Thursday, March 5, 2009

Waiting for the weather window to open

We're in fort Lauderdale, waiting for a weather window to jump over the Gulf Stream into the Bahamas.  Waiting for a weather window is a pretty common thing when you're a coastal cruiser.  In fact, you've heard us talk about it ever since we were stuck in Naples for an additional week.  If we ever head further south than the Bahamas, you're going to hear us talk about it even more.

So I thought I'd explain it a little, so you get an idea of what its all about.

When the wind blows, it generates waves.  If the waves are too big, we don't go.  There are a few rules that seem to determine what kind of waves a wind will generate.  The stronger the wind, the larger the waves.  The larger the stretch of water the wind blows over, the larger the waves.  The size of the waves aren't the only factor.  Their shape has a big effect as well.  When there's a chop, the waves have steep sides and are closer together.  This makes the boat bang around and can be pretty scary.  Shallower water tends to make choppier waves.  As does a current, when the waves are moving opposite to it's direction.  Which explains why going out underneath the Golden Gate Bridge when the tide is going out and the westerly wind has picked up can be very dangerous and yet in other conditions its flat enough for kayakers.

The gulf stream between Florida and the Bahamas is a 40 mile wide current going north at 2 - 3 knots.  A knot, by the way, is a nautical term of speed equivalent to about 1.1 mph.  When the wind is from the north, it's brutal.  Choppy waves 4 - 6 feet high.  It's not unusual for there to be a small craft warning in effect if the winds are anything above 20 knots.  When the wind is from the east to south-east, the seas are calmer, but then there's a head wind and we have to run straight into the waves.  Ideally, we want winds from the south or south-west.  By the second day of these winds the gulf stream will have calmed down and we'll have a window of opportunity to get across before the winds go back to the north - east quadrant.  This is our weather window.

Here's the weather forecast for the next few days, taken from the nws web site  :

TONIGHT
EAST WINDS 15 TO 20 KNOTS. NEAR SHORE...SEAS 4 TO 6 FEET SUBSIDING TO 2 TO 4 FEET. IN THE GULF STREAM...SEAS 4 TO 6 FEET. INTRACOASTAL WATERS CHOPPY IN EXPOSED AREAS.

FRIDAY
EAST WINDS AROUND 15 KNOTS. SEAS 2 TO 4 FEET NEAR SHORE AND UP TO 4 TO 6 FEET IN THE GULF STREAM. INTRACOASTAL WATERS A MODERATE CHOP.

FRIDAY NIGHT
EAST WINDS 10 TO 15 KNOTS. SEAS 3 TO 5 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

SATURDAY
EAST WINDS 10 TO 15 KNOTS. SEAS 3 TO 5 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

SATURDAY NIGHT
EAST WINDS 10 TO 15 KNOTS. SEAS 3 TO 5 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

SUNDAY
SOUTHEAST WINDS 10 TO 15 KNOTS. SEAS 2 TO 4 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

SUNDAY NIGHT
EAST WINDS 5 TO 10 KNOTS. SEAS 2 TO 4 FEET. INTRACOASTAL WATERS A LIGHT CHOP.

MONDAY
SOUTHEAST WINDS 10 TO 15 KNOTS. SEAS 2 TO 4 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

MONDAY NIGHT
EAST WINDS 5 TO 10 KNOTS BECOMING 10 TO 15 KNOTS. SEAS 2 TO 4 FEET. INTRACOASTAL WATERS A MODERATE CHOP.

TUESDAY
SOUTHEAST WINDS 10 TO 15 KNOTS. SEAS 2 FEET OR LESS NEAR SHORE AND UP TO 2 TO 4 FEET WELL OFFSHORE. INTRACOASTAL WATERS A MODERATE CHOP.

So it looks like by Tuesday things are settling into good - though not ideal - conditions.  If, over the next few days, we see "UP TO 2 TO 4 FEET WELL OFFSHORE" continuing to extend through the week, we're off!  The key seems to be ready to go and then wait.  A catamaran sail boat opposite us couldn't leave last Saturday - someone had his boat keys - and he missed his window and has to wait.  He's ready though!

Not too surprisingly, the weather is a popular topic of conversation.  What's the weather doing where you are?  And by "weather", I mean wind.  And by "wind", I mean waves.  :-)

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