Long Range Forecast

UKMO 3 Month Outlook – Autumn 2024 verification

I thought that I’d look back at the three month outlook for autumn 2024 [SONSON Meteorological Autumn - September, October and November] issued by the UKMOUKMO The 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 on the 27 August. The outlook is split into three distinct areas, temperature, precipitation and wind speed. It’s relatively easy to assess how accurate the outlook was for temperature and precipitation, but not so for wind because the UKMO don’t issue monthly gridded mean wind speed data. They must have this data because the three month outlook itself contain three month anomaly charts for wind speed. The one climate statistic that they did omit is sunshine, important not only summer, but also in autumn and winter, as this gloomy November highlighted only too well. Here’s a table of climate statistics for the UKUK The 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. for the three months that make up meteorological autumn and anomalies for temperature, precipitation and sunshine.

How accurate was the forecast of temperatures?

The outlook stated that there was a 40% chance of it being a warm autumn, with a fifty-fifty chance of near average temperatures. In the end, the mean temperature for the three months that make up meteorological autumn was +0.3°C above the 1991-2020 long-term average, so it was only marginally warmer. WRONG, autumn was not noticeably warmer than average, although they were right about ‘cool spells’ later in the season, but cold spells towards the end of autumn are far from uncommon.😉

How accurate was the forecast of precipitation?

The outlook stated that there was a 35% chance of autumn being wet, with a 55% of it being near average. In the end precipitation in autumn 2024 ended up 89% of the long-term average. So a drier, rather than a wetter autumn. Despite flooding from storm Bert, the first half of November was very dry across the whole country, WRONG.

How accurate was the forecast of mean wind speed?

The outlook stated that there was a 35% chance of autumn being windier than average, with an increased risk of stormy conditions. As I said earlier, there’s not an easy way of measuring the accuracy of this one. There were three named storms during autumn, one of them named by the KNMI, the other by Met EireannMet Éireann Met Éireann, the Irish National Meteorological Service, is the leading provider of weather information and related services for Ireland.. The first half of November was anticyclonic which would have reduced the mean speed for the whole of autumn a fair bit. UNDECIDED.

December 2, 2024

Autumn, Long Range Forecast, UKMO

UKMO 3 Month Outlook – Autumn 2024 verification Read More »

Was the cool unsettled start to July anticipated?

16-30 day UKMOUKMO The 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 text forecast

Was the cold and unsettled start to July in anyway expected by the UKMO in their long range (16-30 day) forecast? As far as colder than average temperatures are concerned that’s a definite no, with mean anomalies for the period from 29 June to the 12th of July between one and three degrees below the LTALTA Long Term Average. This is usually defined as a 30 year period by the WMO.. There was no mention of such a dull start to the month either, with sunshine widely only 60% or less of the LTA. Sunshine may have been in short supply but rainfall totals were widely above average in the 14 day period, with large areas seeing totals 200% or more of the LTA. So the short answer to the question, as measured by mean temperature, total sunshine and rainfall, is a most definite no, the cool, dull and wet start to July was not anticipated.😜

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July 13, 2024

Long Range Forecast, UKMO

Was the cool unsettled start to July anticipated? Read More »

Our changing weather patterns: a tale of abrupt transitions

The blog above was published on the 5th of February by the Met OfficeUKMO The 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, it looks ill timed and a bit of a publicity disaster for both them and their GloSeason seasonal prediction system, especially with this week being exceptionally mild.

Rather than seeing a plunge of “very cold air from the Arctic”, this week has turned out to be an exceptionally mild one, both here in the UKUK The 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 over a large part of NW Europe. The latest forecast 2M temperature anomaly charts from the ECMWFECMWF The European Centre for Medium-Range Weather Forecasts is an independent intergovernmental organisation supported by most of the nations of Europe. It is based at three sites: Shinfield Park, Reading, United Kingdom; Bologna, Italy; and Bonn, Germany. It operates one of the largest supercomputer complexes in Europe and the world's largest archive of numerical weather prediction data. (15 February) doesn’t foresee any cold weather turning up in the next ten days either. Perhaps the very cold weather will arrive in March, who knows, the GloSeason system doesn’t seem to.

