A BLOCK from a dome of warm air reaching from Africa up to Northern Europe has caused the latest heat wave we have been experiencing. This phenomenon is not unknown but according to the National Institute of Meteorology (INM), on this occasion it has been very persistent and hotter than other years. Sr Rivera, the head of Area Forecasting from the Institute, explained that for a significant number of days, we have had that mass of air with a very pronounced north-south axis that has encompassed the whole of the Iberian Peninsula. As a result, the skies have been almost cloudless which has meant that the strength of the sun has prevented lower levels of air providing a cooling effect. These lower levels became hotter when they are not allowed sufficient time during the night to cool down. Rivera explained that we know that these conditions exist and that they remain for two or three weeks. There are two questions that have been raised, however, by the events of this year. Why has it been so persistent, and why has this warm mass of air been hotter than other years? It is difficult to know why, and further investigation will be required before a satisfactory answer can be given commented the meteorologist. When asked about the unknown elements that cause these abnormal episodes, he acknowledged that we have been through three months, June, July and August in which these conditions have persisted on a continuous basis. Then, referring to the advice of the World Meteorological Organization (WMO), he announced that this body warned of a tendency in the last years for a rise in the intensity of heat. This growth is being clearly noticed and is even higher in temperature than predicted. It is known that Man is himself responsible in part. What cannot be done is to quantify this responsibility, furthered Rivera who insisted that the WMO theorises on the probability of an increasing number of adverse phenomena. We have to get used to these violent episodes and bear them in mind for forecasting. Regardless, he returned to a more refreshing theme. This warm mass of air is giving clear signs of collapse he stated, and during the weakening process, the axis leans in the east-west direction, with the result that colder, more humid air will encompasses Eastern Europe and Spain. The development will bring a drop in temperature which between Thursday and Saturday will affect nearly all regions, although he stressed that the change will be witnessed at first throughout Galicia today. During Friday and Saturday the cooler front will continue to extend until its maximum is reached on 17 August. Relief will be clearly noted in nearly all regions, except in the south-eastern Peninsula area and in the Balearic Islands where only a slight drop in temperature will be experienced, he detailed.