Weather Forecasts

Lake County Mail, Issue 44, 7 April 1948, Page 7

Weather Forecasts

How reliable are weather forecasts? Few people notice when the meteorologists are right but many comment when the forecast is wrong. The weather cannot be predicted with certainty yet, but our meteorologists are more often right than wrong and they give us a guide which is much more reliable than our personal observations could be.

With improved instruments, better communications, and more observation posts, weather forecasting is becoming more reliable every year, but meteorologists make no claims of infallibility. Our forecasts are far from mere guesswork as they are based on information throughout the South Pacific. In New Zealand alone there are 80 observation stations which report local weather conditions regularly to the Meteorological Office Weather Bureau, Wellington. About 20 of the main observation stations are directly connected with Wellington by a teletype circuit and the weather in every part of the Dominion is recorded hourly at head office. Basis of Forecast The observation stations report local changes in the weather, the temperature, the direction and speed of the wind, atmospheric pressure, humidity, and type of cloud formation. Charts arc plotted in Wellington summarising all this information from stations in New Zealand, the Pacific Islands, Australia and ships at sea. Thus a complete picture is formed of weather developments converging on New Zealand and influencing local changes. Providing sufficient information is received, future weather conditions can be determined in a scientific manner; it is when the data is incomplete (as when there is no shipping in the Tasman to report conditions at sea) that a forecast can be upset by the previously unknown factors. The forecasting for the whole Dominion is done in Wellington. The data

is studied for possible changes, and as the evidence is weighed different possibilities are eliminated until there is only one left —this becomes the forecast for the day. Public Demand It is difficult to satisfy everyone with forecasts that cover large areas within which variations in weather occur. New Zealand would have to be cut into very small forecasting areas, with observation posts every few miles, to predict minor variations in the weather. Meteorologists discriminate when important differences are likely, but it is not easy to anticipate a thunder or hail storm in a small part of the forecast area when it is fine over the larger portion. Unusual land formations sometimes cause highly localised variations in the weather. Sections of the public are interested in different periods. Farmers would like to know the weather a week ahead, the housewife doing her washing wants the forecast to cover a day, while the city worker is interested in the periods about 8 a.m, and 5 p.m. so as to know whether he need take an overcoat. The range of time in which reliable predictions can be made varies from a few hours to about 36 hours. The scope of the general forecasts makes it. impossible to satisfy individual needs on the daily broadcasts. However, the Meteorological Weather Bureau provides a service for individuals who need weather information at certain periods, and in particular localities.