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lorenzo

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lorenzo last won the day on December 25 2023

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About lorenzo

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    Scottish Weather & Regional Banter. Teleconnections, ENSO, MJO, Research Papers & Learning, Hurricanes, Atlantic Lows & Windstorms, Stratosphere Monitoring
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  1. Bit of a boring hiatus this, but some mad stuff ongoing - Spain Top Temps, the Jet Stream and Omega Block across the states is - one for the ages chart, just exceptional. In the heart of the cold hangover and dreadful NWP output is a real 'meh' for excitement... But, lots of winter to go -- would normally leave that as .. a ha maybe stuff ahead.. But it is looking like being slow - burn and lagged... mid Feb is the one to watch ( even in the extended - for trends) vs. NWP right now.
  2. 948 on latest surface plot, some really powerful gusts here, strong winds right at the hook.
  3. Some fierce gusts out there now, hang on to everything those out west, stay safe!
  4. Last visible on the in-flow before IR , fascinating dual low pressure structure.
  5. The wrap up continues - nice satellite loop from yr.no to highlight https://www.met.no/en/weather-and-climate/satellite-images
  6. Looks like things continue to evolve, @Jo Farrow added into the Storm Isha thread that the MetO warning matrix had been adjusted for Scotland to a lower likelihood re: impact. Small margins here one would think.. Starting to wrap up now https://www.met.no/en/weather-and-climate/satellite-images
  7. Current Obs align well to the Met Office Fax from earlier, still some deepening to go on Isha, and this deepening phase happening right on our doorstep. Another 10mb to drop and you can see the extent of the wind-field on UKV which has ushered in the Amber warnings for Englandshire / most of the UK ( hard to tell from the Met Office map given it's got so many overlaid warnings on it!) Second pulse slams into Western Isles by midnight
  8. Current Obs align well to the Met Office Fax from earlier, still some deepening to go on Isha, and this deepening phase happening right on our doorstep. Another 10mb to drop and you can see the extent of the wind-field on UKV which has ushered in the Amber. Second pulse slams into Western Isles by midnight
  9. Had to rewind my mind back to 2009 - 2011 to get this one disentangled - there was a paper which referred to both the Ural High regime in combination with the Aleutian Low, and cited the NPAC low as a 'stratospheric starter pistol', a nice turn of phrase which sticks in the memory, which of the papers at the time examining precursors - have not been able to recall. Looking at more recent analysis - found this paper which summarises both precursors and how they enhance wave activity / wave driving and create vortex perturbation. It has been shown that pressure changes in certain regions, when in phase, can constructively interfere with the climatological wave-1 and wave-2 patterns and thus lead to an overall increase of wave driving (e.g. Garfinkel et al., 2010; Smith and Kushner, 2012). In particular, the Ural blocking pattern as part of a wave-1 anomaly has been recognised as a precursor pattern for SSWs (e.g. Garfinkel et al., 2010; Cohen and Jones, 2011). Moreover, this blocking pattern has recently received additional attention, as it plays an important role in dynamically linking Arctic amplification and sea-ice loss to changes in mid-latitude circulation patterns via a robust but highly intermittent stratospheric pathway (Jaiser et al., 2016; Hoshi et al., 2019; Cohen et al., 2020; Siew et al., 2020; Jaiser et al., 2023): The strong reduction of Arctic sea ice in autumn and winter, in particular in the Barents and Kara seas, and the associated heating of the overlying atmosphere favour more frequent blockingtype ridges over northwestern Eurasia in early winter, which facilitate the enhanced propagation of wave energy into the stratosphere, where wave breaking can lead to a disruption of the stratospheric polar vortex (Overland et al., 2016; Crasemann et al., 2017). On the Pacific side, Ineson and Scaife (2009) demonstrate that a deeper Aleutian Low positively interferes with and strengthens the stationary wave-1 amplitude. Moreover, Bao et al. (2017) identify the positive phase of the Pacific–North American pattern (PNA) as a precursor of SSWs by means of constructive interference with the climatological planetary wave-1 pattern. Whereas the Ural blocking plays an important role in Arctic–mid-latitude linkages, the Aleutian Low and the PNA have been identified as a pathway connecting the tropical phenomenon of the El Niño– Southern Oscillation (ENSO) to the strength of the stratospheric polar vortex in winter (e.g. Ineson and Scaife, 2009; Domeisen et al., 2019). In relation to the graphic it is clearly a different flavour of warming this year given it does not match the precursors shown, I do wonder if much of this is related to the Canadian Warming after effects from earlier in the season. We are either in a place where we have better tools to see CW type events more clearly - given the last few seasons has witnessed Nov / Dec wave activity akin to the CWs of early 80s, this season perhaps was a true CW event vs the prior seasons simply being early wave impacts on the developing vortex. It would be worthy of some re-analysis - am sure the boffins will be on the case and produce papers to examine the lead in to the short reversal over the next 12m. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019786
  10. Looking at GWO - you can see an argument for emergence from the circle of doom into a P4/5 circuit, the composites of which do advertise the initial scandi development , then into p5 heights building over Greenland.. Looking much further aloft day 10 sees the mid level vortex on it's travels to the Siberian side, we do have some grim charts on the face of things to muddle through in the immediacy, however the NWP will surely be toying with these type of solutions in earnest before too long..
  11. Not a surface chart - but did find this https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2003/record-breaking-maximum-temperatures---26_27-january-2003---met-office.pdf
  12. Had to rewind my mind back to 2009 - 2011 to get this one disentangled - there was a paper which referred to both the Ural High regime in combination with the Aleutian Low, and cited the NPAC low as a 'stratospheric starter pistol', a nice turn of phrase which sticks in the memory, which of the papers at the time examining precursors - have not been able to recall. Looking at more recent analysis - found this paper which summarises both precursors and how they enhance wave activity / wave driving and create vortex perturbation. It has been shown that pressure changes in certain regions, when in phase, can constructively interfere with the climatological wave-1 and wave-2 patterns and thus lead to an overall increase of wave driving (e.g. Garfinkel et al., 2010; Smith and Kushner, 2012). In particular, the Ural blocking pattern as part of a wave-1 anomaly has been recognised as a precursor pattern for SSWs (e.g. Garfinkel et al., 2010; Cohen and Jones, 2011). Moreover, this blocking pattern has recently received additional attention, as it plays an important role in dynamically linking Arctic amplification and sea-ice loss to changes in mid-latitude circulation patterns via a robust but highly intermittent stratospheric pathway (Jaiser et al., 2016; Hoshi et al., 2019; Cohen et al., 2020; Siew et al., 2020; Jaiser et al., 2023): The strong reduction of Arctic sea ice in autumn and winter, in particular in the Barents and Kara seas, and the associated heating of the overlying atmosphere favour more frequent blockingtype ridges over northwestern Eurasia in early winter, which facilitate the enhanced propagation of wave energy into the stratosphere, where wave breaking can lead to a disruption of the stratospheric polar vortex (Overland et al., 2016; Crasemann et al., 2017). On the Pacific side, Ineson and Scaife (2009) demonstrate that a deeper Aleutian Low positively interferes with and strengthens the stationary wave-1 amplitude. Moreover, Bao et al. (2017) identify the positive phase of the Pacific–North American pattern (PNA) as a precursor of SSWs by means of constructive interference with the climatological planetary wave-1 pattern. Whereas the Ural blocking plays an important role in Arctic–mid-latitude linkages, the Aleutian Low and the PNA have been identified as a pathway connecting the tropical phenomenon of the El Niño– Southern Oscillation (ENSO) to the strength of the stratospheric polar vortex in winter (e.g. Ineson and Scaife, 2009; Domeisen et al., 2019). In relation to the graphic it is clearly a different flavour of warming this year given it does not match the precursors shown, I do wonder if much of this is related to the Canadian Warming after effects from earlier in the season. We are either in a place where we have better tools to see CW type events more clearly - given the last few seasons has witnessed Nov / Dec wave activity akin to the CWs of early 80s, this season perhaps was a true CW event vs the prior seasons simply being early wave impacts on the developing vortex. It would be worthy of some re-analysis - am sure the boffins will be on the case and produce papers to examine the lead in to the short reversal over the next 12m.
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