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FrenchScotPilot1

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  1. FrenchScotPilot1
    It looks like the polar vortex is reforming at higher levels as indicated by the mean zonal winds on the ECM at T+0: http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=a12&var=u&lng=eng And: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_UGRD_MEAN_JFM_NH_2013.gif Higher stratosphere is currently colder than average and the opposite is true for the lower stratosphere, with the recent warming downwelling: http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_JFM_NH_2013.gif I know it is far in the future and at a less reliable level but a ridge is shown to build at 100 hPa on the ECM (T+240) : http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ec.php?alert=1&level=100&forecast=f240&lng=eng The GFS supported the idea until T+204: http://www.netweather.tv/secure/cgi-bin/premium.pl?action=gfs;sess=e715497de74cb61e04244e54cfe63354 But the pattern seems to flatten out after this. Wishful thinking... Anyway guys, your contributions have been invaluable to increase our understanding of the phenomena. Thank you very much! Stephane
  2. FrenchScotPilot1
    Once again, very good post chiono! Would it be fair to say that the cold snowy event we're experiencing just now is a result of the first strat warming that happened at the start of Dec '12? Thanks, Stephane
  3. FrenchScotPilot1
    Almost 100 pages. And VERY good, informative posts. Thanks for the contributions guys. Keep them coming. Stephane
  4. FrenchScotPilot1
    Here's a picture of nacreous clouds last night over Scotland: https://forum.netweather.tv/gallery/image/16814-gallery/
  5. FrenchScotPilot1

    Gallery

    FrenchScotPilot1 posted a gallery image in Member's Gallery

    Gallery

    From the album: PSC

    Polar Stratospheric Clouds over Scotland at sunset on 9/12/12
  6. FrenchScotPilot1
    I'll put some pics tonight. So it just confirms that the strat temperature over the UK is very cold. In line with what models tell us for now. It doesn't seem to herald anything else then.
  7. FrenchScotPilot1
    Maybe slightly off topic but would it be a link with the apparition of Polar Stratospheric Clouds in the UK skies last night?
  8. FrenchScotPilot1
    Very roughly, Eliassen-Paml vectors represent the amount of heat and momentum fluxes from the troposphere to penetrate the polar stratosphere. If I remember correctly vertical vectors are synonymous of heat and any deviation from the vertical indicate momentum. Therefore, long vertical vectors indicate a good propagation and vertical flow of heat (good wave propagation). Please correct me if this is wrong.
  9. FrenchScotPilot1
    Is this a warming at 1hPa starting on day 9 over Spain? http://wekuw.met.fu-...st=f240&lng=eng
  10. FrenchScotPilot1
    No problem lorenzo. Congrats about the baby! I always appreciate your enlighting posts.
  11. FrenchScotPilot1
    Thanks sebastiaan
  12. FrenchScotPilot1
    Thanks lorenzo, what is BDC?
  13. FrenchScotPilot1
    Would the following scenario be fair: 1. Meandering Rossby waves (from barotropic and baroclinic instabilities) enhance surface high and lows 2. A blocking high may form and deflect further planetary waves off mountain ranges upwards 3. Given the right conditions (wave 1 or 2 in light westerly flow around the tropopause), may cause a breakdown in the polar vortex 4. This breakdown in turn reinforces the blocking high Once again some sort of positive feedback. Thanks, Stephane
  14. FrenchScotPilot1
    Very interesting read. For some reasons I thought SSW lead to HLB (and not the other way around) but once again it all seem connected. Blocks look like a good ingredient for SSW which in turn reinforce the blocks, however not all blocks end up in SWW. As usual it depends on conditions. The same way as we need low level and high level vorticity anomalies to be positioned exactly right with each other to lead to their coupling and explosive cyclogenesis. So complex but yet extremely fascinating!
  15. FrenchScotPilot1
    Well all this is consistent with the NAO going negative during the 3rd week of November. We could be getting an arctic shot for early December.
  16. FrenchScotPilot1
    Thanks for a professional sum up Matt. I guess most people follow the evolution on the Berlin site but is there a possibility to access the EC 32 Day or is it only available to professionals? Thanks, Stephane
  17. FrenchScotPilot1
    Looks like the latest run of ECMWF for 240 h is showing wave 2 backing down a bit from yesterday. E.g. geopotential is only 500 where is was forecast to be 650 yesterday (http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=f240&var=ha2&lng=eng)
  18. FrenchScotPilot1
    Easterly propagating (phase) large Rossby planetary waves lifted by large mountain ranges or land/ocean differential heating propagate into the stratosphere given the right conditions (long wavelength (wave number 1 or 2) and weak westerly flow). They interact with the PV and dissipate create warming. I gave it a shot I hope I got it right. Please correct me. Stephane
  19. FrenchScotPilot1
    Thanks C. So to sum up: at 60N around 5hPa, the wave lifts an area 650m higher than normal?
  20. FrenchScotPilot1
    How can this graph actually be interpreted? I understand (to a degree) wave temperature, wave heat flux but I'm not too sure about wave geopotential. Thanks, Stephane
  21. FrenchScotPilot1
    Thanks chionomaniac, it sounds it little more complicated than what I thought but what else to expect. As for the summer set up, it makes perfect sense. If you guys need me to translate from french sites, it will be with great pleasure, I may as well be useful Stephane
  22. FrenchScotPilot1
    One thing I fail to get my head round is what causes the warming in the stratosphere from dissipation of planetary waves. Ok the Rossby waves interact with the mean westerlies in the vortex but given the right circumstances why does this cause a warming? I've read the waves descend in the vortex and cause adiabatic compression but I still don't see it... And during the summer, when the vortex is easterly, why are the waves not able to penetrate it? It seems to be a bit of a mind puzzling situation just now but great professional posts guys, it is fascinating. Stephane
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