Model Output Discussion - 15th March onwards

[Eagle Eye]

In my last post I did a bit about the A-Level paper on Cyclone Freddy I'm starting before I've done my GCSE's as well as the forecast 

A bit more from my paper so far and then the latest update;

"The closer setup that provided the ability for cyclogenesis. The setup provided a monsoon trough in the eastern Pacific and Indian Ocean area with large convection along the coasts of Indonesia stretching to northern Australia and east Timor.  In northwest Australia the moisture stream advects NW’wards up from the Broome to Darwin area through the Kimberly Plateau with the topography of the region playing a role in enhancing convection and forcing along the Wunaamin Milwundi ranges. The convection envelope along the southern coast of Indonesia helps with localised transportation of heat and mass exchange for an area of stronger convection for a certain area to form and if divergence is weak enough and low-level convergence can occur then that’s the very general idea of tropical cyclogenesis formation.

This setup is a good example of how the intertropical convergence zone (ITCZ) can help with formation of tropical storm systems given the ITCZ’s effect on the MJO and the link between the two. The ITCZ is the band of convergence around the equator where trade winds from the northern and southern hemisphere meet. A pre-existing ITCZ can sometimes help with convective layer growth strengthening in the MJO as it did with Indian Ocean convection here. The modulation of MJO strength from weak convective layer upscaling strength with a strong ITCZ is at about a 30% rate for MJO strengthening events but this appears to be one of them with the convective envelope diffusing down from an initial ITCZ appearing to modify MJO strength.

The Indo-Pacific MJO modified temperature pool is a big factor in pre-conditioning for the intensification over the Indian Ocean into an equivalent category 5 strength tropical cyclone. The outflow from the convection envelope west of Indonesia develops its own cold pool with the convection warm pooling and that’s important because that cold pool is dynamically lifted equatorward and along the northern edge of that cold pooling is the strongest shearing sector parallel to the cold pooling and so the MJO pre-modifies the shearing in the Indian Ocean. The warm pool meanwhile has little shearing associated and as shearing plays a big role in whether a Tropical Cyclone forms

The MJO convection envelope also increases the absolute vorticity in the general vicinity with the best lobe of vorticity showing between Australia and the northern edge of Indonesia increasing the convergence in the tropics area and the MJO clearly has quite a big influence on the development of the trough system with the best low-level characteristics of high convergence, large amounts of energy and low shearing for cyclone Freddy to eventually form.

There’s also a cold dry air slot on the other side of the convection with the outflow that’s part of the suppressed MJO phase for that area with a noted ‘Gill response’ like movement in moisture either side of the dry slot with the main mode of the convection being westerly as it was around that time that the westerly winds associated increased in the area and the low-level wind field started becoming more cyclonic around the area of formation.

The primary source of energy in the tropics is the latent heat release meaning that the strongest source of the storage of potential energy is the small-scale temperature gradients. The localised heat flux being important in transferring surface energy to the atmosphere and modification of low-level wind fields via energy and meridional wind budget redistribution from the replacement of heating.

The low-level atmosphere moisture is of course linked to the amount of latent heat released and impacts upon the convective rain which is important for the energy budget in the atmosphere and has more of a response in the tropical atmosphere than stratiform rain. Therefore, the distribution of smaller scale heat diffusion within CCKW’s here are linked more to the MJO convection envelope than their independent uniform quasi-geostrophic balanced gradients.

The latent heat release at the surface is related more to the MJO’s effect on the ITCZ and the orography of regions than relatively larger CCWK’s. The MJO and a CCKW are not completely independent of each other though; the synoptic scale zonal winds linked to a passing CCKW are noted to have similarities when understanding MJO and the supressed and active phases. The area between pre-CCKW easterlies and the westerly winds are often an area of the active MJO phase before it becomes mostly stratiform precipitation with the westerly wind burst as the convection gets suppressed. You can even see that on the diagram with the lift and moisture just above the surface skin across the Oceania region followed by the less buoyant dry air that’s reached south of the Semarang area.

