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About sebastiaan1973

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  1. The latest plot of the tropospheric polar cap geopotential heights (PCHs) shows well above normal PCHs in the troposphere (Figure 10) consistent with a persistent negative AO. The strongest positive anomalies are initially in the lowest troposphere but then move into the lower stratosphere with positive PCHs extending even into the mid-stratosphere next week. The reason for the warming PCHs in the stratosphere is strong upward pulse of Wave Activity Flux (WAFz) or poleward heat transport predicted by the GFS (Figure 11). It is unusual to observe such a strong pulse of WAFz so early in the season so some skepticism is warranted until it is predicted by all the weather models. The impact of the predicted near record WAFz pulse can be seen in the stratospheric AO forecast, which shows the stratospheric AO dropping into near record low territory in late October and early November (Figure 1). If the GFS forecast of a fully coupled weak stratospheric and tropospheric PV and a negative AO both in the stratosphere and the troposphere is correct, this would likely result in an early start to winter across widespread regions of the Northern Hemisphere mid-latitudes. The regions mostly likely to experience an early winter chill include Siberia and East Asia. However there has been a tendency for the blocking near the Urals to be further north relative to last winter and the tendency for the NAO to be negative, therefore I feel this increases the probability of the cold air in Siberia flowing west into Europe as well. The Eastern US is a tougher call and would also depend on the circulation in the eastern North Pacific where troughing/negative geopotential height anomalies would favor the Eastern US remaining warm while ridging/positive geopotential height anomalies would favor colder temperatures in the Eastern US.
  2. at the american forum they discuss the possibility of a Modoki La Nina, which correlates with a positive NAO
  3. The last three months 30mb zonal wind at the equator, zonal average : 6.25 10.07 10.48 (september). So it seems a wQBO for sure.
  4. According to some posters at american weather the lastest EC seasonal shows a negative AO and NAO (easterly variant) . Although not certain how reliable this source is. We have to wait for Fergie.
  5. So there will be no eQBO this winterseason but another wQBO? We are in a declining phase (positive NAO), next winter in a minimum , so perheps this development is better. 2017/8 with a an EQBO and low solar activity.
  6. An interesting update of GLOSEA5. With higher than normal pressure in the north and lower than normal pressure on the continent and sourthern Europe. Fingers crossed!
  7. Cohen's view on the winter of 2015/6 Summary Winter 2015/16 is probably best characterized by record warmth. Every month since May 2015 has been record warm and the streak of record warm months likely peaked in February 2016. Stratosphere-troposphere coupling was very active this winter and in my opinion dominated the dynamical story of winter 2016. I believe that the dynamical evolution of the winter cannot be understood without analyzing the polar vortex (PV). The stratospheric PV experienced extreme variability this winter, starting the winter record strong and ending the winter record weak. But typically it is the first half that is most influential on surface weather and the record strong early PV likely contributed strongly to the warm winter. Though the record weak PV in March is contributing to a cool spring in the North Atlantic sector. Poleward heat flux started slowly but was unusually active during the winter months. Spikes in winter surface temperatures coincided with peaks in poleward heat flux. Despite the record strong PV, the Arctic Oscillation (AO) was slightly negative for the winter. The AO bottomed out in mid-January, which coincided with a record snowstorm for the Mid-Atlantic and was the start of a troposphere-stratosphere-troposphere coupling event that resulted in record cold for the Northeastern US in mid-February. The Niño 3.4 index achieved record high values heading into the winter and the strong El Niño dominated the narrative of this winter. However the atmospheric response did not match the forecasts and in fact temperature and especially precipitation anomalies more closely resembled those associated with La Niña than El Niño. This winter should have showcased using ENSO for climate forecasts, instead in my opinion, it highlighted the vulnerability of relying solely on ENSO in producing seasonal forecasts.
  8. A predictable pattern of winds in the stratosphere recently changed in a way scientists had not seen in more than 60 years of record-keeping. Credit: NASA This disruption to the wind pattern -- called the "quasi-biennial oscillation" -- did not have any immediate impact on weather or climate as we experience it on Earth's surface. But it does raise interesting questions for the NASA scientists who observed it: If a pattern holds for six decades and then suddenly changes, what caused that to happen? Will it happen again? What effects might it have? "The quasi-biennial oscillation is the stratosphere's Old Faithful," said Paul Newman, Chief Scientist for Earth Sciences at NASA's Goddard Space Flight Center, Greenbelt, Maryland, and lead author on a new paper about the event published online in Geophysical Research Letters. "If Old Faithful stopped for a day, you'd begin to wonder about what was happening under the ground." Winds in the tropical stratosphere, an atmospheric layer that extends from about 10 to 30 miles above Earth's surface, circulate the planet in alternating easterly and westerly directions over roughly a two-year period. Westerly winds develop at the top of the stratosphere, and gradually descend to the bottom, about 10 miles above the surface while at the same time being replaced by a layer of easterly winds above them. In turn, the easterlies descend and are replaced by westerlies. This pattern repeats every 28 months. In the 1960s scientists coined it the "quasi-biennial oscillation." The record of these measurements, made by weather balloons released in the tropics at various points around the globe, dates to 1953. The pattern never changed -- until late 2015. As the year came to a close, winds from the west neared the end of their typical descent. The regular pattern held that weaker easterly winds would soon replace them. But then the westerlies appeared to move upwards and block the downward movement of the easterlies. This new pattern held for nearly half a year, and by July 2016 the old regime seemed to resume. "It's really interesting when nature throws us a curveball," Newman said. The quasi-biennial oscillation has a wide influence on stratospheric conditions. The amount of ozone at the equator changes by 10 percent between the peaks of the easterly and westerly phases, while the oscillation also has an impact on levels of polar ozone depletion. With this disruption now documented, Newman and colleagues are currently focused on studying both its causes and potential implications. They have two hypotheses for what could have triggered it -- the particularly strong El Niño in 2015-16 or the long-term trend of rising global temperatures. Newman said the scientists are conducting further research now to figure out if the event was a "black swan," a once-in-a-generation event, or a "canary in the coal mine," a shift with unforeseen circumstances, caused by climate change.
  9. SSTs seem to me a lot better than in previous years. Please notice the warm water in the norther part of the Atlantic.
  10. @Gael, seems to me as a delay. -> Weak La nina. GLOSEA5 shows a positive NAO-phase, similiar of the declining phase of solar activity. I need that hat!
  11. Winter 2017. LIkely a weak La Nina, Solar activity in the declining phase. Which resembles a positive NAO phase and QBO in it's easterly phase (right now it is still westerly ->
  12. In my opinion we are in the declining phase. Which resembles a positive NAO phase.
  13. Well we are still in the declining phase. -> temperatures. However, the clearest pattern of the temperature anomalies is not found during sunspot maximum or minimum, but during the declining phase, when the temperature pattern closely resembles the pattern found during positive NAO. Moreover, we find the same pattern during the low sunspot activity cycles of 100 years ago, suggesting that the pattern is largely independent of the overall level of solar activity. So i.m.o. nothing interesting in terms of solar activity coming winter.
  14. Hi Nouska, what's opinion. Is the winter of 2017 still in the 'declining phase'?