Spring Model Discussion 21st March 2013 006z onwards...

[peterf]

Probably working, doing what he gets paid for weather wise, rather than the superb voluntary posting he does on here.

Your post was made 15 minutes after his live BBC Points West forecast so I expect he was on a break or beginning to work on

the late evening forecast.

I cant believe Ian would be stopping for a break with the current potential.

[lorenzo]

The Greenland High. Everyone's favourite late Winter Guest.

NWS have it cranking in at 1074mb...!!!!!

[-uksnow-]

In my eyes that ensemble mean is excellent!!to show a clear undercut on a mean chart that far out is brilliant!!looks like it supports the operational to me!

The op ^ - in my eyes, not huge similarities, low not undercutting half as well, but at 7 days away is to be expected, clearly there is some support for the op, i just said the mean seems fairly distorted, indicating there are several other conflicting options.

-eded-

[Man With Beard]

One question I've been thinking is - just how long could this go on for?

Taking the T240 chart which I imagine would be one of the more extreme endings:

you can see the cold feeds to the north and east finally dwindling, but there's still enough cold there for a further few days. So I'd say there is up to two weeks left of continuous nationwide snow/winter cold potential in the models (if everything falls into place of course). Just speculation of course.

[damianslaw]

A very wintry synoptical outlook - northern parts in particular will struggle to see maxes much above 2 degrees in the coming days with very harsh frosts from Sunday night onwards. The current synoptical output is the kind of set up that delivered the famous winters of yesteryear - a locked in cold pattern with robust heights over the pole and greenland, a bitter cold pool of air to the NE and a very southerly tracking jet, the three key ingredients to a freezing winter...

The reason for why the set up is so cold is largely thanks to the extensive cold pool to our NE which has been in residence for a very long time with virtually no atlantic influence all winter - hence the sub -10 uppers being forecast. In other years the current synoptics wouldn't be delivering the projected cold weather as normally the air to the NE would be a few degrees milder than it is now, thanks to atlantic impacts - especially in the last 20 years or so, exceptions winter 95/96 when the air to the NE was very cold.

NW Russia and Scandi must on course to record one of their coldest Marches of the last 100 years I'd imagine.

Looking towards easter - no sign of anything particularly mild, easter looks like being cold, or average at best.

[Iceni]

Below is the up to date zonal wind profile, would think that with the complete deletion of postive zonal winds over such a period of time it is hard to rule out a lagged influence from the SSW, although not an exact fit with expectations at the time of the SSW and the Cohen climatology ideas.

Looking at the balance of probabilities and this March turning out the be exceptional. We had a strong SSW event and therefore a strong response.

In consideration of March temp records 47 /62 / 63 am sure have been mentioned in posts regarding colder March months of previous years, perhaps someone who has links for these can review, I don't have any bookmarked.

Chionos last post in detail is here. Would be good to read his thoughts on this.

From my memory (I was 11) the snow started melting the first week of March 1963 and had all gone by the 13th in West Sussex.

[Summer Sun]

Well the ECM ensemble starts to shift the coldest uppers away later next week

And the ensemble in full the control and Op both get into positive territory eventually

[legritter]

Brilliant charts again for us cold snowy lot with more good news if you like it cold .reading todays posts yes its been an unusual March and some have had snow but not all .March was due a cold and snowy spell thats the weather folks ,given our position being fairly well north even april could deliver .and just a thought, i read somewhere last summer /autumn that this winter could be the warmest ever because of low sea ice and higher sea temperatures ,lets continue to enjoy these charts and data before the Atlantic comes powering through .im looking for a tiny channel low next week, but it must keep just south of IOW , off with wife for 5 days break ,cheers gang hip hip hip Hooray for the charts .will they one day control the weather .

[Harsh Climate]

Latest NAE is a huge upgrade for some!

[Matty M]

Big totals now likely for the midlands and surronding parts, a foot of snow (30cm) possible in major cities such as greater Birmingham area.

The second front is set to tilt around its axis Friday night/Saturday dumping a serious fall of snow.

Per NAE.

