May 2021 – Circulation second most cyclonic in 150 years

Data courtesy of NCEP/NCAR reanalysis

Higher than average pressure north of Iceland (+7 hPa) and lower than average pressure over Denmark (-7 hPa) produced an elongated belt of low pressure that extended from Newfoundland to Latvia across the mid Atlantic during May, and explained the rather cold and very wet conditions we saw through much of the month. The mean pressure in May across IONA was almost 6 hPa below average and the month itself was the second most cyclonic in the 150 year long Objective Lamb Weather Type series maintained by the CRU, the most cyclonic occurring as recently as 1983. There were two potential named storms which occurred during the month and that the UKMO didn’t see fit to act upon, low Eugen on the 3rd and 4th and low Marco on the 20th and 21st. There have been a number of less worthy extratropical lows, especially early in the naming trial, that were named and which failed to match either the wind speeds or amount of rain that fell from either low Eugen or low Marco.

Data courtesy of UKMO and CRU at the UEA
Click image to enlarge

1 thought on “May 2021 – Circulation second most cyclonic in 150 years”

  1. and in complete contrast to last May when we had high pressure centred over the UK. Don’t you just love the British weather ???

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