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Singularity

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Singularity last won the day on September 14 2018

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About Singularity

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    MSc Meteorology

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    New Forest (Western)
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    Meteorology - Science and Observations | Cycling - On and Off Road | Walking or Hiking | Electronic Music Creation
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    The Extremes! Passionate Hater of Drizzle.

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  1. Indeed - from observations it's become apparent to me that some events are more convection/precipitation-dominated (OLR/VP200 measurements), others wind pattern-dominated (zonal wind anomalies), while some find a good balance between the two. It generally seems (at least in my experience) that the more of these components are strong, the more impact the MJO event tends to be on N. European weather patterns if and when it travels past the Dateline.
  2. To be fair, the MJO event does appear to be lacking in certain components, especially in the Northern Hemisphere, which will limit its ability to influence our weather patterns. So, we see the subtropical highs tending not to make it beyond mid-latitude status. Meanwhile, the tropospheric 'polar vortex' looks to become focused toward Siberia for a time, but without some HLB to its west, this makes for a very unstable N. Atlantic, with cyclogenesis there giving the UK a hard time tapping into much cold air. You never know though, we could get lucky with a 'runner' into the base of the major trough to our NE. Not something to place bets on - just worth keeping an eye out for.
  3. Okay, so here's the proposal by the modelling. GLAAM rises sufficiently, in response to an active MJO propagating across the Pacific, to send a significant pulse of energy from the Pacific to the high Arctic. That triggers a rapid 'bottom-up' polar vortex split, which reaches the mid-levels (hardly any effects being depicted for 10 hPa and 1 hPa). This is a transient event, but may still yield a noteworthy bout of cold weather for western Eurasia. Reasons to be cautious, however: Models are prone to changing AAM too enthusiastically. EPS are not as keen to propagate the MJO across the Pacific and GEFS. Even GEFS aren't reliably producing enough of an AAM rise to yield an effective polar vortex split. We can also interpret this in FV3 based on the high variability of recent runs. Usually when the MJO doesn't make it past P7, mid-latitude blocking is favoured in the vicinity of the UK. The proposed outcome is an unusual scenario that depends on developments the other side of the hemisphere. Possibly it's only even possible due to the unusually strong nature of the MJO activity across the Maritime Continent and into the West Pacific. Regardless, unusual means less likely to come off. Overall, reasons to keep an open mind to a dramatic change in temperatures (at least for a time) by late Jan, but not (at this stage) to expect it by any means.
  4. For whatever reason, GFS is making quite a bit more of the eastern LP in the N Atlantic on D6 than any of ECM, UKMO, JMA, GEM and ICON. So, it’s the only one that diverts the northerly flow away from the UK for D6+. Go figure
  5. A Nina-like atmospheric state with a poorly organised tropospheric polar vortex (despite the stratospheric one being much more so) can facilitate some nice 'tall' mid-Atlantic ridges in Oct-Nov, maybe early Dec. Not sure how much longer the trop. vortex will really be able to stay so disorganised, though. Anomalously large Arctic heat + moisture fluxes are a wildcard, as usual in these times of huge sea ice deficits. Regardless, I expect we'll have a few 'toppler' scenarios to ponder over in the coming weeks. Going to be tough for low levels to get much wintry weather out of such things, though. It's not going to help sanity levels that the FV3 core of GFS still seems to have a bit of a cold bias with troposphere temps.
  6. Great read, thanks for sharing. It's funny really, how our official measurements are of conditions that most of us don't experience very often, but of course the point of it is to capture the weather in its 'rawest' form with the least possible modification by humans (excepting the large-scale effects of added CO2 etc). This does mean, though, that there's some value to those unofficial readings from a 'what most of us experience' perspective, provided they're not taken in direct sunlight. Hence I find sites that display those to be of some use when gauging what to expect when heading away from home for a day trip.
  7. Thanks for the blog compliment @Geordiesnow . Good update, definitely worth the double-post - there's a lot of thin, fragmented ice drifting around with the winds. Every time I look around with WorldView, the poor visual state of so much of the ice leaves me feeling a bit unwell. The minimums for extent and to a lesser degree area will be largely down to chance; however the various highs and lows happen to move around during the next fortnight. The central HP cell currently looks short-lived, but the models haven't been doing a great job since the decay of the major blocking regime that dominated the summer, so who knows how long it might actually stick around for. During the refreeze, I gather high pressure is best to have around for the first few months to facilitate a quick initial freeze, after which low pressure is preferable to provide a thick layer of snow cover to protect the ice during the following Apr-Jun. I'm not 100% on this, though!
