sebastiaan1973

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About sebastiaan1973

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  1. Well I think his comment is in line with Finnish research. 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. http://onlinelibrary.wiley.com/doi/10.1002/2013JD021343/abstract
  2. Sorry to say, but I think the early SSW won't be accomplished. Perhaps later on?
  3. http://iopscience.iop.org/article/10.1088/1748-9326/10/10/104007/pdf Some research. There has been a great deal of recent interest in producing weather forecasts on the 2–6 week sub-seasonal timescale, which bridges the gap between medium-range (0–10 day) and seasonal (3–6 month) forecasts. While much of this interest is focused on the potential applications of skilful forecasts on the sub-seasonal range, understanding the potential sources of sub-seasonal forecast skill is a challenging and interesting problem, particularly because of the likely state-dependence of this skill (Hudson et al 2011). One such potential source of state-dependent skill for the Northern Hemisphere in winter is the occurrence of stratospheric sudden warming (SSW) events (Sigmond et al 2013). Here we show, by analysing a set of sub-seasonal hindcasts, that there is enhanced predictability of surface circulation not only when the stratospheric vortex is anomalously weak following SSWs but also when the vortex is extremely strong. Sub-seasonal forecasts initialized during strong vortex events are able to successfully capture the associated surface temperature and circulation anomalies. This results in an enhancement of Northern annular mode forecast skill compared to forecasts initialized during the cases when the stratospheric state is close to climatology. We demonstrate that the enhancement of skill for forecasts initialized during periods of strong vortex conditions is comparable to that achieved for forecasts initialized during weak events. This result indicates that additional confidence can be placed in sub-seasonal forecasts when the stratospheric polar vortex is significantly disturbed from its normal state.
  4. I spoke today to someone of MeteoGroep (group) Netherlands. They expect a warm januar and possibilities in februar for cold weather. In their opinion the  chance for a minor SSW is high.    
  5. The AO is currently positive and is predicted to trend negative but still remain near neutral. The negative AO trend is reflective of the model forecast of initial low pressure/geopotential heights over the North Atlantic side of the Arctic transitioning to more high pressure/geopotential heights.  Though the models are not predicting necessarily cold weather it should result in damping of the large positive temperature anomalies for Europe, western Asia and the Eastern United States. However the models predict low pressure/geopotential heights to continue on the North Pacific side of the Arctic.  This will likely result in any cold weather being focused in Western North America for much of the remainder of December. Models are predicting an increase in energy transfer from the troposphere to the stratosphere starting the third week of December.  This will likely lead to perturbation of the polar vortex during the latter half of December.  The more the vortex is perturbed, the higher our confidence in a cold second half of winter. Longer-term high latitude boundary conditions favor a negative bias to the AO including extensive Eurasian snow cover and low sea ice extent in the Barents-Kara seas.  The key will be how strong the energy transfer from the troposphere to the stratosphere is in late December and how much the polar vortex is perturbed. If the energy transfer does not significantly weaken the polar vortex, the AO will likely remain mostly positive and mild temperatures will dominate the mid-latitudes. The duration and amplitude of the atmospheric energy transfer or WAFz is likely to be critical for the weather during the middle and later parts of winter.  We continue to anticipate the active transfer of energy from the troposphere to the stratosphere and a weakening of the polar vortex starting in December and continuing into January.  Following the weakened polar vortex we would further expect a negative AO and cold temperatures across the Northern Hemisphere continents.  However if the active WAFz does not persist and/or strengthen in amplitude then the polar vortex will recover and remain strong, and it becomes increasingly likely that the stratosphere and troposphere will couple in a way that favors a positive AO with mild to even very mild temperatures across the Northern Hemisphere mid-latitude continents.   http://www.aer.com/science-research/climate-weather/arctic-oscillation
  6. Recretos aka Mr Angerfist  Didn't know this kind of music was popular in eastern Europe. Something else.. http://onlinelibrary.wiley.com/doi/10.1002/2014JD022022/full Abstract It has been suggested that the Sun may evolve into a period of lower activity over the 21st century. This study examines the potential climate impacts of the onset of an extreme “Maunder Minimum-like” grand solar minimum using a comprehensive global climate model. Over the second half of the 21st century, the scenario assumes a decrease in total solar irradiance of 0.12% compared to a reference Representative Concentration Pathway 8.5 experiment. The decrease in solar irradiance cools the stratopause (∼1 hPa) in the annual and global mean by 1.2 K. The impact on global mean near-surface temperature is small (∼−0.1 K), but larger changes in regional climate occur during the stratospheric dynamically active seasons. In Northern Hemisphere wintertime, there is a weakening of the stratospheric westerly jet by up to ∼3–4 m s−1, with the largest changes occurring in January–February. This is accompanied by a deepening of the Aleutian Low at the surface and an increase in blocking over Northern Europe and the North Pacific. There is also an equatorward shift in the Southern Hemisphere midlatitude eddy-driven jet in austral spring. The occurrence of an amplified regional response during winter and spring suggests a contribution from a top-down pathway for solar-climate coupling; this is tested using an experiment in which ultraviolet (200–320 nm) radiation is decreased in isolation of other changes. The results show that a large decline in solar activity over the 21st century could have important impacts on the stratosphere and regional surface climate.
  7. Thanks a lot for this piece of work. I placed a link at weerwoord.be, so the Dutch & Belgium weatherlovers can enjoy your forecast as well.
  8. Of course we see some wave activity, but temperature wise we are still & in the forecast under the normal temperature.
  9. HI Chio, did you read this forecast? http://www.americanwx.com/bb/index.php/topic/47251-my-winter-outlook-2015-16/
  10. SIberian high   http://www.americanwx.com/bb/index.php/topic/47140-griteaters-winter-outlook-15-16/?p=3737459 yet another winter forecast.
  11. I'm surprised nobody refers to Fergie's post The latest Contingency Planning summary is N-D-J. That GloSea5 output is J-F-M. Note cautionary comment by seasonal team re increased SSW potential late season in today's update. In other words, the message remains consistent: coherent, cross-model support for notion of milder/wetter/poss stormier start to winter, but potential for colder flip later (this clearly v uncertain of course). But the notion of broadly +ve NAO conditions into winter at least initially has been strongly signalled by the key output (GloSea5, EC Seasonal, EuroSip) for a while now.  https://forum.netweather.tv/topic/84126-winter-201516/page-34#entry3275001         
  12. According to Judah Cohen in his blog SAI and SCE are above average, altough not that high as in the last two winters. https://www.aer.com/science-research/climate-weather/arctic-oscillation   It is our experience that above normal polar cap geopotential height anomalies tend to persist this time of year, with embedded variability, until vertical wave activity flux becomes active.  Therefore assuming near normal vertical wave activity flux, we feel that the prediction of above normal polar cap geopotential height anomalies over the next two weeks favors above normal polar cap geopotential height anomalies and a negative bias in the AO longer term.  However for wave activity flux to become more active, the atmospheric pattern will need to project onto the tripole pattern that we have shown is favorable for increasing the energy transfer or wave activity flux between the troposphere and the stratosphere (Cohen and Jones 2012).  The models do not predict this solution for at least the next two weeks but it is still early and is something that needs to monitored.
  13. In Conclusion:   We are essentially in uncharted territory since at least 1950 in terms of a basin wide El Nino event of this strength, when combined with a warm Indian Ocean, very warm waters compared to Hawaii to California and a very warm N. Pacific. However, there is evidence that the warm Indian Ocean may act to cause somewhat more MJO activity that what is common during stronger El Nino winters, and in general, the warmer waters elsewhere in the East Pacific tended to pull the Aleutian low farther west when compared with other moderate to strong basin wide El Nino events. This suggests that a +PNA may become more likely as the winter goes on, after Pacific air likely floods a good portion of the CONUS in December.   In general, basin wide El Nino winters favor a negative NAO as you head farther into winter, although not as strongly as modoki events. The three moderate to strong basin wide El Nino events since 1950 that had a +QBO as we’ll have this winter featured decent AO/NAO blocking by February, after a warm December and up and down January. Research done on October snow advance in Eurasia by Dr. Judah Cohen and on October N. Pacific sea level pressure by Al Marinaro both suggest that trends this month also support a –AO/NAO this winter.   In general, a rising +PNA could limit California/west coast rainfall by later in winter. Hopefully they’re very active before then, as they desperately need the rain. The eastern US looks cold/active for the second half of winter, after a potentially very slow start.   The potential bust factor here revolves around how the Nino behaves. Other basin wide El Nino events with such a warm Indian Ocean (1987-88, 2002-03) saw more MJO activity than normal for stronger EL Nino winters, which likely contributed to a favorable pattern for eastern US snow. If this event becomes more strongly east based, this may not be able to occur. Another overall question mark is if all of the correlations discussed, small sample size for some of them notwithstanding, hold up with such a strong El Nino. We may learn quite a bit this winter…hopefully not at the expense of this forecast.   Analogs, based on good SST matches globally and QBO:   1957-58, 1987-88 (2), 2002-03, 2006-07 http://www.americanwx.com/bb/index.php/topic/47089-my-2015-2016-winter-outlook/   A winter forecast from the States. When you sign in, you got the possibility to see the charts.
  14. From the Dutch/ Belgium weather website http://www.weerwoord.be/uploads/111020152338550.png http://www.weerwoord.be/includes/forum_read.php?id=2132991&tid=2132957   http://www.weerwoord.be/includes/forum_read.php?id=2132984&tid=2132957   You can read Cohen's vision in his blog https://www.aer.com/science-research/climate-weather/arctic-oscillation A new update probably this Monday!
  15. http://onlinelibrary.wiley.com/doi/10.1002/2013JD021343/abstract -> we are in a declining phase of the solar cycle. Using 13 solar cycles (1869–2009), we study winter surface temperatures and North Atlantic oscillation (NAO) during four different phases of the sunspot cycle: minimum, ascending, maximum, and declining phase. We find significant differences in the temperature patterns between the four cycle phases, which indicates a solar cycle modulation of winter surface 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 the pattern described by Chio could be the right one.