A quick look at the objective LWTLWTLamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. data from 1871 to find the most anticyclonic November reveals that 1942 and 1988 (60%) are at the top of the pile. Not a lot of people know that. 🙂
November 1988November 1942
As you might expect, November 1942 and 1978 were both quite dry and cold months.
I have no idea if this is an analog for the coming winter, but I’ll do a bit more digging and see what I can find out what the following winters were like.
A month of mixed weather types, a negatively zonal start gradually became more zonal, with alternating cyclonic and anticyclonic spells through the month, which gradually became more anticyclonic in nature as pressure gradually rose.
Higher than average pressure across southern Greenland and central Russia, with lower than average pressure in the central North Atlantic help produce a fairly strong SW’ly mean flow for the month across the British Isles. The track of a number of tropical cyclones helped dig a path of lower anomalies from Florida by the look of it too.
Christmas Day 12 UTCUTCCoordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean solar time (such as UT1) at 0° longitude (at the IERS Reference Meridian as the currently used prime meridian) and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT). 1979-2023
This post is more of a reminder to myself about an application I wrote to display a grid of charts it downloads from Wetterzentrale. You can choose to display CFS, ERAERAERA stands for 'ECMWF Re-Analysis' and refers to a series of research projects at ECMWF which produced various datasets (ERA-Interim, ERA-40, etcetera). or NOAANOAANOAA is an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; provides weather reports and forecasts floods and hurricanes and other natural disasters related to weather. reanalysis charts either as charts of isobars overlaid over colour filled contours of 500 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar heights, or as charts of isolines of 850 hPa geopotential heights, overlaid on colour filled contours of 850 hPa temperature. I think it produces a pretty useful grid of charts to view a month, or a season, but in truth I haven’t used it that much in the last 12 years. The example above displays surface pressure charts for Christmas day.
Winter [DJFDJFMeteorological Winter comprising the months of December, January & February] 1962-63
The grid of images above, is for daily MSLPMSLPMean 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. and daily 500 hPa geopotential heights for each day of the infamous winter of 1962-63.
The other innovative thing that I added to the application, was a colour analyser (above image). This does a lookup on the colour of each pixel across the map of the British Isles in the downloaded image, and calculates an overall average which it uses to plot a graph and fill a table with the daily 850 hPa temperature or the 500 hPa geopotential height. A crude but quite effect way of gauging just how warm or cold it is on any given day. There are problems with the app, but out of my control, in that Wetterzentrale for some years, use a slightly different resolution and size for their images. I could fix it but it’s fiddly. They also seem now not to load the ERA reanalysis images on their server. Who knows for how much longer they’ll maintain the CFS and NOAA images, it would be a real loss if this went.
I’ve added some code to my LWTLWTLamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. application to display graphs of 365 day moving averages for some of the daily indices that the objective series generate. I thought it might be easier to pick out trends using an extended period like this, although the application is flexible enough to allow shorter periods. At a glance you can see that mean MSLPMSLPMean 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. over the last 10 years across the British Isles is currently at its lowest at the moment, and positive cyclonic vorticity has also been at a ten year high in 2024 as well. What it all means remains a mystery but it kept me busy this afternoon. 😜
Unusually high pressure in September to the southwest of Iceland and Greenland (+8 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar) and across Ukraine (+11 hPa). This effectively neutralised the usual Icelandic low, effectively pushing a band of lower pressure from northern France to the Black Sea. That left the British Isles in a col as far as mean pressure for the whole month was concerned, which doesn’t quite tell the whole story.
MSLPMSLPMean 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. was below average for much of the summer [JJAJJAMeteorological Summer comprising the months June, July & August] with a strong mobile W or SW flow with an above average GIGIGale Index. Brief anticyclonic interludes that got briefer as the summer went on. The NW flow in June backed into a SW’ly from the middle of July.
Anomalies of -15 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar to the SE of Iceland displaced the usually shallower Icelandic low east to produce a broad SW’ly flow across the UKUKThe United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. and Ireland during August. The semi-permanent Azores high remained with pressure a little higher (+2 hpa) than average enhancing the flow.
July 2024 was a very zonal month, and cyclonic at times, with below average MSLPMSLPMean 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., but a little more anticyclonic towards the end. It looks like I’m going to have to search for missing charts on the 10th and 11th. Sunday the 28th looks a rare day when the UKMOUKMOThe Meteorological Office is the United Kingdom's national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy couldn’t find a single frontal structure or trough near IONAIONAIslands 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..
A mobile, and at times a quite cyclonic month for June across IONAIONAIslands 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. started anticyclonic enough, but the flow steadily veered more northwesterly up until the 11th, when a low tracked slowly eastward from the 14th to the 18th leaving a northerly behind it. The circulation gradually became more southwesterly until the 24th, when a brief anticyclonic couple of days gave way to a low that tracked northeastward across the northwest of the UKUKThe United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. on 27th & 28th, with winds veering more northwesterly, as high pressure built in from the southwest.
May was a generally quiet month with four or more cycles of cyclonic and anticyclonic spells, as much positive meridional than it was negative, with more negative zonality than positive. It’s no wonder that the mean pressure pattern for the month was slack.
