Some ensemble members are even entertaining 5-6 sigma IVT anomalies over England sometime between the 24th-30th, indicating early possibility of a true extreme event (but not something that is currently likely)

Keeping an eye on the end of Jan, ECMWF currently predicts low pressure over the East Atlantic from the 24th onward. There's a lot of uncertainty in position and detail at this lead time, but a look at the Z500 precip precursor for southern england shows a high chance of bad weather on the way:

This is well captured from the flow precursor perspective: the 'north norway' and 'sicily' Z500 precip precursors represent two halves of the current tripole pattern and are both are well over 2 std deviations from normal.

You might not guess that the weather in sunny sicily has much in common with Tromso up at the top of the world. But at the moment the same tripolar structure of geopotential height over Europe is bringing heavy rain risk to both regions, where a breaking ridge is augmenting low + high lat lows.

Further afield, I've noticed that Tunis and the surrounding area are in for a (relatively) rainy week. Strong cutoff low activity developing by Monday, coincident with a low-latitude wave train passing over North Africa:

If you're in the south of the UK, you might be enjoying some cool clear weather now, but the month looks set to turn: in general there are some weak mean signals towards cyclonic flow over the UK, with a larger-than-usual number of ens members predicting strong atmopsheric rivers.

We can also see this with the precursors, if we look at typical patterns of integrated vapour transport (IVT). We see clearly that this IVT precursor metric picks out the three peaks in the current forecast, each corresponding to the predicted passage of an atmospheric river over the North sea:

OK, so winds are one thing, but as we all know, you need moisture for rain. The large-scale flow may be setting the stage for precip, but is anyone ready to 'perform'? Unfortunately for Bergen, yes, we have three atmospheric rivers predicted to hit on Mon, Tues and Sat :( See these IVT EFI plots:

In fact we can see this even more clearly if we look at the upper level zonal wind precursor: these strong westerlies are exactly the sort of weather which bring rain to west Norway.

But from the 13th to the 20th the index flips positive, indicating a shift towards potentially more rainy conditions. In this case this looks to correspond to a building of high pressure over western Europe, with strong mid-level westerlies in the North.

Let's take today. There is currently a big ridge extending up to Iceland, keeping West Norway cool and dry: somewhat opposite to our Z500 precip precursor above. If we look at the current ECMWF forecast for this Z500 precursor index, we can see that the index should stay negative for the next days.

If we turn to ERA5 reanalysis, and look at composites of the weather associated with heavy DJF precip in West Norway, we find an NAO+ like dipole of geoopotential height, strong westerly winds over the North Sea, and southerlies over the UK and norway -- that is, a strong, SW-NE, tilted storm track.

Lets take an example. What weather patterns accompany heavy (>90th percentile of daily, area averaged) precip over West Norway in winter?

Yes Bergen rains a lot, but when it doesn't, it can look like this 😍. Don't need a textbook to study orographic precipitation here.