Model output discussion - 1st December onwards

[Norrona2015]

MO forecasting sleet then snow for Tuesday and Wednesday next week for my location.

[West is Best]

19 minutes ago, IDO said:

That is semantics, yes differences between GEM, GFS and ECM in the short term but if they all agree at D7-8 with a burst of the Atlantic barging through, any good work in the intervening period is nullified. I really do not see the Atlantic being stopped even with the initial trough disruption from the undercut, this has been de facto the outcome from the GEFS for days. Anyway just my opinion and I am not a mild ramper, just a realist. 

D10 GEFS: 

The default position in the UK is west to east Atlantic flow so 99/100 there's nothing especially smart about sticking to the belief that it's the default. Been there done that. However, what always happens in pattern changes from my experience is that the models struggle to adapt, precisely because they're geared to the Atlantic procession. That's why it's important with blocking highs and amplification to keep a much bigger than normal focus on the short term developments. The 18z GFS, for instance, was a major model shift. The 0z UKMO and, to a lesser extent, the ECM and GFS are radically different from 24 hours ago. 

These are the times when the really smart thing is to admit you don't know. If 'Fergie' from the Met Office can be that humble, maybe the rest of us should too?

Edited December 31, 2015 by West is Best

[northwestsnow]

Just now, Norrona2015 said:

MO forecasting sleet then snow for Tuesday and Wednesday next week for my location.

Yes i would imagine NE Scotland is the sweet spot next week for snow potential.

[fergieweather]

1 minute ago, Norrona2015 said:

MO forecasting sleet then snow for Tuesday and Wednesday next week for my location.

Bear in mind unmodified model GRIB data drives web output on UKMO/BBC sites and apps, though.

[marksiwnc]

Ever thankfull for having Ian around Hopefully there will be a spell of easterly winds soon as the amount of rain that has fallen for us here in nw Wales and Northern England and Southern Scotland then a change of wind direction would be beneficial for us to have some shelter.  Can't you tweak the weather patterns please Ian lol

[Ali1977]

Still no signs of winter then Ian?

[nick sussex]

Some interesting thoughts from the New York state NCEP forecaster for the outlook into January. This for model obsessives is one of the best reads you could wish for in terms of explaining the MJO influence and the overall global picture. The nor'easters they mention   can be high risk sometimes for the UK because the thermal difference can cause a lot more energy off the eastern USA however the weather for the UK depends on whether we see enough amplitude so those nor'easters run ne and provide sufficient WAA to develop strong high pressure to the west. Its a long read but worth it so get the espresso on and indulge yourselves!

OVERVIEW ...

INTERROGATING GLOBALLY ... THERE APPEARS TO BE A CONNECTION BETWEEN
THE PHASE CHANGE OF THE MADDEN-JULIAN OSCILLATION TO 7/8 YIELDING A
E-SHIFT IN ANOMALOUS H2/H85 WESTERLIES. INTO MID-JANUARY ... AXIS OF
STRONGEST H2/H85 WINDS STRETCHES FROM WARMER-THAN-AVERAGE EQUATORIAL-
PACIFIC WATERS NE ACROSS THE GULF OF MEXICO INTO THE NW-ATLANTIC. NO
SURPRISE CLIMATOLOGICALLY AS THE MJO SHIFTS FROM PHASE 7 TO PHASE 8
THE TEMPERATURES OVER THE E-CONUS SHIFT FROM ABOVE-AVERAGE TO BELOW.
ECHOED WITHIN THE GLOBAL FORECAST SYSTEM AND ENSEMBLE MEANS ... THE
AO/NAO SHIFT NEGATIVE AS THE PNA BECOMES POSITIVE. TROUGHING DEEPENS
OVER THE NE-CONUS WITH A POSSIBLE POLAR VORTEX RETURNING TO THE N.
THERE WOULD BE A GREATER OPPORTUNITY FOR ENERGY TO BE CAPTURED THRU
THE S-STREAM BY THE AFOREMENTIONED E-SHIFT IN STRONGER-THAN-AVERAGE
WESTERLIES OUT OF THE SUB-TROPICS ONLY TO POTENTIALLY DEEPEN ACROSS
THE NW-ATLANTIC PER GREATER BAROCLINICITY BETWEEN A POTENTIAL POLAR
VORTEX N AND WARMER NW-ATLANTIC WATERS. IN OTHER WORDS ... WE MAY BE
MOVING INTO A FAVORABLE SYNOPTIC PATTERN FOR NOR`EASTER DEVELOPMENT.
ONLY TIME WILL TELL.

