Ontwikkeling van de QBO, zonneactiviteit, ENSO, MJO en de winter 2020/2021

[Sebastiaan]

Abstract
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In recent years, many components of the connection between Eurasian autumn snow cover and wintertime North Atlantic Oscillation (NAO) have been investigated, suggesting that November snow cover distribution has strong prediction power for the upcoming Northern Hemisphere winter climate. However, the non-stationarity of this relationship could impact its use for prediction routines. Here we use snow products from long-term reanalyses to investigate interannual and interdecadal links between autumnal snow cover and atmospheric conditions in winter. We find evidence for a negative NAO-like signal after November with a strong west-to-east snow cover gradient, which is valid throughout the last 150 years. This correlation is consistently linked to a weak stratospheric polar vortex state. Nevertheless, decadal evolution of this link shows episodes of decreased correlation strength, which co-occur with episodes of low variability in the November snow index. By contrast, periods with high prediction skill for winter NAO are found in periods of high November snow variability, which co-occur with the Arctic warming periods of the 20th century, namely the early 20th-century Arctic warming between 1920 and 1940 and the ongoing anthropogenic global warming at the end of the 20th century. A strong snow dipole itself is consistently associated with reduced Barents–Kara sea ice concentration, increased Ural blocking frequency and negative temperature anomalies in eastern Eurasia. https://esd.copernicus.org/articles/11/509/2020/

[Karel]

Abstract
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In recent years, many components of the connection between Eurasian autumn snow cover and wintertime North Atlantic Oscillation (NAO) have been investigated, suggesting that November snow cover distribution has strong prediction power for the upcoming Northern Hemisphere winter climate. However, the non-stationarity of this relationship could impact its use for prediction routines. Here we use snow products from long-term reanalyses to investigate interannual and interdecadal links between autumnal snow cover and atmospheric conditions in winter. We find evidence for a negative NAO-like signal after November with a strong west-to-east snow cover gradient, which is valid throughout the last 150 years. This correlation is consistently linked to a weak stratospheric polar vortex state. Nevertheless, decadal evolution of this link shows episodes of decreased correlation strength, which co-occur with episodes of low variability in the November snow index. By contrast, periods with high prediction skill for winter NAO are found in periods of high November snow variability, which co-occur with the Arctic warming periods of the 20th century, namely the early 20th-century Arctic warming between 1920 and 1940 and the ongoing anthropogenic global warming at the end of the 20th century. A strong snow dipole itself is consistently associated with reduced Barents–Kara sea ice concentration, increased Ural blocking frequency and negative temperature anomalies in eastern Eurasia. https://esd.copernicus.org/articles/11/509/2020/

Dank Sebastiaan voor deze informatie. Even hardop denken levert het volgende op.

De sterke west-oost gradient in het sneeuwdek is nu duidelijk aanwezig. Wat het effect daarvan is (NAO-) moet op termijn blijken. De warmte ten westen van de Oeral houdt nog een ongeveer 5 dagen aan volgens het ECMWF ensemble van vanmorgen. Daarna moet blijken of hogedruk boven Scandinavië in voldoende leden van het ensemble gaan verschijnen. Zo ja dan werkt de MJO ontwikkeling fase 6,7,8,1 blijkbaar door na 5 dagen. Afwachten maar.

[Sebastiaan]

Game over.

[Paul]

https://www.essoar.org/doi/10.1002/esso ... 8M.twitter

Over de sprong in de QBO, 2016 en dit jaar. Met dank aan weerwoord (Stan).

[Sebastiaan]

Central Pacific (CP) La Nina (Modoki)
"By contrast, the SST anomaly center associated with the CP La Niña is shifted westward into the CP west of 150°W and small cooling SST anomaly is found over the EP". In contrast to the canonical EP event, which advances somewhat westward to as much as 150* longitude and decays faster, the CP event decays more slowly and remains in place, while propagating only a small amount in either direction". These differences in zonal location of SST anomaly and their evolutions suggest the possibility of different underlying dynamics, which is indeed the case. Modoki la nina are largely the product of a local air-sea interaction that develops and decays in place over the central Pacific. The reduced cooling over the east may also be further attenuated by a modified Walker cycle, according to Zhang, which features a displacement to the west of the easterly trades responsible for upwelling. In the modoki la nina, the EP trades are replaced with an anticyclone, as a direct result of the cool SST anomalies being shifted west to the CP.

[Sebastiaan]

The EP and WP forcing associated with the "modoki" la nina generally features an inverse pattern from that of a modoki el nino across North America. This resultant N. American pattern is more akin to an east-based, canonical el nino. however, we obviously have the prominent Aleutian high as opposed to the Aleutian low during el nino due to opposite anomalies over the tropical Pacific. The Aleutian high is in this composite is appreciably flatter and displaced to the southeast in relation to its canonical counterpart, as alluded to.

[Sebastiaan]

Zoals jullie kunnen zien in de compositie, pakt UKMO erg goed het patroon op van een CB la Nina.

[Karel]

Zoals jullie kunnen zien in de compositie, pakt UKMO erg goed het patroon op van een CB la Nina.

Het wordt dus geen winter van afwachten op wat er misschien komen gaat, maar veel dagelijkse activiteit in het weerpatroon in onze omgeving. Interessante depressiewinter voor mij.

[Karel]

De koude pool in de stratosfeer komt boven Midden Siberië te liggen de komende week. Meer kans op Noord-West circulatie in onze omgeving.
Boven de Evenaar zijn de oostenwinden tot op 20 hPa afgezakt. Afwachten wanneer de 30 hPa wordt bereikt in de december.

[Sebastiaan]

https://twitter.com/BenNollWeather/stat ... 6853102594
The ECMWF indicates the potential for a sudden stratospheric warming event in January 2021
These events can disrupt the polar vortex, with Arctic air masses becoming dislodged and affecting parts of the Northern Hemisphere.