ENSO

Alles wat betrekking heeft op het buitenlands weer. Tropische stormen, orkanen, etc.
Sebastiaan
Berichten: 12243
Lid geworden op: 31-12-1977

ENSO

Bericht door Sebastiaan » 14-04-2022 20:42

La Niña continues in the tropical Pacific, with both the ocean and atmosphere clearly reflecting La Niña conditions. The current forecast favors the continuation of La Niña through the summer (59% chance), with a slightly lower chance into the fall (50-55% chance). A third-year La Niña would be pretty unusual—we’ve only seen two others since 1950. I’ll run the numbers to see how current conditions add up and what’s factoring into the odds for La Niña later this year.

Paint by numbers
Let’s take stock of current ENSO conditions (ENSO=El Niño/Southern Oscillation, the whole ocean-atmosphere El Niño/La Niña system) in the tropical Pacific. In March, the sea surface temperature in the key ENSO monitoring region (Niño-3.4) was still well within the La Niña range, about 1.0 °C cooler than the long-term (1991-2020) average, based our most reliable historical record, ERSSTv5. Remember: the La Niña threshold is a temperature anomaly—a difference from the long-term average—in the Niño-3.4 region of -0.5 °C or lower. March 2022 was the 6th most negative March sea surface temperature anomaly in Niño-3.4 since 1950.

Line graph of tropical Pacific temperature anomalies for current La Niña compared to all other multi-year La Niñas
Monthly sea surface temperature anomalies (difference from average) in the Niño 3.4 region of the tropical Pacific for 2020–22 (purple line) and all other multi-year La Niñas (gray lines) starting since 1950. Climate.gov graph based on ERSSTv5 temperature data.

As you can see from the graph, March 2022 was also tied for the coldest of the nine second-year La Niña events on record, for this time of year.

One plus one
While the ocean surface temperature confidently indicates that La Niña is still going strong, it’s not unusual for this time of year, and wouldn’t necessarily tell us much about how long this La Niña might last. Things start to get interesting when we look at the atmosphere, though, providing a bit more insight into why forecasters are favoring La Niña to continue through the summer.

ENSO Blog frequent flyers will know that ENSO is a coupled ocean-atmosphere system. Changes in the tropical Pacific Ocean temperature influence the circulation of the atmosphere (the Walker circulation); those atmospheric changes in turn affect the ocean temperature, and so on. For example, La Niña features cooler-than-average surface water in the central and eastern equatorial Pacific and warmer-than-average surface water in the far western Pacific. This cool-versus-warm pattern leads to less rising air and storms over the central Pacific and more over Indonesia, amping up the normal Walker circulation and driving stronger near-surface winds along the equator—the trade winds. Stronger trade winds further cool the surface and keep even more warm water piled up in the far western Pacific, reinforcing La Niña… you see where I’m going! For more details, visit Michelle’s post on the mechanics of ENSO.

Baby, don’t lose my number
Enough preamble—what’s the Walker circulation doing right now? I thought you’d never ask. It’s really feeling its oats these days, as several different atmospheric measurements tell us.

First, let’s talk Equatorial Southern Oscillation, an index that measures the relative sea level pressure in the far western Pacific vs. that in the eastern Pacific. When the EQSOI is positive, it indicates lower-than-average pressure over the west (more rain and clouds) and higher-than-average pressure over the east (less rain and clouds), i.e., evidence of a stronger Walker circulation. In March, the EQSOI measured 1.4, the 6th strongest since 1950.

As I mentioned above, stronger trade winds are key to the La Niña feedback between the ocean and atmosphere. The trade winds were enhanced through March, and remain stronger than average into mid-April. You want a number, you say? Okay! There’s an index that measures the near-surface winds in the central Pacific region of 5°N–5°S, 175°W–140°W; it was 4.3 meters per second (9.6 miles per hour) faster than average in March. This is the strongest March value on record, but there’s a catch—this record only goes back to 1979.
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One last measurement today—let’s look under the surface of the tropical Pacific Ocean. The amount of cooler-than-average water under the surface increased in March. This cooler subsurface water provides a supply of cooler water to the surface, contributing to ENSO forecasters’ prediction that La Niña will remain into the summer. Index-wise, last month the water under the surface was the 9th coolest March since 1979.

