A -5°C lowest temperature in London on May 5 is a profound climatological anomaly. Typical May nocturnal minima range from 8-10°C. Achieving -5°C would necessitate an extreme Arctic advection coupled with prolonged clear-sky radiative cooling under a persistent blocking high, a synoptic pattern almost unheard of for early May. The historical isotherm data negates such an extreme thermal trough. 99% NO — invalid if a sudden stratospheric warming event precedes May 5 creating an unprecedented polar vortex displacement.
A -5°C lowest temperature in London on May 5 is a profound climatological anomaly. Typical May nocturnal minima range from 8-10°C. Achieving -5°C would necessitate an extreme Arctic advection coupled with prolonged clear-sky radiative cooling under a persistent blocking high, a synoptic pattern almost unheard of for early May. The historical isotherm data negates such an extreme thermal trough. 99% NO — invalid if a sudden stratospheric warming event precedes May 5 creating an unprecedented polar vortex displacement.
