Focussed Model Discussion

[knocker]

The main feature of the first ten days of the gfs run is major upper troughs dropping into the Atlantic from the 'zone' of North America and battling east against the subtropical high pressure attempting to amplify

The NH 500mb and surface analysis for midnight and the 0300WV image

The band of rain from the cold front is currently lying down central England and east Wales with showers over Scotland, of snow on the high ground. The rain will continue to track south east leaving much of the country quite sunny with the odd shower but the south east not quite so lucky as it wont clear here until mid after noon. Much less cold than of late but still nippy in northern Scotland

So mainly clear skies tonight but really the only signs of frost are in northern Scotland and the north east of England with perhaps the odd fog patch but by early morning some light rain will reach western regions courtesy of a warm front associated with the first of the aforementioned Atlantic lows.

After the clear and frosty start the cloud and rain will gradually traverse the country through Tuesday introducing much milder air with temps above average in England and Wales.

The rain will continue through Tuesday evening but eventually clearing as the fronts move into the North Sea leaving the UK in a breezy south westerly on Wednesday with some showers in western coastal regions.

At the same time the low south of Iceland has been filling and drifting east and an occlusion on this will bring more concentrated showery rain and more snow on the mountains to Scotland on Thursday  Mainly dry elsewhere with some showers down western regions.And the next trough has appeared on the scene in the western Atlantic.

And this next low moves fairly rapidly east and the associated fronts bring bands of rain across the country on Friday as well as some very mild air

[knocker]

To continue briefly with the gfs. The low then tracks north of Scotland and fills resulting in a breezy weekend with sunny intervals and showers some of which will again be wintry in the north

Returning to the theme touched upon at the beginning of the above post by Monday the next trough has developed in the western Atlantic and the subtropical high is managing to amplify quite strongly over the UK but alas to no avail

Edited February 4, 2019 by knocker

[knocker]

The ecm on the same page as the gfs but the ridge still hanging in there at the end of the run

[knocker]

A lot of moderate rain in the SE quadrant of England but very mild

[IDO]

My worry is that the predicted downwelling is contrary to what the models are now forecasting.

Looking at the D10 500 mb charts and the PV is gaining strength and realigning towards the pole:

The three main models at D10^^^

Looking at the 850hpa chart and it appears the split sister lobes have made up.

It is hard for me to see mid-February charts like the above when we have been told a full-downwelling has happened? The GEFS support this.

Could the recovery of the strat around the same time be fooling the models into a QTR, or could there be a QTR?

Either way, the downwelling should be warming the tropospheric arctic field, and this is clearly not currently showing on the D10 models. Faced with the SSW mute signal the prospects for Feb cold are far less enticing. Overall a steep learning curve.

[knocker]

The back edge of the front which is taking it's time

And haven't looked at the SSTs for a while

Edited February 4, 2019 by knocker

[sebastiaan1973]

I wonder if we get some impact of the MJO moving through 6-7. 

[bluearmy]

7 minutes ago, sebastiaan1973 said:

I wonder if we get some impact of the MJO moving through 6-7. 

Ec has it into Phase 8 whilst gefs is amplified in 7 - prefer ec ! 

Issue I have is that so far the MJO analogues haven’t imprinted too well - perhaps the speed through the phases hasn’t helped .....

[knocker]

And of course as with all of these teleconnections they are not straightforward, particularly if the forecasts are at variance. And of of course other factors have to taken into account such as the Strat-trop coupling. This from:

The Influence of the Madden–Julian Oscillation on Northern Hemisphere Winter Blocking
STEPHANIE A. HENDERSON, ERIC D. MALONEY, AND ELIZABETH A. BARNES

The teleconnection patterns associated with phases 3 and 7 are also important for Atlantic blocking. In agreement with Lin et al. (2009) and Cassou (2008), 10–15 days after MJO phase 3 a positive NAO pattern develops over the Atlantic. We find that Atlantic blocking frequency is more than halved in association with the positive NAO pattern. In contrast, MJO phase 7 is followed by a negative NAO pattern, which coincides with a high-amplitude wavelike flow and an increase in blocking frequency. Atlantic blocking frequency is almost doubled following phase 7, reaching 116.5% relative to climatology. Approximately 14%–15% of all DJF Atlantic blocked days follow phase 7.