I had vaguely heard of the GloSea seasonal forecasting system before, although I have no idea where you can see output from it.

Mild start to autumn 2023

According to the 42 day forecast for 2M temperatures from the ECMWFECMWF The European Centre for Medium-Range Weather Forecasts is an independent intergovernmental organisation supported by most of the nations of Europe. It is based at three sites: Shinfield Park, Reading, United Kingdom; Bologna, Italy; and Bonn, Germany. It operates one of the largest supercomputer complexes in Europe and the world's largest archive of numerical weather prediction data., it looks likely to be a mild, if not warm start to meteorological autumn 2023 across much of Europe. Let’s hope they’re forecast is wrong, it has been before.

ECMWF didn’t see the recent cold snap coming

6 Feb – 20 Mar 2023
2m Mean Temperature Anomalies

The ECMWFECMWF The European Centre for Medium-Range Weather Forecasts is an independent intergovernmental organisation supported by most of the nations of Europe. It is based at three sites: Shinfield Park, Reading, United Kingdom; Bologna, Italy; and Bonn, Germany. It operates one of the largest supercomputer complexes in Europe and the world's largest archive of numerical weather prediction data. are brave enough to let you turn the clock back on their 42 day forecasts and see how they performed. Not very well in the case of last week as it happens.

6-13 Mar 2023
Mean temperature anomalies

When this kind of thing happens, it always knocks your confidence as regards their promise of a milder than average April.

13 Mar – 24 Apr 2023
2m Mean temperature anomalies

March 13, 2023

ECMWF, Long Range Forecast, Temperature

ECMWF didn’t see the recent cold snap coming Read More »

Accuracy of Long range Forecasts from UKMO

I’ve been archiving text LRFLRF Long Range Forecast. Usually 16 to 30 days or more. from the UKMOUKMO The 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 for a month or two now so I thought I would take a look and see just how accurate they’ve been. The recent cold and snowy start to March 2023 seemed a perfect period to evaluate, so here is the text for the 16-30 day forecast issued on the 9th of February, and the 6-15 day forecast issued on the 24 February.

16-30 Day

The ‘bands of rain and strong winds… in the northwest’ in the 16-30 day forecast is clearly wrong, and looked so even when it was first published on the 9th of February. An intense high persisted over N Scotland from the 26th of February to the 4th of March. The ‘low probability of some much colder weather’ is also clearly far from accurate and really should if anything have read ‘high’.

6-15 Day

‘There is also potential for a spell of more unsettled weather in the far north‘ again this is inaccurate. The weather types in the N of Scotland during this period was either A or AN, and the two unsettled spells that did occur were associated with lows that crossed the country much further south than the N of Scotland. ‘A low chance of more organised rain or snow spreading south’ is another faux pas with many areas across N Ireland, N Wales and N England seeing a spell of heavy snow on the 9/10 February. ‘Temperatures generally on the colder side of average’ is partly correct, but anomalies for the 1-10 February were generally between -2°C to -3°C below the LTALTA Long Term Average. This is usually defined as a 30 year period by the WMO. across the UKUK The 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 Altnaharra recording two consecutive nights with minima of -15.4°C and -16°C, the coldest March nights since 2010.

Summary

The accuracy of NWPNWP Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. forecasts beyond T+120, sometimes T+96 takes a nosedive, so I don’t know why I should think LRF can be in anyway be more than vaguely accurate. My main complaint with it is the lack of consistency in how they’re written, and the fact that the 16-30 day forecast can remain the same for as long as a week at a time, which can’t be right.

March 10, 2023

Long Range Forecast

Accuracy of Long range Forecasts from UKMO Read More »