    I have a bit of a thing about swimmers not learning more about tides and just accepting what is often flawed information, based on a theoretical flat lunar model, taking no account of local factors. I say it because that's what I used to do as a surfer. Ireland, as an island, situated far from the nearest null tidal spot in the west Atlantic, is a very complex tidal location, (as is the UK and the Channel).

    Edit: posted before I was finished.
  • david_barradavid_barra NYCharter Member
    edited February 2013
    There are data buoys all over the world. Some transmit very basic data, others; tons. I have an ipad app "Aye TIdes XL” which enables me to access this data by clicking on any of these buoys. Blue diamond “T”’s or “push pins” will bring up a a month of tide charts, by clicking any day, you can open a window that contains sine wave info like high and low tide times, sunrise, sunset, nautical twilight, moon cycle, etc. Click on a red diamond “C” and a sine wave chart for for current speed will come up. You can view that info in mph, knots, etc. There are many fewer “C”s on the map than “T”s.

    For nautical charts, I love the Navionics HD apps and use them for route planning as well as back up charts for my boat. They are often more detailed than other digital charts available. Knowing how the depths vary is perhaps the most important bit of information one can have to determine where those funky currents might be.

    The main factor that isn’t considered when these tide and current prediction charts are made... weather. There are some really great websites that present the wind, surface current, and surface temperatures in almost real time. Search “wind guru” for your area.

    I took a few screen shots of these apps, but can’t quite figure out how to post them here. If anyone likes I can send them via e-mail.

    ...anything worth doing is worth overdoing.

  • RonCollinsRonCollins Clearwater, Florida, USAMember
    edited February 2013

    Ron Collins Clearwater, Florida DistanceMatters.com

  • Looks useful Ron. Where are you getting that?
  • RonCollinsRonCollins Clearwater, Florida, USAMember
    The .gif above is from http://pritchard.marine.usf.edu/ It's a flow model of Tampa Bay.

    Ron Collins Clearwater, Florida DistanceMatters.com

  • SydneDSydneD Senior Member

    I am bumping this thread because I have the need to understand more about this. I have a swim in mind, that I've had in mind for years, and I need help with understanding currents and drift. I'm looking at a circumnavigation that will take many hours and need to understand the variables at work during a swim of probably 7-8 hours.

    Apps recommended? Things to read? And keep in mind that I need some pretty basic info to begin with as I grow my knowledge base. I'm starting as a novice in the planning department in terms of this.

    And yes, I am also reaching out to an organization in the area of my dream swim.

  • JenAJenA Charter Member
    edited June 22

    Pilots with good navigation software can figure things out in real time by letting their boat drift for a couple of moments.

    It's more micro-local data than wide-local data, but it's actual vs. predicted.

  • IronMikeIronMike inch.houseboat.primeCharter Member

    If I recall, @loneswimmer had some blog posts some time ago about tides. Maybe @evmo, too. If you tell everyone where, someone might already have info for you.

    Good luck!

    SydneD

    http://blogs.marathonswimmers.org/ironmike

    Where the hell is IronMike located? Find out here: https://what3words.com/

  • SydneDSydneD Senior Member

    Is it silly that I don't want to say yet? It's still in the works and is a swim that has not been done before. I almost want to go, swim it, then hand over my observer logs when it's all over. (I am a strangely private person that way.) Not worried someone will scoop it up, just don't want to put it out there yet. :)

    IronMikerosemarymint
  • timsroottimsroot Charter Member

    @SydneD - I get it. I'm somewhere in between, but I completely understand. Just make sure you get enough help

    SydneD
  • ChrisBChrisB Issaquah, WAMember

    Came across this...

    http://www.deepzoom.com/

    SydneD
  • JenAJenA Charter Member

    You could try calling up local oceanographers. In Canada, anyway, government oceanographers are responsible for publishing the tide tables. Every time I've called one up, they've been overwhelmingly supportive and helpful. They've always seemed delighted to discuss things with me. I suspect they don't get many calls from the public. :-)

    As I understand it, storm surge water causes large deviations from predicted conditions. Oceanographers tend to keep on top of such things to predict potential damage and public safety crises. I imagine they'd have a lot of helpful predictive data, and would generally be able to explain the conditions you could expect to face.

    SydneD
  • swimrn62swimrn62 NY, NYMember

    I would say local fisherman first, or paddlers and (if there are any) swimmers would be most helpful. No one knows local waters like those who are on it every day.

    SydneD
  • evmoevmo San FranciscoAdmin
    edited June 24

    SydneD said: I need help with understanding currents and drift. ... Apps recommended? Things to read? And keep in mind that I need some pretty basic info to begin with as I grow my knowledge base.

    NOAA is the big player in tide+current prediction for US waters:

    http://tidesandcurrents.noaa.gov

    There may be equivalent (probably government-funded) websites in other countries (?)

    A simpler interface for browsing NOAA-produced tidal models is here:

    http://tbone.biol.sc.edu/tide

    You may notice there are far more tide predictions than current predictions. And as a swimmer, you're sometimes more interested in the currents (water flow) than the tides (water levels). Though there are exceptions, such as when a coastal swim may be disrupted by extreme low or high tides.

    The reason is that currents are more difficult to model than tides, and depend a lot on specific and ever-changing features of the shoreline and bottom.

