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Where is the center of this storm? Photograph by the Author
The second in a series of articles on weather for
woodsmen, for the previous article, go HERE –
Author’s Note
Did you ever wonder if you could tell where the center of the storm
was? Because if you could, you would
know if the storm was already past you or had yet to arrive. In the days of sailing ships, it was vital to
know where the storm center was because there was no radio, no weather
forecasts, no satellites, etc., so if you didn’t know where the low-pressure
storm center was, you wouldn’t know what weather was coming. Oh, and remember, in the temperate latitudes
of both the southern and northern hemisphere most of the weather travels from
west to east, so if the storm center is west of you, then it is on its way!
Well, here is good news, you can tell where the center of both the high-pressure
and the low-pressure storm is by the direction of the wind, so let’s talk about
the how and the why.
The highs
and lows of weather...
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An excerpt from Almanac and Weather Forecaster, by Eric Sloane, page 40.
The
weather that surrounds us is caused by atmospheric convection currents, the
Coriolis effect, and areas of high and low-pressure air. Low-pressure areas are called “depressions” and
are marked on a weather map, or synoptic chart, as a “L”, and high-pressure
areas are marked on weather maps as a “H”.
High pressure air is descending air that is cold and dry and generally
brings clear skies. Low pressure air is
rising warm air that is moisture laden, saturated, and generally brings rain or
snow.
High
and low-pressure systems move from the west to the east in in the temperate
latitudes, which are between 30o and 60o north or south
latitudes, of both the northern and southern hemispheres. The temperate latitudes include, in the
northern hemisphere, all of Europe, Central Asia, and North America below the
arctic, and in the southern hemisphere they include the southern portion of
South America and the southern tip of Africa.
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Excerpts from Farm and Garden Rule-Book, by L. H. Bailey, page 5 and 6.
When
the atmospheric convection currents push a bulge of warmer air into an area of
colder air, a storm is born. Since the
warm air is less dense than the colder air around it, it creates a pocket of
low-pressure air that the surrounding high-pressure air tries to fill. The Coriolis effect causes the in-rushing
winds to begin to swirl, counter-clockwise in the northern hemisphere and clockwise
in the southern hemisphere.
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An excerpt from Farm and Garden Rule-Book, by L. H. Bailey, page 9.
Also,
a moving low-pressure frontal system pushes air ahead of it creating a
“snowplow ridge” or, “bow-wave” of high-pressure air, that initially will bring
a period of good, clear weather ahead of the oncoming storm1.
Also,
remember, winds are named for the direction that they are blowing from, not
from where they are blowing to.
Since
the winds swirling into a low-pressure area in the northern hemisphere circle
in a counterclockwise pattern, the winds from a storm as it approaches you will
blow first from the northwest and west, then from the southwest and south and then
as the center of the storm has passed to the east of you, the wind will blow
from the northeast, the east and lastly from north and northwest.
 |
An excerpt from Land Safety and Survival: Volume 3, page 269, which can be purchased HERE, showing the counter-clockwise wind pattern surrounding a low-pressure area and the clockwise wind directions around a high-pressure area in the northern hemisphere.
This
is reversed in the southern hemisphere because the winds rushing into fill a
low-pressure zone to circle in a clockwise pattern, so as a storm approaches
you from the west the winds will first blow from the north east, north and
northwest and after the center of the storm has passed to the east of you the
winds will blow from the west, southwest and later the south.
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An excerpt from Land Safety and Survival: Volume 3, page 269, which has been modified by the Author, to show the clockwise wind pattern surrounding a low-pressure area and the counterclockwise wind directions around a high-pressure area in the southern hemisphere.
Buys-Ballot’s
Law...
 |
A portrait of Christophorus Henricus Diedericus Buys Ballot (1817-1890), from Wikimedia, HERE.
