IDO

The upcoming pattern change. At D9 on the three models: The trough looks nailed, so we are looking at variations on a theme. This also applies to the ensembles on the GEFS and GEM. This will last a few days before another pattern change to a more amplified NH. GEFS and GEM D8-16 mean: Alaskan Ridge and heights rising close to the UK in that Atlantic sector. The Arctic high looks a player as well.

Why there was so much scatter on the GEFS is evident with the 06z -v- 0z at D9: Subtle variations where the trough dives and differences in flows that can cut off the cold uppers, as well as how the cut-off UK low develops, mean massive differences in surface condition, average temps 06z and rain versus colder and snow on 0z at the same time period.

Any HL blocking still looks 13 days away, according to the GEM ensembles (D8-16): The Alaskan Ridge and Icelandic Ridge. It could be engaging with the omnipresent Arctic high, but too far out for specifics. In the interim, from around D5, we see a low ejected off the ESB that interacts with the jet and sends the jetstream further south, impacting the UK from around D8 as it fills around the UK. GEFS mean D8-16: The ensembles have a lot of variation and how that transpires on the ground. The 2m temps highlight this (London): Nothing cold, IMBY, according to the mean. Further north, there may be better chances of a brief spell of below-average conditions before the trough migrates east by D10-11. Fingers crossed, we get the GFS OP take rather than the GEM.

The EC mean is uninspiring: The GEFS mean is similar at D10 and goes forward as so: Though a cooler spell post the current milder spell:

The ECM mean is similar to GEFS: 850 ensembles for EC for the next ten days, also similar to GFS, so some level of consistency in the means:

I am still not seeing anything too interesting in the next ten days, but there are possibilities as we head towards mid-February, maybe the last chance saloon. The GEM mean at D16 is the paradigm for a cold spell: upstream Alaskan ridge and the corresponding Atlantic push: The GEFS mean is not quite there yet at that time scale but sees the Alashan amplification: The upcoming eight days for London looking dry and relatively mild: After that, a trough attempts to sink south/SE but is thwarted by a rising Azore/Iberian High (mean D8-15): Maybe some westerly-based wishy-washy 850s from that outcome.

Post D8 looks like fluid. Look at D11-12 on 06z versus 12z: Those wedges come and go run to run (06z - Icelandic wedge). But the general theme looks interesting for mid-February: more seasonal offerings. At least from GFS, GEM is more in line with the mean. D10:

D10 ECM charts are not helpful in setups like this, where wedges dictate the flow. The op at D7 is already an outlier: The D10 op and mean show how the wedge changes the picture and is strictly JFF: It's not impossible, but a wedge like this usually disappears 12 hours later.

@CoventryWeather Yes we will be moving post-D7 from a milder jet placement to a colder one on the mean: The London ensembles highlight this. But not what we seek as the clock ticks down on this winter. And the NH mean suggests little to no chance of high latitude blocking for Arctic cold and snow.

No changes as far as I can see. The GEFS mean, D8-16: This has been consistent for over a week, and at D16, the tPV has returned to the Greenland region with no clear signal that the stuck-in-the-mud NH profile is in any mind to change. The promise that background signals will kickstart a rejig seems lost in the mire of an unrelenting overriding base troposphere pattern, so I am not hopeful for February. These rarely go on forever, so expect something cooler and wetter by spring.

I was hoping, not expecting, that the GFS yesterday was onto something, but the mean remains as per the last week: The tPV circulates to our north, Greenland to Scandi and back again. The Azores/Atlantic high tries to break north but the jet is not dictated by the tPV, it is running underneath and as it ejects out of the Conus it spawns spoiler lows that cut off any ridge. There are ebbs and flows within the LP systems off the jet and the circulation of the tPV, so a brief ridge dragging colder uppers may pop up or be modelled but at the range of post-D8, of little confidence. Good news IMBY the weather will be average to mild and little rain and no storms. For London, the next 8 days 850s and 2m temps:

There were signs on yesterday's 12z that background signals may be showing as we saw the flow slow down. Mainly on the GFS and today's 0z and 06z run with that theme. A watching brief to see if this is what is likely, and if it is, how will it develop? Nice to see though, D8-14:

@Dennis I am not sure those datasets equate to a GH; well, not a blocking high. This is a GH, but not really much help: The 12z suggests the tPV is losing momentum in FI. D15: A bit wedgy. Maybe changes as we move towards mid-February?

The op --v-- the mean in FI: That is one BIG outlier! Looking at the ensemble members, zero support outside the control: I wonder what made the op go on a wild journey...?

This is D16 on the GFS op, a run that follows the mean for a change: GEM & GEFS mean: The mean has been steady as a rock and continues to show a poor setup for cold as we head for mid-February. The same issues of mean Alaskan & Siberian High keeping the pattern locked in. The tPV is circulating Greenland to Scandi, ad finitum. Waiting for MJO and other background signals for a reset or forcing.

