Cold spell - 14/15th January onward
-
12-01-2024 3:55pm#1
A very cold spell of weather is expected from later Sunday through the following week up to Friday at least, with an anticipated return to less cold conditions next weekend.
This thread enables us to discuss pre-120hrs and post-120hrs model output without diluting/separating the conversation in the other pre-existing threads.
This spell of weather has been signalled by model output for the last 10 days + and, in fact, has been touted as a strong possibility by the UK Met Office the week leading up to Christmas. Significant anticipation had built up due to talk of a PV split and solid Greenland blocks. Expectations have subsequently been tempered by the present outlook of 5-6 days of very cold and relatively dry weather. This is not 2010 nor is it 2018 and expectations for same should be dropped. However, cold spells like this in January have been as rare as hen's teeth over the past decade and therefore, merits a thread of its own.
As things stand (Friday afternoon pre 12z runs), the forecast slow moving and relatively unstable northerly airflow will likely bring snowfall across Ulster, west Connacht and Munster and perhaps further inland, while any troughs that pop up would widen the risk area. These finer details are days away from becoming clearer and can be discussed here.
Daytime temperatures will hover around 2-4c in all but exposed coastal locations (slightly higher), and will invariably struggle to get above freezing in some locations due to a variety of, as yet, difficult to forecast conditions e.g. existing snow cover, freezing fog, inversion etc. Shaded spots away from the light northerly wind will likely to stay frozen throughout the period and untreated road surfaces will be tricky to negotiate.
Met Éireann and @M.T. Cranium are suggesting a less cold solution and this thread is in no way set up as a challenge to their forecasts.
Beyond next Friday, conditions are expected to become less cold as the Greenland High dissipates and a mobile, cold zonal Atlantic pattern takes over (based on current guidance this afternoon). This is a long way off and will be subject to change.
I will continue to report what the models are saying for my part and I look forward to an interesting week of winter weather.
Enjoy!
www.x.com/wolfeeire
66
Comments
-
-
-
-
-
-
Advertisement
-
-
-
-
The GFS 850s mean is about 1c-1.3c colder than the 0z mean from Wednesday morn through Friday. It is a tad less colder than the 00z on Tuesday afternoon and night as I explain below. An upgrade overall for cold.
That mild sector (best visualised through the below 85s table) on Tuesday continues to show up on the GFS, UKMO and ICON 12z and is much more progressive in these op runs than the 00Z. It doesn't have much of a bearing on daytime temps (staying very low), but it's not as conducive for snow from any showers feeding into northern and western coasts. The greatest risk of snowfall continues to be Ulster and western counties.
Aside from the above, the 12z GEFS mean is colder than the 00z from Wednesday through Friday.
Wednesday and Wednesday night temps below. That is based on the op run. All very much subject to change.
All show a breakdown on Saturday as anticipated with the 'dismantling' of the Greenland High and an intense low spilling out of Newfoundland. Interestingly, the GFS has a more an easterly tilt to the jetstream rather than the ENE tilt of the 00z so it doesn't get quite as mild as @VILLIAN has alluded to as a possibility in the 120+ thread. The jetstream shifts more southward as the GFS op run goes on into that week leaving us in a very mobile and somewhat cold zonal pattern.
By the beginning of the following week we are in a relatively cold and raging zonal pattern.
Finally, the GEM was a milder op run than the 00z. I will post the ens when they are out to see where the op lies.
www.x.com/wolfeeire
5 -
Not much snow away from Scotland on that GFS run with Atlantic air mixing too much, temperatures across the north-west look too marginal for snow so snow restricted to the hills of Donegal on this one.
1 -
Advertisement
-
-
-
-
The GEM ensembles mean for 850hpas (explanation of what 850s are here) largely mirrors the 12z GEFS and is colder than the 00z from Sunday eve to Tuesday morn and Wednesday morn to Friday morn. It is a little more progressive with the slow warm up Friday PM on though. That mild sector is again cropping up. It is unlikely to have much of a bearing on surface temps but does make any shower activity on Tuesday PM into early Wed more marginal for snowfall.
In terms of precipitation you will notice the difference in totals between Letterkenny and Dublin. These charts are based on this run and will change.
www.x.com/wolfeeire
2 -
-
-
-
-
-
-
Advertisement
-
-
-
-
-
-
-
-