In Europe, a significant blocking increase follows phase 6, with up to 11.4% of all DJF European blocked days occurring within 15 days of MJO phase 6. We identify two possible precursors to the phase 6 blocking:

1)  a preexisting anticyclone over the Atlantic and 2) a negative PNA pattern. The first precursor was discussed by Cassou (2008), who noted the positive NAO pattern from MJO phase 3 could provide the anticyclone that later would transition into the European block. While Cassou (2008) hypothesized the phase 6 European blocking is primarily a result of phase 3-driven NAO variability, we propose a second precursor, a negative PNA pattern, as a link between the MJO and European blocking. In agreement with the daily PNA life cycle discussed by Mori and Watanabe (2008), we argue that through forcing of the negative PNA by the MJO, European blocking coincides with phase 6. The negative PNA pattern then acts as a Rossby wave energy pathway influencing the European blocking, as indicated by the W vectors

Future work should focus on further understanding the mechanisms between the MJO and blocking, in addition to the PNA pattern. More work is needed to understand how changes in MJO heating and the basic state influence the relationships observed between the MJO and blocking. This is particularly true for Europe, in which MJO heating differences and the basic state may play a role in the development of the negative PNA pattern preceding phase 6 blocking.

[knocker]

Another terrific high res MODIS image at 1230 (courtesy Dundee Satellite Receiving Station)

[knocker]

Interesting. Looking at the 1200 analysis, a frontal surface on the Camborne sounding at 600mb?

 

[phil nw.]

12z gefs still favouring the development of a high building in week 2.A slowing down of Atlantic mobility still looks the trend next week with a building ridge from the south.The current probability is of a high settling just south of the UK.

Euro temp 2m 5 day anomalies days 11-15

Gentle south westerlies would then seem the order of the day,It well could feel quite pleasant where we see cloud breaks and the sun shines.

Edited February 4, 2019 by phil nw.

[stodge]

Evening all

Interesting to see the variation between the main models at T+144:

UKMO:                                                         GEM:

GFS OP:                                                  GFS Parallel:                                               ECM:

UKMO is the slowest with everything - the LP is still over the British Isles and the LP is heading north over the eastern seaboard and into Canada thereby offering a greater chance of promoting the mid-Atlantic ridge or of lifting heights NE from the Azores into Scandinavia. The key is the secondary LP which the UKMO develops and sends across the British isles next Monday - GEM hints at it but it's not on GFS or ECM which has the LP already well clear of the country and the next LP able to begin to move across the Atlantic and flatten the ridge.

The delay also allows a wedge of heights to try and develop over eastern Greenland (hinted at on GEM and to an extent ECM).

[bluearmy]

In respect of the extended eps, joe b has noticed an issue over the rockies. The low uppers anomoly intensifies as the run progresses between days 10 and 14 when statistically the ens mean shouldn’t be doing such a thing. He feels it’s a feedback issue in the modelling (ec has often had a feedback bias in the west of n America) and the upper trough is therefore wrong in the extended period ....... we shall see what happens if that deeply low anomoly on 850’s changes once/if  the initial deepening drops away. Obviously what happens ove n America dictates what happens downstream 

[ICE COLD]

That storm looks nasty at T102 on the GFSP 18z . It’s bang over the uk ?. 

Edited February 4, 2019 by ICE COLD

[knocker]

According to the the EC46, after the last half of Feb. dips to around average temps, western Europe, including the UK, becomes quite toasty in March,

[knocker]

Outlook - unsettled but less cold

The NH 500mb profile and the surface analysis for midnight and the 0300 surface chart

A varied start to the day in different regions of the UK, With the front still lingering the south east continuing mild with low cloud. mist and patchy drizzle whilst in the north east frost and freezing fog in places. And frost is in fact pretty general apart from the far south west where it is becoming increasingly cloudy as the next frontal system approaches from the west.

