Previsões longo prazo (Outono/Inverno 2019/2020)

Tópico em 'Seguimento Meteorológico' iniciado por algarvio1980 30 Ago 2019 às 20:25.

  1. luismeteo3

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  2. Tonton

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    Previsão Sazonal do S5.

    Se não fosse tão falível, seria assustadora em relação às anomalias da precipitação para o Centro e o Sul do Continente... :shocking:

    Edit: Ainda por cima, excepto este mês, reparem nas tendências da temperatura estar acima do normal...
    [​IMG]
     
    #32 Tonton, 7 Nov 2019 às 18:33
    Última edição: 7 Nov 2019 às 18:39
  3. luismeteo3

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  4. luismeteo3

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  5. Ricardo Carvalho

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    Para um mês que praticamente já era dado como perdido por muita gente, as previsões até não estão nada más

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    Enviado do meu SM-A510F através do Tapatalk
     
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  6. Orion

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    CPC (Washington) vs ECMWF vs MetOffice (Exeter)

    [​IMG]

    Claro que para o sul basta uma outra região depressionária para invalidar as previsões relativamente à precipitação.

    Anomalia K=ºC
     
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    N_Fig, joselamego, Aine e 2 outras pessoas gostaram disto.
  7. Ricardo Carvalho

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    Tudo muito democrático , assim está bem :D:rain::thumbsup:

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    #37 Ricardo Carvalho, 14 Nov 2019 às 18:12
    Última edição: 14 Nov 2019 às 18:25
    N_Fig, frederico, MSantos e 8 outras pessoas gostaram disto.
  8. luismeteo3

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  9. irpsit

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    As previsoes sazonais de um modelos e do outro nao podiam ser mais opostas.

    O S5 preve um inverno seco e com temperatura acima da media em Portugal e Mediterranico (excepto Novembro e Dezembro), e chuvoso e temperatura acima da media no UK e Europa central e do norte.
    O tweet preve um evento de quebra do vortex polar, que causaria NAO- e frio seco ou neve no UK e Europa do norte, e frio/chuvoso em Portugal e Europa do sul.

    Neste momento o padrao parece ter uma tendencia enorme ao segundo cenario, de NAO- em Dezembro e Janeiro, com um bloqueio a formar-se na Escandinavia e um comboio de depressoes a passar por Portugal, Espanha e Italia. Mas se calhar os meses que se seguem (Fev, Mar, Abr) vao ser secos e com tempetaturas acima da media, com um bloqueio grande na Europa.

    O S5 nao modela o comboio de depressoes e frio na Europa do Sul, que e tipico de situacoes NAO-.


     
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  10. Aurélio Carvalho

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    Todos os anos pr esta altura comecam estas teorias da treta sobre nao- quebra do vórtice e afins.. Daqui a 2 semanas, 4 se as 6 semanas e depois foi o que se viu... É provavelmente será tb o que se verá este ano..
    Quanto aos modelos sazonais 90% deles prevê temperatura acima da média e precipitação abaixo num padrão claro de nao+
     
    Aine, VILA REAL, joselamego e 1 outra pessoa gostaram disto.
  11. joralentejano

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    Afinal não são só outros membros que são pessimistas e dramáticos, como por vezes dizes. Não estou com qualquer esperança de que este ano possa ser diferente e o inverno seja chuvoso, mas essas situações vão-se vendo aos poucos.
    No ano passado, muitas previsões sazonais previam um janeiro chuvoso e depois foi o que foi. Atualmente, os modelos estão num constante tira e põe (como é habitual), ou seja, está tudo incerto e por isso mesmo não vale muito a pena estar a olhar para o longo prazo. Estar na sombra de um anticiclone com um comportamento cada vez mais incerto, dá nestas coisas e infelizmente sabemos o cenário que é sempre mais provável, mas por vezes podemos ter surpresas.
    Apenas vou dar mais razão às previsões sazonais caso o bloqueio do costume se estabeleça a partir de Dezembro, mas depois até pode mudar em janeiro quem sabe...É sempre uma incógnita.
     
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  12. Aurélio Carvalho

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    O meu comentário referia se a esse tweet concretamente, é fiz uma analogia com as previsões sazonais.
    Portanto, eu não faço ideia se os modelos sazonais acertam ou não, não tenho bola de cristal, mas na minha opinião eu acredito que este inverno tenhamos nao+ ou neutra!!
     
    Aine e joselamego gostaram disto.
  13. Ricardo Carvalho

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    Não façam futurologia em meteorologia pessoal, ainda não existe nenhuma garantia que o AA regresse no final do mês ;)

    [​IMG]

    :malandro:


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  14. Dias Miguel

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    Arctic Oscillation and Polar Vortex Analysis and Forecasts
    November 18, 2019

    Special blog on winter 2018/2019 retrospective can be found here - http://www.aer.com/winter2019

    Special blog on winter 2017/2018 retrospective can be found here - http://www.aer.com/winter2018

    Special blog on winter 2016/2017 retrospective can be found here - http://www.aer.com/winter2017

    Special blog on winter 2015/2016 retrospective can be found here - http://www.aer.com/winter2016

    Dr. Judah Cohen from Atmospheric and Environmental Research (AER) recently embarked on an experimental process of regular research, review, and analysis of the Arctic Oscillation (AO) and Polar Vortex (PV). This analysis is intended to provide researchers and practitioners real-time insights on one of North America’s and Europe’s leading drivers for extreme and persistent temperature patterns.

    During the winter schedule the blog is updated once every week. Snow accumulation forecasts replace precipitation forecasts. Also, there is renewed emphasis on ice and snow boundary conditions and their influence on hemispheric weather.

