Saturday, 5 March 2016

St Helena Outbound Day 12

Hi everyone,
We are currently in position 09 45S 026 29W, saillng at 5.5 knots on a course of 300M. The wind is ESE at 14-16 knots with a 1.5m SE sea and a 1m S swell.  We are sailing under double-reefed main and full yankee.  Scattered small cumulus clouds, some with very light rain underneath.  Our day's run was 128nm, our DMG was 100nm and we have 2639nm to go.

Winds have been quite stable over the last 24 hours.  The boat is loving it, just cruisin' along nicely.  Occasionally the sea state is confused but generally its pretty good.  Overall this really is champagne sailing.  Can't last!

In fact it certainly won't last.  In 4-6 days we'll be entering the ITCZ (Inter-Tropical Convergence Zone or "doldrums").  There we are sure to encounter unpleasant weather (as mentioned yesterday).  We've been positioning ourselves to try to minimise our exposure to nasty weather as we approach the ITCZ.  That's why we're quite a way south of the rhumb line.

We obtain various weather information, most of which is in the form of GRIB files (GRIdded Binary).  GRIB files can contain various data including wind speed, wind direction, atmospheric pressure, wave height, swell height and others.  Three of the "others" we use are rain, CAPE and current.

Rain is pretty obvious, showing where and how much (in mm/hour) rain is expected.  As you can see below, we're well away from the heavy rain area.


CAPE stands for Combined Available Potential Energy and is a measure of how much the air "wants" to rise.  High CAPE means thunderstorms are highly likely.  High CAPE is seen at the ITCZ all the time and also along cold fronts and deep troughs.  As you can see below we're keeping well south of the high (brown & red) CAPE areas for the time being.


Depending on how the wind, rain and CAPE forecasts develop over the next few days we may continue west for quite a way.  As you can see below there is a nice N setting current up the coast of Brazil, which then turns W following the coast.  It may we worth getting on that oceanic travellator!  We'll certainly ride the current along the N coast of Brazil.


On a different tack altogether, one of the things we do most mornings and evenings is listen to the news on the HF radio.  We've found both the BBC World Service and Voice of America on various AM shortwave frequencies.

The BBC transmits from:
  • Ascension on 6005kHz, 9915kHz, 11810kHz, 15400kHz and 17640kHz; and
  • South Africa on 12095kHz.
VoA transmits on:
  • 6080kHz, 7465kHz, 9885kHz, 15580kHz.

Note that all of these frequencies are active at particular times each day, mainly in the morning and early evening.  You may find other stations transmitting on these frequencies at other times.

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