NOAA tides and currents observations web page

[Captain Larry-DH]

Here’s a good page to bookmark- it shows ACTUAL tide and current observations updated every 6 minutes. (This is very different from predicted).
https://tidesandcurrents.noaa.gov/stations.html?type=Water+Levels

This can be very helpful if you’re thinking of squeezing under a bridge or transiting through thin water.

PS- I found out about it from the Sherer’s Cruising The ICW website http://fleetwing.blogspot.com/. Another great resource.

 

[smokey73]

Interesting data but will take a lot of "interpolation" to have much use on the ICW for the bridges along there. The active tide stations are few and far between, at least here in South Carolina and Georgia, where there is a lot of thin water along the ICW and where there are bridges that have clearances less than 65 feet at high tide. I guess one could find the nearest active tide station that is covered in this data and then interpolate some assumed info for your location. For instance, if this morning it was 1 foot below the predicted tide a station XYZ 20 miles from here then it might be expected to be some number below the predicted tide station here at this bridge with marginal clearance. Awful risky at least for me with my 64 foot mast head height above the water. Not something I'd want to bet my rigging on. You'd have to do lot to know what is causing the change from the predicted? Is it wind driven? Is it driven by heavy rains upstream at a tide station influenced by river flow? Is it Global Warming? You'd need to know a lot of info probably not available to make a whole lot of use of these tables in everyday transits, especially since they are "past time" and "real time" and don't predict anything but show what "was" and what "is". Not sure how you'd use this for "what will it be right here" and even "what it is right here" unless you are right at the active tide station or know a whole lot about what is driving the change from predicted. If you know the latter, you probably are a local sailor there and already know what effects the tides (strong north wind, heavy rain yesterday, etc.)

What I found interesting is that in almost all of the cases, at least for the last few days at all but one of the tide stations I looked at in South Carolina and Georgia, the actual tide was 1/2 to 1 foot above the predicted tide. Why? The only tide station where it was near the predicted was at Ft Pulaski on the Savannah River at the entrance to Savannah Georgia?

Interesting data and thanks for posting the link

 

[smokey73]

I went to the blog referenced and it has a pretty good explanation on how the writer used the info. He is using Ft Pulaski as his data point for Fields Cut which can get very thin. Ft Pulaski isn't too far away so that makes some sense and is in keeping with what I indicated above. Not spot on but sufficiently nearby to be of some use. He also gives some data points on the NOAA site that are useful so I'm assuming he's already picked places that are a problem and stations that are nearby so that is a great resource. I still wouldn't be inclined to use the info for bridge heights (at least for my boat) since my air draft is so high. At his height I wouldn't worry to much about bridge height anyway so ripping his mast off is a concern, but not quite the concern I would have on "cutting it close". I'll keep using the bridge clearance gauges if they have them and local knowledge for those that don't where I live. By the way - be very cautious at the McTeer Bridge in Beaufort SC above about predicted mid tide!!! It has no bridge clearance boards and frequently is below 65 feet! It has claimed more than a few apurtanences at the top of a mast.

By the way, I didn't go looking everywhere so maybe there are some locations where it is spot on or very nearby a troublesome bridge or thin water and would be a great help. I just can't fathom the use in South Carolina except as a general knowledge, point of interest kind of thing.

 

[jssailem]

You guys ever use DeepZoom http://www.deepzoom.com/

 

[smokey73]

You guys ever use DeepZoom http://www.deepzoom.com/

Yep - great easily accessed info for predicted tides at various locations. Use it all the time. I assume the data for DeepZoom are the NOAA predicted tide tables. I can't imagine any other source. If so, the discussion was about using the "actual" tides observed at only selected tide stations to use that information for transiting thin water and bridge clearances at other locations.

Love DeepZoom since it is a one step process to get to the tide tables for a location though.