And by 0900  patchy rain will be effecting N. Ireland, Wales and the south west which will spread east during the day, introducing milder air as it goes. albeit the north east and Scotland remaining quite chilly until later. Becoming quite windy

The frontal system will continue to track east this evening and overnight bringing more rain and strong winds to most areas but clearing from the north west from around midnight with wintry showers developing over western Scotland

The wintry showers will continue over N. Ireland and Scotland on Wednesday and although England and Wales will be mild with sunny intervals there is a slight complication. The cold front is still trailing back near the south coast and is starting to wave a tad and a patch of moderate rain runs north east through the morning.

Overnight Wednesday and through Thursday the deep low associated with the frontal system continues to drift and fill to the north west of the UK leaving the latter in a breezy westerly resulting in frequent showers along western regions which could well be wintry in the north west courtesy of the odd trough embedded in the flow. Temps still generally a tad above average, And to note the next trough has appeared on the scene in  the western atlantic and starting deepen quite rapidly

And deepen it does with some explosive cyclogenesis and by 1200 Friday is 958mb west of Ireland bringing gales and rain to the UK as the associated fronts sweep across the country.

On Saturday there is a complex area of low pressure residing over the eastern Atlantic and the UK with the latter in a strong westerly wind with frequent heavy showers. Temp varying around the average

[knocker]

Continuing briefly with the gfs. Still showery on Sunday but as the low pressure moves east the wind veers northerly and reintroduces colder air resulting in a widespread frost Monday morning

This is but a brief digression and from this point it's all about the subtropical high pressure amplifying in the eastern atlantic and warding off sustained attacks from the trough in the west. This it manages to do, just, with some help from the Bermuda high, despite the fact there is still an impressive amount of energy exiting the eastern seaboard.

Edited February 5, 2019 by knocker

[knocker]

The ecm also has the wind veering northerly on Monday but this ridge is very transient and fonts sweep through on Tuesday with more wind and rain.The high makes further efforts but is now centred to the south east which initiates some WAA into western Europe

[knocker]

Notwithstanding some differences I think I detect a persistent trend towards an early Spring.

 

Edited February 5, 2019 by knocker

[Man With Beard]

Very interesting following the progression of the clusters this morning, as it shows the tiniest of differences at T120 are predicted to mushroom into ever increasing differences all the way into the second half of February. It really does seem that the outcome of the D5-D7 period is crucial for D8-D15.

D5

Just the tiniest difference in the Atlantic. 

But look how that difference has grown by D7

 

The runs with the largest Atlantic ridge at D5 now have a small block holding up the Atlantic, allowing heights to get that little bit more established further north - but the runs with the smallest ridge at D5 have fully collapsed.

And the differences keep getting more pronounced:

The question is - which will be right? At the moment is seems like UKMO+minor models vs GFS/ECM.

Normally you'd expect the op runs to lead the way by D5, and also to expect op runs to pick up on developments around Iceland better between D5/D6 than the ensembles. But the persistence of the UKMO and the fact the ECM op has gone against its mean for a few runs now makes one doubt that progressive solution will definitely be right (though I feel the progressive solution is still the most likely). 

Surely by this time tomorrow morning this will be sorted, and, quite possibly, the majority of February will then be sorted too?

[knocker]

Surely this is not surprising in a somewhat fluid pattern where there is still a lot of energy in the mix and minor adjustments of the distribution of this will increasingly produce differences in a 51 member suite?

[feb1991blizzard]

Somehow i don't think the micro scale short term setup is going to necessarily make much difference to the 20th Feb, which is when the ensembles go out to.

[frosty ground]

2 hours ago, knocker said:

Notwithstanding some differences I think I detect a persistent trend towards an early Spring.

 

Aren't they both showing big ridges in Alaska? Which promotes a slack pattern down stream , not sure spring would develop from that pattern 

[knocker]

8 minutes ago, frosty ground said:

Aren't they both showing big ridges in Alaska? Which promotes a slack pattern down stream , not sure spring would develop from that pattern 

The Alaskan ridge promotes another cold trough down North America which in turn pumps up the jet exiting the eastern seaboard north of the Bermuda high What happens at the eastern end of the Atlantic rather depends on how the interaction between the east bound energy and the amplifying ride develops but either way the temps are looking around average or a tad above. Just my take on it of course