Now That's What I Call Snow

 After being somewhat dismissive of the recent snowfall in Hereford, this was the scene when we woke up this morning:

Photo 1: Snowy Back Garden Scene (9/3/23)

And here is a short video of the same scene:

Video 1: Snowy Back Garden Scene (9/3/23) 

The photograph and video were recorded at 8 o'clock in the morning (9th March 2023) when the outside temperature was 0 ℃. It was raining quite hard by 10.30 am, coinciding with a temperature rise to 2 ℃. By late afternoon (4 pm), much of the snow had disappeared. Figure 1 plots the outside temperature along with the amount and rate of rainfall. Strictly speaking, we should describe rain as precipitation because it will include snow as well as rain.

Figure 1: Temperature & Amount/Rate of Precipitation on 9th March 2023

Estimating the amount of snowfall from the Weather Station data is non-trivial because it also includes rain precipitation. If it had not rained today it would have been possible to obtain a reasonably accurate measure of snowfall.

It snowed overnight and probably started at the first precipitation event around 2 am (Figure 1). It was still snowing at 8 am when Photo 1 & Video 1 were recorded. Snow will have collected in the rain collector but would not trigger the measuring buckets until it melted.

We can be reasonably confident that any precipitation recorded before it started to rain (i.e. before 10.30 am) is melted snow; 2.4 mm of rain was recorded by the Weather Station between 2 am and 10.30 am. Damp new snow has a 'typical' density of between 0.1 to 0.2 kg/m³ and we will assume, for simplicity, that liquid water has a density of 1.00 kg/m³ at 0 ℃. Thus 2.4 mm of liquid water would be equivalent to 12 - 24 mm of snow (0.5 to 1.0 inches).

So, up to an inch (25 mm) of snow. Impressive for Hereford. Not so impressive for lots of other places.


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