Weatherwatching

Here we are in paradise. It would be easy to find people who would tell you that the only drawback to the Caribbean is the propensity for hurricanes to visit the area.  As of this writing, Friday Sept. 3, 2010, Hurricane Earl is off the North Carolina Outer Banks. Gaston, the seventh named weather system of the season, has been downgraded to a low pressure area, but might reform into a tropical cyclone.

Earl, Fiona, Gaston's remnants, and a tropical wave

Water vapor - Earl is the big swirl at the top

Hurricanes typically start as lows off the coast of Africa and work their way west across the Atlantic towards the Caribbean. If conditions are right (or wrong, depending on your point of view) they grow in wind speed.  At 34 knots (39 mph) or greater they are tropical storms. At 64 knots (74 mph) they are hurricanes. Luckily, atmospheric conditions usually steer them north before they reach the islands.  If the steering conditions are weak or move, they can push a storm farther south or just keep it heading west longer than usual.

If a storm travels west too long before it turns north it will impact the Caribbean islands and can continue all the way to Mexico or turn north towards the south coast of the US.  Because storms tend to turn north, the farther south or west you are in the Caribbean, the less likely you are to experience a storm. 

This is reflected in yacht insurance practices.  Most companies define a hurricane box that encompasses the southern US and the Carribean.  If your boat is damaged by a named storm while in the box during hurricane season you are either not covered or your deductible goes up.  Hurricane season for us is June 1 through November 1.  Our hurricane box starts in North Carolina and extends south to Bequia.  Statistically speaking, our insurance company is not worried about us.  (The picture at the top of this post has a red line showing the bottom of our hurricane box)

So what has happened here in Grenada? According to Wikpedia (http://en.wikipedia.org/wiki/Grenada):

“In 2004, after being hurricane-free for forty-nine years, the island was directly hit by Hurricane Ivan (September 7). Ivan struck as a Category 3 hurricane and caused 90 percent of the homes to be damaged or destroyed. The following year, 2005, Hurricane Emily (July 14), a Category 1 hurricane at the time, struck the northern part of the island with 80 knots (150 km/h; 92 mph) winds, causing an estimated USD $110 million (EC$ 297 million) worth of damage. This was much less damage than Ivan had caused.”

So part of the morning ritual here is to get up and check weather sites like the National Hurricane Center (http://www.nhc.noaa.gov/) or Passage Weather (http://www.passageweather.com/) to see what’s going on.  Then at 7AM or a little after, Chris Parker, our weather router, comes on the shortwave radio and gives his analysis of the developing weather.  His discussions are pretty thorough and they help you understand why he thinks the weather will do what he predicts and what the chances are for various scenarios.  Unfortunately, the shortwave radio reception is subject to the vagaries of atmospheric conditions so it can be hard to hear Chris’s forecast because of static.

Bowling for Cruisers Saturday, Sept. 4

Twenty four hours have elapsed since I started writing this.  You can see from the chart that Earl has moved north and is nearing Nova Scotia and Fiona has weakened from a storm to a low.  But the remnants of our old friend, Gaston, are likely to reform into a storm, and possibly a hurricane.  There is a big question as to where he will go, but it looks like he could hit as far south as Martinique.

Gaston - now a 70% chance of reforming into a tropical cyclone

I watch the paths of these weather systems as they cross the Atlantic aimed more or less at us and then hook north and it reminds me of bowling.  The ball goes nearly straight down the alley and then hooks just before it hits the pins.  The timing and strength of the hook determines where the ball will strike and how many pins will fall.  These storm systems follow similar paths and the timing and strength of the hook determine what land – if any – they will impact.  We cruisers here in Grenada are a bit like the 7 pin at the far left of the back row. Pretty far out of the way, but not completely safe.  It’s a bit like bowling for cruisers.

Bowling ball paths

Earl's actual track as of Friday

So we watch and wait and hope that Grenada will stay out of the way of these meteorolgical bowling balls.  If one looks like it might get too close, we will most likely raise anchor and head south for Trinidad.

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One Response to “Weatherwatching”

  1. Dale Says:

    Earl left us good wind for all three days of Annapolis race week. As usual, we raced! Had lots of fun but didn’t win anything. Pam is talking about getting serious this winter, caulk board training, steady team, new sails, work on Bump, etc. Sounds great.

    Give Jackie my best.

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