    NOAA has a great explanation of why currents are challenging to model here:

    https://tidesandcurrents.noaa.gov/meascurr.html

    Along the top horizontal menu of that page -- a link to an "Education" section. Read all of those articles -- very informative.

    https://tidesandcurrents.noaa.gov/education.html

    SydneDDanSimonelliIronMike
  • malinakamalinaka Seattle, WACharter Member

    Nothing beats good old fashion observation. Find a way to get out on the water and take some measurements. I once spent a day with a handheld GPS tied to a rescue tube tied to an anchor in a place NOAA didn't have any predictions, and it was the best current info I've ever found.

    ChrisgreeneIronMikeSydneD

    I don't wear a wetsuit; it gives the ocean a sporting chance.

  • pavlicovpavlicov NYCSenior Member

    @SydneD I read a lot of Wikipedia and subsequent links. But I am still ocean-clueless I think. Experience and talking to local people is always the best. Going to the fisherman bar near the beach and talk ...

    I don't know where you want to swim but I would be your crew anywhere in the world. Good luck planning it!

    SydneD
  • JenAJenA Charter Member
    edited June 24

    I think some people can read the shoreline and the bathymetry (underwater topography) and make decent guesses about the surface currents. It would be a really cool skill to have! I'm not sure how you develop it, though.

    One oceanographer I spoke with said that the data they predict off of (in the geography I was interested in, anyway) has a 2km resolution. He suggested that I probably wanted resolution of 100-200m. IE: the data they have on hand is appropriate for understanding the bigger picture, but it isn't precise enough to predict the more local phenomenon, such as eddies.

    Edit: Cool wikipedia fact? Eddies can be hundreds of kilometres in diameter, and can persist for years. Huh. I had no idea. :) Wikipedia: eddy.

    SydneD
  • SydneDSydneD Senior Member

    With the swim I am planning, I wouldn't be able to be there for too long before it so sadly, can't use personal observation over time. But, it's an area where there's a great kayak/water activity shop I have visited before. When we rented kayaks, they helped us navigate where they would drop the boats for us, and where we could reasonably get to for pickup later in the day. I want to reach out to them and discuss it, but right now, still figuring out when it might be reasonable for me to think about doing this. (It's going to be a little bit. A lot going on.)

    I've been in the water for hours there, and it varies widely depending upon where you are. (And isn't that part of the fun??)

    I also have a client working his way through the courses to get his captain's license and he has given me some resources in terms of just understanding drift and currents more generally. (Sidebar--he is incredible. Going to be 70 in August and wanted to learn how to swim because he loves boats and wants to get his license, just because. He's also a busy juvenile court judge and jazz drummer! The man can do anything!!)

    I almost feel like I want to read a book called "A beginner's guide to the ocean!" Sounds ridiculous but I think I am way too ignorant for someone who loves this sport as I do. And as I want to put together more of my own swims, it's a gap in my knowledge that I want to fix! I have depended upon the knowledge of race organizers way too much, and while they are generally fantastic, that feels silly to me.

  • NiekNiek Heiloo, NetherlandsCharter Member
    edited June 25

    @SydneD If you live at a sea coast you can practice your swimming with and against currents.

    As a general rule the currents coincide with the tides. At least here in the Netherlands and in the Channel they do strongly. The directions changes with the flood-tide or ebb-tide. Time between one flood and the other flood is around 12 hours and 15 minutes.

    If the tidal water has to squeeze between isles, around ness or the like the speed there will increase. venturi

    But there are the additional ocean currents that go 1 way despite the tides. They will affect the local tidal currents.

    Even river currents are effected by the tides. With high tide the river can even flow back in the direction of the source!

    So in general you have to know for your swimming spot in which direction it flows with ebb and which with flood. Around 6 hours later it flows the other way.

    Locally it will vary because of the geology. In the Waddenzee the ebb tide last longer than the flood tide. Water can't flow away as easy with the ebb tide as it can flow in with the flood tide.

    http://openwaterswimming.eu - Cold, wind, waves, sunburn, currents, jellyfish and flotsam! Hop in and join the fun!

  • SharkoSharko Sonoma County, CACharter Member

    Niek's advise is good and relates to our conditions on the west coast of California/San Francisco Bay....Study the published tides but then venture out in a safe test swim to develop experience and confidence. Try to have an exit plan if you make some wrong choices (how and where to get out) a kayak, boat and radio is a good idea in large bodies of water where you can be swept away from land....Tide charts don't capture things like the affects of wind and water run-off that can affect the tidal affects and currents. There is usually an expert on tides and currents in any sailing or rowing community.

    "I never met a shark I didn't like"

  • JenAJenA Charter Member
    edited June 25

    Several months ago, PBS did a documentary on the escape from Alcatraz. This documentary might be of specific interest to @suziedods, @evmo, and anyone else living in the SF area, and possibly @Niek for national pride and local contacts, as the oceanographers were all Dutch. :-)

    The documentary showed the use of software and even physical modelling to help understand the currents of the San Francisco bay. Some parts of the documentary give interesting insight into how oceanographers approach and solve problems.

    If you are in the US, the documentary is viewable here: http://www.pbs.org/wnet/secrets/alcatraz-escape-full-episode/2762/?button=fullepisode Those outside the US can console themselves with this computer simulation of the currents around Alcatraz: http://sfist.com/2014/12/16/play_this_dutch_scientists_escape_f.php

    The physical modelling was really interesting to me, especially because they chose not to solve the problem with software. Apparently, they have a small scale, detailed replication of the SF Bay that they use for predicting the origins of bodies that wash up shore. The physical model is small enough that they can replicate a 12-hour tide cycle in 15 minutes.

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