Tides and Currents

[Jim Hawkins]

Hey Gunni,

I have yet to visit the Gulf Stream. I've been out by the light at American Shoals when the stream has been close in and I've seen the dark blue waters out there but haven't gone into the current yet. I never go past the last channel marker without GPS, food, water and VHF etc. I'm a nervous sailor.

 

[Gunni]

Your caution is well founded, I can remember nearly 6kt current in the stream. And if the wind opposes the flow - look out!

 

[JohnShannon]

Well I was fooling around with open CPN at your location. It doesn't show the gulf stream current at all ??
But around your keys you see currents of varying directions and amplitudes i.e tidal in nature.

 

[Anonymous 121765]

Jim,

I liked what Stu, Head Sail & Gunni offered.
Know the wind & current times for your area.

I take alot of folks out that have little boating experience in my sailboat.
I always contour the day's sail to make it enjoyable for them based on their experience.
Sometimes, it's alittle boring but, hey, it's for them. I'm just looking to set the hook.

I also use the adage that sailing, "Is merely hours & hours of total enjoyment & relaxation intermittent with moments of shear terror." Remember, you are only flying sideways & you don't want to scare your guests and/or work hard.

CR

 

[rpwillia]

On the Potomac River, which is a tidal river, going with the tide can turn a 11 to 12 hour trip into an 8 hour transit. Or trying to sail against the tide with little to no wind will result in you sailing backward. Get a good tide app for your smartphone.

 

[gettinthere]

Navionics ap does a pretty nice job with current predictors. But there isnt much for Hawk Channel. The cuts between the islands indicate about 1.8k full flood and over 2k on the ebb. There is one indicator south of Key West that showed .2k flood and .6k ebb in a pass between Hawk and deep water. So evidently there isnt a lot up where you were out in Hawk Channel.

 

[MitchM]

I've been blown out to sea off the west florida coast on a hobie cat with a leaky pontoon. that was my first experience tides and currents, which at age 21 i hardly knew existed. the experience wasn't very pleasant after the 3 of us r realized we were miles away from home with nothing to drink .

so i offer the following: your local US power squadron has a great course called Advanced Piloting. the book alone is worth the nominal price of the course, about $75 for 8 weeks of classroom work with good videos, plus 2 books. The explanation of tides and currents , and how to calculate and predict them, is very good. and if you finish the course you'll get a perpetual discount on your boat insurance.

 

[Gunni]

Well I was fooling around with open CPN at your location. It doesn't show the gulf stream current at all ??

Find the lighthouses and you will find the edge of the GS.

 

[Jacktar]

Just a note to all the gulf stream is in the gulf (duh) it comes in from the south , goes around the edge of the gulf then south and east around the keys and back up to north along the Atlantic coast and then to Britain. But it also give rise to spin off currents that run counter to the main direction and when these hit certain land masses reverse again. So just heading out from shore you can hit three layers of currents in many areas. These gyrols are very powerful and when added to the tidal leakage from the Atlantic into the gulf thru certain openings between the keys and back plus the seich effect in the gulf that makes it only a two tide system things can get very interesting. Add in local winds and shallows which bend currents and change wave heights and its gets really tough to predict. This is why Local knowledge is so precious.

 

[JohnShannon]

my remark was that open CPN doesn't seem to show the GS current, although shows the centerline i.e location.
I think their current model just looks at tidal flows. But in FL that would be kinda a big omission

 

[Jim Hawkins]

NOAA always gives the position of the Gulf Stream in their reports and it varies quite a bit. Sometimes it's right snug up to the Am. Shoal Light and other times 35 miles out. I'll get out there later this summer I suppose when it's close in and the seas are calm. I assume it will be easier to predict than the eddies and currents around these islands although I'm sure the current will be far stronger.

THE APPROXIMATE SHOREWARD EDGE OF THE GULF STREAM CURRENT...AS OF JULY 22...
5 NM SOUTH OF DRY TORTUGAS LIGHT...ON LOGGERHEAD KEY.
1 NM SOUTH OF COSGROVE SHOAL LIGHT...OFF THE MARQUESAS KEYS.
2 NM SOUTH OF SAND KEY LIGHT...OFF KEY WEST.
4 NM SOUTH OF LOOE KEY...OFF BIG PINE KEY.
5 NM SOUTH OF SOMBRERO KEY LIGHT...OFF MARATHON.
4 NM SOUTHEAST OF ALLIGATOR REEF LIGHT...OFF ISLAMORADA.
1 NM SOUTHEAST OF MOLASSES REEF LIGHT...OFF KEY LARGO.
1 NM EAST OF CARYSFORT REEF LIGHT...OFF OCEAN REEF.

 

[agprice22]

Jim, yes. Tides create currents that can run in apparently opposite directions than prevailing ocean currents. Depending on the tide, sailing along the coast, you could have encountered a tidal current that aided your speed and moved you downstream of your destination or whatever. These tidal currents will change relative to the tide and topography in your area. That means that you could be running against the current one minute and with the current another minute in relation to inlets, streams, or rivers. Strong currents also create eddies that can be large and create currents that run the opposite direction of the prevailing tidal current as effected by bottom structures or shore structures. As an example, go to the beach in Florida and stand in the water. Unless you are at slack tide, there will be a current, probably heading away or toward the nearest inlet depending on whether the tide is incoming or outgoing to the inlet. Swim out a little bit. The current could be heading the opposite direction depending on whether there is a point or sand bar or jetty. Thus, knowing ocean currents is one thing, but knowing tide currents is very different.

 

[Stu Jackson]

I assume it will be easier to predict than the eddies and currents around these islands

There are all sorts of "models" of different conditions at different locations.

 

[Jim Hawkins]

Once again thanks all for the input on this. Although I suppose there's a whole science to tides and currents I think I picked the wrong name for this thread. I believe the best explanation for my original question of - How did I go so far when it seemed like I was hardly moving?, was best summed up in Gunni's post #16 and most likely had little to do with the tide, or currents for that matter.
After reading Gunni's post I saw right away in my head the concept of a boat heading dead downwind in a 5 knot breeze. If the foresail looses it's shape and gets slack it could only mean that the boat is moving nearly the same speed as the wind easing the pressure behind the sail. The deception of the ripples moving in the same direction was even easier to understand. Next time out I'll pay attention to the GPS and cipher on this a little more but I'm satisfied my question has been answered.
Thanks again.