Blessed Weather

A quick follow up to the above..... I'm in the Black Forest, Germany, with family and friends and this is the Christmas Day sunset looking down Lake Titisee towards the snow covered hills in the distance.

I'm a great believer in pulling the plug out and starting again. But seriously, try clearing your cache and restarting your mobile. If that doesn't work please put a post in the 'Help' thread and I'm sure Paul will help you sort it out. Anyway, may I hope you and everyone in our Regional thread is having a happy and peaceful Christmas.

There are presentation slides available from a 2015 study that looked at the verification stats of the 4 daily cycles over a long period (2008 - 2015). Findings were that "GFS 06Z and 18Z cycle are less skillful than the 00Z and 12Z cycles". Here's the key slide: Zooming in: Of course since 2015 you might expect NCEP to have worked on the differences, although it appears that a variance in the amount of input data at different times of the day are likely behind the issue: You can download the full slide pack if you Google 'Comparison of Forecast Skills between NCEP GFS Four Cycles' and click on the search results link.

If you use the Netweather MOGREPS chart viewer you can select to see the member average (as per screen shot below) or all members. Lots of other options too including the max or min temperature, MSLP, 2m temps, etc. Link: https://www.netweather.tv/secure/cgi-bin/premium.pl?action=mogreps;sess=

A bootiful sunrise today, here in Suffolk.

MeteoGroup buy in data from the big 3 models ECM, GFS and UKMO and then use their own internal computer modelling plus human tweeking by their own meteorologists to arrive at the final forecast provided to customers such as the BBC. Full details in their own document: https://medium.com/@meteogroup/the-making-of-a-weather-forecast-4ee5bfcc942e

Can't argue about the consistency issue, but I thought it very interesting that on 13 days out of the 21 day period on the chart I showed, JMA out-performed the GFS and so I felt didn't deserve the dismissive criticism it was receiving. Anyway, let's hope that for those of us wanting to see a bit of festive snow JMA's Christmas Day chart Mike showed is "bang on".

As there's been a few people knocking JMA without providing any evidence, if I may Mike, I'm using your post as an excuse to show the latest day-5 model verification graph for Europe from the ECMWF website. On balance it's a respectable performance from JMA, mostly in the middle of the pack. I've highlighted a couple of days when it was the top performing model and on one instance (the 22nd Nov) whilst it was top the ECM was bottom. Mind you, equally there are some days where JMA clearly loses the plot and plummets to bottom. If only we could dig deeper and establish the reasons behind the various models good/bad day performances. A final point of interest - over the last couple of weeks the performance of NCEP (the GFS) has been less than spectacular for Europe, often bouncing along the bottom. The higher score the better performing on the following 500hPa anomaly correlation chart. Source: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=Europe&day=5&score=Anomaly correlation Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4978195

As there's been a few people knocking JMA without providing any evidence, if I may Mike, I'm using your post as an excuse to show the latest day-5 model verification graph for Europe from the ECMWF website. On balance it's a respectable performance from JMA, mostly in the middle of the pack. I've highlighted a couple of days when it was the top performing model and on one instance (the 22nd Nov) whilst it was top the ECM was bottom. Mind you, equally there are some days where JMA clearly loses the plot and plummets to bottom. If only we could dig deeper and establish the reasons behind the various models good/bad day performances. A final point of interest - over the last couple of weeks the performance of NCEP (the GFS) has been less than spectacular for Europe, often bouncing along the bottom. The higher score the better performing on the following 500hPa anomaly correlation chart. Source: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=Europe&day=5&score=Anomaly correlation

I have just moved a couple of dozen posts over to the Winter Chat/Moans thread where they should have been made in the first place. Can people please be more considerate to their fellow members who want to log-in and head to the Model thread to catch up on the latest output and to read serious discussions about our weather prospects. What folk don't want is to have to wade through post after post of one-liners such as "winters over" and "Decembers aren't the same any more". So let's please keep this thread on-topic and informative. Thank you.