The smaller scale latent heat release is not a direct link with the CCKW and more to do with the diffusion of warm air from MJO forcing on sub-synoptic scales therefore the MJO plays a big role in the active distribution of heating and energy in the tropics important for forcing Kelvin and Rossby waves on tropical and planetary scales as well as being a predictor for wavebreaking on both spatial and temporal scales.

You can see the large-scale moisture and warmth fall from the equator and poleward (this is situated in the southern hemisphere) and that’s probably characterised best by the warm air over Australia and that also managed to reach New Zealand as the Rossby Wave train (RWT) passed towards the southern Pacific. However, that is besides the point.

It is more difficult (compared to the MJO) to attribute localised moisture returns to a CCKW as these are much smaller scale than a kelvin wave is and the strongest outflow and wind anomalies may not be delineated by the strongest convection and subtle troughs also attributed to the MJO cannot be picked up well (usually) by a CCKW diagram.

"

A few quotes from my recent forecasts

28th February;

"So we have a double AAM spread with the MJO Indo-Pacific linear time linking. This looks to put tension on eastwards movement in the North Atlantic and drag the jet back. So this is really looking like a sign that this upcoming event may not be it if we can get it all to time together for just before late March though anytime before then is good really if we can get the best fetch in terms of easterly or northerly."

The forecasts do suggest something on the chilly side but I think it's too late for anything really that cold away from Scotland but I'm still quite happy with that given that it's monthly forecasting. I think people will have more memory of the first one though.

March 8th

"This is a setup similar to the PM air around mid-Jan for the UK with the SE US ridge and mid-Atlantic ridge. That helps with the trend towards a PM airflow for the next effects of the RWT. Initially, the pull is just from the WNW and that really struggles to pull in cold but as the high moves further North it pulls it more from the NNW and so mid March may bring in chilly air again."

It ended up being late March but I'm fairly happy with that, it was in line with the models at the time and time give credit to them at Day 12 or so they were only a week under the time it's sort of expected at.

March 13th

"This WWB likely destructively interfered with the holding pattern signal as the SSW's influence weakened into just the retrogressing RWT and that' where we begin to see the North Pacific return to the low pressure above the ridge given the shift towards jet retraction given the -VE EAMT over the coming days supporting a return to semi-zonal/UK-Scandi high to be more influential as we move towards April."

Boom, really happy with that though it was perhaps an easier forecast than the others.

The destructive influence of the WWB can be seen at just day 3 really well now and it'd setting up a more semi-zonal kind of setup with a jet retraction rather than an equstorward jet as the AAM falls from the recent -VE EANY though the retraction is unlikely yo be large. The SE US ridge isn't entirely stable in terms of advection given that it's the start of US storm season it can easily be pulled up via WAA from troughs and that may favour a weak RWT like pattern especially as momentum rises rather than falls over the North Atlantic and so I could see the rising of the UK-Scandi high possibly sometime around April. AAM is unlikely to rise enough for it now and the North Pacific Jet stays slightly retracted buy I think eventually we'll see a poleward shift/extension and as we go into Spring that may favour AWB that leads to a UK-Scandi type high. Given the nuetral/Nino ENSO state expected and how the AAM has been acting over Winter, there may be a slight favour towards a warmer summer however thers only if the high is forced correctly. As it could quite easily be forced into the mid-Atlantic if the SE US ridge remains in place as that's the typical response given that setup as a Rossby packet 'pushes through'. Alternatively, if the forcing from the background signal is for AWB similar to early March then unlikely early March; the high might be pushed more towards a UK-Scandi high and that's typically a warm summer flow as far as I know. It's what some of the seasonal models are showing with an Ekman pumping esque WAA scenario which is really not good for the heat haters.