Immense run for some of you lads. Get your sledges ready!

[Methuselah]

Well the ECM ensemble starts to shift the coldest uppers away later next week

And the ensemble in full the control and Op both get into positive territory eventually

Nice to see Algeria warming up a tad, Gav...

[Harsh Climate]

lol @ 18z NAE - 2 foot+ snow falls for the high ground of northern ireland and sheffield.

[pandit-scholar]

I would go with this too, I think the SSW was about a 6 week period or so. On that basis, today is 7th Feb or thereabouts. Would it have been colder had there not have been a SSW?

The sun is unusually quite at the moment. May have an effect but the research on this is still at the early stages!

[Matty M]

Parts of eastern NI still remain in a severe red zone. Some upland parts there could be absolutely snowed in by Saturday evening, under 2 feet or more. INSANE.

[shaky]

Latest NAE is a huge upgrade for some!

Oh my days am gona get buried!!

[Harsh Climate]

Parts of eastern NI still remain in a severe red zone. Some upland parts there could be absolutely snowed in by Saturday evening, under 2 feet or more. INSANE.

As Ian Ferguson mentioned earlier, power line accretion looks very likely, I can see whole villages/towns having there power cut off.

I think a red warning certainly needs to be put up now for high parts of northern ireland and north east wales at the very least.

Edited March 21, 2013 by Harsh Climate

[kev238]

Can't help thinking that this event could be more serious than warnings suggest, a red warning was issued in January for the valleys of wales and this event looks at least as severe for the peaks!! nae defo boosts amount of precipitation, can't find out as yet heat it suggest falling from sky! Might have decided to turn everywhere wet although this seems unlikely!!

[chris55]

As Ian Ferguson mentioned earlier, power line secretion looks very likely, I can see whole villages/towns having there power cut off.

I think a red warning certainly needs to be put up now for high parts of northern ireland and north east wales at the very least.

accretion,lol.

[Cheshire Freeze]

As Ian Ferguson mentioned earlier, power line secretion looks very likely, I can see whole villages/towns having there power cut off.

I think a red warning certainly needs to be put up now for high parts of northern ireland and north east wales at the very least.

You could probably draw a triangle of high risk....Liverpool across to Sheffield down to Birmingham. Then parts of NI.

[shotski]

You could probably draw a triangle of high risk....Liverpool across to Sheffield down to Birmingham. Then parts of NI.

That would be the four cornered triangle then

[UV-RAY]

That would be the four cornered triangle then

An Irish triangle.

[SomeLikeItHot]

Certainly a lot more precipitation into East Anglia on both GFS and NAE on this run.

[Cheshire Freeze]

That would be the four cornered triangle then

No the triangle I'm referring to is Liverpool-Sheffield-Birmingham

[Harsh Climate]

Will be nice to see the NAE rain/snow charts when they update, should look lots better

Edited March 21, 2013 by Harsh Climate

[fergieweather]

Where is ian ferguson?!want to know where he thinks the highest accumulations are gona be over the next 48 hours!

Sorry - having to focus tonight on nowcasting for my BBC Sport colleagues in Sepang.

Basically, good cross-model support now for widespread 5-10/15cm at lower levels up to early Sat (E.g. EURO4 has 10cm across likes of Essex-Herts-Beds; 5cm Cotswolds; 10cm Chilterns; fading to 1-2cm into M4 corridor with patchy trace amounts down to Salisbury Plain, Mendips Plateau etc.). The core risk area (note that more ambers may be added elsewhere tomorrow) remains as before, e.g. Shropshire hills etc: 30-40cm here and much deeper drifts. The stark high-res topographic shadows such as across Manchester are considered overdone, wIth a 'smoother' mappIng preferred as eventual outcome, albeit they highlight a fair steer on overall story of very variable local amounts.

The substantial weakening and reduction of PPN rates/amounts by early Saturday onwards into S/SE has good continuity now, i.e. as the upper forcing tends to overrun....

Anyway, gotta get back to my other duties now focused on steamier climes! Hope this all helps... cheers...