AWD

Increasingly noteworthy wave 2 activity forecast for the turn of the year now; http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/figs/ecmwf1/ecmwfzm_ha2_f240.gif This is likely to make NWP output rather volatile in FI.

From Ian; "W COUNTRY 0550GMT UPDATE F'cast remains consistent re earlier advisories. Add potential 50+mm rain totals Forest of Dean #FOD to previous. Rain establishes from W into AM rush-hr & no widespread relaxation of wet weather until early hrs Tues. Winds pick-up later this morning & into midday. Considerable localised flux on gust strength/impacts but to 50-60mph fairly widely."

Latest from Ian; "W COUNTRY Latest met office assessment indicative of widespread 50-60mph gusts inland tomoro with potential to 70mph as far N as M4 corridor. However, rainfall tally gives greatest concern: 25-50mm looking fairly broadscale, especially further S where totals highest. 60+mm feasible over uplands of e.g. Dorset Downs; S Wiltshire, etc. Expect locally to ca. 40+mm over Mendips/Cotswolds. Many of you asking re air travel tomorrow. Cannot pre-judge this, so please follow @OfficialBRS for any guidance/status tomorrow."

From Ian; "W COUNTRY Rain establishing from SW/W across region from Mon AM will continue - aside temporary drier interludes - through to early hrs Tues. Rainfall totals widely 10-40mm; highest (potentially circa 40-60mm) in S areas, e.g. SE #Somerset, #Dorset, S #Wiltshire. Very windy Mon too; a lot of local variation but strongest gusts to S'rn districts, potentially 60+mph e.g. Dorset/S Wilts. Winds widely gusting 40-50+mph elsewhere across region. Combined with many hrs rainfall, sig travel issues/disruption likely."

Don't the the boundaries or figures too literally, they're just there for a broad brush story of where both the wettest and least wettest places are likely to be tomorrow. Only you will know your environmental nuances that can affect rainfall accumulations local to yourself.

Here's my look at the upcoming weather situation for the next 24 hours or so. Firsty, a brief scour of the 12z High Res model output and where our low is currently. A look at the Atlantic satellite imagery shows our low starting to form now; This will rapidly deepen thanks to a strong thermal gradient consisting of both Canadian Arctic air and Atlantic Maritime air, fuelling a strong Jet stream with the UK as it's eastern target; This therefore, means a "cyclonic bomb" is heading our way; A look at what the 12z High Res models (primarily the NAE & EURO4) forecast for our region specifically then. We can see the rainfall hitting Cornwall tomorrow morning and spreading to most of the region by midday tomorrow; You can see there, once the rain arrives, it's with us for most, if not all of the day. The mass of PPN highlighted here; During the afternoon, to make matters worse, windspeeds will also become more notable, especially around coastal fringes. Winds currently modelled to gust around the 60mph - 80mph mark widely; I'm not going to dwell too much on the wind side of things though, as I feel windspeeds will be a more local, rather than regional issue and for many of us, rainfall accumulations will be a rather more problematic issue than windspeeds. I'll leave you with this chart courtesy of Meteogroup, which details Windspeed forecasts rather well IMO; One thing I will say though, is the tornadic possibilities tomorrow strengthen markedly, so be aware of localised structural damage if your in any squall/tornadic activity; Back to the more pressing issue of rainfall accumulations then and by the end of day tomorrow, both the NAE and EURO4 models show marked rainfall volumes across a large swathe of our region; Respectable agreement between the two there. If these were to verify, which is looking increasingly likely they will now, then we are certainly looking at flooding issues and river flooding over the Christmas period. With further, although less dramatic, rainfall progged for Tuesday, the 48hr accumulative rainfall charts look startling to say the least; Before I get onto my personal forecast, I'll leave you with the updated Meto FAX chart for tomorrow; A sub 930mb low possible tomorrow, centered NW of Scotland with gales/severe gales over much of the UK. Not often you'll see a depression as noteworthy as this over these here shores. Anyway, here's my summary of where I think we stand regarding tomorrow; The areas in red are the main areas at risk of high rainfall totals and flooding tomorrow. These include much of Devon, especially the moors, much of Dorset, SE Wiltshire and South Hampshire. Rainfall totals over the next 24/48 hours are expected to exceed 50mm widely within this area, locally much more too. You will notice a black circle over Dartmoor inparticular too. I strongly advise those of you within this black circle to be prepared and take action. Dartmoor and surrounding areas could receive biblical rainfall totals causing serious flooding, structural damage and a possible threat to life. This is no joke, the area within the black circle is in real danger of alarming rainfall totals. The area in orange, which includes much of Gloucestershire, North Wiltshire, Oxfordshire and also Cornwall will also receive high rainfall totals, although falling just short of those within the red areas. Areas within the orange zones should be prepared for upto 40mm widely, locally a little more. This again could cause flooding problems but hopefully not as severe as those within the red areas. The yellow area, which includes the Bristol and Somerset areas should get off lightest. Although still very wet, limited minor flooding is likely with many areas just experiencing obese puddles really. Typically 30mm in this area. That's my take on things anyway. I should be around a little more over the next 48 hours so of you have any questions etc, I'll try to answer them or if I can't, I'll pass it on to someone more knowledgable. I'll leave you with the latest BBC amber warning area which differs slightly to mine, but is equally, if not more important; Stay safe all and have a safe Christmas!

