March's sudden stratospheric warming could significantly impact our weather, but what exactly does this mean for us? Let's break it down.
The Stratospheric Polar Vortex Explained:
The stratospheric polar vortex (SPV) is a natural, annual atmospheric phenomenon that occurs in the stratosphere over polar regions during their respective winters. It's like a giant whirlpool of air high in the atmosphere, separating cold polar air from warmer tropical air.
Impact on the Jet Stream:
The SPV plays a crucial role in shaping our weather by influencing the jet stream, a powerful wind current high in the atmosphere. When the SPV is strong and stable, it adds momentum to the jet stream, keeping it further north and more zonal (west to east). This can lead to active storm seasons in northwest Europe. However, when the SPV weakens, it can cause the jet stream to shift south, bringing higher-than-normal pressure to polar regions and potentially leading to cold outbreaks and rain.
Sudden Stratospheric Warming (SSW):
SSW happens when the SPV breaks down completely during winter due to tropospheric wave breaking. This causes a sudden spike in stratospheric temperatures and a reversal of winds from westerly to easterly. This disruption can last for weeks and potentially influence weather patterns for months. SSWs can take two forms: displacement or split. A split SSW is more likely to cause dramatic weather shifts in northwest Europe.
What's Happening Now?
The SPV has been weaker than average this winter, leading to a displacement SSW in late November. This contributed to higher pressure in the Arctic and a south-shifted jet stream, resulting in cold outbreaks and rain in Ireland.
Forecasting the Future:
Currently, a split-type SSW is predicted for early March. While this increases the likelihood of weather pattern changes, the exact impact is uncertain due to the complex interplay of global weather drivers. SSWs have historically had varying effects, sometimes bringing major weather events like 'The Beast From The East' and Storm Emma, while other times having little influence.
Stay Tuned:
Keep an eye on forecasts, as the easterlies' penetration into the troposphere will determine the weather's day-to-day changes. This March's SSW could bring significant weather shifts, so stay informed and prepared!