FOR THE TIME BEING ... ANOMALOUS WESTERLIES ARE ORIENTED FROM THE
CENTRAL-EQUATORIAL PACIFIC NE ACROSS THE CONUS. FLY IN THE OINTMENT
AS WE SHIFT INTO PHASE 7 MJO ... A REX-BLOCK SETS UP ACROSS THE W-
CONUS ACTING TO PROMOTE TROUGHING ACROSS THE NE-CONUS FOR A GOOD
CHUNK OF THE 7-DAY LONG-TERM FORECAST TIME-RANGE. IT IS ONLY AFTER
THIS REX-BLOCK PATTERN BREAKS DOWN WHERE THE MORE CLIMATOLOGICALLY
FAVORED PATTERN RE-EMERGES ... WITH PREFERRED STORM DEVELOPMENT OVER
THE SW-CONUS ... WITH DOWNSTREAM RIDGING AND ABOVE-AVERAGE TEMPS FOR
THE E-CONUS. BUT HOW LONG THIS PATTERN LASTS UP AGAINST A SHIFTING
NAO/AO TO NEGATIVE ... PNA POSITIVE ... AND MJO TO PHASE 8 REMAINS
UNCLEAR.

OVERALL ... A PREFERRED TROUGHING PATTERN THROUGH WHICH A SERIES OF
UPPER-LEVEL DISTURBANCES REINFORCE COLDER AIR ACROSS THE REGION WAVE
AFTER WAVE ... EACH ONE INVOKING SOME LAYER OF ASCENT YIELDING A MIX
OF RAIN/SNOW SHOWER ACTIVITY. THE PATTERN CLOSES OUT TUESDAY MORNING
WITH SOME OF THE COLDEST AIR OF THE SEASON. A MODERATING TREND THERE-
AFTER INTO THE MIDWEEK ... THEN SPECULATION GROWS PER INDICATIONS OF
S-STREAM ENERGY PERHAPS BECOMING INVIGORATED ACROSS THE E-CONUS. WAY
TOO EARLY TO DISCERN WITH CLARITY ... BUT DOES BEAR WATCHING PER THE
CHANGE IN THE GLOBAL PATTERN NOTED EARLIER.


 

 

[Cloud 10]

Some interesting FI shenanigans from the GFS control run this morning.

 

 

Ensemble mean for the same time....

 

 

.....MJO forecast and composite anomaly added.

 

That seems straightforward enough then.

Edited December 31, 2015 by Cloud 10

[Polar Maritime]

27 minutes ago, West is Best said:

These are the times when the really smart thing is to admit you don't know. If 'Fergie' from the Met Office can be that humble, maybe the rest of us should too?

I don't think anyone is 'admitting' to knowing are they? Just probability's being posted with charts to back them up which is what this threads all about, And to respect others opinions..  Fergie's musings via meto do not conclude/end any model discussion, As valuable as they may be.

Edited December 31, 2015 by Polar Maritime

[shaky]

Ecm and ukmo identical with the shortwave at 48 and 72 hours in having it further south!!gfs on its own!!

[nick sussex]

In terms of which model NCEP prefer over the ne USA unfortunately they haven't yet come down on one preference.

Just noting the differences, for the UK you do want the slower more amplified solution. The UKMO is the most amplified with that at T120hrs out of the big 3 and the result is the Azores ridge extension.

GENERAL TROUGHINESS WILL EXTEND ACROSS THE NORTHEAST WITH CLOSED
LOW WELL TO THE NORTH ACROSS NRN ONTARIO THIS WEEKEND. THIS CLOSED
UPPER LOW LIFTS NORTHWARD EARLY NEXT WEEK AS REINFORCING ENERGY
CARVES OUT LOWER HEIGHTS ACROSS THE GREAT LAKES REGION/NORTHEAST
MONDAY INTO TUESDAY. THERE ARE TIMING AND STRENGTH DIFFERENCES
NOTED...WITH LATEST ECMWF MUCH SLOWER/MORE AMPLIFIED WITH THE
APPROACHING TROUGH MONDAY AND TUESDAY. THUS...SFC HIGH IS SLOWER
TO BUILD TOWARD THE AREA WHEN COMPARED TO LATEST GFS AND CANADIAN.

DRY AIRMASS REMAINS IN PLACE...WITH PERHAPS A FEW WEAK SHORTWAVES
AIDING THE DEVELOPMENT OF FLURRIES ACROSS THE INTERIOR FRIDAY
NIGHT AND POSSIBLY SATURDAY. DRY THE REMAINDER OF THE FORECAST.
THE ONLY CAVEAT WOULD BE SLOWER/STRONGER TROUGH APPROACHING MONDAY
ALLOWING COASTAL LOW PRESSURE FORMATION OVER THE WESTERN ATLANTIC
TO RESULT IN AREA ON THE WESTERN PERIPHERY OF PRECIP SHIELD PER
LATEST ECMWF MONDAY NIGHT/TUESDAY. THIS TREND WILL NEED TO BE
WATCHED.
 

 

Edited December 31, 2015 by nick sussex

[NO LONGER POSTING]

Same thing happening as last year..

 

Cold comes into frame... Stays there till around +250 hours then vanishes.. comes back in FI and we repeat that cycle 

[IDO]

22 minutes ago, West is Best said:

The default position in the UK is west to east Atlantic flow so 99/100 there's nothing especially smart about sticking to the belief that it's the default. Been there done that. However, what always happens in pattern changes from my experience is that the models struggle to adapt, precisely because they're geared to the Atlantic procession. That's why it's important with blocking highs and amplification to keep a much bigger than normal focus on the short term developments. The 18z GFS, for instance, was a major model shift. The 0z UKMO and, to a lesser extent, the ECM and GFS are radically different from 24 hours ago. 

These are the times when the really smart thing is to admit you don't know. If 'Fergie' from the Met Office can be that humble, maybe the rest of us should too?

Yes no one knows for sure, but that does not stop me from giving my opinion, and it is good that there is some discussion? All I see at D8-10 on the GEFS is the Atlantic piling into the UK, both ECM and GEM agree, and to be honest this is the first time in a week or so we have had general agreement at that range. For me, coming from a statistical view point, the mist is clearing. It was always whether a block, starved of WAA could hold back a mass of lower heights powered by a resurgent Pacific, forcing the jet? There has been too'ing and throwing, but the GEFS say "yes" to the Atlantic in no uncertain terms and of course they could be wrong, but you have to go with the current output and trend. That block's direction of travel is now strongly inclined E/SE. The second wave with the N Pacific high latitude block, that will likely move E as well, and I suspect that is what is causing the uncertainty in the US, that block's direction of travel and interaction over the N. US; lots of uncertainty on that one still? Of course by the second third of Jan that block could change the pattern downstream.

I have been wrong many times and will be many times in the future, we are always learning with weather, but I just cannot see the few days of trough disruption morphing into a cold snowy setup for the UK! 

JMA have just updated and their w1 and w2 anomalies pretty much aligned to the GEFS:    

[Gibby]

May I take this early opportunity to wish all Netweather folks a Happy New Year for 2016 and thanks for reading my reports here throughout the year. I know they have been missing for some time but I have maintained them on my website and now the worst of my pre Christmas workload is now over I should have more time to get to my PC to post them here again soon.

Edited December 31, 2015 by Polar Maritime

[bluearmy]

Looking at NAEFS  and I'm struggling a tad to work out the charts in week 2. It seems to want a positively tilted East Atlantic trough above a s euro high anomoly. the GEFS and GEM ens are not showing this anomoly. Seeing as NAEFS is produced as a combo of the two model outputs, I'm confused. 

Incidentally, there is now a disagreement between GEFS and ECM ens re the AO/NAO. GEFS keeps the AO very negative throughout the two weeks whereas ECM slowly returns it to around neutral. the NAO remains slightly negative to the end of week 2 on GEFS but returning to slightly positive values on the eps. 

