Jump to content
Holidays
Local
Radar
Pollen

sebastiaan1973

Members
  • Content count

    609
  • Joined

  • Last visited

Community Reputation

653 Exceptional

Profile Information

  • Gender
    Male
  • Location
    Netherlands

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. Well according to the 'pluim' we get over here in the Netherlands indeed 30c's. Sometimes EC underestimates the temperature, especially with lot's of sunshine, so it can even get hotter than shown. July 2018 could be the driest and sunniest july 'ever'.
  2. https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.721 We present a case study of long range forecasts for Northern Hemisphere winter 2015/2016. This winter produced the strongest El Niño event since 1997/1998 and equatorial Pacific sea surface temperature anomalies exceeded 3 °C. Other factors relevant to the Northern Hemisphere extratropical atmosphere circulation included a strong westerly phase of the Quasi‐Biennial Oscillation (QBO) and very strong winds in the stratospheric polar night jet in early winter. At the surface, intense cyclonic extratropical circulation anomalies occurred in early winter in both the North Pacific and North Atlantic, consistent with known teleconnections to these phases of El Niño–Southern Oscillation, the QBO and the polar night jet. The midlatitude flow was very westerly in early winter and less westerly and sometimes northerly in late winter, when sudden stratospheric warming events also occurred. We show that initialised climate predictions were able to capture the winter mean flow pattern at seasonal lead times from well before the start of winter. In this special case, not only the winter mean flow pattern, but also some aspects of the sub‐seasonal evolution were skilfully predicted. We show that the winter of 1982/1983 was closely analogous to winter 2015/2016 in both the predictable driving factors and the forecast winter circulation. This case study adds to the evidence that the north Atlantic circulation can be predictable on seasonal timescales and advance warning of the increased risk of intense rainfall and storminess which caused extreme flooding in the UK in December was possible in this case.
  3. This study uses reanalysis datasets and numerical experiments to investigate the influence of the occurrence frequency of the individual phases of the Madden–Julian oscillation (MJO) on the interannual variability of stratospheric wave activity in the middle and high latitudes of the Northern Hemisphere during boreal winter [November–February (NDJF)]. Our analysis reveals that the occurrence frequency of MJO phase 4 in winter is significantly positively correlated with the interannual variability of the Eliassen–Palm (E–P) flux divergence anomalies in the northern extratropical stratosphere; that is, higher (lower) occurrence frequency of MJO phase 4 corresponds to weaker (stronger) upward wave fluxes and increased (decreased) E–P flux divergence anomalies in the middle and upper stratosphere at mid-to-high latitudes, which implies depressed (enhanced) wave activity accompanied by a stronger (weaker) polar vortex in that region. The convection anomalies over the Maritime Continent related to MJO phase 4 excite a Rossby wave train that propagates poleward to middle and high latitudes, and is in antiphase with the climatological stationary waves of wavenumber 1 at middle and high latitudes. As the spatial distribution of the convection anomalies during MJO phase 7 has an almost opposite, but weaker, pattern to that during MJO phase 4, the occurrence frequency of MJO phase 7 has an opposite and weaker effect on the northern extratropical stratosphere to MJO phase 4. However, the other MJO phases (1, 2, 3, 5, 6, and 8) cannot significantly influence the northern extratropical stratosphere because the wave responses in these phases are neither totally in nor out of phase with the background stationary wavenumber 1. https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-17-0476.1
  4. I wonder if and when we see the effects of MJO phase 7. Which has a composition of an Atlantic high.
  5. Hi John, pink is high pressure. Have a nice stay at Mauritius. This MJO-composite would apply after 10 april.
  6. Yes, as always we have to wait. Latest GFS shows a typical MJO phase 7 chart.
  7. I wonder what the impact will be of the reemerging MJO in the Western Pacific. The composites show high pressure in the Atlantic west of the British Isles and phase 8 around Greenland. http://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html
  8. Thanks to paul123 for this chart. Date of SSW is 30. A quick drop of the AO. So I find the NH output of EC12h rather strange (quite positive AO at day 10) .
  9. A chart made by Paul123 (NL, https://www.vwkweb.nl/index.php?page=Forum&articleid=138&reference=ref261795&threadpage=7) Day 30 is SSW taking place. Black line is AO blue line temperature De Bilt. On average we see a drop in AO. I find it hard to understand the EC 10 day NH chart.
  10. http://kachelmannwetter.com/de/modellkarten/euro/europa/m0_luftdruck/20180221-1200z.html This would be terrible. An easterly but no beast! Nature is creative in disrupting our winter chances.
  11. Hi Chio, so this signal is so strong, it overrules the MJO phase 7 Scandihigh which we 'would' see in 7-10 days time?
  12. sebastiaan1973

    Model output discussion - mid-winter

    Amazing EC control run this morning. http://kachelmannwetter.com/de/modellkarten/euro/europa/m0_luftdruck/20180128-1200z.html
  13. Abstract We investigate the connection between the equatorial Madden-Julian Oscillation (MJO) and different types of the Northern Hemisphere mid-winter major stratospheric sudden warmings (SSWs), i.e., vortex-displacement and vortex-split SSWs. The MJO-SSW relationship for vortex-split SSWs is stronger than that for vortex-displacement SSWs, as a result of the stronger and more coherent eastward propagating MJOs before vortex-split SSWs than those before vortex-displacement SSWs. Composite analysis indicates that both the intensity and propagation features of MJO may influence the MJO-related circulation pattern at high latitudes and the type of SSWs. A pronounced Quasi-Biennial Oscillation (QBO) dependence is found for vortex-displacement and vortex-split SSWs, with vortex-displacement (-split) SSWs occurring preferentially in easterly (westerly) QBO phases. The lagged composites suggest that theMJO-related anomalies in the Arctic are very likely initiated when the MJO-related convection is active over the equatorial Indian Ocean (around the MJO phase 3). Further analysis suggests that the QBO may modulate the MJO-related wave disturbances via its influence on the upper tropospheric subtropical jet. As a result, the MJO-related circulation pattern in the Arctic tends to be wave number-one/wave number-two ~25–30 days following phase 3 (i.e., approximately phases 7–8, when the MJO-related convection is active over the western Pacific) during easterly/westerly QBO phases, which resembles the circulation pattern associated with vortex-displacement/vortex-split SSWs. http://web.gps.caltech.edu/~kfl/paper/Liu2014.pdf
  14. sebastiaan1973

    Model output discussion - into 2018

    You can check the EC-Oper, control and it's members overhere http://kachelmannwetter.com/de/modellkarten/euro/europa-afrika/m48_geopotential-500hpa/20180115-0600z.html
×