There's a lot less teleconnection forecasting that can be done for Spring and Summer though and you rely a lot on essentially composites based off how the monsoon seasons go around the world surprisingly. I think it's too early to base Summer of the SSW though as its destructive influence is likely to end sometime in April as the WWB in the ENSO seeks to have had more of an effect on the setup particularly in North America over the recent week or so. So despite SSW's typically having really bad Springs for people who like moderately warm Springs, this might not be too bad. Though I do still worry about the SE US ridge because if it can't get too high then we may have a windier Spring than Winter and if it can't get too low then we may be chillier because it promotes mid-Atlantic blocking and polar maritime air as a side effect. It has to be just right if it remains there.

The problem with wanting little precipitation in early Spring is that it tends to come from the dry air pattern that can remain through Summer like last year and so droughts become a risk. Then if one trough comes along and a big thunderstorm is formed then flash flooding can be a major risk.

 

[Cambrian]

Without a doubt, a lively week and weekend of weather coming up, but I like the 12z UKMO for attempting to keep it as simple as possible over the next 7 days - steady eastward transfer of the low from Newfoundland across the Atlantic and then it ploughs on, through the whole of Europe to northern Russia, with the next low deepening as it moves into the mid-Atlantic looking to follow.

 

Starting mild, but turning decidedly colder as the low pressures gets to our east and draws down a northerly. 

But there’s always a complication! This time in the form of that little runner through the English Channel on Sunday - a bit further north and mixing with the cold air, easy to imagine that as the kind of runner that could bring some snow on its northern edge, 

  

like with 12z GEM that brings the precipitation a bit further north as the cold air digs south, and appears to set off a bit more activity more widely further north too as the low links up with the trough over the North Sea and the Scottish Borders.

   

Still plenty of time for adjustments north or south, and potentially more interaction with the trough too - one last snowfall from the dark half of the year would be a great way to kick off British Summer Time! 

[stodge]

Evening all

Not too much to add this evening - the clash of airmasses across North America seems set to generate LP systems which trundle out into the Atlantic and toward us.

No all-powerful jet stream or PV at work but the north vs south battle we often see across North America at this time allows for cyclogenesis where the air masses meet and, as we know, at this time there's plenty of risk of severe weather including tornadoes.

The Greenland HP continues to wax and wane and we're now seeing a signal for renewed heights from the south which is usually the signal for something warmer, drier and more settled and I'm beginning to think we could soon see a better spell (perhaps around the turn of the month) as HP builds in from the southwest  but that's a very long way off. The signal for Greenland ridging south east seems to have faded for now but it's hard to believe we won't see any northern blocking as we move into April.

[Stuie]

Looking at ENS from the GEFS/ECM and ICON, the rest of the month is neither BBQ weather or SLEDGE. Wellies will be required though.

How the ECM has managed at least 5 days without and outlier (yes nearly further on) is a deffo reset internally. It`s tighter than a Scotsman`s wallet (Yip I am Scottish).

EDIT: Why the GFS continues with a snow row is beyond...

Edited March 20, 2023 by Stuie

[Stuie]

Looking at the AO across the pond, you can see why the GFS OP has really been in question also. SSW or not, agreement has been poor. If someone could post model verification stats from all models this year that would be great.

[Rain All Night]

3 hours ago, Stuie said:

Looking at the AO across the pond, you can see why the GFS OP has really been in question also. SSW or not, agreement has been poor. If someone could post model verification stats from all models this year that would be great.

Here's what I've got. I don't know where to get the NOAA verification graphs that Met4Cast posts, which have the NAVGEM and the Indian GFS on them (though not the NASA model).

Recent det runs at forecast day 5, by date, higher score is better: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=NHem Extratropics&day=5&score=Anomaly correlation

Det runs across one month (not sure which month), by forecast day, lower score is better: https://charts.ecmwf.int/products/plwww_m_wmo_mean_extratr?area=Northern Hem Extratrop&parameter=z500 ...although half of the models seem to be missing from this plot at the moment...