Add it all up
There are two main information sources for ENSO forecasters: current atmosphere-ocean conditions and computer model predictions. Computer models have a harder time making successful long-range predictions in April, during the spring predictability barrier, although they remain a critical tool. Current model predictions are mostly split between staying in La Niña or transitioning to neutral in summer. Looking out to next fall, the North American Multi-Model Ensemble is leaning toward La Niña conditions.

There is a lot of uncertainty in the current forecast, which is reflected in the probabilities. The odds for La Niña to remain through the next few months are fairly confident, bolstered by the cooler subsurface water and the current strong Walker circulation. The chance of a third-year La Niña has a slight edge for the fall, over the chance of neutral conditions. El Niño is unlikely—less than 10% chance. None of the models are predicting El Niño for the fall, and none of those March atmospheric conditions I described earlier have been followed by El Niño later in the year. It’s not impossible—nature is full of surprises—but very unlikely.

The official CPC/IRI ENSO probability forecast. The bars show the seasonal chances for each possible ENSO state—El Niño (red), La Niña (blue), and neutral (gray)—from spring 2022 through winter 2022–23. The forecast is based on a consensus of CPC and IRI forecasters, and it is updated during the first half of the month, in association with the official CPC/IRI ENSO Diagnostic Discussion. It is based on observational and predictive information from early in the month and from the previous month. Image from IRI.

La Niña influences the hurricane season (more storms in the Atlantic, fewer in the eastern Pacific), has links to springtime tornado activity (complicated links!), and can increase the chance of drought in some regions. Given all these important relationships, we will closely watch the forecast and look forward to starting to emerge from the spring predictability barrier in the months ahead. https://www.climate.gov/news-features/b ... -measuring

Daniël
Berichten: 1480
Lid geworden op: 31-12-1999

Re: ENSO

Bericht door Daniël » 29-05-2022 20:14


Karel
Berichten: 3189
Lid geworden op: 31-07-1978

Re: ENSO

Bericht door Karel » 30-05-2022 12:14

Al eerder (april 1954-oktober1956) was er een zeer lange La Niña met opvallend weer in onze omgeving. Wat een verschil met de huidige periode vanaf juli 2020. Afwachten of de huidige periode langer (ook na dec 2022) gaat aanhouden.

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Sebastiaan
Berichten: 12243
Lid geworden op: 31-12-1977

Re: ENSO

Bericht door Sebastiaan » 07-06-2022 21:15

Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.

Karel
Berichten: 3189
Lid geworden op: 31-07-1978

Re: ENSO

Bericht door Karel » 02-07-2022 11:41

ENSO is nu in de neutrale fase beland aan de oppervlakte, Op enige diepte is behoudens direct voor de kust van Zuid-Amerika een warme periode aangebroken. Is dit het beeld voor de komende herfst en winter. Afwachten maar of de modellen te veel oostenwinden berekenen.

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Karel
Berichten: 3189
Lid geworden op: 31-07-1978

Re: ENSO

Bericht door Karel » 02-08-2022 19:42

Het is nu begin augustus en het beeld in de Central Pacific geeft duidelijk de ontwikkeling van een CP La Niña aan. Met de sterk negatieve PDO (een zeer warme Central Pacific) is het beeld voor de komende winter een sterk positieve NAO. Dit beeld is ook in de computermodellen te zien. De kans op een te warme winter is dan sterk vergroot. Gunstig voor de energievoorziening. Afwachten maar. De ontwikkeling in deze herfst geeft een belangrijke definitieve aanwijzing.

Bronnen: https://journals.ametsoc.org/view/journ ... xt-display
[urlhttps://www.google.com/url?sa=t&rct=j&q=&esrc=s ... 2KxcqE1url]

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Daniël
Berichten: 1480
Lid geworden op: 31-12-1999

Re: ENSO

Bericht door Daniël » 02-08-2022 21:43

Karel schreef:
02-08-2022 19:42
Het is nu begin augustus en het beeld in de Central Pacific geeft duidelijk de ontwikkeling van een CP La Niña aan. Met de sterk negatieve PDO (een zeer warme Central Pacific) is het beeld voor de komende winter een sterk positieve NAO. Dit beeld is ook in de computermodellen te zien. De kans op een te warme winter is dan sterk vergroot. Gunstig voor de energievoorziening. Afwachten maar. De ontwikkeling in deze herfst geeft een belangrijke definitieve aanwijzing.
Betekent dit dan ook een natte winter in onze omgeving, of zal het sterke Azorenhoog ook in de komende winter alsmaar sterke uitlopers onze kant opsturen die zich vervolgens tot krachtige Eurohogen zullen ontwikkelen? Vanwege de huidige extreme droogte hebben wij juist een natte winter nodig.

Karel
Berichten: 3189
Lid geworden op: 31-07-1978

Re: ENSO

Bericht door Karel » 17-08-2022 08:56

Daniël schreef:
02-08-2022 21:43
Karel schreef:
02-08-2022 19:42
Het is nu begin augustus en het beeld in de Central Pacific geeft duidelijk de ontwikkeling van een CP La Niña aan. Met de sterk negatieve PDO (een zeer warme Central Pacific) is het beeld voor de komende winter een sterk positieve NAO. Dit beeld is ook in de computermodellen te zien. De kans op een te warme winter is dan sterk vergroot. Gunstig voor de energievoorziening. Afwachten maar. De ontwikkeling in deze herfst geeft een belangrijke definitieve aanwijzing.
Betekent dit dan ook een natte winter in onze omgeving, of zal het sterke Azorenhoog ook in de komende winter alsmaar sterke uitlopers onze kant opsturen die zich vervolgens tot krachtige Eurohogen zullen ontwikkelen? Vanwege de huidige extreme droogte hebben wij juist een natte winter nodig.
Een CP La Niña met hoge luchtdruk en te droog in onze omdeving volgens het laatste plaatje.

Sebastiaan
Berichten: 12243
Lid geworden op: 31-12-1977

Re: ENSO

Bericht door Sebastiaan » 28-08-2022 22:17

Abstract
The El Niño-Southern Oscillation (ENSO) events of recent decades have been divided into the two different types based on their spatial patterns, the Eastern Pacific (EP) type and Central Pacific (CP) type. Their most significant difference is the distinguished zonal center locations of sea surface temperature (SST) anomalies in the equatorial Pacific. In this study, based on six operational climate models, we evaluate predictability of the two types of ENSO events in winter to examine whether dynamical predictions can distinguish between the two spatial patterns at lead time of 1 month and tell us more than simply whether an event is on the way. We show that winter EP and CP El Niño and La Niña events can only be distinguished in a minority of these models at 1-month lead, and the EP type tends to has a more realistic zonal positions of SST pattern centers than the CP type. Compared to the SST patterns, the differences between the two types are less apparent in precipitation especially for the two La Niña types in the models. Examinations of the extratropical teleconnections to the two ENSO types show that some of the models can reproduce the differences between EP and CP teleconnections. Evaluations of model predictions show that the EP El Niño event has the same level hit rate with the CP El Niño and the CP La Niña event has much higher hit rate than the EP La Niña. While the multi-model ensemble increases Niño index prediction skill, it does not help to improve forecast skill of center longitude index of the SST patterns and distinguish the two types of ENSO events. Although ENSO skill is very high at this lead time, the rapid loss of the initialized information on the different ENSO types in most of the models severely limits the predictability of the two types of winter ENSO events and more research is needed to improve the performance of climate models in forecasting the two ENSO types.

https://link.springer.com/article/10.10 ... 366-1#Abs1

Sebastiaan
Berichten: 12243
Lid geworden op: 31-12-1977

Re: ENSO

Bericht door Sebastiaan » 03-09-2022 19:55

Zeer warm SST Atl. Oceaan bij Newfoundland en Pacific noordelijk deel.
Je hebt niet voldoende permissies om de bijlagen van dit bericht te bekijken.

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