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Found 21 results

  1. This article contains an overview of Seasonal Forecasting and its challenges with a focus on the UK Met Office seasonal model GloSea and its sub-models. First some background: The Met Office has a range of models, each with a particular focus and ranging from daily weather forecasts to climate forecasts for the next century. Since 1990 their strategy has been to integrate the individual models into a Unified Model system that can be used for prediction across a range of timescales. This from their website: “The Unified Model applies this seamless modelling approach, which means that the same dynamical core and, where possible, the same parameterization schemes are used across a broad range of spatial and temporal scales on a traceable frame work. The model is suitable for numerical weather prediction (NWP), seasonal forecasting and climate modelling with forecast times ranging from a few days to hundreds of years. Furthermore, the Unified Model can be used both as a global and a regional model.” The Met Office’s Seasonal model, GloSea, sits within the Unified Model structure and is described as the main prediction system currently used for seasonal timescales (up to 6 months) and sub-seasonal timescales (between 2 to 6 weeks). It is an ensemble prediction system using a coupled ocean-atmosphere model (a variant of Met Office climate prediction model: HadGEM3 family), to generate probabilistic forecasts up to six months ahead. The model family is shown in this diagram: The latest iteration - GloSea5 - runs daily with 28 ensemble members for sub-seasonal forecasts and weekly with 42 members for seasonal forecasts. It has two components: the real-time forecast and a companion set of hindcasts, also called historical reforecasts, used for post-processing (bias correction and calibration) and skill assessment. In the forecast suite, initial states (start conditions) for the atmosphere, land surface and ocean are calculated daily. The atmosphere and land surface resolution (grid spacing) is 1.875° × 1.25° to 0.833° × 0.556°. The grid spacing in the ocean and sea‐ice models is 0.25°. System initialisation includes the following data: atmosphere and land surface components from the Met Office operational numerical weather prediction (NWP) model; fully resolved stratosphere as part of 38 vertical levels of the atmosphere; ocean surface temps (SST), ocean vertical temperature and salinity profiles, ocean currents, AMOC strength; atmosphere–ocean coupling; sea ice cover and thickness, ice-berg calving; solar forcing; climate forcings (e.g., aerosols, methane, CO2, Ozone, etc.). Specific teleconnections and other key components modeled include: ESNO (El Nino Southern Oscillation) MJO (Madden-Julian Oscillation) QBO (Quasi-Biennial Oscillation) NAO (North Atlantic Oscillation) AO (Arctic Oscillation) WNPSH (Western North Pacific Subtropical High) Tropical Storms (tropical storm number, spatial distribution, accumulated cyclone energy index, and landfall frequency) Global 1.5m Temps Global Precipitation Global SSTs (sea surface temps) Total cloud amount Pressure at mean sea level Insolation (solar radiation) Outgoing longwave and shortwave radiation Clear-sky outgoing shortwave and longwave radiation Shortwave and longwave cloud forcing Geopotential height at 200, 500, 850 hPa Temperature at 200, 500, 850 hPa Zonal wind at 200, 500, 850 hPa Meridional wind at 200, 500, 850 hPa Relative humidity at 200, 500, 850 hPa Specific humidity at 200, 500, 850 hPa The latest forecast accuracy of GloSea5 forecasts versus actual observations (measured as the correlation coefficient) for key teleconnections are: ESNO correlation of 0.80 MJO correlation of approx. 0.78 for a 5-day forecast and 0.70 for 10-day. NAO correlation of 0.62 AO correlation of 0.63 WNPSH correlation of 0.80 Below are GloSea5 overall skill maps for Precipitation, SSTs and 1.5m Temps. Values above 0.5 denote useful skill compared to climatology. Whilst forecast accuracy continues to improve, seasonal forecasting still presents many challenges, particularly: the very complex interaction of teleconnections, the unfolding impact of rapid Arctic Amplification (warming) on previous understanding and teleconnections impact; the challenge of getting initialisation data for the entire globe absolutely correct so that the “butterfly effect” of a small error in starting data doesn’t rapidly escalate to forecast errors. Further reading on the challenges facing seasonal forecasting can be found in the following short paper from the Imperial College London titled: The challenge of seasonal weather