Ensembles across three months, by forecast day, higher score is better: https://charts.ecmwf.int/products/plwww_3m_ens_tigge_upper_mean?area=Northern Extra-tropics&parameter=Geopotential 500hPa ...it will be really interesting to see this graph after the ECMWF ensemble has had all of its members upgraded to det run resolution!

Strangely the ICON (DWD) is only shown on the ensembles graph, and also strange, is that I'm not aware of any enthusiast site that has the ICON 7-day global ensemble, only its 5-day Europe and 2-day Central Europe ensembles.

Thanks go to Blessed Weather from whom I originally learned of these links.

Edited March 21, 2023 by RainAllNight

[Rain All Night]

9 hours ago, mushymanrob said:

Possibly, but at this range i wouldnt worry about the detail, and i have no idea how accurate those precip prediction charts are. It must be said though that the EPS 00z wasnt as progressive with the ridge on the 12z i posted. The main theme is an expected ridge to build to our near South, the 546DAM is over most of England and Wales, how much ppn we get will depend on how strong the ridge builds, and i find that sometimes its the timing thats out more than the pattern..

 

Here we go, the models are a little more willing to commit this evening.

Edited March 21, 2023 by RainAllNight

[daz_4]

ECM OP went little bit off rail this morning for my location. 

[Cambrian]

The ECM extended range weather regimes forecast from yesterday extends the duration of the majority NAO+ signal to the end of the month, compared to around the 26th from Thursday’s forecast. The signal through to the end of week 3, around the 10th, is stronger too. 20th / 16th

 

Continued extension of this NAO+ period into April is likely. Though the weekly mean height and mean pressure anomalies for the next three weeks do pick up on a build of heights to the south in week 2, this remains to the south of the UK and Ireland and is shortlived. A general westerly flow is sustained throughout, great for surfers. 

  
  

More widely, the signal for northern heights, from Greenland to the top of Scandinavia, that we have had for months on these extended forecasts, is being lost. 

The 0z ECM mean for day 3 is representative of this week, showing a strong Atlantic trough, unsettled, wet and windy.

 

The day 10 chart is more positive with the height anomaly to the south, bringing the best chance for something a bit more settled for a brief while around the end the month, but the mean chart shows an uninterrupted straight westerly flow from North America, low pressure in place all the way from Newfoundland to Norway, and no substantial change by day 15.

  

The 0z GFS mean is more entertaining of building heights to our south in around a couple of weeks time, day 15 here, but it’s still a NAO+ profile with low pressure over the North Atlantic feeding a westerly flow into Northwest Europe, in keeping with the precipitation charts showing good totals for the UK and Ireland and a continued increase through the last few days of the month into April - these are from the 0z GFS op for day 7 and 14. Again, no signal any more for northern heights, a healthy looking core PV over the pole. 

   

Two points:

The loss of northern heights - After a year or two of a very quiet Atlantic, it would be quite the irony if it is finally waking up for a sustained spell heading into the middle of spring after a double-warming SSW. 

The NAO+ pattern - With the summer to come, and hot and dry spells very likely indeed, this is a great looking spell, indeed a potential lifesaver, for the rivers, lakes, aquifers etc. Let’s enjoy the rain. 

[Rain All Night]

10 hours ago, RainAllNight said:

Here we go, the models are a little more willing to commit this evening.

The ECM 0z ensemble drops an anvil quite quickly on the ridging effort at the end of the month as Cambrian describes, the GEFS 0z is still willing to give it a go at connecting with Greenland but I am expecting that to be gone on the 6z which is loading now...

Edited March 21, 2023 by RainAllNight

[jamesthemonkeh]

A couple of things have taken my interest in the models - firstly this Friday sees moderate levels of CAPE over the southern half of England, and Ireland, so some of us should see some tasty showers, maybe some hail and thunder mixed in.

