Commencing with 1918, January 1, a new method of analysis has been adopted in the case of the elements "wind force" and "weather".
The old and new methods are compared below:
Old method. 1896-1917
(1) Wind Direction:
The forecast wind direction is considered successful if the wind at Gap Rock blows the greater part of the 24 hours from a direction that does not differ more than 45° from the forecast. Thus, if the forecast wind direction is NE, and 4 out of the 6 reports from Gap Rock give wind direction between N and E the forecast is correct in this element.
(2) Wind Force:
The wind force forecast "Light" is successful if the mean force registered at Gap Rock is a light breeze, or if the wind force does not reach the force of a moderate breeze. "Moderate" if the mean is a moderate breeze, or if the wind force exceeds a light breeze and falls short of a strong breeze. "Fresh" if the mean is a fresh breeze, or if the wind force exceeds a gentle breeze and falls short of a moderate gale. "Strong" if the mean is a strong breeze, or if the wind force exceeds a moderate breeze and falls short of a fresh gale. "Gale" if it blows more than 40 miles per hour at Gap Rock.
(3) Weather:
The weather forecast "Fine" is successful when the mean amount of cloud is below 7 (10=an overcast sky), if sunshine or starlight
New method. 1918
(1) Wind Direction:
The same as in old method.
(2) Wind Force:
The wind force forecast is successful if in 9 of the observations at Gap Rock, Waglan, or Hongkong the force is within the ranges given in the following table:
Forecast Range (Beaufort Scale) Light 0-3 Moderate 2-5 Fresh 4-6 Strong 5-7"Gale" is correct if the wind attains force 8 at Gap Rock, Waglan, or Hongkong.
(3) Weather.
The weather forecast is successful if the amount of cloud and rainfall is in accordance with the following table: