El Nino forte está em desenvolvimento?

GabKoost

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Eu não disse que o " El Nino " influencia de forma decisiva o nosso clima , apenas referi isso como curiosidade .

Eu também não disse que tu disseste isso.

Apenas referi que o El Niño não tem a importância decisiva pelas nossas bandas do que se lhe tenta atribuir. Ou seja, os nevões que acontecem cá dificilmente são resultado de El Niños. Aliás, como disse, nem os especialistas são unânimes nas influências deste fenómeno na Europa pelo que, até existirem maior número de amostras estudadas, mais vale dizer que o El Niño não é determinante de nada no nosso continente.
 


MeteoAlgarve

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Segundo li um El Nino Modoki tem tendencia a causar um aumento da temperatura na Europa e tempo seco no Mediterraneo. Caso seja um El Nino somente nomeadamente moderado tem tendencia a nos favorecer mais como por exemplo em 2009/2010. Um El Nino forte tem tendencia a reforcar o Jet stream mais a norte e tempo mais seco a sul. Contudo e apenas mais um factor entre outros que tambem sao importantes. De uma forma ou de outra todos estes efeitos apenas se denotam no inverno, seja aqui ou nos EUA. Pra finais de Novembro.
 

Vince

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What impact does 'El Nino' have on the weather over Europe?
The 'El Nino' phenomenon, or more strictly the warm El Nino -Southern Oscillation (ENSO) event is coupled closely to remarkable shifts in weather patterns in the immediate Pacific basin, and adjacent areas: e.g. parts of North America. For example, it is clear that the altered distribution of warm/cold water across the equatorial Pacific is the primary reason why excessive rain can fall in places like Peru, and a general deficit of rainfall is experienced in Indonesia, parts of Australia and the Philippines. There is also a generally accepted link between a less-than-'normally' active Atlantic hurricane season and the notably warm event that characterises what has come to be called, THE El Nino.

It is becoming clear from recent studies that we can now rule out the 'No Effect' case: this leaves us with two options -

(a) There IS an effect, but it is on a scale that is dwarfed by regional variations closer to home, e.g. long-term thermal inertia in SST distribution in the N. Atlantic, or continental/oceanic temperature differences across the North America - North Atlantic - Eurasian 'super-region'.
(b) There is a direct, and marked effect that leads to verifiable modification of the weather types across the NE Atlantic/European - Mediterranean region.

(a) appears to be the most likely if we take the year overall; indeed, even in studies published which set out to prove the link between warm/cold ENSO regimes, and impacts over Europe, caution is always advised relating to local/regional scale modification.

(b) is climbing higher in the 'probability' stakes, at least if the 'winter' season only is considered. There are an increasing number of studies published that show a direct link between a warm ENSO season, and, for example, altered rainfall/temperature anomalies across west/central Europe. No lesser person than J.Bjerknes postulated in 1966 that altered activity in the equatorial Pacific appeared to significantly alter the strength/orientation of the PFJ over and downwind of the NE Pacific, which in turn must have at least some effect on the long-wave structure downstream. This appears to have been accepted in later studies & developed further using datasets going back over two centuries or more.

http://weatherfaqs.org.uk/book/export/html/88




Boa sorte nisso de relacionar coisas localmente.
O forte Nino de 1997/98 trazem à memória episódios extremos de chuva no sul do país e Açores, no Outono.O de 1983 o famoso nevão em Fevereiro. Mas já o Inverno chuvoso de 2001 foi Nina. E já houve secas com Nino. Etc.

Mas deixo a tabela para se entreterem, a vermelha Nino, a azul Nina

Nym5CVB.png

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml


dNhOOou.png





September 2015 El Niño Update and Q&A
Author:
Emily Becker
Thursday, September 10, 2015


The CPC/IRI ENSO forecast says there’s an approximately 95% chance that El Niño will continue through Northern Hemisphere winter 2015-16, gradually weakening through spring 2016. It’s question & answer time!

How strong is this El Nino now?

