Model Output Discussion 18z 28/07/13

[Frosty.]

The Gefs 06z mean looks fantastic for those of us hoping for one final very warm and settled spell before the end of summer, high pressure builds in strongly across the uk and shows no sign of going anywhere fast once it's established, it looks like being a great end to summer if the mean keeps this trend going.

[Frosty.]

The Gefs 06z control run looks pretty good too, the anticyclone drifts around quite a bit and this would mean regional variations from day to day as to where the warmest weather would be on a particular day but how could anyone really complain about charts like these in late august?..if something like this verifies, most of us will be happy, only those wishing for cool and unsettled will be disappointed.

Edited August 12, 2013 by Frosty039

[summer fun]

wow, not sure I can honestly answer your question.

The major driver is ENSO and what follows from that, again my knowledge is not high enough to be able to give you your answer. My attempts at longer range forecasting is limited to the 6-20 day time scale. This is why I use the anomaly charts with constant reference to other drivers, ENSO, MJO, AO, NAO although the latter two are more important in winter. They of course simply mirror what the synoptic models may show, high latitude blocking or mobility although they are useful.

For summer and winter I find the 6-15 day range is best served, in terms of the major upper air pattern by using the 500mb anomaly charts. Like any other chart they need to be used carefully and in conjunction with other drivers I've mentioned. When all fit together then one can be resonably confident of the upper air pattern within that time scale. They can and do go wrong just like any other prediction in meteorology but over the 12 months I rate them much higher than the synoptic outputs at that range, something like 70%+ correct in the whole 12 months. That is the upper air pattern and not the surface which is much more diffcult to solve correctly due to a number of factors. One of which is the one that bedevils all attempts at forecasting, even at short time ranges, moisture.

There are two periods when they are less reliable, one is the major change over periods of northern hemisphere summer to winter and the winter to summer period. The other is the next few weeks leading into that first change, the Atlantic hurricane season. Both involve such huge changes in energy within the atmosphere that any model from MJO downwards in time scale finds it extemely difficult to work out how the upper air pattern will be affected.

hope that helps a bit, others will be able to give you more advice about the longer term drivers I am sure.

 

Thanks again John,

 

Very useful information to help my understanding  of meterology. Thanks

 

[summer fun]

Just a comment on hurricane season. When we lived in Bermuda I followed the hurricane season pretty closely. There was often a theme that if the hurricane season off the baha peninsular, California was busy (as it is this year) the Atlantic season was very quiet.

It is looking like this for 2013 season, therefore less likely for any ex tropical storms to come our way.

 

I think according to the weather channel, the increased thunderstorm activity in the pacific is expected to move into the gulf of mexico later this week and into next week. Also that the warmer/drier air over the atlantic of africa looks like becoming more favourable over the next few days into next week but all in all still looking quiet.

[The Northern Ramper]

Waiting now for the ECM to give the full set of high pressure building from the south, very consistent modelling for next week.

[draztik]

The gfs 12z op does not have ensemble support! A warm outlier from the 12z tonight!

this is becoming a consistent pattern. A heatwave still not the likely evolution. The only thing that does look apparent, is for hp to build- leaving us with a settled 7 days, maybe longer!

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

[Costa Del Fal]

The gfs 12z op does not have ensemble support! A warm outlier from the 12z tonight!

this is becoming a consistent pattern. A heatwave still not the likely evolution. The only thing that does look apparent, is for hp to build- leaving us with a settled 7 days, maybe longer!

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

However the mean looks likely to go near 10c especially in the South which is only slightly below what it was in July so could become pretty decent for many - not Hot though.

[draztik]

However the mean looks likely to go near 10c especially in the South which is only slightly below what it was in July so could become pretty decent for many - not Hot though.

you're right, the SE does look like it may be in for some rather warm temperatures!! But still don't see this being a UK wide hot spell!

away from this, next Monday looks cool

[The Northern Ramper]

Waiting now for the ECM to give the full set of high pressure building from the south, very consistent modelling for next week.

