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Interitus

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  1. Not sure the links can be as precise as to determine a cold, snowy spell for the UK in the last third of December, but certainly links between June temperatures and winter NAO have been investigated eg. Summer snow extent heralding of the winter North Atlantic Oscillation http://onlinelibrary.wiley.com/doi/10.1029/2002GL016832/full Clearly the conditions leading to these situations would probably also influence June CET to some degree.
  2. Annual CET

    After the warm June, this year had moved up to 5th place, 0.22°C behind leader 2007. The previous 30 year average (1987-2016) would see 2017 end up in 7th place with 10.61/10.63°C (monthly/daily values). The provisional figures up to July 29th show that briefly 2017 became the warmest year on record to July 20th (though of course only a small downgrade at month end would prevent it) - this is as a result of ongoing cooler weather in 2007, and the next day sees record warm year 2014 hit top spot for the first time. Interestingly, the previous 30 year average would see 2017 return to 1st place from 20th-23rd August before ending 0.04°C warmer on 10.65/10.67°C which in a close cluster of years means 3 places higher in 4th.
  3. Back in the here and now, just glad the GFS is moving away from this - 4-5 inches of rain for the Lake District this weekend.and a camping trip? Ugh, the 3 inches instead will be just a bit of drizzle.
  4. The 0z ECM may appear more mobile with the low not lingering into next weekend, however it brings lower 850 temps on Thurs/Fri than any other model.
  5. Autumn thoughts

    Not virus, it's the Horse Chestnut leaf miner - the caterpillars of a moth which live in and eat the inside of the leaves. First spotted in Wimbledon in 2002, it has now spread over most of England and Wales and has been spotted in Scotland. Discovered as recently as 1985 in Greece and described as a new species in 1986, where was it before then? Strange, because the damage they cause appears devastating when seen for the first time, but apparently does not seem to cause the trees too much harm - though, to bring things back to the weather, how the trees will respond under our different climatic conditions is unknown and is being monitored. https://www.forestry.gov.uk/horsechestnutleafminer
  6. This set-up is reminiscent of an article in the journal Weather regarding a sea-breeze front in June 1995 during a spell of the then highest June temperatures since 1976. Not strictly the same synoptics as not a pure sea breeze in this instance, but the similar effect of the penetration of low level cool maritime boundary layer and associated cloud from the North Sea, it's an interesting read - 'Sea breeze front reaches Birmingham and beyond!' http://onlinelibrary.wiley.com/doi/10.1002/j.1477-8696.1997.tb06266.x/pdf In the 1995 instance, temperatures had been in the 30s before falling back into the teens, with falls of 10 degrees within an hour.
  7. Not just high temperatures, look at these dew points, tropical values in some places
  8. Annual CET

    Correction, pipping 2014 by one-hundredth of a degree! The warm first half of June (provisional figures to 17th) has seen this year reach 5th place from the start of the year on a number of days, and the 30-year average to 2016 would see the year end at 10.55 / 10.57°C (monthly / daily values) in 8th place. Having made up some ground, 2017 is now 0.17 deg behind 2014 (currently 2nd) but quite some way off the warmest year to this point, 2007, by 0.44 degrees.
  9. You wanted a chart to show heatwave in France and then stated that "nowhere near 35C in France"?? Lol
  10. A long way off, but pushing 40°C in the southwest next weekend
  11. Annual CET

    Well the 11°C year is still unlikely. 2017 is only ranked 6th warmest to the end of May and the average of the last 30 years would see a final CET of 10.48°C by monthly values or 10.50°C from the daily figures, ranking 16th in both cases. The average of the last 10 years pushes it a little lower to 10.44°C monthly / 10.47°C daily and 18th for both. Only a final 7 months like 2006 would achieve 11 degrees - albeit a ridiculous 11.40°C monthly / 11.43°C daily. And only one other year would give 2017 a new record, with the June - December of 1959 if repeated achieving 10.93°C monthly / 10.96°C daily, just pipping 2014 by a tenth of a degree. At present 2017 is 0.23°C behind 2014.
  12. This piqued my interest, the AC is generally > 0.9, but during the periods of lower predictability, is there a possible strat effect? The impact seems more important if a greater depth of stratosphere is affected by vortex weakening than just considering the 10 mb level alone.
  13. Annual CET

    When I posted something similar, bearing in mind similar maritime climates, it's like shifting the CET zone roughly a thousand miles north to northern Iceland, or a thousand miles south to central Portugal.
  14. Well it was suggested that this was given too much prominence. The total angular momentum is a combination of the motion relative to the earth, in this case the QBO, but more importantly the motion caused by the earth which is a function of latitude. Theoretically, a parcel of air will gain around 134 m/s eastward velocity just by moving from the equator to 30°N, which is an order of magnitude greater than the relative motion of the QBO. It doesn't achieve this velocity because of turbulent mixing and looking at the region of the subtropical jet, the average April zonal wind speed at 30°N/250mb is 27.9 m/s (NCEP reanalysis). Also, momentum is calculated for a unit of mass i.e. proportional to density, and air at 30mb has a little over a tenth of the density of that at 300mb for example so the momentum is further diluted. Using the March QBO figures from 1956 onwards, the 20 strongest (westerly) QBO average 8.91 m/s, 20 weakest (easterly) average -13.34 m/s. The corresponding April 30°N/250mb wind speeds are 27.6 and 27.4 m/s respectively; the correlation is an insignificant 0.18. Interestingly, for the 500mb wind over London, there's a tendency towards anticorrelation (-0.24) with the 20 strongest QBO have weaker 500mb wind 4.99 m/s vs 7.38 m/s for the easterly QBO. These average zonal winds at 50°N/500mb are not very strong and clearly, the Coriolis deflection at this latitude would dwarf any QBO effect.
  15. There is just far too much importance being applied to the QBO. The time-latitude chart below shows the zonal wind anomalies at the 30mb level from Jan 2014 to end of March 2017 - The phases of the QBO can seen in the tropical anomalies on the left hand side, and the seasonal winter stratospheric vortex development in high latitudes on the right. There is no transfer of QBO anomalies towards the midlatitudes, with the anomalies effectively meridionally confined below 20°N. The reason is that meridional wind flow is very low, in the region of less than a couple of m/s at most. The Holton-Tan relationship describes a link between a weaker winter time vortex with an easterly QBO but this is not because of a transfer of momentum, it is because of the effect of the critical line i.e. zero or easterly flow, on planetary waves generated from the troposphere. These are prevented from moving equatorwards and are directed more towards the pole so more effectively weakening the vortex. The effect of QBO phase can then be seen in stratospheric northern annular mode (NAM) and thence in the tropospheric AO/NAO. This is restricted to wintertime however, as planetary wave propagation is greatly limited by summer polar easterly flow, requiring the presence of the vortex westerlies from autumn onwards. This also affects the major stratospheric meridional motion - the Brewer-Dobson circulation is generated by planetary waves during the winter half of the year, and does provide a northward flow which as it descends adiabatically warms the polar stratosphere significantly above what would be expected from winter radiative cooling. But it is largely above the 30mb level and the velocity is very, very low - tracers such as tropical ozone show that the age of polar stratospheric air may be 4 or 5 years.
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