August 12, 2010

Tis the Season

Hurricane season that is.
From about mid-August through mid-October conditions in the eastern Pacific are conducive for tropical cyclone (aka hurricane) formation. Tropical cyclones are often described as engines that are driven by warm, moist air. For a hurricane to form, the National Oceanic and Atmospheric Administration (NOAA) says several factors need to be in place:
  1. 80 degree, or warmer, water temperature, which is at least 150 feet deep.
  2. A low pressure area with wind disturbance.
  3. A lack of stability in the air, which allows clouds to develop.
  4. A centrifugal force, known as a Coriolis Force, stemming from the earth's rotation.
  5. Moist air, i.e., a thunderstorm, in the lower portion of the atmosphere.
  6. Low values (less than about 10 m/s [20 kts 23 mph]) of vertical wind shear between the surface and the upper troposphere. 

Once all these conditions are in place you get a weather report that looks like this:

today's weather report...
 The chance of this particular disturbance becoming more organized is 60%. And if that happens we switch from monitoring it twice a day, to watching it a bit more obsessively, waiting to see if it becomes a hurricane.
If it does become a hurricane we begin to watch its track. Hurricanes move at 10-20 miles an hour; which is quite a bit faster than our 6 knot motoring speed. So our objective is to predict its path and then get the heck out of the way.

Unfortunately hurricanes aren’t that predictable. So if we have any doubt at all about where a storm is going our plan is to move closer to one of the ‘hurricane holes’ in the northern Sea of Cortez. These are natural harbours that are small (to limit wave fetch) and have very small openings. The most popular tends to be Puerto Don Juan--the place where we sat out hurricane Fausto in 1996. But the very fact that it’s popular (despite its isolation) also means it can get really crowded. And being in a crowded harbour during a storm offers its own dangers…

Puerto Don Juan with a handful of boats--during a hurricane, it's packed
For now we are in wait and see mode. I'm trying to make a quick trip back to Vancouver between storm formations--but we never know which formation might have our name on it, so we watch and wait.

No comments: