I am in the process of conducting a practical experiment in the run-up to the 10th anniversary of Madeleine’s disappearance. It is weather station Luz.
I started this at the beginning of Nov 2016, with a simple aim. I wanted to check how well the weather in Luz correlates with the weather as logged at Faro to the east and Sagres to the west. If there is a high degree of correlation, it means the historical weather logs can be used as an accurate description of weather in Luz around 3 May 2007. And if not, it becomes clear that positing a connection on these records does not stand up to scrutiny.
In the beginning, I was collecting data at 12.37pm. This was the time of day when the sun was at its highest over Luz, giving me an accurate indication of due south.
Portuguese time is identical to UK time in winter and in summer, and the clocks go forward and back at precisely the same time. To all intents and purposes, weather station Luz is on UK time.
In winter, the sun is due south of Greenwich at 12 mid-day. Luz is roughly 8° west of Greenwich. The Earth rotates at 15° per hour. So the sun is due south of Luz at 8/15ths of an hour after mid-day.
Inserting accurate figures, the sun marks due south at 12.37pm in Luz in winter. When we move to Portelas, we are heading somewhat east, at the sun will be due south at 12.35pm.
In summer, these times become 1.37pm in Luz and 1.35pm at our new home.
The data I am collecting is temperature in the shade, wind direction, wind speed (including whether it is subject to gusts) and cloud or haze cover.
When the clocks moved forward, I realised I could improve my experiment by collecting data at 10pm, to see how well evening weather in Luz matches up with the Faro and Sagres weather stations.
A number of significant things have emerged from this experiment.
The weather at 1.37pm is not the best predictor of weather at 10pm on the same day. It can be raining at lunchtime and dry in the evening, or more often vice-versa. The most significant pattern change is that the wind has dropped on nearly every evening. Even when there is a medium wind with gusts at lunchtime, a typical evening pattern is very gentle breeze with very few gusts.
Yesterday, we had a bit of an oddity at lunchtime. Over the land, the sky was 100% clear. Over the sea, the sky was completely cloudy. I logged the 1.37pm temperature as 27°C in the shade, much higher than it has been since my records began. I suspect most of the moisture in the earth of the Algarve has already been burned off, explaining the lack of clouds over the land, whereas the high temperature was evaporating water from the sea to form clouds.
There is one factor in this experiment that I have not emulated. Luz is much like an inverted half-cone, with the sea at the bottom replacing the missing half. My weather station Luz is at the top of the cone i.e. at the top of a hill network that nearly surrounds Luz. Apartment 5A is much closer to the bottom than the top, and that is going to lead to a difference in weather re wind speed. I need to take some measurements close to block 5 around 10pm, as 3 May 2017 approaches.
I have not yet cross-checked my measurements against those of Faro and Sagres. I don’t want to introduce potential bias by tweaking my measuring routine and method. I do not expect to understand the value of weather station Luz until the time we move from Luz to Portelas. At the moment, this looks very much like being after 3 May 2017, as the builders have not yet started on our slice of the house.
Once we have moved, I intend to repeat this experiment in Portelas. This is mere curiosity and has nothing to do with the Madeleine McCann story. Portelas is a fair way inland compared to Luz, and I would like to know how well weather station Portelas correlates with the official stations at Faro and Sagres.