prediction. https://wwwf.imperial.ac.uk/blog/climate-at-imperial/2014/04/14/the-challenge-of-seasonal-weather-prediction/ Despite these challenges, good progress is being made, with the performance of GloSea5 notably improved from its predecessor GloSea4. Sources of information and further reading: GloSea4 https://journals.ametsoc.org/doi/10.1175/2010MWR3615.1 GloSea5 https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.2396 Impact of Atmosphere and Land Surface Initial Conditions on Seasonal Forecasts of Global Surface Temperature https://journals.ametsoc.org/doi/10.1175/JCLI-D-14-00163.1 Statement of Guidance for Global Numerical Weather Prediction (NWP) https://www.wmo.int/pages/prog/www/OSY/SOG/SoG-Global-NWP.pdf Met Office Links: Unified Model: https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/index Seasonal and Climate Models: https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/climate-models GloSea5: Met Office seasonal prediction system: https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/climate-models/glosea5 Coupled forecasting development: https://www.metoffice.gov.uk/research/weather/ocean-forecasting/coupled-development Numerical weather prediction models: https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/weather-forecasting
  2. Hi could someone help me understand how a high pressure in eastern Russia can bring cold air all the way to the UK? Thanks, Ollie.
  3. Are there any "Air Density" forecasts available for the UK? I am extremely interested in finding any such. 3 months ago I was diagnosed with severe COPD, a respiratory disease that leaves you with shortness of breath (SOB). I read on the British Lung Foundation site that a change in the weather can trigger flare-ups which piqued my interest somewhat. Over that time I noticed my SOB was better and other days worse, my first instinct was to make observations between my WX readings and pollution readings with my SOB symptoms to see if there was any sort of pattern showing. Although I need to run the comparisons for a lot longer yet, I have a result that is worth investigating , it is "Air Density" that stands out as the major player. A (specific gravity) reading higher than 0.0745 makes a good day, a reading of less than 0.0740 makes for a bad day, in my personal experience. Knowing in advance of good days would be brill, I have things left to do in life yet.
  4. I'm currently analysing weather records at a location in Yorkshire dating back to the the early 1970's. My query is regarding rainfall, should a day that only records 'trace' as rainfall be included in the 'number.of raindays' in a monthly total ? Thanks in anticipation.
  5. Hi in an SSW the usual west-east winds are reversed in the polar vortex to east-west, can I know why, please? Thank you.
  6. Hi there! My name is Alejandro (or Alex if you prefer) and, although this is my first message on this forum, I've been visiting it with enthusiasm for several years. So, I've seen there are lots of clever people around here and I would like to ask you a question. I'm studying Physics at "Universidad Autónoma de Madrid" and I'm looking for a good master in Meteorology, both in and outside Spain. So, has anyone study a Master in Meteorology, or have you heard about one? I will appreciate all of your answers.
  7. For those wishing to learn the basics about weather, climate and meteorology, this page provides links to the wealth of impartial information and learning material available from a number of national meteorological organisations. Learning about Weather (UK Met Office) https://www.metoffice.gov.uk/weather/learn-about/weather NOAA National Weather Service (USA) A huge source of material: https://www.weather.gov/jetstream/matrix Bureau of Meteorology (Australia) A comprehensive A-Z of learning material: http://www.bom.gov.au/lam/
  8. Hi, I've just read on BBC that snow falls when it's between 0 - 2 degrees. Why does rain fall between those temperatures then? I live on the coast, so that is probably something to do with it, but it rained yesterday and Tuesday and the temperature hovered between one and three degrees. Thanks.
  9. The term "amplification" is used regularly in the hunt for cold thread. Could someone please explain what it means..? What is being amplified and how? Here's an example: "The 6z gfs starts less amplified than the 0z but somehow manages to amplify more than the earlier run by 120 hours."
  10. Newbie to weather observing here! I observed these amazing clouds which I believe to be altocumulus (May be wrong!), however a section appears to have a hole burnt into it with a different type of cloud inside it (second pic). Does anyone know why this and what causes it? Thanks in advance!
