I have a few ‘meteorological’ heroes in my life, and it may come as a surprise to many that Peter Ewins or Julian Hunt don’t feature in the list. At the top of it must come Gordon Manley (1902-1980), whose name I first came across when reading his 1952 book ‘Climate and the British scene’ as a teenager. He is best known for his work on reconstructing the past climate of Central England with his CET series, which was adopted and sanitized by the Met Office, which I noticed that he joined in 1925, but had the good sense to resign the very next year! Along side Manley at the […]
November is not renown for being an anticyclonic month in the British Isles. As you can see (fig 1), November is one of the few times in a year when cyclonicity is on a par with anticyclonicity. So looking at a ranked list of anticyclonic November’s since 1871 (fig 1), the number of any November’s that are over 50% anticyclonic (when using the Objective Lamb Weather Type as a crude measure) is quite small. As you can see, joint top of the list of most anticyclonic November’s along with 1942, is the year 1988, when 15 of the 30 days were pure anticyclonic. An anticyclonic Autumn month in November can […]
July continues it a mood of being mobile and often quite cyclonic at times, in fact that’s how it’s been since the end of May across the British Isles, as this graph of zonality shows (fig 2). The simple answer of why has it been so mobile is that mean pressure in the first three weeks of July 2017, has been 8 hPa below average across Baffin Island, and there has been a band of lower than average mean pressure extending westward across Iceland, before arching around Scandinavia and into eastern Russia. South of that the mean pressure across much of the central Atlantic has been higher than average […]
I noticed that the warmest spring* in the daily CET record back to 1772 in Central England was 1893. I don’t make a habit of looking for exceptional warm springs in the Victorian era, it was just that the spring of 1893 was even warmer than the spring of 2017 which has just ended (fig 1). The other thing that caught my eye was how exceptionally high the mean maximum was (anomaly +3.82°C), and how comparatively normal the mean minimum (anomaly +0.37°). This obviously points to a very anticyclonic regime back in the spring of 1893 to produce very warm days and comparatively cold nights, the graph below (fig […]
You can understand why May ended up being the second mildest on record since 1910, when you see the mean pressure chart for the month (fig 1). There was a large negative anomaly (-13 hPa) in central Atlantic, which distorted the flow around a large elongated low of 1006 hPa (49N 30W), which pushed the Azores high further south than usual, producing a SSW flow over western Britain. Pressure over central Greenland was much higher than average (+15 hPa) pushing the normal Icelandic low south. The Greenland high ridged southeastward into Scandinavia and central Europe, with a mean northerly flow over much of that region.
Another product that I can generate from my reanalysis application is a 4×3 grid of charts for monthly mean pressure and anomalies. Here are the circulation patterns for the last 12 years of April’s (2006-2017). If I ever do acquire a monitor that is larger than my Dell 24″, I may be able to pack more into a single screenshot! There is a broad similarity between 2015 and this April. April 2015 was the sunniest on record in many regions across the UK, and a comparison between it and the incomplete chart for this year show that although the mean pressure anomalies were not as large, the centre of […]
March 1957 stands out as being the mildest in the CET series which started in 1659, and as mild as this current March is, the mean anomaly of which stands at +2.48°C on the 12th, it will have to do a lot more to surpass the mean temperature of 9.2°C of March 1957, which was +3.53°C above the 1960-1991 long-term average (fig 1). Here are the daily surface charts for the month courtesy of Wetterzentrale (fig 2). In fact even 60 years later, the month still holds claim to three of the warmest March days in the CET series, the 3rd, 11th and 12th. The MWR explains how a […]
Lower than average pressure across the central Atlantic (-3 hPa) and higher than average pressure across central Europe (+5 hPa); with even higher anomalies over Asia (+8 hPa); meant that there was a W’SW flow across the central Atlantic and the British Isles in the mean pressure chart for August, this flow extended across the North Sea and into northern Germany, Poland and north and west Russia. You would have thought with that kind of pattern that there would have been more rain across the British Isles than there was, but mean pressures of around 1019 hPa across the south must have warded off most of that.
The changes in the circulation pattern over western Europe and the eastern Atlantic during June are well captured in these three 10 day mean pressure charts. The change from an anticyclonic NE’ly transitioning through a cyclonic and then into a mobile westerly are easy to see. A large area of positive mean sea level pressure [MSLP] anomalies of +15 hPa dominated the first 10 days over and to the NE of Iceland, that gave way to a discrete -1o hPa negative anomaly over the British Isles during the middle of June, before negative anomalies of -9 hpa and lower, became established over Iceland, a complete reversal of MSLP anomalies […]
When statistics can be misleading I’ve always liked monthly mean pressure maps they can be very useful at summing up the weather of a month at a glance. But sometimes they can be very misleading and not at all helpful, take a look at the anomaly chart for May 2016 below as a perfect example: As you can see the central north Atlantic had anomalously higher pressure than average (+2 hPa) in the month of May, with a lower than average pressures (-4 hPa) between Portugal and the Azores and across the bulk of southern Europe. Higher than average pressure to the SW of the Azores produced an intense […]