General Model Output Discussion

[weather eater]

Typical GFS this evening, once we get out of the higher resolution the high falls over like a set of dominoes, allowing the Atlantic back in.

[cyclonic happiness]

Typical GFS this evening, once we get out of the higher resolution the high falls over like a set of dominoes, allowing the Atlantic back in.

Tis weird that, I've noticed that in the ensebles over the past 3 weeks, the 850 temps shoot right up when you get into the low rezz? why would this be, why are they not shooting downwards like they always used to in winter?

We always used to get excited when we saw that downward leap in FI?

[swilliam]

Yes we are,

Wrong chart, he was talking about the 2nd chart he posted for Sunday

This is the chart he and I were referring to

I do not think I need to highlight the 528 dam for you.

[Stu_London]

Tis weird that, I've noticed that in the ensebles over the past 3 weeks, the 850 temps shoot right up when you get into the low rezz? why would this be, why are they not shooting downwards like they always used to in winter?

We always used to get excited when we saw that downward leap in FI?

Very unusual so see a GFS run without any sort of pattern change unless there is an extremely strong overiding signal (usually zonality in the autumn or settled weather in the summer).

Whilst teleconnecting factors are a little in the air, it is probable that GFS in particular because it goes out so far will continue to throw up such scenarios. That said, the ensembles are pointing to at least a reasonable chance of a breakdown to the atlantic so we have to accept that is a possibility.

With regard to the rest of winter, if the jet stays south and pressure stays high to our northeast I think we will be always vulnerable to easterlies from a good old fashioned scandi high into February and perhaps March.

[J07]

Wrong chart, he was talking about the 2nd chart he posted for Sunday

This is the chart he and I were referring to

I do not think I need to highlight the 528 dam for you.

Just a squint at this suggests that the feature would bring snow to inland areas.

First they've drawn occluded fronts, so they are implying no surface change of air mass.

Given the lack of troughing in the surface pressure field it looks like a mid-level feature anyway.

The air at the surface will be very cold.

So the snow falling at mid-levels from this feature will just be falling into left-over cold air from the current cold spell, which will lead to snow likely at sea level. This effect is particularly pronounced in any basin type areas inland. Happens over here all the time in winter. There would need to be a strong push of mild air to flush out the cold stuff from valleys and basins, otherwise snow looks the most likely precipitation type (or, depending on how the temperature profile pans out, freezing rain).

[J07]

J07 - Fancy swapping countries mate?

Fine by me....I'm fed up with the incessant gales here!

[Iceberg]

Re the above and the 528 line, in this kind of setup the 1000-500 thickness is a terrible indicator of snow, if you look a bit more closely 850s are around -8 to -9 as discussed above and the 1000-850 thickness is approx 128 (very much a snow figure).

[Iceberg]

Unrelenting cold and snow still for the next 10 days from the ECM. GFS keeps things slightly less cold, but potentially snowier with fronts from the atlantic making more inroads, due to generally less energy in the southern Jet.

Sunday is still possibly on but how widespread or heavy is totally unknown atm.

Temperatures of -18, DP's of -20 IMO makes this the worst cold spell for 25 years maybe more.

[Methuselah]

A new thread here: