Storm Christoph caused severe flooding and heavy snowfall in parts of the UK in mid-January 2021.
25 January 2021
22 January 2021
By Jochen Kerkmann (EUMETSAT) and Sancha Lancaster (Pactum)
The named Atlantic storm brought heavy rain, snow and strong winds to many parts of the UK from 19-21 January 2021.
The Met Office issued timely amber heavy rain warnings (up to 200 mm in parts) for northern and central England, including Manchester and heavy snow warnings (up to 30 cm for areas above 400 m) for parts of south west Scotland.
The moisture transport from the Atlantic Ocean to southern-central UK (related to cyclone Christoph) can be clearly seen in the 24 hour loop of the CIMSS Total Precipitable Water (TPW) product, which uses microwave satellite data as its main input (Figure 1). At that time most of the rain was falling in Wales and central UK, along a moisture boundary that was quite stationary, while it was still dry over Scotland.
The three hourly infrared loop with Opera radar data overlaid (Figure 2), shows the rain continuing for several days.
The continual heavy rainfall caused severe flooding in parts of northern England and Wales. More than 2,000 homes were evacuated near Manchester, Merseyside, Cheshire and in North Wales.
The heavy snowfall during Storm Christoph caused travel disruption in parts of Scotland, with road and rail disruptions in some areas. Even as far south as Bristol there were heavy hail and thunder storms in the early morning of 19 January.
The highest rainfall amounts reported by the Met Office, between 19 January 00:00 UTC and 21 January 18:00 UTC, show that parts of Powys in Wales had up to 188.8 mm, parts of Cornwall had more than 172 mm and parts of Lancashire in North-West England had up to 169 mm.
The Airmass RGB with the H-SAF precipitation product overlaid, from 20 January, shows storm Christoph rotating over the Atlantic bringing the moisture to the UK. In central UK there was the main rain band, exactly where the two airmasses met — the cold polar air over Scotland and northern UK and the warm, moist airmass over southern UK. Note that, towards the end of the animation, there are some unrealistic high precipitation rates given for the clouds to the north of the Pyrenees. These cloud are high-level wave clouds (not frontal clouds) that normally do not produce precipitation. The wave clouds appear with a bright yellow colour in the Convection (Severe Storms) RGB (Figures 4 and 5), indicating the presence of very small ice particles in these clouds.
Storm Christoph: Evacuations amid floods and snow (BBC News)
Storm Christoph: Travel disruption as snow and rain sweep in (BBC News)
Storm Christoph triggers flooding across the UK as hundreds evacuated (The Telegraph/YouTube)
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