Interitus

This "theory" first did the rounds a few years ago and unfortunately it is as wrong now as it was then. To start with, the Taklamakan desert and Tamir basin are not a source of warm air in winter, it is typically bitterly cold with temperatures below freezing. For sake of argument and assuming anomalous warmth, a bigger issue is that positive omega represents sinking air - negative omega is rising air. But the biggest problem is that it fails to grasp the stratification and stability of the atmosphere. Ironically it is dismissive of moist processes which actually go a long way to overcome the stability, but also the tropopause which magnifies the scale of the problem, and also that adiabatic cooling would continue up to 10mb. A convenient way to examine it is with consideration of potential temperature to compare the density of air at different altitudes. Theoretically, parcels of air with equal potential temperature are equally buoyant and interchangeable. Indeed for much of the atmosphere this holds true with isolines of potential temperature forming natural flow pathways - see isentropic analysis. At the 10mb level in the stratosphere, potential temperature might be in excess of 850K - this would be the temperature an air parcel here would have if brought down to 1000mb. Conversely, an air parcel from near the surface would have to be much more than anomalously warm to remain buoyant at 10mb, rather hundreds of degrees C. Studies of large forest fires have shown estimated surface temperature perturbations of 60C initiating large pyro-cumulonimbus clouds but the significance of latent heat release from adiabatic processes was 3 times that of the sensible heating (ie the fire). This is able to overshoot into the lower strat like regular storms but further uplift is capped by the tropopause. Examination of volcanic eruption plumes shows only the largest would be capable of reaching above the middle stratosphere. In any circumstance it must also be remembered that air parcels in reality are subject to substantial mixing and entrainment of the ambient air. So there is no 'launch pad' producing a plume of warm air to 10mb (even the driest desert air would produce clouds as evidence), mountain uplift creates air parcels which rapidly become denser than the environment and negatively buoyant, returning to their initial level - or actually oscillating above and below this level ie orographic gravity waves.

Breakdowns can sometimes show a tendency to be delayed with cold hanging on, but what's amusing is that when these charts appear is the common insistence is that they are wrong and the colder output is more likely, rather than the writing's on the wall.

Talk of a March easterly and 'downwelling' - where is this downwelling from? Sometimes have to face the fact that tropospheric disruptions may follow an SSW but might not actually be directly caused by one.

Illegal flock ins.

Andrewsfield data is available quite widely as it is a SYNOP site so is carried by Ogimet for example - enter the WMO number in this form - Form to get daily summaries from synop reports WWW.OGIMET.COM Hourly data can be found by clicking on the dates. Skylink offers a wider range of sites, some that weren't available on weathercast. Not convinced by the accuracy of all the stations but a potentially useful and interesting resource - SkyLinkWeather Aviation - Latest Weather for London Stansted SKYLINKWEATHER.COM Current weather for the UK, Europe, Australia and New Zealand Alas no Writtle...... but for that try weatherobs, fantastic site, possibly better than weathercast for viewing observations, which includes the additional Met Office sites as well as the standard WMO SYNOP and METAR locations - Weatherobs WWW.WEATHEROBS.COM Global weather observations (METAR, SYNOP, BUOY, SHIP, TAF, CWOP) decoded to enable display of latest temperatures, weather, snow depths, precipitation, wind and wave conditions and more

Why is your wet bulb temperature warmer than the dry bulb?

The thing is the 528 DAM is deceptive, it is representative of the temperature between 1000-500 mb but despite mention of 'deep cold', it is actually concentrated in the lower levels of the atmosphere. Temperatures up towards 500mb are not especially cold relatively speaking - indeed it soon becomes a westerly flow above the easterly lower down. The repercussions of this means it's cold near the surface, which is want you want for snow, however with regards to shower activity it is largely developing below the 800mb level generated by surface forcing, there is limited deep convection. Taking this precipitation chart for Monday as an example - The black line in the middle from roughly Liverpool out into the North Sea is represented in the cross section below - This shows vertical velocity - vertical air movement. Following the direction of wind flow from the east on the right hand side and comparing to the precipitation chart, there is gentle convection (max at about 700mb) over the North Sea producing showers, shown by the upwards arrows on the chart. Moving leftwards (towards the west) the showers are enhanced on meeting the Lincolnshire Wolds but the uplift is only up to about 800mb, the air is quite stable and the topographic wave forms a descending air at 750mb reducing shower activity inland. Moving further westwards, upon approaching the Pennines, there is strong uplift below 850mb, producing heavier showers, but the topographic wave and strong descent caps development to below 800mb and effectively kills showers to the west of the Pennines, on the left hand side of the chart. One way this flow pattern may breakdown is suggested by this run on Tuesday evening is a convergence zone (sometimes misleadingly described as a streamer).

It's a discussion forum, disagreement should be permitted (unless in the MOD thread, obvs.)

The notable March 2013 snowfall chiefly between 22-24th, a report from the Met Office - https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/weather/learn-about/uk-past-events/interesting/2013/snow-and-low-temperatures-late-march-2013---met-office.pdf

It's not what has been inferred at all, in the same way that it's not been made out the people can't be interested. It has been regularly posted to ignore the precipitation and snow depth charts. Of course showers are parameterised in NWP output, and it isn't always precise, but equally they won't be a million miles out, that's just wishful thinking, unless some trough or other feature etc. materialised. Think your analogy was wrong, you're winning the tenner

However, March 2013 was a frontal system.

Ok, lol, and on these occasions what were depths like in other parts of the country? It's almost like people are insinuating that this area is a match for other areas for snow showers in an easterly, it beggars belief!

People are bigging it up, it's *possible* that there could be widespread notable depths, but the balance of probability is that it is unlikely and it will pale in to insignificance compared to other regions which will be worse affected. Without some frontal activity, that is the reality of the situation for most parts of this region away from the Pennines.

Most of the North west typically gets naff all from an easterly, BFTE was no different. Sure, maybe a few cm here and there, and if that floats your boat then fair enough, but it's not the foot plus that some charts are touting for eg the eastern side of the Pennines or East Anglia.

Indeed, thanks for saving me from explaining it The deceptive thing is how far advanced the precipitation is from the front at the surface - so the milder air is not at the back edge of the snow/rain. There is quite a sharp temperature contrast at the surface eg. North Wales 8°C at Capel Curig, 1°C at Lake Vyrnwy 29 miles and 4°C at Rhyl 23 miles distant; in Herefordshire 9°C at Hereford, 4°C at Shobdon 15 miles away. But the rainfall has long cleared these areas.