    Subscribe to our email list or follow me on Twitter (@judah47) for notification of updates.

    The AO/PV blog is partially supported by NSF grant AGS: 1657748.

    Summary

    • The Arctic Oscillation (AO) is currently negative and is predicted to remain neutral to negative for the next two weeks.
    • The current negative AO is reflective of mostly positive pressure/geopotential height anomalies across the Arctic and mixed pressure/geopotential height anomalies across the mid-latitudes. The North Atlantic Oscillation (NAO) is positive with mostly negative pressure/geopotential height anomalies spread across Greenland; and the NAO is predicted to remain near neutral to negative as geopotential height anomalies remain weakly positive across Greenland over the next two weeks.
    • This week, troughing/negative pressure/geopotential height anomalies over Western Europe are predicted to be sandwiched by ridging/positive geopotential height anomalies in the central North Atlantic and Western Asia. Normal to below normal temperatures are predicted for Western Europe including the United Kingdom (UK) under northerly flow while normal to above normal temperatures are predicted for Eastern Europe under southerly flow. However, over the next two weeks the troughing in Western Europe is predicted to push north into the Barents-Kara Seas setting up westerly flow across Europe with relatively mild temperatures.
    • Currently temperatures are mostly above normal across Western Asia and Southeastern Asia as ridging/positive geopotential height anomalies dominate Western and Southern Asia while temperatures are below normal in Siberia and Northeast Asia with troughing/negative pressure/geopotential height anomalies dominating the region. However, over the next two weeks, troughing to the north with ridging to the south will setup a westerly flow across Asia allowing milder temperatures to overspread much of the continent with below normal temperatures mostly confined to Northern Siberia under the troughing.
    • This week and into early next week ridging/positive geopotential height anomalies are predicted to dominate much of North America with normal to above normal temperatures for Alaska, much of Canada and the Western United States (US) with troughing/negative geopotential height anomalies and normal to below normal temperatures mostly confined to the Eastern US. However, starting next week increasing troughing will bring colder temperatures to Alaska and Western Canada and the Western US with ridging and milder temperatures in eastern North America. However, the ECMWF model is predicting more seasonable temperatures in the Eastern US.
    • In the Impacts section I discuss the implications of the predicted stratospheric polar vortex (PV) disruption on winter weather.
    Impacts

    In my opinion it is crunch time for the Northern Hemisphere (NH) winter. A minor sudden stratospheric warming (SSW where a warming of at least 25°C occurs in the polar stratosphere) is likely and a major mid-winter warming (MMW where the zonal mean zonal wind at 10hPa and 60N reverses from positive to negative) is possible in mid-December. I include in Figure i the temperature animation of the stratosphere and impressive warming is being predicted by the GFS, enough to at least qualify for a minor warming. Based on the GFS forecast, some regions of the polar stratosphere could see a 70°C (126°F) jump in temperature in a matter of days! I saw that some members of the GFS ensemble showed an MMW as early as early December, but I think this is likely too soon.

    [​IMG]

    Figure i. Forecasted average temperatures (°C/°K; countours) and anomalies (°C/°K; shading) across the Northern Hemisphere for 18 November – 4 December 2019. The forecasts are from the 18 November 2019 GFS.

    I believe regardless of the timing and magnitude of the event it will have impacts on the NH weather. I would argue that some of the predicted features in the tropospheric circulation are related to the anticipated PV disruption. The models are predicting a mid-troposphere low pressure over Northern Siberia starting next week. This is very close to the predicted location of the stratospheric PV starting this week. The other predicted main feature in the polar stratosphere is ridging/high pressure centered near Alaska. This will likely be associated with a tropospheric feature/reflection as well. Something similar occurred last December with ridging in the interior of North America and very mild temperatures across the continent. A repeat is possible but my sense of the trends this fall is that the ridge will likely setup further west, forcing a colder solution but admittedly it’s a tough call.

    In last week’s blog, I argued that the increase in the vertical energy transfer and the PV disruption is looking more like an “absorptive” event and less like a “reflective” event and that seems to be even more true this week. Leading up to an “absorptive” event while the stratospheric AO trends negative the tropospheric AO trends positive with milder temperatures across the mid-latitudes and colder temperatures in the Arctic. Though many of the trends are not particularly strong, based on today’s forecast plots included in today’s blog all those trends are apparent. The forecast for Europe is consistent with these expectations with an increasing westerly flow and milder temperatures. Milder trends are also predicted for eastern North but those trends might run into more resistance due to record low sea ice in the North Pacific sector of the Arctic and the well above normal sea surface temperatures (SSTs) in the eastern North Pacific especially in the Gulf of Alaska. Those features could help to promote ridging near Alaska/Gulf of Alaska with downstream troughing in North America with colder temperatures bucking the trends from the vertical energy transfer.

    Regardless of the amplitude, I expect some cold weather from the SSW most likely in eastern North America and Northern Asia. However, if the predicted SSW is relatively minor with a quick recovery in the stratospheric AO, even possibly becoming strongly positive, would favor a positive tropospheric AO. Then an extended mild to very mild period across the NH mid-latitudes could ensue from late December through much of January. I would expect at some point another PV disruption that would reverse the weather to colder but by then an overall mild winter would be almost a certainty.

    Para saber mais: https://www.aer.com/science-research/climate-weather/arctic-oscillation/ Caso o vosso inglês não seja grande coisa, clique do lado direito no rato e traduzir (no Chrome).
     
  15. luismeteo3

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