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sebastiaan1973

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Everything posted by sebastiaan1973

  1. sebastiaan1973
    Some more amplification in the USA at 168.
  2. sebastiaan1973
    First, everybody merry Christmas. Update of this morning. More or less in my opinion in the same line of yesterday. -at 10hpa a increase of temperature above normal, declining after some time to normal -at 30hpa near normal So temperature rising takes places especially in the higher levels of the stratopshere The zonal wind drops at 1hpa and continues at the same level or even rises at 10hpa and 30hpa 60oN Zonal Mean Zonal Wind is back to normal (since the end of october it was above!) GFS FI is still predicting another 'heatwave' at 10hpa. So we have to wait and wait and wait....
  3. sebastiaan1973
    Chio, is it a coincidence that the highest ozon levels are found near the Aleoeten (I'm not sure this the right word in English, I'm Dutch)? We often see high pressure in La Nina years in this area.
  4. sebastiaan1973
    It's only 1 run, so from that perspective we don't have to worry. Besides that 'always' we needed a second wave to disrupt the vortex even more to get a more favourable situation at a lower altitude.
  5. sebastiaan1973
    Although it's far away it seems to me the zonal wind reversal is less strong than earlier was predicted (?)
  6. sebastiaan1973
    At this site http://www.wzforum.d...096#msg-2320096 I read today 'Momentan haben wir einen der stärksten Polarwirbel seit 1948, also seit Aufzeichnungen des Archivs. Die extrem negative Geopotenzialanomalie zieht sich wie ein Faden bis in die Bereiche der Troposphäre und beschert uns letztendlich auch das westgeprägte Wetter seit Ende November.' (written in german) So I wonder is this true. Do we have the strongest polar vortex since 1948 and an extreme negative geopotential anomoly?
  7. sebastiaan1973
    Not looking good according to EC
  8. sebastiaan1973
    I presume this board http://www.americanwx.com/bb/index.php/forum/20-weather-forecasting-and-discussion/
  9. sebastiaan1973
    In my opinion we don't necesarilly need a SSW for cold weather. Going back to normal temperatures in the stratosphere would increase the chance for some high pressure to develop at a more high latitude.
  10. sebastiaan1973
    Altough I would rather see some snow or low temperatures so I can skate, I do like the quietness of being patience and knowing there's nothing special on the short term. Last year was a rollercoaster of emotions. It's such a clear picture of the current state of the atmosphere.
  11. sebastiaan1973
    I think the recent rising of the temperature is just temporarily (like Chio stated earlier in this page) and he uses not this picture, but a more broader view. Anybody a clue why this year the atmosphere is so extremely cold?
  12. sebastiaan1973
    -9.09 in november at 30hpa, 8.5 at 50hpa http://www.cpc.ncep.noaa.gov/data/indices/qbo.u50.index
  13. sebastiaan1973
    chio, these are monthly data, in stead of daily, so I can't help you.
  14. sebastiaan1973
    Hi Stewart. Nice presentation. I have placed a link to your presentation at the Belgium website weerwoord.be, the largest community of weather lovers in the Low Countries. http://www.weerwoord...564&tid=1501564 Ben has a made a comment in this post, and I thought it might interested you. http://www.weerwoord...099&tid=1501564 In Dutch Ze gebruiken voor het maken van de composiet een (oude) heranalyse van NCEP. Daarbij relativeren ze niet de zwaktes van heranalyses in het algemeen en deze heranalyse in het bijzonder. Waarom worden er voor het composiet geen waarnemingen gebruikt? Als je de twee belangrijkste heranalyses van de NCEP naast de waarnemingen zet (GISS), zie je dat de (nieuwere) 20th Century Reanalysis van NCEP een beter beeld geeft dan de heranalyse die Netweather gebruikt heeft. Het grootschalige patroon blijft hetzelfde, maar voor verwachtingen op landniveau zijn er toch her en der belangrijke verschillen (zie Spanje en IJsland bijvoorbeeld). In onze regio geeft de inschatting van NetWeather een normale winter (binnen 0,5°C van normaal over 1981-2010). Translation in highlights He wonders why you use the old NCEP reanalysis while there is a new one (20th Century Reanalysis). And the reason you didn't use temperatures (GISS)? In general terms the the temperature are the same but regional there are some differences.
  15. sebastiaan1973
    Well GP tells in his presentation that his own forecast is quite different from the models. So I wonder who will be right. The models (computers) or Human?
  16. sebastiaan1973
    The difference in ozon levels
  17. sebastiaan1973
    Is it not to soon to look for any signs? As the SSW would come in january? Right now it's 25th of november.