 

[jssailem]

@smokey73 As best I can figure the Deep zoom app uses the NOAA tide data. There is a check box in the “settings” feature.
As with most navigational issues you need to use all of the data you can develop.
For instance, I keep notes when I run through challenging routes. Write in a log, like sailors have done for years. . Tide levels, soundings at shoal crossing times, then comparisons to known sites. Deep zoom can provide a quick way to identify this data.
I speak with locals to glean their knowledgeedge and compare their input with the data I develop. One way to extrapolate data is to know the data at a specific sight and any local knowledge about the advance or delay for the tide level/currents at a remote location.
Bridges and shoals often have tide boards near critical locations. Checking the level before going under a bridge only make sense to the careful sailor.
There are also guide books and on line resources like Active Captain.
It is about using all the resources so you can develop an understanding of the area and plan for safe passage. Then record the results so you can refer back to it at a future time when you sail through the area.

 

[smokey73]

John,

I couldn't agree more. The NOAA actuals are one piece of data but one that requires a lot of knowledge and can be very susceptable to "misuse" if you don't understand what is causing the variation. For instance I know the bridge at Bell Haven NC on the ICW is heavily influenced by strong southerly winds so on my transit down the ICW I looked for that and since it was the case, went the long way around Roanke Island to avoid it. Using "local knowledge" is key but even that has to be taken with a grain of salt. On that same transit (around Roanoke Island) I pulled in at a fueling marina where the marina operator said to "favor the greens". Its of course my fault as the captain for not asking further questions but in my book "favor the greens" means be closer to the greens than the reds (maybe 3/4s of the way towards the greens, etc). In his book that meant be able to hug the greens (be able to reach out and touch the greens). It turned out the good water was actually outside the greens! Needless to say I ran aground but was able to get off.

I keep the same data and have actually been plotting the predicted tide at the nearest tide station (Downtown Beaufort SC) against the local knowledge at the McTeer Bridge for about a year now since there are no bridge clearance boards on that bridge. For the life of me I still can't seem to figure out the variation I'm getting but the data spread is narrowing with each measurement. Hence my caution about going through it at anything above about mid-tide if you have a 65 ft air clearance. I have to go through that bridge to get to the best sailing area! With my plot I can plan for when to get underway and be able to clear the bridge. Planning only though, still use the local knowledge until I get something better. Someday I'm going up on that bridge and drop a 100ft tape and get actuals for the bridge. You are absolutely correct to use every tool you have in your ditty bag, but one needs to be careful about the limitation of the tools you are using and know how to use them. That was my point about using the NOAA actuals. Without knowledge of the causess of the variation, unless you are very near the active station posted by NOAA its a tool that should be used with great caution.

 

[jssailem]

We are on the same navigational track.
We have discussed what is locally known as the “Ditch” on the Pacific NW Cruising forum here. @Terry Cox is a veteran of the ditch variations. There are shoals and local hazarads to be aware. Depending on your keel depth and pucker factor we have some tide levels that should not be challenged even when you are within the marked channel.
@LeslieTroyer and I ventured through at a plus 2 tide aboard his S/V Mahalo 6ft keel draft. Our passage went smoothly but there was a 100 yard section that gave us pause, as the depth sounder shrunk to and dipped below 1 foot. I asked several times, “your sure the sounder is adjusted to the bottom of the keel. Is there any additional fudge factor?”. In our discussion after words Les thought the plus 2 foot tide is a bit slim. We had been told by Terry that he uses a plus 1 tide as a guide.
And now for the rest of the story. We later learned that Terry describes his boat as having a shoal draft 5ft keel.

 

[Terry Cox]

We have discussed what is locally known as the “Ditch” on the Pacific NW Cruising forum here

The south end of the Ditch definitely gives pause to the puckersville idiom. However, over the years my tolerance for thin waters in these parts has increased considerably, unless of course it deals with rocks, then my stress level becomes elevated.

 

[heritage]

Noaa has a product that is new to me named Nowcast. Here it is for the St. Johns river.

https://tidesandcurrents.noaa.gov/o...fsregion=sj&subdomain=0&model_type=wl_nowcast

For the St. Johns, there is also a Nowcast that animates the predicted currents.