This morning, I watched as my aneroid barometer here in Harrogate, North Yorkshire slowly crawled upwards towards 1030 hPa. It’s a far cry from the forecast surface pressure in the next few weeks across the USA, but it’s also a far cry from what was happening on this day 4 years ago.
At least in Harrogate, 18 December 2013 marked the start of the infamously cyclonic winter of 2013-14. I took “daily” barometer observations throughout that winter. (Rather unscientifically, I don’t actually know what time each day I took these readings and it definitely wasn’t consistent – but it still serves as one record of the extraordinary winter.)
The transition on the 18th from a strong anticyclonic regime to the cyclonic “hell” that followed is clear, and I’ve shown that with 2 different averages (dashed lines). The period during February also pushed my barometer to its limits…the scale runs to 965 hPa, which is the minimum value I’d noted down during the winter (Feb 8th).
I distinctly remember the onset of the winter reminding me of the wet summer of 2012, as both came on the back of a dry spell (though 2012 was much more significant in that regard) [and believe it or not, I stood beside Thruscross Reservoir in early December 2013 and remarked of its low water levels that “if we don’t have significant rain soon, we’ve got a problem”…we ended up with a very different problem!]. The swing from extreme to extreme is a signature of how both events were driven by stationary amplified patterns in the jet stream – both before and afterwards – something which has been a subject of recent research in the context of climate change.
Based on analysis from a Met Office report and subsequent journal articles, an enhancement of convection in the equatorial western Pacific (plus a few other things en-route) played a strong role in driving the wet winter of 2013-14 in the United Kingdom. Isn’t it just fascinating to think of torrential tropical downpours in Indonesia – an entirely different kind of rain – driving wet day after wet day in the UK? I think this serves as a reminder to always enjoy the weather – there’s always some fantastic dynamics behind it, even if it is just another rainy day.
I co-authored a summary report of the winter whilst studying Synoptic Meteorology Laboratory at the University of Oklahoma last year, which if you’re interested is available here: Winter 2013-14 Summary.