FetchCB

I believe someone mention ( cannot recall who) that the most destructive SSW's occur when the Vortex is at its strongest ie blows itself apart. It would seem to make sense that if the vortex is not mature ( structurally sound) then this may lead to such an event? The maths in the link are beyond me but the conclusion does seem to be that the structure of the vortex can lead to an SSW http://www.columbia.edu/~lmp/paps/matthewman+etal-JCLIM-2009.pdf

I think Ian did explain that these models are used to guide as opposed to outright forecast. The maps that have been posted on here do carry a health warning from the Met in regards to the conclusions that may be drawn from them and from reading the material that accompanies the charts i would say that they owe just as much to statistical science as they do to actual NWP.

Page 8 of interest ...similar pattern to this year for December ? Cold frosty start to December ,milder middle part of December...... https://www.rmets.org/sites/default/files/abstracts/Mar/16032013-burt.pdf

http://www.bbc.co.uk/news/world-asia-38088036 I've seen several references to 1962 in the model and Strat thread so far this Autumn.............

Just to expand the previous answers. Your camera has contrast-detect auto-focus which means it looks for contrast in the picture to decide what to focus on. When there is no lightening the contrast is low ( low light levels) and as such the auto-focus has to hunt for something to focus on. When there is lightning the contrast in the cloud as well as light levels improve so it can focus on the clouds. Manual focus set to infinity will mean everything from approx 1m to infinity will be in focus assuming you are shooting at the widest available view

Thing is warnings have a function that sit outside of just warning us weather geeks that the weather is going to be 'out of the ordinary'. In addition to warning the public they also set off protocols within the emergency services & responders. Therefore the area being warned may be larger because of the potential to disrupt needs to be planned for and without an official warning those resources will not be in place.

Hi Chris Yes its true to a degree. This link from Reading University explains how weather models are affected by Chaos Theory http://www.met.rdg.ac.uk/~ross/Documents/SchoolTalkA.html For this reason, put very simply, Met Offices run ensemble forecasts varying the initial conditions to get a range of outcomes. Your comment in regards to the data sets is I believe a well accepted fact ( or is it an urban myth) it certainly seems to be the case when the models try to model say an Arctic High then the variability of the models can be extreme

Looking at the following page http://www.jma.go.jp/jma/en/Activities/nwp.html it would appear that they only use low resolution ensemble forecasts for 1 week out. However there is a number of reports on the strat available here http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/

Feb 2009 Streamer analysed by Paul Sherman https://forum.netweather.tv/topic/53635-thames-snow-streamer-event-12nd-feb-2009/

Interestingly the Met Office forecast on the Met Office Home page as of midnight last night says that the snow will push all the way across to East Anglia although it may take its time and that it will be heavy at times.

I thought this but then again if the front is going through quicker...less snow

I thought this band was to slow up as it moved east? Appears to be moving through quite quickly

Up til now been fairly relaxed...Heathrow has been showing snow event, now according to the forecast it shows sleet.....*begins nailbiting*

met office have tweeted in response to a question for NW London with 5-10 cm overnight Saturday and Sunday Morning

Just watched the forecast on the BBC website...unequivocally snow not turning to rain heavy and disruptive. my fear....I have recollection of such an event back in the early 90's I was in Twickenham and the front got to within 20 miles of us. It was snowing heavily in Slough but virtually nothing in Twickenham

Love the line "It appears that insufficient attention was paid to stratospheric winds in this period" Surely the skill of forecasting is about the weighting of various factors and that weighting must be consistent ?

As defined by the National Hurricane Centre Tropical Cyclone: ( of which a hurricane is a classification of) A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects). By the time Katia hits our shores she will have morphed from being a Warm Core Tropical Cyclone into a Baroclinic Storm and this was the point that Peter Gibbs was making.

Given nature abhores a vacuum then the lower the air pressure the higher the sea level. In effect the low pressure creates a dome of water under the eye http://en.wikipedia.org/wiki/Storm_surge

According to NYC Office of Emegency Management http://www.nyc.gov/html/oem/html/home/home.shtml a CAT 3 could cause storm surge that would flood Wall Street

Potential impact on NYC and Long Island of a storm surge http://www2.sunysuffolk.edu/mandias/38hurricane/nys_storm_surge_zones.pdf

A Forum site that covers the Carribean http://stormcarib.com/

Photography is always going to be a compromise on what the human eye sees and even then everyone else sees the same scene different. In some respects this is the analogue versus digital argument that has raged all spheres of arts. When i started photographt we used film and filters to "change/enhance" what we saw. Even then the film we chose could give differing characteristics of print. To my mind I see no problem in post production because in effect "photoshopping" is no different from what was done in the darkroom. If you wanted a punchy picture you would slightly underexpose and print onto a specific paper. It still takes skill, albeit a different one. the only difference is and to me this is the biggest plus , is that I can take a picture and get a decent result, sometimes a great one whereas in the analogue age I would take a picture and a week later I would discover whether it was any good and if not well the momemnt had gone. I see the term natural being badies about and wonder what that is. Does that mean unprocessed but all jpeg photographs are processed with differeing manufacturers having there own algorithm. So is the true natural RAW but again we are subject to manaufacturers processes, is it the human eye? but recently an opthalmic surgeon is suggested that JWM Turner, suffering from early, slight colour-blindness and later cataracts, was painted exactly what he saw but when you or I look at we struggle to recognize the scene. I think the phrase "beauty is in the eye of the beholder" sums it all up

Looking at the Ensembles it looks if the Op run has overdone the depth of the pressure( as the GFS is prone to doing) .It is on its own and I supsect that is why it goes off on a tangent like it does in blasting away the European Block

Where is the warm front?

The met office have a finer resolution model but that does not go out to anywhere near 12 days. No model can be that specific. GFS does go out that far but to take it as gospel borders IMO as lunacy