  11. Hi, As a part of my Ph.D. (Aircraft Performance), I want to calculate the height of the tropopause in any temperature deviations from ISA! How this can be calculated? any formula used for this? Thank you very much
  12. A look at the official recording of air temperature and surrounding conditions. Hourly official weather observations and the daily NCM National Climatological Message which records max and min temp, sunshine hours, rainfall and visibility https://www.netweather.tv/weather-forecasts/news/9018-uk-temperatures-who-takes-the-official-weather-observations-and-how Thanks to the Observers at Winterfield Weather enclosure Dunbar
  13. Hi all... I am Greek man 30 years old living in Germany... While during the nights and especially during 5-7 am i feel the cold, during the days the situation is different. I need 12 degrees C, to feel cold with short sleeve shirt and there will be the need to wear long sleeve shirt and then i need 7-8 degrees C to wear a jacket, while Germans wear long sleeve shirt with jacket from 17-18 degrees. So everything is ok with me, i am just different or i have a health problem? Soon, I am gonna have health exams, so what exactly i have to focus on? Thanks in advance.
  14. Hi All, I'm struggling a bit getting my head around the AM side of things, before I move on to the GWO orbits etc .. to be honest I have for a long time!, so I'm hoping I can tap in to the hive mind and get a better understanding .. My understanding is:
  15. Can I ask someone... anyone... a favour? I should start my saying I have autism spectrum disorder and, while I am very high functioning and pretty intelligent, I often hit mental hurdles with some things which seem impossible to overcome. I’m trying to look at the options for distance learning in meteorology but I’m just getting so overwhelmed every time I try and look and I’m basically hitting a major hurdle which is preventing me from continuing to search and finding answers. Like the letters and descriptors are confusing me to buggery. I’ll love anyone forever if they can link me to some relevant courses to investigate. This is to further my learning and hopefully getting a meaningful qualification in forecasting for the U.K. I don’t know if I would do anything with it but my son (who also has autism) has additional needs which aren’t compatible with my working right now and I would love to put my natural passion here to good use and have more qualifications under my belt.
  16. I really need help with how fog is formed, all of the websites online are quite complex. Firstly, is fog white because light from the sun is trapped in its suspended water droplets? If the heat from sun melts these suspended water droplets, is the light released and thus...the fog burned off? This is my understanding of fog, is this correct? Please explain your answers very simply as I am struggling to piece it all together...
  17. i have just been thumbing through old met office reports from around the time of the first world war..and notice they did not use the Fahrenheit or Celsius scale for measure temperature but something with an acronym of A for example it states the temperature reached 273.2 A in Camden on such and such a date or the month was 4.5 A above normal. does anyone know what scale this is? i had a look at the various temperature scales on google but it doesn't seem to match any given on there https://en.wikipedia.org/wiki/Scale_of_temperature
  18. HI Can anyone tell me what sort of cloud this is please and how it is formed? Taken just a few mins ago over Milford Haven. It is still there though a it wider now. Many thanks
  19. Hi everyone. First of all, I am a bit of a newbie when it comes to meteorology, so please forgive me for sounding a little dumb. Please correct me if I'm wrong, but isn't high pressure meant to bring settled dry weather with few or no clouds? At the moment, despite having high pressure in charge, the weather is grey and damp over here. In fact, if it wasn't for my barometer, I would probably think that the pressure is a little on the low side right now. The only thing I can think of is that maybe the anticyclone brought along with it some moisture as it was travelling along the sea? Thanks in advance.
  20. I understand that a ridge is an upper high (occuring below the tropopause) that is associated with warm air advection. However I was trying to figure out the difference between a ridge and an inversion. I'm guessing a ridge is assiciated with the horizontal axis, and an inversion to do with warmer air rising vertically from the surface? Any help greatly appreciated. Thanks
  21. Hi there, I've always been curious, but does snow rate equal to 10 times the rain rate? e.g. 10 cm/hr equals 100 mm/hour or can the rate differ depending on atmospheric conditions? Thanks, William
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