Originally Posted by NoTies
Seriously, has nobody heard of Buys Ballot law or know how to use it? It takes into account any change in storm direction and if used in plenty of time is bullet proof. Pure, basic, simple seamanship that seems to be missing from so many cruisers nowadays.
A real lesson in highs and lows.
Report of the 33 Meeting of the British Association for the Advancement of Science
Aug and Sept, 1863
On the System of Forecasting the Weather
pursued in Holland
Director of the Royal Netherlands
In the plan pursued in Holland
, observations are taken at four principal places: Helder, Groningen, Flushing
, and Maestricht. On the indications afforded at these places the forecasts are based.
For every day of the year, and for every hour of the day, I have very carefully determined the height of the barometer in the place of observation at that height above the sea where it is suspended. This is a cardinal point not sufficiently observed in England
, and not at all in France
. The difference of an observed pressure from that calculated on, I call the departure of the pressure—positive when the pressure is greater, negative when it is less. Those departures, besides the observations of the other instruments, are communicated from post to post.
is now very simple. If the departures are greater (more positive) in the southern places than in the northern, greater at Maestricht or Flushing
than at Groningen or Helder, the wind will have a W. in its name ; when the departures are greater in the northern places, the wind will have an E. in its name.
More accurately, you may say, the wind will be nearly at right angles with the direction of the greatest difference of pressures. When you place yourself in the direction of the wind (or in the direction of the electric
current), you will have at your left the least atmospheric pressure (or the north pole of the magnet).
When the difference of pressure of the southern places above the northern is not above four millimeters, there will be no wind of a force above 30 1bs. on the square meter. Moreover, the greatest amount of rain will fall when the departures are negative; and, at the places where the departures are most negative, there also the force of the wind will be generally stronger.
Moreover, there will be no thunder if the barometric pressure is not less than two millimeters above the average height, and when at the same time the difference of the departures of temperature is considerable.
These rules, and especially the first two, were laid down by me in 1857, in the Comptes Rendus; and on the 1st of June, 1860 the first telegraphic warning by order of the Department of the Interior
was given in Holland. It was unfortunate that those telegraphic warnings were not introduced four days sooner, for in that case the first communication would have been a first warning against the fearful storm of May 28, 1860, called the Finster-storm.
All of you know how amply Admiral FitzRoy has arranged the telegraphic warnings all over England
. The rules used in Holland have answered well, as is shown in the translation of a paper by Mr. Klein, captain
of a merchant-ship, whereto I have added my observations and signals compared with the signals of Admiral FitzRoy. My own paper dates from June 1, 1860, and is extracted by Mr. Klein; but I preferred that the less complete and precise paper of a practical man should be translated, because I thought that the seamen would put more reliance on it. From the tables added to that translation, it appears that I have warned from my four stations just as Admiral FitzRoy has done from his twenty.
It must, however, be recorded that, besides those four stations, there are also some stations—Paris, Havre, Brest, in France
, and Hartlepool, Yarmouth, Portsmouth, Plymouth, in England—that send me their observations. Generally they arrive too late; and therefore they throw very little light on the forecasting.
For the future, the normal heights of barometric pressure, or, better, of the barometers which are read, must be conscientiously taken; the observation must be made at more points once a day, and mutually communicated; and at days when there are greatly different departures—that is to say, of three millimeters—or when there is change of inclination, there must be sent a message at noon or in the evening of the same day. In all cases, not only the pressure in the morning, but likewise that at night should be given. A critical indication is when on the previous day the northern stations had greater departures, and on the following day the southern had greater departures, even when the difference in the latter case was small. A caution should be given when the difference of the departures is four millimeters.