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Aidan Karley[_2_] · April 5th 08, 02:43 PM posted to alt.talk.weather,uk.sci.weather

In article fb28e3b6-c840-448f-9399-
, Dawlish wrote:
Could it be that it only takes a variation of 1mb for a high pressure
to be changed to a low pressure on the chart? The system has remained
in the same position and has altered it's characteristics marginally,
but its meteorological name has changed, as it has crossed that
arbitrary 1013mb, average atmospheric pressure, threshold?

You're wasting your breath trying to have a sensible discussion with the
object that describes itself as "weatherlawyer". He's a kook, but small
scale.
Meteorological lows and highs are marked by their pressure compared to
the surroundings - lows have lower atmospheric pressure than the
surroundings ; highs have higher pressure. You could probably define
them in a more computer-analysis-friendly manner by talking about the
second derivative of pressure against location - highs have a negative
second derivative in all directions, lows have a positive second
derivative in all directions. The switch-over case where the second
derivative is positive in some directions and negative in others is a
col, but isn't particularly interesting meteorologically.

I killfile the 'weatherlawyer' object, so I don't know the particular
event he's talking about having "switched" from being a low to a high.
Going from the normal level of his acuity of observation and
understanding of observation, science and technology, he's simply got it
wrong and either missed a weather chart or not noticed a trend in the
movement of air masses. He probably thinks that the change in the
weather in Linconshire is due to a butterfly being disturbed by an
earthquake in the South Pacific. (Which is why I've trimmed
sci.geo.earthquakes from the posting ; the "weatherlawyer" object often
behaves as if he wants to prevent this group from functioning.)

--
Aidan Karley, FGS
Aberdeen, Scotland
Message written at Sat, 05 Apr 2008 13:10 +0100, now I'm back on
shore.