Intraseasonal Teleconnections Leading To Heat Waves In Central Chile

The ability to anticipate meteorological extreme events beyond the synoptic range of similar to 1 week offers direct applications, for example, to limit their ecological and socioeconomical impacts. This study focuses on precursors of summer (December-February, DJF) warm events, particularly heat waves, in central Chile (CCh), which are typically induced by low-level anticyclonic anomalies located to the south of this region. Considering that such atmospheric configuration can be part of a large-scale wave-train circulation pattern located upstream of CCh, we investigate signals that might provide guidance concerning the genesis of warm events in CCh. For a historical period (DJF 1872-2010) based on the 20th century reanalysis version 2 (20CR), our results present teleconnections that indicate higher probabilities of occurrence of such warm events with respect to expected climatological values. These signals can be monitored at least similar to 2 weeks in advance. Specifically, we explore the relationship between warm events in CCh and (a) the Madden-Julian Oscillation (MJO) as a tropical source of variability, and (b) an extra-tropical index (ETI), representative of the internal dynamics of the Southern Hemipshere mid-latitudes, presented as an original contribution from this study following a novel approach. Both signals, and apparently their constructive superposition, seem to contribute to the organization of the large-scale circulation anomalies leading ultimately to heat waves in CCh. We confirm these results for recent decades (DJF 1981-2020) using temperature observations and further data sets, namely the NCEP-NCAR Reanalysis (NNR) and the Climate Forecast System Reanalysis versions 1 and 2 (CFSR and CFSv2, respectively). Finally, we describe three recent heat wave events in CCh (DJF 2019-2020) to illustrate the suitability of this conceptualization.