Weather and Climate Forecasting

The Biblical quotation above is an ancient example of attempting to make meteorological predictions based on empirical observations. The idea it contains tends to work as a forecasting scheme, and it has been expressed in many different ways in the subsequent 2,000 years. it is one of many sayings and rhymes of folklore that provide a qualitative description of the weather. In the 17th century, the introduction of instruments to measure atmospheric variables meant that meteorology became a quantitative science. By the 19th century meteorological data was being collected all over Europe. It was during the 1800s that many scientists began lamenting the fact that the collection of meteorological data had far outpaced attempts to analyse and understand this data (Lempfert 1932). Attempts had been to find patterns in tables of meteorological, but these had usually ended in failure. One example is the efforts to link weather to celestial motions made by the Palatine Mteorological Society of Mannheim (the World's first such society) in the late 18th century. The breakthrough came when scientists began plotting the growing meteorological database on maps; the tendency of mid-latitude low-pressure systems to advance eastward was discovered: clouds in the west provide a red sky at dawn before bringing bad weather, clouds in the east redden the sky at sunset before making way for clear skies. The discovery of mid-latitude eastward flow not only explained the success of ancient folk wisdom, combined with the telegraph it also provided a means to extend predictability beyond the horizon. The late 19th and early 20th century saw many efforts to identify cycles in time series of weather data. One the most prolific cycle seekers, and ultimately one of the few successful ones, was Sir Gilbert Walker. Walker collated global weather data and spent years seeking correlations (Walker 1923, 1924, 1928, 1937, Walker and Bliss 1932) During this work he discovered that the pressure i,n Tahiti and in Darwin were anti-correlated. This discovery withstood the subsequent tests and is called the "Southern Oscillation". It is now known to be the atmospheric component of El Nine-Southern Oscillation climate phenomenon. Many other claims for the existence of weather cycles were made, but few withstood the scrutiny of statistical tests of robustness. By the 1930s, mainstream meteorology had largely given up attempting to forecast the state of the atmosphere using statistical approaches based solely on data (Nebeker 1995). Since then, estimates of the recurrence time of the atmosphere have implied that globally