 

 

Secondly, the GFS ensembles showing a chance of something a little warmer, briefly, around weekend of 1st April - tentatively backed up by the ensemble charts from @RainAllNight, though I'd suggest low confidence right now.

 

 

Hopefully I'm not the only one wanting something warmer now!

 

Edited March 21, 2023 by jamesthemonkeh

[Rain All Night]

1 hour ago, RainAllNight said:

The ECM 0z ensemble drops an anvil quite quickly on the ridging effort at the end of the month as Cambrian describes, the GEFS 0z is still willing to give it a go at connecting with Greenland but I am expecting that to be gone on the 6z which is loading now...

The GEFS 6z does indeed follow the ECM 0z back towards continued mobility:

Both suites have teased with the faint hope of a lovely Spring day from one of the ridging attempts some time around the 30th...

Edited March 21, 2023 by RainAllNight

[Summer8906]

Hoping the GFS 06z doesn't come off, this really is stuff from hell.

Nothing but damp, dismal southwesterlies from that right out to the end of the run, except a brief northerly on the 26th, ridge on the 27th and a southerly overnight 30th/31st.

This will be the worst "spring" for many, many years if that comes off.

I hope it's an outlier; the 00z does give some hope for something better once we get into April.

[Guest]

6 minutes ago, Summer8906 said:

Hoping the GFS 06z doesn't come off, this really is stuff from hell.

Nothing but damp, dismal southwesterlies from that right out to the end of the run, except a brief northerly on the 26th, ridge on the 27th and a southerly overnight 30th/31st.

This will be the worst "spring" for many, many years if that comes off.

I hope it's an outlier; the 00z does give some hope for something better once we get into April.

March is looking pretty normal to be honest. Not settled but not overly cold. Re the worst spring you seem to have forgotten about 2021 which contained one of the worst April/May combinations on record….

[Summer8906]

3 hours ago, Cambrian said:

The ECM extended range weather regimes forecast from yesterday extends the duration of the majority NAO+ signal to the end of the month, compared to around the 26th from Thursday’s forecast. The signal through to the end of week 3, around the 10th, is stronger too. 20th / 16th

 

Continued extension of this NAO+ period into April is likely. Though the weekly mean height and mean pressure anomalies for the next three weeks do pick up on a build of heights to the south in week 2, this remains to the south of the UK and Ireland and is shortlived. A general westerly flow is sustained throughout, great for surfers. 

  
  

More widely, the signal for northern heights, from Greenland to the top of Scandinavia, that we have had for months on these extended forecasts, is being lost. 

The 0z ECM mean for day 3 is representative of this week, showing a strong Atlantic trough, unsettled, wet and windy.

 

The day 10 chart is more positive with the height anomaly to the south, bringing the best chance for something a bit more settled for a brief while around the end the month, but the mean chart shows an uninterrupted straight westerly flow from North America, low pressure in place all the way from Newfoundland to Norway, and no substantial change by day 15.

  

The 0z GFS mean is more entertaining of building heights to our south in around a couple of weeks time, day 15 here, but it’s still a NAO+ profile with low pressure over the North Atlantic feeding a westerly flow into Northwest Europe, in keeping with the precipitation charts showing good totals for the UK and Ireland and a continued increase through the last few days of the month into April - these are from the 0z GFS op for day 7 and 14. Again, no signal any more for northern heights, a healthy looking core PV over the pole. 

   

Two points:

The loss of northern heights - After a year or two of a very quiet Atlantic, it would be quite the irony if it is finally waking up for a sustained spell heading into the middle of spring after a double-warming SSW. 

The NAO+ pattern - With the summer to come, and hot and dry spells very likely indeed, this is a great looking spell, indeed a potential lifesaver, for the rivers, lakes, aquifers etc. Let’s enjoy the rain. 

