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Norman[_2_] · January 14th 08, 08:36 PM posted to uk.sci.weather

wrote:

On Jan 14, 6:59*pm, "Jack )"
wrote:
I agree Norman. *As an ex-aviator, I never bothered with terms like
gales, strong winds, etc. *It was NUMBERS (30, 45 knots, etc). *Do
mariners do the same? *Indeed, I have little idea nor need to know
how a gale is defined in terms of actual speeds.

Martin. *You used to do the shipping forecasts. *Was it the user or
the supplier that wanted the terms gale, etc?

... a long way before my time, but in my copy of 'Weather Map' which
has examples of the Shipping Forecast from the early/mid 1950s, the
numerical value assigned to the wind is not present: e.g.
" Sole, Fastnet, Lundy, - Wind south-westerly, fresh increasing to
strong to gale. (etc.)"

If I had to guess (and it would be that), a change occurred whereby
the forecast wind was defined using the Beaufort notation in terms of
a 'Force' number, and the terms 'Gale', 'Severe Gale' etc., were
retained for emphasis at the higher values.
Any changes in my experience come from the user.

I agree with Norman: bad practice and confusing to boot!

Martin.

The Beaufort Wind Scale does, of course, have its origins in marine
meteorology. It was devised long before the days of instrumentation
and, essentially, is a scale based on the appearance of the sea. This
is why it relates to the mean wind speed and not to gust speeds. It is
only in more recent times that wind speed ranges were assigned to the
various Beaufort numbers to give the Beaufort Scale as we know it
today. Even more recently a so-called Scientific Scale has been
introduced, still using the Beaufort numbers but with slightly
different wind speed bands assigned to the numbers. This is not used
operationally but is used in research work.

Traditionally, wind speed reports from ships were made from an
assessment of the sea state. The observer might decide, for example,
that the sea state looked like the low end of a Force 8 and would
therefore give, say, 35 knots as the wind speed for synoptic
observation purposes, although the log entry would simply be Force 8.
State of Sea cards were issued to ships to assist in assessing the
Beaufort Force. A database of winds assessed in this manner now extends
back well over 100 years. In more recent times the database has become
greatly contaminated by the progressive introduction of anemometers on
ships. It is generally considered in the marine meteorological
community that the body of wind data based on estimates from the sea
states is more reliable than the body of data based on measurements
from anemometers installed on ships. Fortunately, the synoptic code
differentiates between instrumentally measured winds and winds
estimated from the sea state so the two data sets can be separated out.

Norman
--
Norman Lynagh
Chalfont St Giles, Buckinghamshire
85m a.s.l.
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