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knocker

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Everything posted by knocker

  1. Quite an impressive display if the scoreline flattered England a little. Certainly more of an idea now on what Jones considers his best team and the equally as good fall back position.
  2. The main energy flow is running south of the Greenland block via the Atlantic trough to be westerly over the UK in the 5-10 period. But in the latter stages the European subtropical high is starting to amplify north west and this continues in the ext period neatly cutting this off portending more settled weather
  3. Not too bad at the moment with a few large Cus around
  4. The ecm is better than the gfs in that it doesn't establish a lnk south of Greenland to the trough and thus facilitates the European high to ridge north west and initiate more settled conditions for the UK
  5. Although the GEFS has a bit of a struggle vis trough/ridge later next week it does eventually have the ridge gaining a foothold Cross model agreement even more essential here and getting NOAA on board
  6. According to the gfs the next few days and through the weekend is essentially a struggle between the active trough to the NW/W, controlled by the TPV over northern Russia and the struggle by the European high to get a foothold. Complicated further by the trough getting a boost from a conduit established south of the now isolated high cell over Greenland And unlike in previous runs it fails to get a foothold and thus the weather becomes generally unsettled, Given the uncertainty of all of this I have no confidence whatsoever that this will be near the money
  7. The NH 500mb profile and the North Atlantic surface analysis for midnight. Things are slowly improving and many areas will see less showers today but still a few around, mainly effecting wales and the south west. A more insistent band, associated with the occlusion, currently effecting central Scotland will move slowly south during the day to reach as far as northeast England by dusk The showers mainly confined to northern and south west coastal areas tonight whilst elsewhere quite a chilly night with the odd mist/fog patch By tomorrow the influence of the low will at last have disappeared as the ridge edges in from the west so a much better day all round with plenty of sunny periods once any mist/fog has cleared. Might be a few showers in the north where the northerly wind will be quite fresh. Generally quite a cool day The ridge more or less in control on Monday so a fine day after a frosty start in places, but a shallow low is quite adjacent to the south east so some rain here A not dissimilar day on Tuesday but the pattern that has been previously discussed is unfolding and there is now an elongated trough with a positive tilt to the west and this willbring some rain and strengthening winds to the north west late in the day Over Tuesday night and through Wednesday developments occur along this active trough and by Wednesday there is quite a deep surface low to the north west of Scotland and this will effect the norther half of the country whilst the south remains under the influence of the ridge
  8. The EXT EPS not dissimilar to the GEFs with the European high ridging norh west between the TPV and the Atlantic trough
  9. Indeed ba but i didn't post this originally/ Just trying to ensue that there is no misunderstand vis the anomaly
  10. Yes but not entirely. Superimposed on a MSLP analysis.which you can read in the normal way
  11. knocker

    Kenwyn

    A peaceful Autumn stroll through one of Cornwall's 'living' churchyards
  12. The ext GEFs is certainly not without interest with the expansion of the European high between the TPV over northern Russia and low pressure to the south and west of the UK
  13. Everyone is aware of the preamble so just a brief look at t144 .> T192 with the gfs this evening Essentially it can be summed up by the Atlantic trough disrupting as the European high pressure amplifies west resulting in the N/S split over the UK becoming more generally dry and sunny. And to enter briefly into the spirit of the thread, a toasty Europe
  14. Equally one could say a weak trough covers the Atlantic centered near Iceland probably indicating south westerly zephyrs Lovely jubbly
  15. Glacier ice volume in Switzerland has decreased from about 70 to 50 cubic kilometres since year 2000. Red numbers show years with more than 2% ice volume loss. The frequency of such catastrophic years is obviously increasing... Also this summer has been hard for our glaciers. https://twitter.com/matthias_huss
  16. As expected frequent heavy and squally showers here today with some impressive Cbs around. So the midday ascent no surprise. clouds tops up to 20,000ft maybe
  17. No I haven't paid but I don't know who has access to papers on here via academic institutions/libraries. etc. Yes the book is excellent, if rather expensive when I bought it, but I freely admit much of it is way above my pay grade