The only real way to answer this is to throw a bunch of numbers at you. Essentially, it’s “pretty strong.” The three-month, June-August average of sea surface temperatures in the Niño3.4 region (the Oceanic Niño Index) is 1.22°C above normal, via the ERSSTv4 data set. This is the third-highest June-August value since records start in 1950, behind 1987 (1.36°C) and 1997 (1.42°C).

The August average is 1.49°C, second behind August 1997 (1.74°C). The August Equatorial Southern Oscillation Index (which measures the strength of the atmospheric part of ENSO) was -2.2, second to 1997’s -2.3. There are many ways of measuring El Niño, so the ranking of El Niño will change depending on which variable (winds, pressure, etc.) or time period (monthly, seasonal) you want to examine.

When is El Niño going to hit?

El Niño isn’t a storm that will hit a specific area at a specific time. Instead, the warmer tropical Pacific waters cause changes to the global atmospheric circulation, resulting in a wide range of changes to global weather. Think of how a big construction project across town can change the flow of traffic near your house, with people being re-routed, side roads taking more traffic, and normal exits and on-ramps closed. Different neighborhoods will be affected most at different times of the day. You would feel the effects of the construction project through its changes to normal patterns, but you wouldn’t expect the construction project to hit your house.

Okay, then… but what’s going to happen in my home town?

The expected changes in regional weather patterns due to El Niño are a big part of the NOAA Climate Prediction Center’s seasonal forecasts. Over North America, the Pacific jet stream (a river of air that flows from west-to-east) often expands eastward and shifts southward during El Niño, which makes precipitation more likely to occur across the southern tier of the United States. Check out the winter (December-February) forecasts here.






Chances of possible temperature (upper map) and precipitation (lower) outcomes for December 2015-February 2016: above normal, below normal, or near normal. Above or below normal means temperatures in the upper or lower third of the range of historical temperatures. White does not mean "near normal;" it show places where the chances for above-, below-, and near-normal temperatures are equal. Maps by NOAA Climate.gov, based on data from the Climate Prediction Center.





Why winter?

The weather in the winter is controlled more by global atmospheric flow than summer weather is, when small-scale events like thunderstorms tend to be more important. Since El Niño’s remote effects are felt though its modulation of global flow, winter is when the most noticeable impacts occur.

Winter in the Southern Hemisphere is just winding down. Did El Niño have an impact on their winter?

A few months ago, Tony wrote about expected effects of El Niño during June-August. Most of the El Niño-related changes that have been identified during past events are in the Southern Hemisphere during their winter; there are also significant effects in the tropics. These include warmer weather in some areas of South America, dry conditions in India, Indonesia, and Australia, and warm and dry conditions in Central America and the Caribbean. Also, more rain than average in part of Chile, and some cooler temperatures in part of Australia.






Observed temperature (upper map) and precipitation (lower) from June-August 2015. Observations are shown as their ranking in the period 1948-present: for example, a 90th percentile temperature means this June-August was warmer than 90% of the past June-August averages. Climate.gov figure from CPC data.



Much of South America did experience a very warm winter; in some areas, it was the warmest winter since these records began in 1948. Parts of Argentina, Uruguay, and Chile received a lot of rain during July-August. Central America and the Caribbean are very dry right now, with the June-August rainfall deficit just adding to a severe drought throughout the region. Also in line with expected conditions during El Niño, rainfall in some portions of India and Indonesia were well below average, and very few areas in this region saw more rain than average.

However, as we’ve said before (here and here, for example), El Niño impacts are not guaranteed, and an example of this is Australia’s recent winter, which was not nearly as dry as it has been during past El Niños.

What about the places that are directly affected by all that warm water? I heard the surface temperatures were more than 90°F in some places!

The warmer-than-average tropical Pacific waters can have a big impact on marine life. For example, there were large coral bleaching episodes (coral die-offs) during past El Niños, and it’slikely we’ll see a lot of coral bleaching this year. The warmer water can also affect fisheries, seaweed farms, ocean mammals, and birds.

What about the hurricane season? That’s supposed to be affected by El Niño, right?

El Niño can amp up the hurricane season in the Pacific, by providing lots of warm water to power the storms, and reducing the vertical shear (the change in wind speed/direction as you go up in the atmosphere). On the other hand, the shear is increased over the Atlantic, which makes it difficult for storms to form and strengthen. So far this year, the Pacific has been very active, and the Atlantic has been pretty quiet. There have been some unusual events in both basins recently – Tom wrote about them here and here.

Could El Niño die before this winter?

It’s unlikely. There is a large reservoir of warm water just below the surface of the tropical Pacific that will help to keep surface temperatures relatively high for at least a few more months, and the atmosphere is in sync with the ocean. However, the strength of the atmospheric response over the next few months is still to be determined. In 1997, the near-surface winds along the equatorial Pacific weakened so much that they reversed from normal, and blew from the west to the east, helping to reinforce the warm sea surface temperatures. We haven’t seen behavior like that yet, and it’s hard to predict right now if we will.

I keep hearing how the “Blob” (a large area of warm ocean temperatures off the West Coast of the U.S.) is going to be in a battle with this strong El Nino this winter. Which one will win?

El Nino and “the Blob” are not on an equal playing field, so the short answer is we expect El Niño to dominate the large-scale atmospheric pattern over the Pacific-North America this coming winter.




Sea surface temperatures during August compared to the 1981-2010 average. Climate.gov figure, based on data from NOAA View.



The Blob is not capable of changing the overlying atmospheric pattern in a significant way. In the Tropics, changes in ocean temperatures can easily lead to changes in the atmosphere above it. But outside of the Tropics, such as over the North Pacific Ocean, the physics are different, so ocean temperatures can’t effectively change the large-scale atmospheric flow or circulation pattern. The amount of heat in the Tropics is an enormous engine that drives rising motion and affects the whole globe’s circulation; the Blob is like a Fisher Price Power Wheel in comparison.

That said, the way that El Niño might affect water temperatures off the West Coast, or how those water temperatures might affect storms that are steered into the area by El Niño, is really hard to tell. As with any forecast, there are a lot of elements at play. However, El Niño is the dominant factor shaping the overall global picture for this winter.

Are you really naming El Niño?

No. That was a joke!

https://www.climate.gov/news-features/blogs/enso/september-2015-el-niño-update-and-qa
 

Chingula

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Apesar de se saber que o El Niño influencia o clima de maneira global, em Portugal não há uma correlação significativa. Apenas nas regiões mais perto do fenómeno (América e Oceania) há uma ligação directa e evidente.

PS: Mas sempre seria um exercício interessante ir ver como foi o ano 1997 em Portugal e, caso se confirme o forte El Niño este ano, verificar se houve ou não semelhanças!
No ano de 1997 ocorreram temporais nos Açores e em Portugal Continental, de 17 a 27 de Outubro e de 1 a 7 de Novembro...situações referenciadas em local próprio do Meteo.pt a precipitação em Monchique foi excepcional de 25 para 26 de Outubro.
Fenómenos da escala global (em meteorologia) afectam os fenómenos das outras escalas - sinóptica, mesoscala e escala local

Apesar de se saber que o El Niño influencia o clima de maneira global, em Portugal não há uma correlação significativa. Apenas nas regiões mais perto do fenómeno (América e Oceania) há uma ligação directa e evidente.

PS: Mas sempre seria um exercício interessante ir ver como foi o ano 1997 em Portugal e, caso se confirme o forte El Niño este ano, verificar se houve ou não semelhanças!
 

Chingula

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Não tenho duvidas que o fenómeno da escala global aqui referenciado, embora o nome se refira à época do Natal (historicamente assim referenciado) é um processo dinâmico devendo ser acompanhado durante todo o ano. O facto de cientificamente ainda não estar directamente relacionado com o nosso tempo (condições meteorológicas em Portugal), nem com o que se passa na Europa é interessante o relacionamento já comprovado com a actividade dos ciclones tropicais no Atlântico (em numero, intensidade e duração). ...antes dos temporais de 1997, recordo que se falava de intensa seca no país...
 
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