Winter Model Discussion 18Z 16/1/13 onwards.

[Buzz]

Interesting post from Ian F on the south west regional thread:

"Ps front splits Fri hence heaviest snow is AM with intensity easing into afternoon as it feeds away N. Coastal wIndward districts in S (e.g. Lyme Bay) an awkward raIn-sleet-snow mix really, but obviously no such marginality on N coasts (Bristol Channel)."

He doesn't say where it splits though.

[Fozfoster]

18z nae is bit slower than the 12z with eastward push of precip. 18 z totals

London 2mm

Brum. 7 - 8 mm

Bristol 8 - 11 mm

Manc. 2-4 mm

Hi BA, have i got this right, mm not cms ?

[David 'Minty' Hill]

Interesting post from Ian F on the south west regional thread:

"Ps front splits Fri hence heaviest snow is AM with intensity easing into afternoon as it feeds away N. Coastal wIndward districts in S (e.g. Lyme Bay) an awkward raIn-sleet-snow mix really, but obviously no such marginality on N coasts (Bristol Channel)."

He doesn't say where it splits though.

Now thats more like it thanks for that Buzz

[IDO]

EssexWeather

New Met Office run has the heavier snow dying out over Buckinghamshire on Friday. Essex is left with 1-2cm by end of day.

16/01/2013 21:22

Looks like UKMO now suggesting minimal snow east of M1. Changing every 6 hours!

[manutdmatt1986]

NAE 18z precip accumulations show another westward shift for Friday, btw before anyone says, precip accum is out before the main NAE output so it is 18z

On weatheronline the NAE 18z precipitation charts are only out to +3 hours.

[randomwalk]

48 hour accumulated precip suggests a stalled front -man above is right

[bradymk]

On weatheronline the NAE 18z precipitation charts are only out to +3 hours.

Like i said, precip accumulations come out before all the others, so click on precip accumulations and you have the 18z data. It comes out alot earlier for some reason.

[Timmytour]

Timmy,

I don't mean to put out your fire so to speak but the GFS isn't the best model. It's the best model at being 3rd best and has been for a long long time. The verification stats say it all. I know your a fan but the fact is it's not the best performing model.

I'm hoping the 18z swings it back the way of the others so i can banish all reservations! For me it was the first one to show the way after the December That ECM (now we need the month in the description!)....so I'm wary of how it wants to go, but then again i know it has continually put back the encroach Atlantic over the past few days.

I'm really hoping that this time it doesn't rain on our parade!

[picog]

Hi BA, have i got this right, mm not cms ?

I think so, but that is rain total and you need to convert to snow. About 1mm rain = 1cm snow, I think.

[manutdmatt1986]

Like i said, precip accumulations come out before all the others, so click on precip accumulations and you have the 18z data. It comes out alot earlier for some reason.

That's what I'm looking at.

+3 hours is from the 18z.

+6 to +186 hours is from the 12z.

[Theresnoway]

Even at T15, there is a slight westward correction on the GFS for precipitation compared to the 12z

Edited January 16, 2013 by Theresnoway

[IanM]

Could anyone tell me what the equivalent of 1mm of rain is in terms of snowfall amounts is 1cm?

It's typically a ratio of between 6-8 to 1, so 1mm of rain would produce around 6-8mm of fresh snow.

[Fozfoster]

Cheers All . Not bad for starters!!!

[Jimmy0127]

The Met Office is a public institution whose purpose is to advise on the potential meteorological impact on our lives.

The warnings are the product of likelihood and impact. They need to maintain credibility for their own survival, as well as the survival of others.

It is important that their warnings are heeded, and communicated, but not to be confused with model discussion.

The ECM 144 looks important to me. It's all about that GIN corridor. If that becomes established, then this could become tricky.

[Summer Sun]

13:00 Friday the main band of snow is in the west and some showers are along the eastern side

[Carlrg]

The BOM is showing cold uppers right through to FI 240 with the milder air never looking like breaking through.

http://www.meteociel.fr/modeles/bome_cartes.php?ech=6&code=0&carte=0&mode=1&archive=0

[Summer Sun]

The same front is still in the same areas at t48 only moving east very slowly

t54

[Tony Beets]

What data does the NAE use then to produce these precip charts?? Is it gfs? Thanks.

[bluearmy]

What data does the NAE use then to produce these precip charts?? Is it gfs? Thanks.

Its a very high resolution met office model. Nothing to do with gfs

I hope the morning will resolve these issues with the eastward extent of the front and its intensity as it fizzles and splits.

Rough guide : 1MM RAIN = 1CM SNOW

Edited January 16, 2013 by bluearmy

[Timmytour]

The high is beginning to sink south which is holding up the fronts from making as much progress east and, on the pivot, as much progress north. North London was going to be hit both ways...now doesn't look like taking much of a blow at all on friday/saturday

[johnholmes]

Sorry PL that is tosh the rule is 1mm rain equals 1cm of snow

Neither is tosh it depends on how moist the air is, how cold, what the dewpoint is etc

[patrickshere]

NAE precip accum. for people asking:

Only runs out to 6pm at the moment, hard from that to work out what'll happen afterwards. That's a lot of precipitation though on that chart, especially for north wales. Just another run though, and there's shifts with every one.

[Met4Cast]

Is this the "how much rain = snow" thread or is this the model thread?

The 18z shifts the PPN Westwards, though we pickup a better Easterly flow as the low clears into France

[swfc]

looking good at 84 hrs with very cold 850s and snow showers.block looking strong

[thegreat316]

Could well be that those in the East could see more snow out of that convective wind then many in the west from the decaying front.