There we go, hp building in on the ECM at exactly the same time as the rest.

[ANYWEATHER]

There we go, hp building in on the ECM at exactly the same time as the rest.

The gfs builds pressure much more quicker then the ecm, but the ecms 12z run is better then its previous!   I think the ecm is playing Kiss chase with the gfs!  

Edited August 12, 2013 by ANYWEATHER

[draztik]

Highlighting the difference..

models at 240

The Gem, gfs, ecm..

given the gfs ensembles do not support the op, i think the ecm could be closer to the mark!

[Frosty.]

I'm happy with tonight's Ecm 12z because the trend to a warmer and settled outlook is on track with pressure beginning to build from the southwest as early as T+168 hours and progressing from there, i'm sure the ecm would continue to look better and better beyond T+240 hours with the PFJ being forced into retreating even further northwest as time goes on with high pressure building in strongly, the Gefs 06z mean shows what lies ahead for late august, before then, becoming warmer and more humid as this week goes on, becoming fine towards the southeast for a while but progressively more unsettled further northwest, this weekend looks like becoming generally more unsettled with temperatures dropping back to average as a deep low pushes east to the north of the uk but then the recovery begins during the first half of next week and then very summery weather making a comeback..

so i'm happy, and we won the ashes...

Edited August 12, 2013 by Frosty039

[William of Walworth]

you're right, the SE does look like it may be in for some rather warm temperatures!! But still don't see this being a UK wide hot spell! 

More than just the SE, next week, from most recent output -- not  a nationwide heatwave no, but no-one's even suggesting that. Just pleasant and settled.

[Captain Shortwave]

put me on ignore, it would save you a lot of bother :)as for the models, i only state what i see! I realise it may not be to your liking, but that isn't my problem.

can you post the ecm t240 chart and the gfs mean for the same time (pressure chart). on the train so cant chart watch but i bet the two look much different. Edited August 12, 2013 by Captain shortwave

[I Cumbria Marra I]

put me on ignore, it would save you a lot of bother

as for the models, i only state what i see! I realise it may not be to your liking, but that isn't my problem.

It is your problem though, B.I.A.S.

[ANYWEATHER]

It is your problem though, B.I.A.S.

No point arguing over the model output, the weather will do what its gonna do, nothing we can change or do! 

[I Cumbria Marra I]

No point arguing over the model output, the weather will do what its gonna do, nothing we can change or do! 

I know, just is there any need in being so blatantly biased?  

[Frosty.]

The Gefs 12z mean continues to firm up on a warmer and more benign further outlook with the azores/atlantic anticyclone ridging in during next week with increasing warmth and sunshine with temperatures back into the mid 20's celsius for at least the southern half of the uk, probably low 20's c for northern britain but pleasantly warm. There is some ebb and flow with the centre of the high holding back to the southwest compared to the 6z mean but the weather would still be fine and warm, just look how far north the PFJ retreats, right up into the high arctic, hope it stays there for a while.

 

In the meantime, becoming warmer and more humid as we draw tropical maritime air around the top of the azores anticyclone, by the weekend, cooler mid/north atlantic air mixing out the Tm airmass with more average temps but then next week the temperatures will be on an upward curve.

Edited August 12, 2013 by Frosty039

[J10]

Julian, its an old chestnut about no forecast input. In my view of watching these over 3 years I am hard pushed to give any credence to changes into or out of the weekend.

In terms of the time scale to what they are showing they go no further, with NOAA, than 15 days; with ECMWF-GFS 10 days. Anyone using them beyond that time scale must be even more careful than during the time scale. They, to me, all of the main 3, I do not use NAEFS simply because I have no first hand knowledge, unlike with the other 3, of how well or not they perform. Those 3 have consistently shown an upper trough for days on end now, they predicted this change well, and I see nothing in any of the 3 to be able to say they are changing yet. They may do, but I do not tend to suggest any change until all 3 have got the same or very similar change showing after at least 2 and usually 3 days. So far there is nothing to show any marked change. The anomaly part of the charts shows nothing of any substance near the UK, 30DM is neither here nor there, particularly in the middle of a sizeable upper trough with a strong 500mb flow across the Atlantic. Beyond 15 days then I do not pretend to have a great deal of knowledge at that distance.

 

ps 

the only slight change is in the direction of the upper flow into the UK, that is a bit further back, almost south of west which may (note the word) may be the start of a shift in the wavelength.

 

I am always a bit cautious on weekend charts by NOAA, even if in this case, the trend is what I would like.

 

Going by some today's charts I was a bit overcautious.

 

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

 

Bank

 

To be fair the 6-10 day version isn't that bad either.

 

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Edited August 12, 2013 by J10

[I Cumbria Marra I]

Looking at them charts im 90% certain there will be a heatwave in the last third of August. WOOOHOOOO, HEATWAVE INCOMING, JETSKI  READY, SHORTS (TICK), VESTS/T-SHIRTS (TICK), SUNGLASSES (TICK), SNORKLING GEAR (TICK). CANT WAIT. MID TWENTIES, LOW THIRTIES EVERYWHERE!!!!. yeh really.

[johnholmes]

The anomaly charts from NOAA have shifted in emphasis over the last few days, on the 8th the 8-14 predicted the trough to be just west of the Uk with a height anomaly of about 30DM close by the SW.

Over the last few days the 8-14 has gradually shifted the trough further and further west. On the 8-14 tonight it suggests it being about 30 west giving a WSW flow to the 500mb contours into the UK. Having kept the 30DM height anomaly, and as I suggested in previous posts, this is neither here nor there unless it is associated with some sign of ridging. Tonight it has upped the anomaly slightly and has it over the UK.

Although it has not total support from the other two this shift is starting to indicate that perhaps the anomaly is shifting from trough dominated to less so. I hesitate to say ridge dominated as the chart, link below, is far from that yet. However the unsettled spell may be coming to an end in the 8-12 day time frame and by that time the anomaly charts MAY be showing some kind of ridge-unclear yet but it just might. 

In short becoming less unsettled over much of the UK, how warm is not for the anomaly charts really. With the heights they are predicting one would not anticipate hot for sure warm probably especially areas with the most sunshine. Not too warm in the evenings though as the air is originating from mid states not southern states but still suggesting heights of 576DM for southern areas, so respectable temperatures for late August.

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

Edited August 12, 2013 by johnholmes

[bluearmy]

A semi drift away from the settled spell that looked likely post the weekend. The odds are still on a better spell but the anmolys no longer as certain or strong as saturday's 12z's or sundays's 00z's

oh and just to note that yet again the gfs fi again well out of sync with the ens

[Biggin]

Gotta love the models agreeing on semi settled situation for the near future, The 2  ( you know who you are ) "breakdown comin soon"  2-3 weeks ago and "downhill til winter" posters will eventually get what they "predict" Till then am loving the decent summer weather we have atm and have had for a fair while.  Celebrate it, dont wanna be the first to predict the "breakdown" you wont win any medals.

 

Big up to Frosty  too !!! love your posts. Say what you see not what you hope for.

[snowwonder]

With my limited knowledge of reading the models I am confused to say the least about weather from sat onwards. I'm on the Norfolk broads then. Would I be right in saying models show an unsettled weekend but then getting better with some reasonable days from next mon?

[The Northern Ramper]

With my limited knowledge of reading the models I am confused to say the least about weather from sat onwards. I'm on the Norfolk broads then. Would I be right in saying models show an unsettled weekend but then getting better with some reasonable days from next mon?

Yes, it appears to be the case for now.The Gfs this morning brings in the hp next Monday and then the heat follows soon after.