154 ROBERT FITZROY
that most of the large storms
that blow in the mid-latitudes show
this cyclonic depression shape.
So the direction of the wind gives
a clue as to whether the storm is
approaching or receding.
In the 1850s, better records of
weather events, and the use
of the new electric telegraph to
communicate over long distances,
almost instantly revealed that
cyclonic storms, which form over
land, move eastward. In contrast,
hurricanes (tropical North Atlantic
storms) form over water and
migrate westward. So in North
America when a storm hit one
place far inland, a telegraph could
be sent to warn places farther
east that a storm was on its way.
Observers already knew that a drop
in air pressure on the barometer
gave warning of a storm to come.
The telegraph allowed such
readings to be relayed rapidly over
great distances and therefore gave
warnings much further in advance.
Synoptic weather
FitzRoy understood that the
keys to weather prediction were
systematic observations of air
pressure, temperature, and wind
speed and direction taken at set
times from widely spread locations.
When these observations were
sent instantly by telegraph to his
coordinating office in London,
he could build up a picture or
“synopsis” of weather conditions
over a vast area.
This synopsis gave such a
complete picture of the weather
conditions that it not only revealed
current weather patterns on a
wide scale, it also enabled weather
patterns to be tracked. FitzRoy
realized that weather patterns were
repeated. From this, it was clear to
him that he could figure out how
weather patterns may develop over
a short time in the future, from how
they have developed in the past.
This provides the basis for a
detailed forecast of the weatherat any and every point within
the region covered. This was a
remarkable insight that formed
the basis of modern forecasting.
The observation figures alone
were enough, but FitzRoy also used
them to create the first modern
meteorological chart, the “synoptic”
chart that revealed the swirling
shapes of cyclonic storms as clearly
as satellite pictures do today.
FitzRoy’s ideas were summed
up in his book, titled simply
The Weather Book (1863), which
introduced the word “forecast” and
laid out the principles of modern
forecasting for the first time.
A crucial step was to divide
the British Isles into weather areas,
collate current weather conditions,
and use past weather data from
each area to help make forecasts.
FitzRoy recruited a network of
observers, particularly at sea and
in ports in the British Isles. He also
obtained data from France and
Spain, where the idea of constant
weather observation was catching
on. Within a few years, his networkI try, by my warnings of
probable bad weather, to avoid
the need for a life-boat.
Robert FitzRoyFitzRoy colored his daily “synoptic”
charts in crayon. This one, made in
1863, shows a low-pressure front
bringing storms toward northern
Europe from the west. The lower right
of the chart reveals a cyclone forming.