  18. Some very brief notes on transport processes in the Stratosphere and Troposphere Introduction Transport of air across the tropopause plays an important role in determining the chemical composition, and hence radiative properties, of both the troposphere and stratosphere. Quantifying this transport presents a significant challenge on account of the many multiscale processes involved from the global scale mean meridional circulation, through intermediate advective and convective processes, to molecular diffusion. It has long been recognized that tropospheric air enters the stratosphere principally in the tropics, and moves poleward in the stratosphere. To understand the large-scale circulation in the troposphere and stratosphere, it is useful to look at transport processes averaged around a latitude circle. Ozone production mainly takes place in the tropical stratosphere as the direct solar radiation photodissociates oxygen molecules (02) into oxygen atoms (0), which quickly react with other 02 molecules to form ozone (03). But most ozone is found in the higher latitudes rather than in the tropics, i.e., outside of its natural tropical stratospheric source region. This higher-latitude ozone results from the slow atmospheric circulation that moves ozone from the tropics where it is produced into the middle and polar latitudes. This slow circulation is known as the Brewer-Dobson circulation. 7.2 The Brewer-Dobson Circulation Figure 7.1 shows the zonally averaged circulation in the middle atmosphere superimposed on top of an annual average ozone density. The Brewer-Dobson circulation is represented by the thick arrows. The figure also shows the seasonally averaged ozone density from north pole to south pole. The Brewer-Dobson circulation is a slow circulation pattern, first proposed by Brewer to explain the lack of water in the stratosphere. He presumed that water vapor is freeze-dried as it moves vertically through the cold equatorial tropopause (see Fig. 7.1). Dehydration can occur in this region by condensation and precipitation as a result of cooling to temperatures below 193 K. The lowest values of water are found just near the tropical tropopause. Later Dobson suggested that this type of circulation could also explain the observed high ozone concentrations in the lower stratosphere polar regions which are situated far from the photochemical source region in the tropical middle stratosphere. The Brewer-Dobson circulation additionally explains the observed latitudinal distributions of long-lived constituents like nitrous oxide and methane. This conceptual model has since been refined but not drastically altered. That Brewer-Dobson circulation is controlled by stratospheric wave drag, quantified by the Eliassen-Palm flux divergence, sometimes lays claim to the extratropical pump (as shown in Fig. 7.2), with the circulation at any level being controlled by the wave drag above that level. However, the wave drag can be difficult to compute accurately and it is common to diagnose the mean circulation from the diabatic heating. It is possible to estimate the net mass flux across a given isentropic surface from the diabatic heating. On the other hand, transport of material along isentropic surfaces, such as that between the tropical upper troposphere and the lowermost stratosphere, is more difficult to quantify, especially the net transport of a given species that results from the two-way mixing. Observations show that the composition of the lowermost stratosphere varies with season, and suggest a seasonal dependence in the balance between the downward transport of air of stratospheric character and the horizontal transport of air of upper-troposphere character. For any time period, the integrated mass flux to the troposphere at middle and high latitudes is the sum of the mass flux across the 380 K potential temperature surface, the net mass transported between the tropical upper troposphere and the lowermost stratosphere, plus (minus) the mass decrease (increase) of the lowermost stratosphere (Appenzeller et al. 1996). The first quantity is easy to compute, but the last two quantities are sensitive to small-scale processes, including synoptic-scale disturbances and convection. The classical picture of the stratosphere-troposphere coupling has evolved over the last few years. Such developments and tuning are essential for a good description of processes that are important for the stratosphere-troposphere coupling. Source: K. Mohanakumar, "Stratosphere Troposphere Interactions
  19. The ext EPS mean anomaly pretty much as expected. A fairly diffuse vortex N. Canada > N. Russia (main center), ridging into Greenland and a week trough in the eastern Atlantic. Ergo a slack westerly upper flow suggesting a quiescent period of weather with temps average or a tad below The hills are alive to the sound of music
  20. Effects of the QBO in the Stratosphere and Mesosphere Although the QBO is observed to be confined to within about 25° north and south of the equator, its effects extend throughout the stratosphere (Naito and Hirota 1997). Coupling to the extratropical stratosphere is understood to depend on the modulation of planetary-scale waves. During the winter season, when stratospheric winds are strong and westerly, planetary-scale waves propagate upward from the troposphere and are refracted equatorward in the stratosphere, depending on the structure of the zonal mean wind field. By modulating the direction and reflection/absorption of the planetary scale waves, the QBO induces a remote effect at high latitudes in winter, especially in the northern hemisphere where planetary-scale waves are largest. The effect of the annual cycle of planetary wave propagation, together with the QBO’s effect, is observed to modulate dynamical quantities, such as