A Backing Wind

Sailors have historically called a wind that changes direction in a counterclockwise manner with respect to the compass a backing wind. Conversely, a veering wind changes direction in a clockwise manner. Sailors have developed a vast amount of nearly impenetrable sailing lore with many terms for different kinds of wind and the behaviour of wind in general. There is science behind many of these terms. Sailors had to be scientists. They were good observers and tried to come up with sound explanations that provided repeatable best-practices. Knowing what to do when conditions change in particular ways could mean the difference between life and death.

The most likely explanation that we can come up with for this event is that a low pressure system moved slowly south and west of the station (approximately). Winds would blow from the west south of a low and from the east north of a low (we're in the northern hemisphere). If the low passed to the east of the station the winds would have rotated the other direction. The plot of atmospheric pressure confirms this (generally speaking). The centre of the low seems to be moving closer and closer to the station. You can see in the week-long plot of pressure that it reaches its lowest value early on the following day and the pressure begins to increase again as the local low passes by completely.

The wind direction observed on 2012-02-19.

The windspeed observed on 2012-02-19.

air pressure for 2012-02-19

The air pressure observed on 2012-02-19.

temperature for 2012-02-19.

The temperature for 2012-02-19.

A week of pressure values.

A week of wind directions.

The video below doesn't really show much since it is the surface winds we are measuring and those winds aren't really visible in the video. It's included here for the record. We need to include a wind sock in the field of view.

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