nick sussex

The ECM shows why the behaviour of those shortwaves in the Atlantic is crucial , however as long as the shortwave to the south doesn’t deepen too much before engaging the trough over the UK this can be overcome .

Good to see the UKMO dropping it’s underwhelmimg output and after the shortwave frenzy this morning the mists are beginning to clear slowly. However we’re not there yet and so my Code Red remains! Its not so much that we won’t see some build of pressure near Greenland but getting that clean northerly flow south is still subject to shortwaves upstream behaving . Overall so far this evening an upward trend for coldies.

Atlantic shortwave frenzy means the road to gold is littered with huge obstacles! Dear me not the best start to the day with now a convoluted and traumatic evolution to the promised land. The shortwave love-in in the west Atlantic means any evolution is Code Red with extra conselling on offer! We've lost the clean evolution of last nights ECM and GFS and gone to the Da Vinci Code.

They just have, not been modified they’re a carbon copy of the op run.

True! I’ve got the NW helpline on speed dial for tomorrow morning! Given how close in the differences are with 6 hours newer data surely the UKMO must be wrong given the GFS isn’t interested. We have a few more 18hr outputs to come out, let’s see whether they turn to the dark side!

If the UKMO is wrong it will go down as one of the epic fails ! Close to surpassing even some of the GFS specials of recent years . The GFS has shown absolutely no interest in following it on the 18hrs run.

This thread seems to have taken on a rather negative tone with some sniping. Its like The Walking Dead where the humans (coldies ) start turning on each other instead of fighting the real enemy zombies ( mild mush )! Barring a few mildies who slipped through the vetting procedures we’re all on the same side!

As soon as NOAA trash tonights UKMO I’ll be back to report it!

Very hard to judge what would happen next on that crappy UKMO T144hrs output. It looks like it will amplify the Pacific troughing as it moves east which down stream would sharpen up the pattern over the eastern USA but the issue is that shortwave phasing . Its not a given that we can’t hang onto some colder conditions but it’s impossible for the UKMO to look anything like tonight’s GFS as you’re past the point of no return by T144hrs.

Great from the GFS so far more amplified , the UKMO is poor in comparison and the differences start at just T96 hrs with the handling of shortwave energy to the west . The GFS splits this allowing the high to retrogress at T120hrs hrs the UKMO doesn’t and boxes the high in. It’s like pulling teeth sometimes , can we just have a drama free evolution !

Looks like the models are latching onto the retrogression of the high with the ECM delivering an excellent evolution to locked in cold for some time to come. Strong Arctic high and Greenland ridge in combination with sinking trough is very good, the GFS still not quite as interesting so something to bear in mind. In terms of the upstream pattern a word of caution because the pattern in the east USA which allows the evolution to retrogress the high and then subsequently help the low to drop south is still uncertain. That's effected by an amplified trough heading in from the Pacific which impacts on how energy comes off the ne USA into the Atlantic. The big 3 disagree upstream at T144hrs so still a lot to be resolved.

I'd be a bit wary of the outputs at the moment as they seem to be caught between two evolutions. At this point I'd prefer an easterly or ne as that's possible given our starting point. My reservations re retrogression is whether we'll end up with the block too far west which happened last week. One wasted block is enough in two weeks, a second would be an insult to coldies in here!

Very good point made Feb , that’s why I’d rather the models went for the Scandi high because that’s easier to get through from where we start than the retrogression . We don’t want half measures.

Temps should plummet over the Continent with that decent upper cold and slack flow which could be advected west towards the UK. This retrogression doesn’t look quite right to me , I’d rather have a holding pattern of cold easterly before then!

The ECM looks like it tries to bring a front se shown by that kink in the flow at T144hrs hrs . Possibly some snow off that depending on how much cold is ahead of that. Strange looking T168hrs almost a col over the UK , I’d rather ditch the retrogression at this point and try and get a Scandi high.

The ECM looks messy with some shortwave energy running over the block and trying to head back south . We need the jet loop back sw to cut under the high .

Be annoying! Lol I haven’t seen much about UKMO bias.