@Lukesluckybunch The jet is driving the westerly flow, not the circulating tPV (tPV is just preventing any HLB'ing): So we will see swarming off that jet, LP systems, preventing any ridges from sustaining from the blocking over the US/Pacific. The jet is strong, and it is hard to see anything cold develop from that. It does appear the Asia/Pacific side has got the mid-latitude block that we had over the UK earlier this month that led to cold:

The GFS 06z shows the best-case scenario of a mini-ridge giving a brief cool down but west-based, so the milder end of the cold spectrum: But the overall pattern remains the tPV alpha circulating to our north back and forth between Greenland and Scandi, so any HLB'ing is almost negligible.

No change in the GEM and GEFS mean for D8-16: Flat, westerly and zonal N/S. This takes us to Feb 10, and we seem to be in a rut of a pattern. We await background signals (warming, MJO, etc.) to push some forcing into the regime; otherwise, the alpha tPV seems happy as Larry is stuck on our side of the NH. We are likely to see random op runs and the usual ens that may show something different but with such a strong mean, these charts are likely just aberations of the algorithms.

The GEFS and GEM means are poor. Both are very similar for D8-16: We see the Greenland tPV run across our north to Scandi, but because of the mean Siberian/Alaskan highs, it flows the contours and, by D16, has returned to our NW. This is only the underlying background signal from the models, but it is relatively clean in this range. We do need other factors to dislodge the current state of play, as there appears to be a very low chance of any HLB'ing in the Atlantic/Euro quadrant with that pattern. The best will be wedges and stalling mini-ridges if these means are correct. The next 10 days look to have high confidence of zonal with NW/SE split: Rainfall for 10 days^^^. The London GEFS suggest mild for the south in that period.

No relaxing of the jet in FI on this run, D8-16: The Northern Arm remains strong and keeps the UK on the milder side of the pattern.

The GEFS is showing zonal to D16. Mean at D8-16: As expected, the N/S divide for the worst of it. The members look like there is uncertainty beyond D10, but that is untrue. Just as we move into FI, the timing of each zonal interlude varies, and the sine waves cancel each other out, hence the 850s in FI at 0. With the TPV running the show due to the lack of any force, we are relying on removing the tPV from the Euro/N American side of the NH, and the mean Siberian block continues to thwart that. D16 GEFS mean: These types of charts are winter killers for the UK.

The GFS 06z is something along the lines of my hopes around week 2 with Atlantic pressure rises: D16: D8-16: It is not as stable due to the Siberian high cutting off the Asia tPV, so getting the trough south is a bit harder. This is the trend we will hopefully see during next week, so we get another cold shot in mid-Feb

Just highlighting the GFS in FI. The next 8 days: The FI charts of the last week suggest that the models overplay Scandi heights. This bias and the UK high has disappeared, with the northern arm of the jet too powerful. The retrogression of the Euro heights back to the Azores continues to be the outlook from the GEFS as the tPV moves west to east to our north. D8-16 mean: There is potential in week 2 for Atlantic Heights. Still, I do think we may need help from background signals as there is no sign of upstream forcing by the end of week 1 of Feb. And still a Siberian block making it difficult for the tPV to leak to the Asian/Pacific side of the NH, which would allow more room for trop wave breaking in the Atlantic if we do not get tropical forcing. Overall a typical mix of zonal Winter weather for the next two weeks See the sine wave of 850s and pressure for London: Average winter weather UK-wise. The usual caveats.

I have not noticed the models much recently as I think nothing cold is likely until week 2 of Feb, once the Euro high has retrogressed to the Azores/Atlantic corridor. The GEM mean hinting at that by D16. D8-16 GEM & GEFS mean: But it is a slow process that has been delayed by the shenanigans of a stalling Euro ridge post D8 as it clears east. Both means have little upstream developments to suggest we can break this tPV pattern. The mean Pacific/Asian tPV segment in FI leaks partially to the Greenland sister, making any wave breaking in the Atlantic harder. Until we can disengage the Greenland tPV, we will likely experience the jet's northern arm dictating the flow, making it hard for sustained waves to reach higher latitudes downstream, especially in our NE/east quadrant. So, there is still no optimism of changes before week 2. The usual caveats of background factors popping up.

The 12z run is unlikely as the amplification is due to a wedge of heights in the polar region, well in FI, that bridges with the Euro high: That is likely to be gone on the 18z. It wasn't on the 06z. Those Arctic highs are at that range are not worth the time of day. The caveat is there is lots of uncertainty on the Pacific side with wave activity. So, we need another period of letting the models resolve the background issues and see if the general mean changes.