  18. sebastiaan1973
    Weather Services International Expects Mildest European Winter since 2007-08 Coldest Winter Temperatures Expected across France and Iberia Andover, MA, November 21, 2011 — WSI (Weather Services International) expects temperatures for the upcoming period (December-February) to average lower than normal across France and Iberia with above-normal temperatures common elsewhere, most notably across the Nordic region. “So far, November has clearly been quite mild across most of Europe. While no immediate change to this pattern is expected, we do foresee a trend towards colder temperatures across western Europe and the UK in December,†said WSI Chief Meteorologist Dr. Todd Crawford. “The winter pattern will be dominated by the North Atlantic Oscillation (NAO). During the last couple of years, a strong negative phase of the NAO has been dominant, which has resulted in very cold winters. It does not appear that this extreme negative NAO phase will occur again this winter, which, we think, will result in a much warmer winter. We still feel that there will be enough spells of negative NAO to result in a slightly colder-than-normal winter across parts of France and Iberia. However, we have warmed our forecast temperatures in most western European locations for both December and January due to a continued lack of any sign of a sustained or strong negative NAO pattern. We expect the mildest winter in Europe since the 2007-08 winter.†In December, WSI sees the monthly breakdown as: Nordic Region* – Warmer than normal UK * – Colder than normal Northern Mainland* – Warmer than normal, except France Southern Mainland * – Warmer than normal, except Iberia In January, WSI forecasts: Nordic Region – Warmer than normal UK – Warmer than normal Northern Mainland – Warmer than normal, except eastern sections Southern Mainland – Colder than normal, except Iberia In February, WSI forecasts: Nordic Region – Warmer than normal UK – Warmer than normal Northern Mainland – Warmer than normal, except southern France Southern Mainland – Warmer than normal, except Iberia WSI, providing customized weather information to energy traders, will issue its next seasonal outlook on 19 December. http://www.wsieurope.com/622b54ce-88c6-4dae-a871-2d7c6dfd5e1c/news-scheduled-forecast-release-details.htm
  19. sebastiaan1973
    Chionomaniac, so there are two mechanisms for wave breaking into the stratosphere, is one way leading to both “vortex displacement†or “vortex split†events? Or just one of these two? (specific mechanism for a specific SSW) thanks!
  20. sebastiaan1973
    http://acdb-ext.gsfc..._2000_merra.pdf -> during november and december, but no 'winter weather' for us. As always lots of work has to be done before colder weather can reach us. “Nothing ever exists entirely alone; everything is in relation to everything else.â€
  21. sebastiaan1973
    I found another stratospheric temperature data set that goes back to 1950. This time I focused on the area 50-90N 90E-150W (basically Russia and surrounding areas) where the correlation is strongest. I used 70mb stratospheric temps from the NCEP reanalysis:http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl Based on this I would give us at least a 75% chance of having a +AO in December+January. If the stratosphere remains near record cold for the next 2-3 weeks, our chances diminish even further. There has never been a significantly -AO January following a top 10 cold stratosphere. November stratosphere -The December AO was 1.09 higher following the 10 coldest than the 10 warmest. -The January AO was 1.75 higher following the 10 coldest than the 10 warmest. -The December AO was .63 higher following cooler than average than warmer than average -The January AO was 1.71 higher following cooler than average than warmer than average November + December stratosphere -The December AO was 1.82 higher following the 10 coldest than the 10 warmest -The January AO was 2.81 higher following the 10 coldest than the 10 warmest -The December AO was .72 higher following cooler than average than warmer than average -The January AO was 1.41 higher following cooler than average than warmer than average - 8/10 coldest had +AO Dec, only 1 below -.1 - 8/10 coldest had +AO Jan, none below -.2 -9/10 warmest had -AO Dec, none above +.2 -9/10 warmest had -AO Jan, none above +.3 For reference this is what this Oct 15 - Nov 15 looked like this year: http://img257.imageshack.us/img257/1192/compday1088223617732022.gif Which matches very well to the November stratosphere preceding +AOs. The following is a correlation between the November stratosphere temperature and the subsequent January AO. http://img824.imageshack.us/img824/7527/1088223617732022148.gif In addition, if we look higher in the stratosphere at 20mb the spatial pattern of anomalies 10/15-11/15 has matched that of other Novembers preceding +AO December and Januaries. The similarity is astonishing. The current stratosphere is in a classic "pre +AO pattern." 10/15-11/15 20mb temps this year: http://img812.imageshack.us/img812/1192/compday1088223617732022.gif November 20mb temp correlation to subsequent AO: http://img825.imageshack.us/img825/8510/1088223617732022352.gif http://www.americanwx.com/bb/index.php/topic/29714-negative-nao-coming/page__st__20
  22. sebastiaan1973
    Elsewhere I Found this interesting comment by Glacier Point. Due to the character of my question I put it in this more in depth topic. So in fact, we are going to phase 2 of Cohens snowatmospheric circulation linkage? http://web.mit.edu/j...netal_GRL10.pdf Cohen et al. [2007] put forth a conceptual model of a dynamical pathway consisting of a sixâ€step process starting with a rapid advance in Eurasian snow cover and culminating in a negative surface AO. The six steps in sequential order are: 1) rapid advance of Siberian snow cover in October, (achieved, although the biggest gain was/is in november) 2) a strengthened Siberian high with colder than normal temperatures and higher sea level pressure (SLP) anomalies, 3) increased upward Eliassen Palm (EP) flux or the three dimensional wave activity flux (WAF [Plumb, 1985]), 4) a stratospheric warming, 5) downward propagation of the associated height and wind anomalies from the stratosphere down to the surface and finally 6) a negative surface AO Typically the cycle begins with the advance in snow cover in October and concludes with a lower tropospheric AO response beginning in mid to late January.
  23. sebastiaan1973
    Although some big differences over here. This chart shows the max. temperatures today. http://www.weerplaza.nl/actueel/extremen.asp
  24. sebastiaan1973
    Lorenzo thanks! Where do we find these composite charts for the several different phases?
  25. sebastiaan1973
    The ozone levels in 2009
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