Another beefy hail shower passed over again. Nice dusting of hail for a few minutes.

Indeed.The NW NMM model is also much more detailed. When using charts like the above, I forget the printed figures as they are too vague for regional forecasts, and instead concentrate on the colour-scale bias.

The winds might be negotiable but the rainfall projections over the next 48 hours look startling to say the least. High res EURO4 model showing some places exceeding 100mm over the next 48 hours; I'll do a full forecast after the 12z output tonight, but I would be prepared for some flooding around the region on the run up to Christmas.

Nice hefty hail shower just passed through here. That's the closest I'm going to get to a white Christmas this year anyway. Very turbulent atmosphere though.

Could be an interesting evening for many of us. Snow, sleet, hail, rain, thunder & lightning all possible for a lucky few of us around the region. It does seen to be splitting/weakening as it continues into the West Country though.

EURO4 accumulative chart agrees; Zilch aside from a speck on Dartmoor.

Latest EURO4 output tones down snow signal for tomorrow now, limiting it chiefly to Mendips & Wiltshire plateau area; NAE somewhat differs entirely though, giving Wales the main bulk of wintriness; I'm not too sure how much we can forecast an event like this though when taking into account how borderline and detailed it is. Marginal local nuances & environmental conditions along with PPN intensity and evaporative cooling could ultimately swing it one way or another.

Half way out now. http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=euro4&MODELLTYP=1&BASE=-&VAR=prty&HH=18&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

That's the 0z mate!

Yup, as anticipated, a squall like feature is starting to develop and move E within the mass of PPN.

Latest from Ian; "W COUNTRY Mostly rain/hail showers Thurs PM. Chance of snow very knife-edge for complex reasons but most likely Glos uplands later afternoon. Most of region (if not all) should be ok tomoro & miss snow. Glos northwards into Midlands/Pennines, plus S & E Wales, higher risk. So, we currently run with notion of snow possible Exmoor, Mendips & more especially FoD/Cotswolds later Thurs. Less likely lower.."

Also worth noting the intensity of the rainfall forecast later this afternoon, some right old heavy rain possible, with no doubt, an embedded squall somewhere amongst the mix; And 24 hours later we have this; Bring it on, some active weather at last, even if not all IMBY!

We can't see the freezing level associated with the EURO4 and NAE models but if we look at the GFS, the WBFL never falls below circa 400m, so anything to lower ground looks rather unlikely at this stage, perhaps rather reliant on evaporative cooling etc;

The NAE is still available and running alongside the EURO4 model as of now. Until it gets withdrawn then we have 2 high res models to assess short term forecasting conundrums with. Although I agree, the NAE isn't the best, it will be interesting to see whether the EURO4 model is better.

EURO4 model shows small accumulative snowfall projections for Exmoor, Dartmoor & The Mendips by Fri AM;

I've heard there is a slither of an opportunity for some white stuff tomorrow night for a few of us. Best start getting more involved then now the stalemate Euro high is finally slipping away. EURO4 model gives the moors of SW England a period of rather heavy snowfall tomorrow night; Compared to the NAE, with any snowfall concentrated further north towards the Cotswolds; Now we have access to the EURO4 model, it will be interesting to see how it performs against the NAE for short term forecasting.

Worth noting the EURO4 model differs from the raw NAE, with snowfall forecast further SW, over the moors of Devon & Cornwall especially; Interesting times ahead though, a respectful possibility of some white stuff for some lucky southerners!

A new model to play with soon; "Hot news from http://Weatheronline.co.uk The new UK Met Office 4km model is going to be available from weatheronline today or tomorrow :)"

Agreed: