Temperatures across IONAIONA Islands Of North Atlantic. Yes I know there's an island called Iona, but this is so I don't have to use the term 'British Isles' when referring to the whole of Ireland and the UK. were close to average in January. I suspect the mean MSLPMSLP Mean sea level pressure is the pressure at sea level, or, when measured at a given elevation on land, the station pressure reduced to sea level assuming an isothermal layer at the station temperature. chart is not telling us the full story, because with a mean flow like this, you might have expected temperatures to have been well above average.
If you turn up the granularity the pentad mean pressure charts reveals why January wasn’t much milder. The 7th to 11th was cold and anticyclonic, the 12th to 16th NW’ly and the 17th to 31st was a milder W or SW’ly.