Mean pressure across IONAIONAIslands 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. in May was around 3 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar below the LTALTALong Term Average. This is usually defined as a 30 year period by the WMO.. In fact lower than average pressure was strung out westward across the central Atlantic all the way to the United States. Mean higher than average pressure persisted across Scandinavia (+6 hPa) resulting in a very slack pressure pattern across the country.
February 2024 was a cyclonic month across the IONAIONAIslands 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., with a strong broad W’SW gradient that stretched from central Atlantic into northeast Russia. The Icelandic low was elongated further east into the northern Norwegian sea (-9 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar), and the Azores high displaced to the southeast towards the Canaries (+4 hPa). Mean MSLPMSLPMean 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. was below normal across the whole of IONA by as much as -9 hPA in northern Scotland.
A strange old month with some rapid switches in cyclonicity. Mostly zonal but an anticyclonic second week and three named storms. The Gale Index in the objective LWTLWTLamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. that I calculate from reanalysis data is not the same as the GIGIGale Index that I generate from SYNOPSYNOPSYNOP (surface synoptic observations) is a numerical code (called FM-12 by WMO) used for reporting weather observations made by manned and automated weather stations. SYNOP reports are typically mad hourly and consist of groups of numbers (and slashes where data is not available) describing general weather information, such as the temperature, barometric pressure and visibility at a weather station. observations.
Temperatures across IONAIONAIslands 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 MSLPMSLPMean 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.
MSLPMSLPMean 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. anomalies in December were not too dissimilar to those of November, with the Icelandic low pushed further south into mid-Atlantic by higher than usual pressure across Greenland. Pressure was lower than average across the 55N latitude from Scotland east into the southern Baltic(-8 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar) and higher than average (+5 hPa) to the west of Portugal. This all added up to a tight W’SW flow from the central Atlantic across England and Wales, and eastward on into Germany and Poland. All a result of a south shifted jet stream for much of the month.
December 2023 ended up being a mobile month with the jet stream for much of it south shifted, which made it more cyclonic than normal, and hence a rather windy month too with four named storms. The LWTLWTLamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. zonal index was negative for the first week or more, but went positive in a big way from the second week onward. Quite a few classic analyses from the UKMOUKMOThe Meteorological Office is the United Kingdom's national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy during the month ranging from a plethora (thanks CK) of troughs on the 1st & 2nd to multiple occlusions on the 31st (thanks Mr Occlusion).
Meteorological Autumn 2023 has seen some quite varied weather types, predominantly anticyclonic until mid October and then full on cyclonic. It also contained four named storms, some of which were more deserving than others for being named. I can’t even remember them all, only Ciaran and Debi stick out. Zonality also did a couple of about faces during October and again towards the end of November.
It’s easy to see why August 2023 was such an unsettled month across Ireland and the UKUKThe United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. with temperatures just below the average when you study the MSLPMSLPMean 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. anomalies.
Well the first thing to say is that low’s are not at all unusual in August. Remember the Fasnet storm of 13 August 1979? Tomorrow’s low has a forecast central pressure of 983 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar for midday and is situated close to Birmingham. Below is a graphic of charts drawn using reanalysis data from 1948 so you can make your own minds up. The one that immediately stands out to me is the chart for the 2nd of August 1986, with a GIGIGale Index of 38. Remember this chart uses reanalysis data in a coarse 2.5°x2.5° grid of MSLPMSLPMean 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. values so contours may well be lower.
It just so happens that I have this chart, but as you can see the low close to Tiree is already a filling feature, with a minimum central pressure of 988 hPa at 06 UTCUTCCoordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean solar time (such as UT1) at 0° longitude (at the IERS Reference Meridian as the currently used prime meridian) and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT)., and can’t match the forecast depth of tomorrow’s low. So tomorrow’s low looks very unusual, and is likely the deepest low to affect the UKUKThe United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. on this date in over 75 years!
Winter 2022-23 [DJFDJFMeteorological Winter comprising the months of December, January & February] has been dominated to a large extent by a more intense Azores high than usual. This has kept things fairly mobile especially the north and has also provided a good deal of dry and quiet weather across southern parts, with increased numbers of overnight frost and fog. Anomalies have been generally between 4 and 8 hPahPaA Hectopascal is the SI unit of pressure and identical to the Millibar above the LTALTALong Term Average. This is usually defined as a 30 year period by the WMO.. The only time the Azores high did relinquish its hold was in December of 2022, when the flow across IONAIONAIslands 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. reversed and we saw the only spell of anticyclonic easterlies we’ve seen so far this winter.
The chart shows the mean MSLPMSLPMean 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. over the last 16 weeks across IONAIONAIslands 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. and the corresponding objective LWTLWTLamb Weather Types are often used in UK-based analyses, with individual weather patterns based on the eight primary cardinal directions (N, NE, E, SE, S, SW, W, NW) plus cyclonic (C), anticyclonic (A) and unclassified (U) types. for each of those weeks. It’s evident that the last anticyclonic spell occurred in the third week of September and since then the circulation has been mobile and usually from the W or SW.
