Bob Blog 28 Aug

Bob McDavitt's ideas for sailing around the South Pacific.
Disclaimer: Weather is a mix of pattern and chaos; these ideas are from the
patterned world.

Compiled Sunday 28 August 2022

Monsoon 2022

August rainfall in Pakistan has been between 2.5 and 5 times the 30years
norm, with a death toll currently around 937. At least 184,000 people have
been displaced to relief camps.


Why are they called hectoPascals?
Barometer is coined from Greek words, Baros for "weight" and metron for
"measure".

When the MKS system of units was drawn up in 1960 PASCAL was chosen for the
name for a unit of pressure (a Newton per square metre) as a commemoration
of Pascal's pressure experiment described below. And so, isobars are now
labelled in hectoPascals. The prefix of hecto is from the Greek word hekaton
for "hundred". So 1010hPa means 101,000 Pascals or 101,000 Newtons per
square metre- that's about a tonne per square metre , same as an elephant.
Yes, for a diver, that's the pressure exerted by about 32 feet or 10 metres
of (sea) water.

Pascal was a Frenchman and his experiment was conducted in 1648….

FRANCE, mid seventeenth century:

This was the time celebrated by Alex Dumas in the Three Musketeers. Louis
XIII was King, but the ominous Cardinal Richelieu was in charge, and did
things his way.

You may recall in my blog on 31 July
https://metbob.wordpress.com/2022/08/01/bob-blog-31-july/ I described how in
1642 Evangelista Torricelli, a student of Galileo, produced the first
barometer to make a vacuum. Now Marin Mersenne was a French Priest who
earned the title "the post box of Europe" for he travelled a lot, had many
contacts around the scientific word and was great at making connections. He
visited Italy in 1644 and Torricelli showed him the barometer. He returned
to Paris with a choice collection of writings, including Torricelli's paper.
These he shared in 1646 at the Paris Book Club that included Etienne and
Blaise Pascal.

Back story: Blaise Pascal was born in France in June 1623, the son of
Etienne Pascal, a lawyer. His mother died when he was three. He was educated
by his dad and proved to be a child prodigy in anything mathematical. At the
age of eight the family moved to Paris. When Blaise was 15 Cardinal
Richelieu (then Prime minister of France) imposed some harsh fiscal measures
which his dad opposed and for that had to go into hiding. The following year
his sister Jaqueline (then 17) appeared in a play given before Richelieu and
after a "fine performance" the Cardinal rewarded Jaqueline with a pardon for
Etinenne plus a job offer to the post of Tax collector for Rouen. Side note:
Jaqueline was a child prodigy writing a five-act comedy when she was 11.

The following year young Blaise wrote an article on solid geometry which
drew the attention of Rene Descartes (the main French mathematician at the
time). Descartes couldn't believe such an article could have been written
from anyone so young. The two developed a special relationship.

In 1642, when he was 19, he started work on a calculating machine to help
his dad count those taxes - the first ever digital calculator, called a
Pascalaline, akin to the ones that were popular in the 1940s.

Blaise Pascal's life as a mathematician went on to produce the Pascal's
triangle which is a triangle of numbers starting with 1 and then extending
down left and right with each number equalling the sum of the numbers above
left and right. It gives the values of the polynomial coefficients, useful
in algebra and differential calculus.


Philosophical Disagreements
Blaise was intrigued with these vacuums and spent a few years reproducing
Torricelli's experiments and trying out different liquids such as water
versus red wine. In 1647 he wrote some papers on the properties on the void
at the top of barometer (Expériences nouvelles touchant le vide).
Then he and Rene Descartes have some long chats about this topic. Descartes
could not believe that a void or vacuum existed or that a barometer was
really measuring air pressure. He supported the explanation by Greek
philosopher Aristotle that this space was filled with a substance called
aether, which was extremely tenuous and able to flow through tiny pores in
the glass tube and fill in the space left by the receding water. The aether
was also used by Aristotelians to explain how light from far-away stars
reaches us by travelling through a substance. Things came to a pretty pass.

Scientific experimental evidence
Blaise understood the power of experimental evidence and so he then built a
portable barometer using a glass tube of mercury inverted into a dish of
mercury. Because he had weak knees, he asked Jaqueline's then husband Florin
Périer, to do the hard bit - carry this device up the Puy de Dôme, a
conspicuous mountain in Rouen familiar to Blaise from his childhood, and
take a series of measurements. Sure enough, the height of the supported
mercury column got less with increasing altitude. The amount of fluid in the
tube was responding to changes in air pressure. So, it was air pressure that
was responsible for the height of the column, rather than the size of any
void left over at the top. This experiment was carried out on 19 September
1648 and verified Evangelista Torricelli's original hypothesis about
atmospheric pressure on the equilibrium of liquids.

Le Puy de Dôme in central France, site of famous PASCAL experiment

The Puy de Dôme experiment became famous in the world of science for finally
putting an end to the Aristotelians aether theory, and the principle it
proved became known as Pascal's Law.

Pascal's barometers quickly became the best tool for measuring altitude,
proving accurate enough to give good measures of the depth of coal mines. It
wasn't long before barometers were also adopted by sea-captains to help show
the dropping air pressure that precedes wet windy weather. To this very day,
even though we measure temperature, wind, rainfall, and humidity as well as
pressure—it is the PRESSURE LINES that we draw on weather maps that are
accepted as capturing and showing the weather pattern.

TROPICS
The latest cyclone activity report is at tropic.ssec.wisc.edu and Tropical
Cyclone Potential is from www.ssd.noaa.gov/PS/TROP/TCFP/index.html

HINNAMNOR is storm force near Iwo Jima. There are zones for potential
developments west of Mexico and across the central Atlantic.

WEATHER ZONES
SPCZ=South Pacific ConvL1ergence zone and STR (Sub tropical ridge).

The SPCZ stretches from PNG across Solomons to Samoa and is expected to
drift south to Fiji/Tonga late this week. Avoid.
Low L1 to south of Tahiti is expected to drift to southwest and then to
southeast.

HIGHS and LOWS
High H1 above 1034 over NZ is expected to slowly shift to Chathams by
mid-week then speed off to the east and fade.
Low L2 over Victoria tonight is expected to weaken as it moves into south
Tasman Sea by mid-week then over NZ on Friday. This one looks tame from
Tuesday.
Models are picking L3 to deepen off Queensland at end of the week and move
onto NZ next week. Avoid.
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If you would like more detail for your voyage, then check metbob.com to see
what I offer.
Or Facebook at /www.facebook.com/metbobnz/
Weathergram with graphics is at metbob.wordpress.com (subscribe/unsubscribe
at bottom).
Weathergram archive (with translator) is at weathergram.blogspot.co.nz.
Contact is bob@metbob.com or txt 64277762212
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