Crossing the Gulf Stream from Florida to the Bahamas

What the sources say

• How fast it runs Characteristic average surface speed is on the order of 2.5 knots, increasing to about 4.5 knots off Cape Florida where the cross-sectional area of the channel is least. Those values are for the axis of the stream; the speed decreases gradually from the axis towards the edges.
• What to allow when crossing Crossing the stream at Jupiter or Fowey Rocks, an average allowance of 2.5 knots in a northerly direction should be made for the current.
• Where the inner edge is Between Fowey Rocks and Jupiter Inlet the inner edge lies very close to the shoreline. Along the coast generally, National Ocean Service observations put the average position of the inner edge inside the 100-fathom curve. The axis is estimated to be about 3 to 15 miles seaward of the north wall.
• Both speed and position move Both the speed and the position of the axis fluctuate from day to day, so every published figure for either is an average. On its western side the stream is separated from the coastal waters by a zone of rapidly falling temperature, called the north wall — west wall from Georgia south.
• A northeast wind and the sea it builds The Melbourne forecast office publishes a nomogram of significant wave heights over the Gulf Stream for wind speed and direction with an 18-hour duration. It notes that a 20 knot northeast wind can build sea heights in the Gulf Stream to around 12 feet, and a 15 knot northeast wind to about 9 feet.
• Where the current's position is broadcast NOAA Weather Radio stations from Key West to Cape Hatteras give the distance to the inshore edge of the stream with reference to a navigational light or buoy, its width where that is known, and the maximum temperature. The information comes largely from infrared satellite imagery and is not available during the warmer summer months south of about Jupiter Inlet.
• And where it is written down Gulf Stream location information is included in the coastal waters forecast synopsis written by the National Weather Service offices in Florida — Melbourne, Miami and Key West.