I don't think we can bet on a good summer on the basis of very long term models. Knowing the general pattern since 2007, I'd say we actually need a good spring!

[mushymanrob]

7 minutes ago, Summer8906 said:

Hoping the GFS 06z doesn't come off, this really is stuff from hell.

Nothing but damp, dismal southwesterlies from that right out to the end of the run, except a brief northerly on the 26th, ridge on the 27th and a southerly overnight 30th/31st.

This will be the worst "spring" for many, many years if that comes off.

I hope it's an outlier; the 00z does give some hope for something better once we get into April.

it looks to me like a pretty normal pattern, unsettled and mild... spring 2018 was very wet, 16th wettest out of 258 (source EWP) ...

[Summer8906]

1 minute ago, mushymanrob said:

it looks to me like a pretty normal pattern, unsettled and mild... spring 2018 was very wet, 16th wettest out of 258 (source EWP) ...

Will reply on the moans thread (also comment of @Alderc) as it will drag it off model chat...

Edited March 21, 2023 by Summer8906

[MP-R]

2 hours ago, Summer8906 said:

Hoping the GFS 06z doesn't come off, this really is stuff from hell.

Nothing but damp, dismal southwesterlies from that right out to the end of the run, except a brief northerly on the 26th, ridge on the 27th and a southerly overnight 30th/31st.

This will be the worst "spring" for many, many years if that comes off.

I hope it's an outlier; the 00z does give some hope for something better once we get into April.

Let's see how April turns out and even May first... at this point in March 2006 it was looking like a terrible spring, likewise 2018, but fortunes did change somewhat when May and April came along respectively.

There do seem to be signs of attempts at height rises from the south into April... I'd like to see these play out in future runs and see if it can become a trend. Had a brief spell of warm sunshine this afternoon and it's got me longing for a high pressure spell even more!

Edit: just realised this is not the Chat thread. Mods feel free to move to the Chat thread if you feel it appropriate.

Edited March 21, 2023 by MP-R

[Rain All Night]

I just realised that we'll have to wait an hour longer for each model output after Sunday 

[Stuie]

Looks like a bit of a back edge squall line across EA tomorrow morning as the front passes through.

EDIT: Alaro hinting also (hour later)

Edited March 21, 2023 by Stuie

[Cloud 10]

Nice cross polar Northerly for Sunday on this evening's ECM.

 

[Stuie]

Find this slightly interesting. We have 2 LP`s to the West, cold air being dragged from the pole and also milder air being drawn from the Azores due to HP.

[Cambrian]

Springtime extremes alert….

12z GFS operational run for the UK and Ireland at day 3 - ‘nice’!; at day 9 - actually properly nice ; at day 15 - ‘nice’ again! 

  

Yes, the 12z GFS operational run has something for everyone. For those in the south craving a bit of warmth, there’s 18 degrees in London on the 30th, 16 degrees widely across the English south and Midlands. Dry away from Scotland and the northern half of Ireland. 28 degrees in March in southern Spain. The warmth from the March ‘plumette’ works further north on the last day of the month, with spots in Northern England reaching 18 degrees. 

    

A slightly different feel to things by day 15 with the return of some snow to Scotland, Ireland and the Welsh hills, the warmth by then over Eastern Europe.

 

The real action of course, the wholesale defection of the PV from the Siberian side to the North American / Greenland side of the Arctic - just in time for the Easter holidays. ‘Nice’. 

Meanwhile, 12z ECM operational run is firming up the cold for Sunday / Monday, -8 uppers through the south coast, snow for many parts of Scotland, northern and eastern England, including Kent, by Sunday evening, and transitional snow into the north Midlands and Wales by a week today. 

   

And quite a transition it is too, as following that, like with the GFS, mid to high teens for southern England and the Midlands by day 9.

[Summer8906]

11 minutes ago, Cambrian said:

Springtime extremes alert….

12z GFS operational run for the UK and Ireland at day 3 - ