Mallorca’s 33ºC sea raises autumn heavy rain risk
Water off Dragonera, Mallorca, reached 33ºC a few weeks ago, adding to the conditions that can make autumn heavy rain more intense. But the unusually warm sea will not cause floods or torrential rain by itself, meteorologists say. On 13 August, the Mediterranean’s surface as a whole reached 28.54ºC — its highest temperature since at least 1940, according to the Spanish State Meteorological Agency, Aemet.
Aemet said the Mediterranean set daily temperature records for almost all of August.
Warm water is only part of the picture
Marta Almarcha, a meteorologist at Eltiempo.es, says a warmer sea supplies extra moisture and energy to the lower atmosphere. If unstable weather arrives, that can feed storm systems and bring heavier rainfall.
Several conditions still have to combine for an extreme rain event: instability, moisture, upper-air dynamics, converging winds and a persistent weather pattern. A DANA, also called a cold drop, can trigger such a set-up. A pronounced trough with steady sea winds can also favour extreme conditions, Almarcha said.
Hot sea does not guarantee storms
Samuel Biener, a climatologist at Meteored, says the potential for very intense rain is greater somewhere in the Mediterranean basin this year. But the stored energy needs a weather situation to set off the instability before a major downpour can develop.
Not every DANA brings extreme rain, and not every extreme downpour is caused by one. Biener pointed to recent dry autumns in eastern Spain and the Balearics despite a very warm Mediterranean, when the conditions needed for intense rainfall did not form.
Source: Europa Press / Mallorca.com