Thundersquall

Wow, minus 0.27C! When was the last time the CET for December was negative degrees C? I predict this temperature to rise a little after Boxing Day, so am going to plump for bang on 0.0C.

Why the sudden drop in maximum temperatures between T+174 and T+192 on the GFS? They seem to drop 10C over much of the southern half of the UK. The 850 hpa temps do drop, but certainly not to that magnitude.

The outlook for the next two weeks, and let's be honest, is not just poor, it's worse than poor! Dear me - struggling to max above 10C on 21st May? I know that's FI, but this is becoming a trend this Spring I'm afraid. And a chance of snow next Tuesday morning - oh, dear. Winter just doesn't seem to want to release it's grip just yat!

I think we're turning the clocks back to January, judging by that chart for Sunday 2nd May 2010. Afternoon temperatures in region of +5C to +12C (1200) and +4C to +10C (18Z chart) Despite all the cloud we saw +20C in Bristol - therefore this will be a real and unwelcome shock to the system! http://www.netweather.tv/index.cgi?action=uk7dayx7;page=5;type=free;ct=4215~Bristol;sess=#forecast Brrr! 8C max at 10am, falling to 5C to 7C during the afternoon - not nice at all with that rain!

I didn't have access to a computer at the time yesterday evening, but I noticed some very high clouds lit up by the Sun, very late yesterday evening. It must have been late as EastEnders had already finished (it was about 8:40pm?). Wondered if these could have been Noctilucent clouds or Mother-of-pearl clouds? Also noticed an extremely long slightly spread-out contrail running North-South, and moving slowly eastwards. It must have been long as it was also spotted in Winscombe, about 15 miles to the SW. Anyway it was a very good Sunset.

While as good all passenger planes were grounded over much of Europe, I assume the skies were almost completely clear of contrails almost Europe-wide. A plus side of the enforced ban were the pure blue skies the weekend before last. Surely a lack of contrails followed by a sudden appearance of them this week has had a tamporary but profound effect on the weather and general climate? The difference over Bristol from clear skies once the planes started flying again was very marked!

I was watching the sunset from Durdham Downs Sea Walls in Bristol yesterday evening - may well have seen the "Green Flash" just after the last bit of Sun was disappearing behind the Welsh hills.

What happened to those temperatures of 22 to 26C over the SE UK and much of Europe to our East and Southeast that were showing in the charts about four days ago, albeit in the unreliable timeframe of T+300 hours onwards?

At last, the first signs into FI of some real heat beginning to build up over and to the southeast/east of the UK. The charts into the T+300's hint of temperatures into the low-20's Celsius, and possibly as high as 26C over the continent to our east and southeast.

An example of why we can't trust charts in the T+300's! 18Z T+312: 12Z T+324:

This storm on Sunday is a bit of a concern. Our presenter on BBC Points West described it as being akin to the one that struck in October 1987! Hopefully it will track as predicted and the UK avoids a repeat situation. On another subject I read this morning that we lost 0-3 so I'm not happy today!

Please could you let me know where to access these NAE charts, so I can access them and see previous and later charts? Many Thanks, TS.

With the Greenland High in place on the 12Z up to at least T+126, the Atlantic weather systems can hardly win out for any prolonged length of time. What I mean by this is that this is not a pattern suggesting a return to any form of zonality. That Low Pressure to our SW will probably just mill about with nowhere for it to move. The Jet Stream is also in the wrong place for Atlantic dominance. That strong purple core of 162 knots plus simply dives SSE keeping well away from the British Isles.

Of the face of it the 12Z is a downgrade, as by T+90 the milder southerly flow has become established. But.... is this the beginning of an evolution into a more Southeaterly / Easterly scenario? Well.... maybe, as that High appears over Scandinavia at T+96 and our Low Pressure begins to pivot in an anticlockwise direction. Looks like in reality, the Atlantic is going to try to win the battle by T+114. So a cold snap, yes, however not a long-lasting one.

I would hazard a guess that the boundary between rain and snow will be the area in the 30's millimetres. Anywhere north of this maximum accumulation would in my opinion be more likely to get snow. Bristol's roughly 2cm rainfall equivalent would get a decent 20cms snow assuming it all falls as snow and the temperature stays close to freezing.

On the subject of upgrades or downgrades, the 12Z charts are coming through. The charts are up to T+42, and yes, the track is a little further south and Low pressure is 5mbs higher at 980mb. Looks like a downgrade in terms of the Low pressure being much more filled and much further south and really only just grazing the Bristol Channel.

Could we be talking about damaging winds over Southern England and South Wales if this chart turns out to be accurate?

The 06Z run from GFS shows a Low pressure system moving in from the SW at T+48, then becoming progressively more elongated roughly NEbE-SWbW up to T+72. By T+108 is has resolved itself into a more rounded centre, centered over The Wash. Finally clearing away by T+138, but hot on its heels is another Low Pressure winding itself up off the SW Approaches. That takes a similar path (across the Bristol area?) but zips through and is gone by T+174 by which time it's already just to the East of Denmark. I think Bristol for example is right on the boundary between colder winds coming in from the ENE and slightly less cold winds coming in from the WSW. Any slight shift south of the predicted track (which often happens in these situations) and we stay in the colder air and are more likely to get snow (I am referring to the T+48 to T+90-ish time-scale). The strong Jet Stream core is, I think, too far south over the Straits of Gibraltar to have any oomph to push the track of these successive Low pressure systems a lot further north. And the upper air steering at 200hpa is generally blowing stright along the Low pressure's elongation, and not across it, further preventing any real push northwards.

Could some minimum temperature records for late February be broken next week? Looks like from mid-week there could be minus 11C or minus 12C in places from the Mersey to the Humber southwards.

Erm - Next Friday - Wow! If that comes off then we'd better batten down the hatches!

Minus 12C on Wednesday night for parts of Southern England? The 18Z charts are a stunner! Maybe a bit into FI but it is good to look at all the same.

Not getting my hopes up just yet, but Tuesday on the 18Z shows a massive Channel Low with monster amounts of precipitation centered over the West Sountry / SW Milands! Looks like next week could indeed get very interesting! There I was thinking I've had enough of the snow, was rather hoping for Spring to make an early appearance.

The 18Z is looking absolutely spot on for the South West for Monday morning, but wouldn't wish to be driving to work in the resultant snow if that chart came off! Don't drive anyway but that is beside the point really.

Hmmm - Westerly winds tomorrow morning - Bristol Channel Snow Streamer?

Wow, it would seem next week could see several snow events, as a succession of low pressure systems move across or just to the south of the UK. Monday looks very interesting for many places. Massive temperature gradient about 10C in the English Channel and only -1C over parts of SE Wales and SW Midlands. I admit I'm disappointed about the weekend - yesterday they were predicting mainly sunny weather, now Saturday and Sunday morning could see a wintry mix instead. Very interesing times ahead!