How unusual was the D-Day low?
With all this talk about the 75th commemoration of the D-Day landing and the forecast of Group Captain Stagg, I thought I would look back at the plotted chart for 1300 GMT on the 6th June 1944. As you can see the problem low had a minimum central pressure of 995 hPa on the afternoon of D-Day itself. But just how unusual was the intensity of that D-Day low for British Isles? Well the short answer to that question is not that unusual. I have MSLP reanalysis data back to 1871 which I can access from NOAA. The only problem with that data is the grid is coarse, plus it changes resolution in 1948 from 2×2° to 2.5×2.5°. This is lunacy on part of the Americans because you would have thought that if anything the resolution should get finer and not coarser as the years go by. So this analysis is for the nine MSLP grid point values over the centre of the British Isles (52-5N-57.5N and 7.5W-2.5W) using June data for the years between 1948 to 2018. As you can see there have been many occasions when the MSLP has been lower than 995 hPa, and the lowest pressure in those 70 years of 973 hPa occurred as recently as 18 UTC on the 1st of June 2015. The D-Day low could have been a filling feature of course by D-Day but without the earlier charts I can’t say.