Tornadoes in Portugal

Abstract

In Portugal, research on tornadoes is very recent and has shown that they are not as rare as it is believed by public and even by scientific opinion. As tornadoes only affect a small area, the probability of their being observed at a meteorological station is very small. Thus, most of the existing records are people's recollections, some description in newspapers and some photos. It was possible to find data on 30 tornadoes that occurred from 1936 to 2002. This number is undoubtedly underestimated because the database is always under construction. Those tornadoes were moderate to strongly devastating, some of them causing great damage. The strongest tornado in Portugal, a T7 event, happened in November 1954. The less intense tornadoes are, for sure, underestimated. After the year 2000, a more careful look for reports reveals the existence of some weak tornadoes. Tornadoes occur mainly from October to January in association with strong cold fronts or line squalls. Most cases were in association with deep extratropical cyclones west of Portugal, when there was a moist and warm south–west strong to gale-force flow and a generalised severe weather over the country. Some cases happened in a very unstable westerly flow. There are also records on summer tornadoes, developing from strong thunderstorm cells. Often, such thunderstorms are mesoscale convective systems resulting from strong heating of the centre of the Iberian Peninsula.