temperature, winds, wave amplitudes, potential vorticity as well as chemical constituents like, ozone, nitrogen dioxide (Zawodny and McCormick 1991), aerosols, water vapor, and methane. The QBO’s influence is seen in subtropical ozone variability during the winter-spring season in both hemispheres. Effects of the QBO may also be seen at the stratopause where the descending westerly phases of the stratopause semiannual oscillation are strongly influenced by the underlying QBO. Near the mesopause, observations show a well-defined QBO, which may be driven by the selective filtering of small-scale gravity waves by the underlying winds they traverse. Chen and Robinson (1992) documented a statistical link between the phase of the QBO and the ionospheric equatorial ionization anomaly. A mechanism was proposed in which the planetary waves modulate the tidal wind, and by means of the dynamo effect, change electric fields in the E region, which can be transferred to the F region along geomagnetic field lines to cause variations in the equatorial ionization anomaly. 9.4.2 QBO Effects on the Troposphere The QBO’s effects on the troposphere are suggestive, but are not well understood. Gray (1984) has demonstrated an intriguing and significant link between the phase of the QBO and hurricane formation. The equatorial troposphere shows variability on the timescale of the QBO, but a direct link to the stratospheric QBO has not been established. It is possible that the QBO may influence the high-latitude northern troposphere through its effect on the stratospheric polar vortex. Coupling between stratospheric zonal mean wind and the mid-tropospheric North Atlantic oscillation is strong, but the cause and effect are not clear. It is possible that QBO-induced high-latitude wind anomalies penetrate downward into the troposphere (Gray 2003; Gray et al. 2004). 9.4.3 Stratospheric QBO and Tropospheric Biennial Oscillation Signals of biennial oscillations with periods ranging from 20 to 32 months are noted in the tropospheric temperature over the tropics (Sathiyamurthy and Mohanakumar 2002). The phase of the tropospheric biennial oscillation (TBO) in temperature does not vary with height from surface to the level of tropopause and is found to be associated with the intensity of the monsoon rainfall. Temperature over the tropical region shows Quasi-Biennial Oscillation (QBO) in lower stratosphere. Phases of the QBO and TBO in temperature meet at tropopause level (see Fig. 9.6). Where they meet, phases of the QBO and TBO are unsynchronized during the decade 1971-1981 and synchronized during next decade, 1982-1992. The QBO in zonal wind has neither interdecadal variability nor disturbances. Source: K. Mohanakumar, "Stratosphere Troposphere Interactions
  21. Some further notes on the QBO that may be of interest (or not of course) Role of Quasi-Biennial Oscillation in Coupling Process In the tropical stratosphere, the dominant form of variability is a quasi-periodic (2-3-year) wave-driven descending zonal mean wind reversal, called the quasibiennial oscillation (QBO). The period of the QBO at any level varies from 2 to 3 years, and it could probably be predicted for about 1 year. The QBO is observed to affect the global stratospheric circulation. It modulates a variety of tropical and extratropical phenomena including the strength and stability of the wintertime polar vortex, and the distribution of ozone and other gases (Baldwin et al. 2001). Figure 9.5 illustrates the schematic picture of the dynamical overview of the QBO during northern winter (Baldwin et al. 2001). In the tropics, the stratospheric QBO is driven by the upward propagating gravity, inertia gravity, and Kelvin and Rossby gravity waves. In the middle and high latitudes, it is maintained by the planetary-scale waves. The contours in the tropics are similar to the observed wind values when the QBO is easterly. It can be seen that the QBO extends to the mesospheric region and even above 80 km. The QBO is driven by the dissipation of a variety of equatorial waves and gravity waves that are primarily forced by deep cumulus convection in the tropics. The stratospheric QBO effects extend to Earth’s surface during northern midwinter. There is also observational evidence that the QBO modulates the depth of the troposphere in the tropics and subtropics, affecting convection, monsoon circulations, and hurricanes. Although the amplitude of the QBO decreases rapidly away from the equator, observations and theory show that the QBO affects a much larger region of the atmosphere. Through wave coupling, the QBO affects the extratropical stratosphere during the winter season, especially in the northern hemisphere where planetary wave amplitudes are large. These effects also appear in constituents such as ozone. In the high-latitude northern winter, the QBOs modulation of the polar vortex may affect the troposphere through downward penetration. Tropical tropospheric observations show intriguing quasi-biennial signals which may be related to the stratospheric QBO. The QBO has been linked to variability in the upper stratosphere, mesosphere, and even ionospheric F layer (see Fig. 9.5). Source: K. Mohanakumar, "Stratosphere Troposphere Interactions
  22. The evolution of the ecm next week is not dissimilar to the gfs but some variation with the detail. Some snow over the Scottish mountains next weekend?
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