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Rest of November and into December

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Mark Bayley


[b]Note: Next update either on Thursday or Sunday/Monday. All images below will/have change/d as they have only been hyper-linked, will attach them on the next update [/b]

Thought it would be fun to have a go at a little longer range forecasting. I am by no means expert, however have learnt bits and bobs over last few years of my net-weather membership!

I shall be basing my thoughts on the stratospheric output, MJO forecasts, long range ensemble forecasts and CFS weekly charts. Instead of writing a detailed explanation of how we interpret the stratospheric output, i shall instead refer you to the stratospheric thread in the winter section (see page one).

[b]Stratospheric output[/b]
(I made a recent post about this, so shall take it and adapt it a little)

A rather positive outlook, for those looking for blocking (and something cold). Mean zonal winds are set to decrease at both the 10hpa and 30hpa level, which will strain the polar vortex (PV), as evidenced by the geopotential height charts posted later.
A warming at the 30hpa is also predicted, taking it above average, with the 10hpa not to far behind. Again this will only place strain on the PV, leading to disruption and fragmentation (and a -AO)
[color=#282828][font=helvetica, arial, sans-serif]Looking at the geopotential height charts we see a split in the vortex by day 10 at the 100hpa[/font][/color]
[color=#282828][font=helvetica, arial, sans-serif]With sighs of splitting right up to the 10hpa level [/font][/color]
[font=helvetica, arial, sans-serif][color=#282828]The GFS forecasts are of a simualr nature to the ECM, with a split in the PV at the 100hpa, and splitting as far up as the 10hpa level[/color][/font]
[b][font=helvetica, arial, sans-serif][color=#282828]MJO outlook [/color][/font][/b]
[font=helvetica, arial, sans-serif][color=#282828]The ensemble forecasts for the MJO vary, the UKMO that was keen on a move to phase eight now suggests a low amplitude phase two, which suggests the following composite. Although given the low amplitude im uncertain what effect this would have. [/color][/font]
[font=helvetica, arial, sans-serif][color=#282828][img]http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/UKME_phase_23m_full.gif[/img][/color][/font]
[font=helvetica, arial, sans-serif][color=#282828]The GFS seems determined to drive the MJO into a higher amplitude phase eight, then one. Which would suggest the following composite.[/color][/font]
[font=helvetica, arial, sans-serif][color=#282828]The ECM wants to drive the MJO through low amplitude phase one, two and three. [/color][/font]
[color=#282828][font=helvetica, arial, sans-serif]There seems great uncertainty in the MJO outlook, although on average from all the runs, i would probably suggest phase one seems more likely.[/font][/color]

[b][color=#282828][font=helvetica, arial, sans-serif]CFS weekly [/font][/color][/b]
[font=helvetica, arial, sans-serif][color=#282828]Not the most reliable charts but worth looking at none the less. Week one-two shows strong heights over Greenland, and lower heights to the south of us, which would lend support to a blocked and potentially cold start to December.[/color][/font]
[font=helvetica, arial, sans-serif][color=#282828]Week three to four also shows heights over Greenland, but shows lower heights by the 2nd half of the month [/color][/font]
[b][color=#282828][font=helvetica, arial, sans-serif]Ensemble[/font][/color]s [/b]
[font=helvetica, arial, sans-serif][color=#282828]Will update this later[/color][/font]

[font=helvetica, arial, sans-serif][color=#282828]Overall[/color][/font][color=#282828][font=helvetica, arial, sans-serif] [/font][/color]
Based on the output, i would suggest a blocked start to December, with the PV disrupted and fragmented (and a -AO)[color=#282828][font=helvetica, arial, sans-serif]. I also see support for height rises around Greenland. Despite the models chopping and changing on whether the coldest air will get us, i would suggest at some point, over the next few weeks, that there is a high chance it would. [/font][/color]
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Note the charts will change as i've used image URLS, will attach them as images next time, just in a bit of rush this evening :)

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Nice one! Looks quite concise and holds good use of the stratospherical and teleconnectical devices at hand- something that I would be inclined to trust in forecasts- good luck!

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Thanks :) Just need to remember to attach the charts next time as they keep updating with the change in runs!

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