Update 13 January: Aemet is forecasting increasing instability in the weather and the arrival of a front of low pressure from Sunday night bringing wet and windy weather. Aemet says that this will end what, with 1974 and 1994, has been one of the dryest Christmas periods in the last 60 years.
Rain and a sharp fall in temperatures is forecast from Tuesday, the rain lasting until Saturday, though Aemet says that longer term forecasts such as this are not the most reliable for specifics, but give tendencies. In short, winter is coming next week, and as proof, Aemet anticipates that Teide will be snow-capped above 2,000 metres.
Original post 12 January: As often in the weeks before the real winter arrives, we have a series of calimas or sciroccos, and we have had a few lately. The one that arrived yesterday is quite an intense one, bringing poor air quality, very low humidity and visibility, and unpleasant winds. These conditions are forecast to last until Sunday, when the wind turns to the northeast, and the change will bring fresher wind and clouds, and even some light rain in parts.