Some interesting comments from NOAA tonight re model bias: CONFIDENCE IN THE MEDIUM RANGE FORECAST IS AVERAGE WITH RESPECT TO REGIONAL DETAILS BUT PERHAPS ABOVE AVERAGE ON THE LARGE END OF THE SYNOPTIC SCALE...OWING TO THE FACT THAT THE ENSEMBLE MEANS SHOW GOOD AGREEMENT AND AS EACH OPERATIONAL MODEL SOLUTION MOVES AWAY FROM THE CONSENSUS AT SOME TIME INTO THE FORECAST...IT DOES SO IN A MANNER CONSISTENT WITH KNOWN BIASES. THAT IS TO SAY THE GFS TENDS TO ERR ON THE FAST SIDE AND INDICATES GREATER PHASING AT TIMES. THE ECMWF TENDS TO ERR ON THE SLOWER AND OVER-DEVELOPED SIDE

I see Karlos has posted that. Heres the link for you to bookmark: https://ruc.noaa.gov/hfip/tcgen/ There was always mystery surrounding the UKMO because Fergie posted they did go to T168hrs but we never had public access to it before. Its a shame we don't get the full European and NH views but todays T168hrs is excellent and people in here know I'm hard to please!

Its always a good sign if the models want to retrogress a high over the UK. You can think of it as a bellwether which signifies a lengthier spell of cold. All decent cold spells include retrogression because its very hard to sustain cold without that. In those situations you get a rinse and repeat scenario alternating between easterly and northerly, that's what happened in December 2010. I'm not for one moment suggesting another Dec 2010 is on the cards! That was a historic event and theres a reason its so rare.

Latest from NOAA: ...PATTERN ASSESSMENT AND MODEL CHOICES... INDIVIDUAL MODEL SOLUTIONS CONTINUE TO DIFFER BETWEEN EACH OTHER AND FROM RUN TO RUN FOR IMPORTANT DETAILS, BUT ULTIMATELY THE PATTERN EVOLUTION AND BEST APPROACH FOR REPRESENTING THE MOST LIKELY SCENARIO FOR EACH DAY DURING THE EXTENDED PERIOD HAVE CHANGED LITTLE OVER THE PAST 12-24 HOURS. GUIDANCE AGREEMENT MAINTAINS RELATIVELY HIGH CONFIDENCE FOR THE LARGEST SCALE ASPECTS OF THE FORECAST. EXPECT A PROGRESSIVE WAVE TRAIN TO BECOME ESTABLISHED ALL THE WAY FROM THE WESTERN PACIFIC ACROSS NORTH AMERICA, THEN SLOWING AND SPLITTING AROUND A PERSISTENT BLOCK OVER THE MIDDLE ATLANTIC OCEAN.

Upgrades all round this morning which is great to see. Better trough disruption to the west keeps the high further north. The ECM is now evolving differently with hints of retrogression and a Scandi trough. The UKMO is a huge upgrade on last night its T168hrs even with the restricted view is excellent. If retrogression is going to be the trend then any easterly even if it appears will be short however that's not bad because you might still end up with a northerly after. Things might get a bit messy for a while till the models catch onto the correct evolution but overall some positive signs this morning for coldies.

Heres an example of the infamous jet loop which delivered a short but sharp very cold easterly flow: Dec 26 2005: 12 hours later: Whats interesting about these charts is how even though you've got a mean looking PV to the north west you can still beat those odds and get cold. Although in recent winters that's been much harder. These jet loop easterlies normally happen when you have ridge over or near the UK at the outset and then you get lucky with the evolution. This was the chart a day earlier:

I've filled up the drinks bar in readiness! The ridge topple would be less stressful if the high was sufficiently north, the loop back in the jet way holds many bitter memories!

The GFS 18hrs run was very close to being very good but some shortwave energy popped up to the nw to force the high a bit too far south. If people thought the issues over the shortwave to the nw which heads se this weekend were nervewracking wait for this next drama to start because you'll need the loop back in the jet towards the Low Countries to deliver the easterly with tonights GFS if this is to be the new trend! Code Red initiated!