Model Output discussion in here please folks. This is not the thread for musing over Met Off outlooks. Posts have been moved to the Winter Chat thread. Thank you.

Summer Sun has posted the MO latest update in the MO/BBC Outlooks thread here.

@Catacol The CPC 'expert discussion' of the MJO just published. It certainly confirms what can be seen from the dynamical models, a weakening of the amplitude. But there's some slightly more positive news regarding the extended outlook with the possibility of "reorganization of the MJO signal over the Western Hemisphere" (i.e. emerging from COD into Phase 8 by end December). Since early December, an active MJO has continued to propagate eastward across the Indian Ocean and Maritime Continent and has recently begun to constructively interfere with the low frequency El Nino base state over the equatorial Pacific. Continued eastward propagation of the MJO signal into Western Hemisphere is favored in the RMM forecasts towards the end of December, however dynamical models generally point to some disorganization and loss of amplitude likely tied to competing tropical variability as it crosses the Pacific during the next two weeks. Dynamical models generally favor a MJO signal that slows and reduces in amplitude as it shifts across and Western Pacific during the next 2 weeks. This behavior may be tied to a convectively couple Kelvin wave propagating across the Indian Ocean in the forecasts. Extended range solutions favor some reorganization of the MJO signal over the Western Hemisphere with continued eastward propagation towards the end of December and into early January. Full update: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4974601

@Catacol The CPC 'expert discussion' of the MJO just published. It certainly confirms what can be seen from the dynamical models, a weakening of the amplitude. But there's some slightly more positive news regarding the extended outlook with the possibility of "reorganization of the MJO signal over the Western Hemisphere" (i.e. emerging from COD into Phase 8 by end December). Since early December, an active MJO has continued to propagate eastward across the Indian Ocean and Maritime Continent and has recently begun to constructively interfere with the low frequency El Nino base state over the equatorial Pacific. Continued eastward propagation of the MJO signal into Western Hemisphere is favored in the RMM forecasts towards the end of December, however dynamical models generally point to some disorganization and loss of amplitude likely tied to competing tropical variability as it crosses the Pacific during the next two weeks. Dynamical models generally favor a MJO signal that slows and reduces in amplitude as it shifts across and Western Pacific during the next 2 weeks. This behavior may be tied to a convectively couple Kelvin wave propagating across the Indian Ocean in the forecasts. Extended range solutions favor some reorganization of the MJO signal over the Western Hemisphere with continued eastward propagation towards the end of December and into early January. Full update: https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf

Yes, the CPC expert analysis due later on today is awaited with bated breath Catacol. Apart from BOMM and CFS, all other models are forecasting that whilst the MJO will continue on into the Western Pacific and Western Hemisphere, it will be at such low amplitude that it is effectively 'no signal' and thus no extratropical impact.

My tuppence worth on why the MJO has 'failed' leading to models dropping suggestions of Atlantic ridging/blocking. Looking at the latest MJO forecasts it’s appears to me as if the MJO may have hit the well recognised Maritime Continent (MC) ‘barrier’ as it tried to progress eastward along the equator into the Western Pacific (Phases 6 and 7). Research shows that up to 50% of MJOs fail to make it past the MC. And without the MJO progressing to 6, 7 and 8 at amplitude – certainly by ECMWF and NCEP/GFS models - we have lost meaningful tropical forcing on the North Atlantic synoptic pattern in the output from those models (i.e. Atlantic ridging/high latitude blocking). Here’s the recent progress in RMM charts that illustrates what appears to be a typical eastward propagation collapse: EMON ECM Ens 04Dec 07Dec BOMM 02Dec 09Dec And this could well be the explanation: Observations show that the MJO tends to be significantly weakened when propagating eastward into the MC region; the MJO also often detours around the MC via an oceanic pathway south of Sumatra Island and over the Java Sea in austral summer. Often, the MJO even completely dissipates over the MC and fails to propagate into the western Pacific, known as the MC barrier effect for MJO. About 50% of the total MJO events during the boreal winter are disrupted over the MC. Due to the MJO's significant impacts on downstream high-impact weather and climate events in both the tropics and extratropics, determining whether the MJO will propagate through the MC is crucial for climate prediction. The MC barrier effect, however, is poorly simulated in current GCMs, and most forecast systems exhibit large deficiencies in predicting the MJO propagation through the MC. These model shortcomings in simulating and predicting the MJO propagation through the MC are partially due to our poor understanding of the underlying physics responsible for the MC barrier effect. There is plenty of good reading and further detailed explanation of the MC barrier in this excellent paper: Fifty Years of Research on the Madden-Julian Oscillation: Recent Progress, Challenges, and Perspectives Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4974258

