Interitus

Members
  • Content count

    1,854
  • Joined

  • Last visited

Community Reputation

1,650 Exceptional

About Interitus

Recent Profile Visitors

16,527 profile views
  1. 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.
  2. Not just high temperatures, look at these dew points, tropical values in some places
  3. 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.
  4. You wanted a chart to show heatwave in France and then stated that "nowhere near 35C in France"?? Lol
  5. A long way off, but pushing 40°C in the southwest next weekend
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. Tied in to possibility of active strat final warming coupling with troposphere; here is this morning's GFS (from weatheriscool) showing potential downward progression of zonal wind anomalies -
  12. For a while the GFS has been forecasting an 'active' final warming - active in the sense that it there is a dynamic wave-1 forced baroclinic vortex to produce above average temperatures / wind reversal, rather than purely 'passive' warming as the vortex dissipates through radiative relaxation from increasing insolation. Indeed, some ensemble members forecast wind reversal greater than summer values and the stronger this warming the less likely a weak westerly will return this spring. Generally an effect on the troposphere is unclear, though a couple of runs have suggested a S-T coupling as shown in the downward progression of zonal wind anomaly in the right hand chart below, from 29/03 06z
  13. The above was posted in March 2014 and indeed it went on to become the warmest annual CET on record. With this year now nearing the end of March ahead of target, provisionally requiring 1.39°C for the rest of the year compared to the record annual anomaly of 1.44°C, it may be time to keep an eye on this.
  14. Good reply, but just a couple of thoughts. The height of cumulonimbus clouds are restricted by the tropopause, where the cloud spreads out forming the characteristic anvil shape. There can be a degree of overshoot, but cumulonimbus don't reach 49,000 feet over the UK so lowering the estimated distance. However on the other hand, at night in particular, high cloud layers can reflect the light from the lightning which may otherwise be over the horizon.
  15. This would appear to be a misperception which has happened frequently recently when a seemingly unremarkable month is much warmer than average. According to the MetO Hadcet pages to March 28th, the provisional minimum anomaly is 2.3°C - http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_min.html But the maximum anomaly is 2.7°C - http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_max.html