Cold start to spring

I am reliably informed that the spring vernal equinox will occur at precisely 1615 UTC today this 20th day of March 2018, but the weather is in a fickle mood at the moment, and spring, well at least the start of it, looks like it will be a cold affair in our part of the world. The Met Office in their extended outlook till the middle of April (fig 1) is being its usual unequivocal self about the possibility.

Figure 1 – Courtesy of the Met Office

In line with that outlook, the GFS model for April 1st (fig 2) is forecasting a northerly outbreak which is not at all unusual for spring across the British Isles.

Figure 2 – Courtesy of www.wxcharts.eu

Cold springs are somewhat of a rare commodity these days, and the last one to produce negative anomalies in Central England was back in 2013 (fig 3), and in the last 30 year there have only been three cold springs (2013, 1996 and 1991).

Figure 3

Despite the cold weekend spring sprung last week!

Figure 1

Despite the last record couple of cold days in Central England, I reckon that the average number of degree days between the winter solstice and the vernal equinox was exceeded on the 14th of March this year (fig 1).

This normally would make the first day of spring around a week early, but because springs have been occurring earlier on average (20 days earlier than in 1772 and now around the 11th of March each year), 2018 was around three days late this year, it was also the latest spring to have occurred since 2013.

I personally think that using degree days like this is a crude but effective way of coming up with a date for the start of spring, let me know if you have a better idea.