  8. The 06z on the right has the Atlantic trough more positively tilted again, which cuts of the NE flow sooner. The modelling of this has been pretty poor. The way ECM has gone from the warmest to coolest end of the solutions for Tue-Thu is quite amusing, in a sad sort of way. Just imagine the dramatics that would be occurring if it was January and we were looking for a bitterly cold feed from the northeast!
  9. I've not been able to find any significant correlations with the CET in the UK or 500 hPa height patterns in the eastern N. Atlantic to western Eurasia sector. However, there aren't many past examples of such extreme anomalous warmth covering such a vast swathe of the North Pacific to work with. BUT this does mean we can't be sure that it'll drive a +NAO this winter, even if it is one of the only at all plausible explanations for the DJF updates from the GloSea5 and ECMWF long-range modelling. It'd be just typical though, if it screwed us over when so much else was looking favourable. Using my own past propagation analysis for the QBO, we may even have that in a negative (easterly) state by mid-January, with a bit of luck.
  10. As explained here, the volume situation far outweighs the extent/area one - and it troubles me greatly. Generally, the lower the volume, the more vulnerable the ice is to whatever the weather patterns decide to get up to. Also, not covered in this blog piece (I try to keep them from becoming too complicated), the huge amount of dispersion that has taken place in recent weeks may cause additional trouble. This being if, as I have seen speculated but without much hard evidence (it's difficult to acquire - not enough buoys for starters!), the thin sea ice acts to trap additional heat in the Arctic Ocean by keeping turbulent mixing to a minimum. The ice may also block some radiation of heat into the atmosphere, but I imagine this tends to be insignificant until it starts thickening appreciably Oct-Nov. Given that 2019 has seen an unprecedented (or close to it) amount of oceanic heat uptake due to the exceptional amount of open water during May-July, I'm concerned that the stored heat may restrain the refreeze as much as we saw during the miserable 2016-17 refreeze season. That'd leave the Arctic in need of a summer as extraordinarily kind to the sea ice as 2017's was.
  11. Good response by Jules. Essentially, being a vast, consistently cold and frozen landmass entirely surrounded by gently varying oceans is a far better for your stability than being a smaller, inconsistently frozen ocean flanked on two sides by strongly, rapidly varying landmasses.
  12. We know how much the models struggle with our N. Hemisphere SSWs... so I don't hold out much hope for them resolving the outcome of the much, much rarer S. Hemisphere equivalent. Not sure it's technically a SSW by wind stats yet though; wind still not to -10 m/s at 60*N. Then again, this definition may not be appropriate given the markedly different climatology there.
  13. The cut-off low remains an issue to resolve details-wise. GFS continues to make it a very clean affair, while ECM persists with a slight connection to the polar jet being maintained. The 850s from ECM for this day seem extraordinary for mid-September. Has the 17*C isotherm ever visited the UK this late in the year before? Maybe it did so even later, in 2011? Further into next week, and GFS is still doing the same overall thing as the previous 12z from the model really - just with a trademark adjustment east (so many snowy winter northerlies lost this way...). Some distinctly fresh air still gets wrapped around to bring some cool nights and days falling short of the 20*C mark for most locations next Tue-Thu. Meanwhile ECM continues to keep a weak chain of lower heights in play to the NW and N of the UK, preventing the ridge from building much north of the UK such that we're left basking in stagnating air of mostly tropical maritime air. Could potentially be some issues with low cloud or fog if you're seeking particularly high daytime temps, though. Longer term, continued suggestions of a secondary surge of warmth somewhere in the range of 8-12 days from now by both models. September could prove to be one heck of a two-halves sort of month.
  14. Sometimes cut-off lows can produce some of the wackiest weather patterns at short notice, if the upstream pattern remains amplified. You can really see here, knowing how differently GFS and ECM unfold thereafter, how even the slightest continued connection to the polar jet (the 'nose' formed by the 1020 mb line to the WNW of the UK in the ECM chart) is able to prevent the high pressure across the UK from retrograding to the W/NW of the UK. We've seen that kind of residual connection deny us many a potential wintry northerly in the cold season. For what it's worth, ICON 12z is close to the UKMO 12z, while GEM sits between UKMO and ECM. GEFS and EPS continue to favour the UKMO/ICON 12z or GEM/ECM 12z style outcomes. Even so, I'm keeping an open mind to the cut-off low potential; not going to sit here naively presuming that it will be pleasantly warm during my week off... .
  15. Nice to see some lengthy spells under strong high pressure on offer from GFS. It feels like it's been absolutely ages since we last had one of those! Remains to be seen how far north the high sets up. The ECM 12z offers a near-optimum outcome for very warm days, but GFS 12z takes the high too far north for much of an import of warm air - which we increasingly rely upon in mid-late Sep to lift the temperatures much above the long-term average.
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