Overview
- Meteorologists reported this week that the polar vortex in the stratosphere has weakened and shifted earlier than in modern records, with ECMWF and the Met Office describing the disruption as possibly the earliest observed.
- A sudden stratospheric warming (SSW) occurs when temperatures in the stratosphere jump and the vortex’s westerly winds weaken or reverse, and its effects on surface weather typically appear one to six weeks later.
- Short-range forecasts currently show only limited wintry showers mainly on higher ground in Scotland while agencies continue to watch whether the stratospheric signal will descend into the troposphere and alter the jet stream.
- Scientists say the record-strong El Niño may have amplified atmospheric waves that helped trigger the early disruption, but the Arctic and Siberia are not yet at midwinter coldness so any cold outbreaks could be milder or different than past events.
- If the disturbance does influence surface weather, possible impacts include cold, dry spells, localized snow in eastern Britain, altered storm tracks and pressure patterns, and secondary effects on water supplies and energy demand, so forecasters will keep monitoring and issue warnings as needed.