My tuppence worth on why the MJO has 'failed' leading to models dropping suggestions of Atlantic ridging/blocking. Looking at the latest MJO forecasts it’s appears to me as if the MJO may have hit the well recognised Maritime Continent (MC) ‘barrier’ as it tried to progress eastward along the equator into the Western Pacific (Phases 6 and 7). Research shows that up to 50% of MJOs fail to make it past the MC. And without the MJO progressing to 6, 7 and 8 at amplitude – certainly by ECMWF and NCEP/GFS models - we have lost meaningful tropical forcing on the North Atlantic synoptic pattern in the output from those models (i.e. Atlantic ridging/high latitude blocking). Here’s the recent progress in RMM charts that illustrates what appears to be a typical eastward propagation collapse: EMON ECM Ens 04Dec 07Dec BOMM 02Dec 09Dec And this could well be the explanation: Observations show that the MJO tends to be significantly weakened when propagating eastward into the MC region; the MJO also often detours around the MC via an oceanic pathway south of Sumatra Island and over the Java Sea in austral summer. Often, the MJO even completely dissipates over the MC and fails to propagate into the western Pacific, known as the MC barrier effect for MJO. About 50% of the total MJO events during the boreal winter are disrupted over the MC. Due to the MJO's significant impacts on downstream high-impact weather and climate events in both the tropics and extratropics, determining whether the MJO will propagate through the MC is crucial for climate prediction. The MC barrier effect, however, is poorly simulated in current GCMs, and most forecast systems exhibit large deficiencies in predicting the MJO propagation through the MC. These model shortcomings in simulating and predicting the MJO propagation through the MC are partially due to our poor understanding of the underlying physics responsible for the MC barrier effect. There is plenty of good reading and further detailed explanation of the MC barrier in this excellent paper: Fifty Years of Research on the Madden-Julian Oscillation: Recent Progress, Challenges, and Perspectives

I'm not trying to answer for @Allseasons-Si but thought that maybe the latest 5-day verification charts for Nov 2023 for the North Atlantic sector might be helpful. To my eye GFS and ECM appear to swop places regularly wrt 'best performing' model in that sector. If anyone has the time you could use the archive 500hPa charts for each date plot and see what the synoptics were; it would be interesting to see if there's a pattern to when each are better. Anomaly Correlation (higher values better) Root Mean Square Error (lower values better) Source: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=N Atlantic&day=5&score=Root mean square error

Time for a brand new shiny thread as we approach Christmas 2023. The old thread clocked up 499 pages of chat and discussions since December 2021 - not bad at all. And with talk of a possible cold and snowy spell arriving around the Christmas/New Year period, who knows, we might be clocking up our first one hundred pages in record time. Whatever your weather preference, here's wishing you get lots of it in the weeks and months ahead!

Locking this thread now. Here's the link to the new thread:

That's an ECM chart I believe, available on their website here. It has the legend (description) below it. In laymans terms the velocity potential regions shown with green are regions with enhanced convection and brown suppressed convection and is particularly useful for monitoring the MJO. This description on the Quora website I thought was a nice easy way of getting an understanding: "......the only things that can cause a [velocity potential] divergence at that height are tall cumulus towers from whose tops there is an outflow of air transported up from the atmospheric boundary layer due to condensational heating. Therefore, the 200 mb velocity potential can be used as a proxy for deep convection in the tropics." And a neat technical description from ChatGPT on the same Quora website: The 200 mb velocity potential in atmospheric science represents the large-scale, non-divergent flow in the upper troposphere. It is a measure of the tendency for air to accelerate in the horizontal direction due to changes in the distribution of temperature and pressure. This quantity is useful for understanding the dynamics of the atmosphere at high altitudes and can provide insights into the behavior of weather systems and the large-scale circulation patterns. Hope that helps. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4972075

That's an ECM chart I believe, available on their website here. It has the legend (description) below it. In laymans terms the velocity potential regions shown with green are regions with enhanced convection and brown suppressed convection and is particularly useful for monitoring the MJO. This description on the Quora website I thought was a nice easy way of getting an understanding: "......the only things that can cause a [velocity potential] divergence at that height are tall cumulus towers from whose tops there is an outflow of air transported up from the atmospheric boundary layer due to condensational heating. Therefore, the 200 mb velocity potential can be used as a proxy for deep convection in the tropics." And a neat technical description from ChatGPT on the same Quora website: The 200 mb velocity potential in atmospheric science represents the large-scale, non-divergent flow in the upper troposphere. It is a measure of the tendency for air to accelerate in the horizontal direction due to changes in the distribution of temperature and pressure. This quantity is useful for understanding the dynamics of the atmosphere at high altitudes and can provide insights into the behavior of weather systems and the large-scale circulation patterns. Hope that helps.

Time to move on please folks. The thread is now being clogged with the debate. If you want to carry on please head over to the Winter Chat thread. Thanks.

Plenty of discussions around the accuracy of models in forecasting the MJO. Here's another paper (in addition to the one posted on the previous page by Downburst) which identifies a known weakness of underestimating the amplitude of the MJO as it progresses across the Maritime Continent and Western Pacific: "One of the greatest challenges in current dynamical forecast systems is the fast damping of the MJO signal as the forecast lead time increases, which results in a rapid decrease of forecast skill. This systematic damping of the MJO convection signal is particularly apparent when the MJO starts over the Indian Ocean and is expected to propagate through the Maritime Continent and move further into the western Pacific. The frequency of MJO events not crossing the Maritime Continent in forecast models is more than twice as large as it is in observations, known as the Maritime Continent prediction barrier." Does this help explain the slump of amplitude in many of the RMM forecasts we are currently seeing? Here's the ECM Ensemble Extended Range marked as illustration: In the same paper the Average forecast errors by model (unfortunately no BOMM inclusion): Source: Deep learning for bias correction of MJO prediction I've put both papers into the Netweather Research Library where there's lots of other MJO papers. Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4971007

Plenty of discussions around the accuracy of models in forecasting the MJO. Here's another paper (in addition to the one posted on the previous page by Downburst) which identifies a known weakness of underestimating the amplitude of the MJO as it progresses across the Maritime Continent and Western Pacific: "One of the greatest challenges in current dynamical forecast systems is the fast damping of the MJO signal as the forecast lead time increases, which results in a rapid decrease of forecast skill. This systematic damping of the MJO convection signal is particularly apparent when the MJO starts over the Indian Ocean and is expected to propagate through the Maritime Continent and move further into the western Pacific. The frequency of MJO events not crossing the Maritime Continent in forecast models is more than twice as large as it is in observations, known as the Maritime Continent prediction barrier." Does this help explain the slump of amplitude in many of the RMM forecasts we are currently seeing? Here's the ECM Ensemble Extended Range marked as illustration: In the same paper the Average forecast errors by model (unfortunately no BOMM inclusion): Source: Deep learning for bias correction of MJO prediction I've put both papers into the Netweather Research Library where there's lots of other MJO papers.