Edited December 31, 2015 by bluearmy

[Day 10]

1 hour ago, West is Best said:

 

The three main models aren't in agreement about anything, especially beyond T96 let alone T192. UKMO has enormous potential, as does ECM in the short term. Even the GFS in short term is a considerable improvement on this time 24 hours ago. All the models have been flip flopping as they try to cope not only with shortwave patterns and amplification but the extent and position of the Scandinavian aka Scrussian high. Anyone coming on here claiming sage-like knowledge about the patterns 5-10 days hence, be that for cold or mild, is using shamanism more than science.

My sentiments exactly WIB! Don't the met office even consider day 5 as a 'LONG WAY OFF' nevermind D10 or D16. Anyway for me as long as at least one of the big 3 are still keeping coldies in the game upto D7 at the very furthest then I certainly won't be worrying over D10. Still an absolute ton of weather to come before that!

[Nick F]

On the subject of model agreement, although the broadscale 500mb is, as would be expected, more agreed, little features like Saturday's low moving east aren't agreed on. Look at the differences as close as t+60 (now just over 2 days away) between EC and GFS ops:

 

t+72, EC has low over Nern France, GFS doesn't

Some trough disruption going on from the weekend, but are all the models totally on the ball? Even with all the computer power of NWP today, still think they can slip up on detail = particularly in the mesoscale with track of lows during trough disruptions.

Edited December 31, 2015 by Nick F

[SMU]

Anyone following the 06z is seeing a big swing to UKMO & NAVGEM

.... Pics for comparisons soon

[Ice Day]

Indeed Steve, quite a change at 126

6z 

 

0z 

The low over France is not there on this run!

 

[SMU]

So the feature that the UKMET added back in has now been removed from the 06z as well -

at T96 the atlantic starts to throw a ridge NNE but because the low over the UK is not quite sliding south ( yet ) then the ridge gets swamped & low pressure passes under our main low however

thats a significant swing to the UKMO ( also a massive infill of pressure over Norway at 120 v the 00z

so whilst the outcome is the same on the 06z - 1 / maybe 2 more swings of the pendulum like the GFS does & instead of the energy driving east under the low it will recurve up towards iceland like the NAVGEM

all eyes on the 12s

S

[radiohead]

06Z GFS raises the prospect of additional flooding next week.

 

 

[shaky]

23 minutes ago, Nick F said:

On the subject of model agreement, although the broadscale 500mb is, as would be expected, more agreed, little features like Saturday's low moving east aren't agreed on. Look at the differences as close as t+60 (now just over 2 days away) between EC and GFS ops:

 

t+72, EC has low over Nern France, GFS doesn't

Some trough disruption going on from the weekend, but are all the models totally on the ball? Even with all the computer power of NWP today, still think they can slip up on detail = particularly in the mesoscale with track of lows during trough disruptions.

To be fair latest gfs 06z takes it slightly further south when compared to 00z so maybe ecm and ukmo are right!!

[chris55]

Though I better have a look at the NAVGEM to see what Steve is referring to. Best case scenario for cold!

Here it is 

 

[SMU]

Last one then

 

rewind to 96 area

compare 00z v 06z

00z t90 v 06z 96

 

 

You will see that 00z has a shallow 1000mb wave moving ESE across the atlantic which is the system that goes under the main low & allows there to be a westerly flow over the SW of the UK hence easy for the jet to push through

where as the 06z is not sure this is correct now & seperates the energy into x2 waves - the first one more southerly track & not developing - but behind that a ridge pushing the second wave NE -

As said that not enough this time around to make a difference - but make the same correction again for the 12 & it will - 

look at the wave on the UKMO & NAVGEM - North east on both & the first wave ends up towards portugal -

cheers

s

Edited December 31, 2015 by THE CHOSEN ONE

[Liam J]

7 minutes ago, radiohead said:

06Z GFS raises the prospect of additional flooding next week.

 

 

 

Quite concerning, the rain accumulation charts for next week are showing 100mm+ in places that really cannot take any more water...

Not sure why the NAVGEM is getting in on the limelight over the last 24hrs? Hardly ever mentioned and I'm sure it's been referred to as cannon fodder in the past? It does look good for cold prospects but I certainly wouldn't be pinning any hopes on it.