Christophorus
Henricus Diedericus Buys Ballot was born in 1817 and died in 1890. He was a Dutch meteorologist who, in 1857, was
the first person to provide empirical data to support a phenomenon that had
been first noted by meteorologists J. H. Coffin and W. Ferrel in 1856. Buys-Ballot’s law is a consequence of
Ferrel’s Law and is more of a rule for prediction. In November 1857, in Comptes rendus2,
Buys Ballot wrote “Stand with your back to the wind; the low-pressure area
will be on your left-hand”. This
rule is generally true in the higher latitudes of the northern and southern hemispheres,
although it is reversed in the southern hemisphere.
So where is
the storm?
The
interesting thing about Buys-Ballot’s Law is that there are two variants, one
where you face the wind and one where you stand with you back to the wind. They both supply the same information and
either can be used, to tell you where the center of a storm is as it nears you.
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An excerpt from American Practical Navigator: An Epitome of Navigation, by Nathaniel Bowditch, page 916.
So,
in the northern hemisphere, if you want to find out where the center of the
high-pressure area is or the center of the low-pressure storm is, face into the
wind and extend your arms straight out from your sides, the low-pressure center
of the storm will be a somewhat behind the direction that your right arm is
pointing towards and the center of the high pressure area is little in front of
your left arm.
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An excerpt from Land Safety and Survival: Volume 3, page 270, which can be purchased HERE, which shows the counterclockwise wind pattern surrounding a low-pressure area in the northern hemisphere.
In
the southern hemisphere everything is reversed, and if you want to find out
where the center of the high-pressure area is or the center of the low-pressure
storm is, just like before, face into the wind and extend your arms straight
out from your sides, the low-pressure center of the storm will be in the a
little behind the direction that your left arm is pointing towards and the center
of the high pressure area is somewhat in front of your right arm.
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An excerpt from Land Safety and Survival: Volume 3, page 270, which has been reversed by the Author to show the clockwise wind pattern surrounding a low-pressure area in the southern hemisphere.
So
now that you know how to tell where the highs and lows and the center a storm is,
you will be better able to predict if weather is heading toward you or away
from you.
Don’t forget to come back next week and read “They Can’t Cure Dead ©”,
where we will talk weighing the risks, taking calculated risks and Eli’s philosophy
of “...doing something stupid, carefully”!
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I
hope that you continue to enjoy The Woodsman’s Journal Online and look for me
on YouTube at BandanaMan Productions for other related videos, HERE. Don’t forget to follow me on both The
Woodsman’s Journal Online, HERE,
and subscribe to BandanaMan Productions on YouTube. If you have questions, as always, feel free
to leave a comment on either site. I
announce new articles on Facebook at Eric Reynolds, on Instagram at
bandanamanaproductions, and on VK at Eric Reynolds, so watch for me.
That
is all for now, and as always, until next time, Happy Trails!
Notes
1
From “Red Sky At Night...”, by Donald Johnson and Jean Smith, page 32-33
2 The
entire entry for Buys-Ballot’s law in the 1911 The Encyclopædia Britannica,
Volume 4, BISHĀRĪN to CALGARY, can be found HERE.
reads as follows:
“BUYS
BALLOT’S LAW, in meteorology, the name given to a law which may be expressed as
follows: - “Stand with your back to the wind; the low-pressure area will be on
your left-hand.” This rule, the truth of which was
first recognized by the American meteorologists J. H. Coffin and W. Ferrel, is
a direct consequence of Ferrel’s Law (q.v.). The law takes its name from C.
H. D. Buys Ballot, a Dutch meteorologist, who published it in the Comptes
rendus, November 1857.”
Sources
Alaska Marine Safety
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Falvey, Dan; Jones, Michael; McElrath, Rick and Newell, Shawn; Land Safety
and Survival: Volume 3, [University of Alaska Sea Grant, Fairbanks, Alaska,
SG-ED-38, 2002], https://repository.library.noaa.gov/view/noaa/34660/noaa_34660_DS1.pdf,
accessed April 4, 2022
Bailey, L. H.; Farm
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Johnson,
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accessed March 15, 2022
Sloane,
Eric; Almanac and Weather Forecaster, [Hawthorne Books, Inc., New York,
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accessed April 6, 2022
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