June is a usually rainy month in Chile, both in the central zone and in the south of the country. Rainfall that occur in the sixth month of the year are essential for water records, which have been greatly affected in recent years.
Precisely during June 2021, the situation is not very encouraging. The first fortnight is presented with scarcity of rain, and also, temperatures above normal. In fact, thermometers will average more than 20 ° C. The peak of heat will occur on Saturday, when the figures could reach 25 ° C.
One of the reasons that causes such a reality is the term and absence of La Niña phenomenon, a situation that has been noted in the lack of rainfall and in temperatures, since its moderating effect disappeared.
Diego Campos, meteorologist at the Office of Climate Services of the Chilean Meteorological Directorate (DMC), notes that the so-called hot June is not just a perception, “The data indicate that in these first days of June the average maximum temperature is close to 21ºC, while the normal climatologically speaking is close to 17ºC. That is to say, in this month of June we have an anomaly of 4ºC. And it is a situation that has been dragging on since the last ten days of May, where an average maximum temperature of 3ºC above the climatological normal was also observed ”.
Raúl Cordero, climatologist of the University of Santiago, states that the last few months in Santiago have been very warm. In addition to what was registered in June, “the period from April 8 to June 8 of this year, it’s the warmest room ever recorded, with maximum temperatures almost 2 ° C above the typical values for the same period ”.
In relation to rainfall, the last time no rains were recorded in Santiago During the first half of June it was in 2015, that is, six years ago. Other completely dry months of June are added to the record, such as 1968 (cataloged as a hyper-arid year), 1979 and 2001.
All this corresponds to the sub-seasonal variability, since we are analyzing a period of between 15 and 20 days. “During this period, frontal activity (rainfall systems) has again concentrated in the area between La Araucanía and Los Lagos, with significant amounts of precipitation. When this happens, the central zone is dominated by a more stable condition and prone to the formation of the coastal trough. When this is formed, the wind predominates from the east (down the mountain range) and also favors the descent of air over the Santiago basin, causing a rise in temperatures”Adds Campos.
Cordero says that because June is the rainiest month of the year in Santiago, it is unusual (and bad news) to have such a dry first fortnight. “However, it is still too early to be alarmed. The last time we had no rain in Santiago in the first half of June (2015), the year ended with rainfall exceeding 200 mm ”.
Temperatures have risen so much, “that between May 25 and 27 there was a heat wave in Santiago (very unusual for the time), which indicates that during those days the maximum temperatures reached the category of extreme event, with maximums close to 23ºC (which is a lot for the date) ”, explains the DMC meteorologist.
Also, it hasn’t rained for the whole month. “The precipitation systems have moved, in their journey from west to east, further south, mainly between La Araucanía and Los Lagos, regions in which yes it has rained a lot during this period. That during a period of a couple of weeks it does not rain in one region of the country (understand region as an area and not as political regions) and yes in another, it is normal. Now, the intra-seasonal or sub-seasonal variability tends to have these changing periods ”, establishes Campos.
Unfortunately, drought conditions affect practically the entire country. “From the Antofagasta Region we have marked rainfall deficits. These are marked in the central zone and in the center-south. However, it should be noted that the Osorno area, which two months ago had a rainfall deficit of almost 80%, has been recovering rainfall, and today the rainfall deficit is ‘only’ 50% ”, adds Cordero.
Campos argues that this is a behavior already observed in the last ten winters or so. “And according to our forecast, it should be the tonic of winter (which does not mean that it will not rain or that it cannot be cold in the following weeks). The large-scale patterns that are dominating during this 10-year dry period still hold, such as the presence of anomalies of warm seawater in southeastern Australia, presence of high subtropical pressures reinforced, relatively cold seawater anomalies in the equatorial Pacific (despite La Niña withdrawal) or the positive trend of the Antarctic Oscillation. All these factors combined (and perhaps others) have favored a prolonged dry period in Santiago ”.
A transition of the Antarctic oscillation was observed in recent days, “from a negative phase to a positive phase and that could be related to heavy rains in the south (and therefore with the heat in the central zone). But it is complex on this time scale (on the order of weeks) to be sure what caused what because everything is usually very connected. This timescale is also highly variable and we could eventually have relatively cold weeks in the near future, ”Campos concludes.