Broadly, I have the impression that the forecast models aren't doing the best of jobs accounting for the impact of widely warmer than average sea surface temperatures. It shouldn't be the case, but it's hard to find another explanation for the larger than usual underestimations of temperatures lately.
In my local area of NE Dorset / W Hampshire for example, underestimation frequencies, when rounded to nearest whole, for GFS at 4 days lead time, across 1st-30th May:
5°C: 2 for daily min, 1 for daily max
4°C: 3 for daily min, 6 for daily max
3°C: 1 for daily min, 8 for daily max
2°C: 3 for daily min, 3 for daily max
Some serious errors in there and often it's not been a lot better at shorter lead times, typically 1-2°C closer if it was a large error to begin with, otherwise little to no improvement.
It's a similar, though perhaps less pronounced, story for the CET region, which only adds to the difficulties estimating its final outcome a month in advance. The highest any late April GFS run reached for mid-month was 13.5°C, while the actual was 14.3°C. The 12z of 30th April had a mere 10.2°C for mid-month and no I'm not kidding!
Anyway, it's been a surprisingly warm month and then some! To be honest I'm just glad I went the right side of average 😂
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[email protected] https://twitter.com/peacockreports 2023's Homeland Extremes:
T-Max: 30.2°C 9th Sep (...!) | T-Min: -7.1°C 22nd & 23rd Jan | Wettest Day: 25.9mm 2nd Nov | Ice Days: 1 (2nd Dec -1.3°C in freezing fog)
Keep Calm and Forecast On