Weather satellites have been around for a surprisingly long time. The first one, the American TIROS I, was launched as long ago as 1960, just three years after Sputnik, and meteorologists have enjoyed a bird's-eye view of the weather ever since. The quality of our forecasts has, of course, improved dramatically in the intervening years, but people might be forgiven for thinking that with the benefit of this all-seeing "eye in the sky", forecasters should never get it wrong again. Life and meteorology, however, are not that simple. Satellites are not a panacea; although they show the weather exactly as it is, they tell us little, directly, about the shape of things to come. But they have had a very positive impact and meteorologists are learning how to use them better all the time. At first, satellite images were used simply to pin-point the exact positions of the lows and fronts. Then, as time went by, meteorologists discovered, for example, that winds at upper levels in the atmosphere could be estimated by comparing two satellite pictures taken, say, 30 minutes apart.
The distance travelled in that time by a number of distinctive features of the cloud pattern is observed, and on the assumption that the cloud moves with the wind, the wind speed at that level can be calculated. Such data are particularly useful in those large areas of the world where conventional observations are few and far between, and they now form an essential ingredient for the numerical models that produce computerised predictions. One can also deduce a great deal, however, from the pat- terns of the clouds themselves depicted in a satellite image. Rapidly deepening depressions often have a distinctive "signature" - a characteristic orientation of the clouds in certain critical zones that a trained eye can spot and use to identity potentially troublesome developments. Other signatures may indicate a weakening, perhaps, provide clues to the direction of movement of a low, or to the heaviness of the rain to be expected when a particular disturbance hits our shores. It may well be that features such as these will form the kernel of the talk by Dr Veronika Zwatz-Meise at 8 p.m. this evening. Dr Zwatz-Meise is an internationally recognised expert on the interpretative aspects of satellite meteorology and comes to us from the Austrian Central Institute for Meteorology and Geodynamics - the Met Eireann of Vienna, as it were. Her lecture, organised by the Irish Meteorological Society, will take place in the usual Earlsfort Terrace premises of UCD, and anyone who wishes to attend is welcome.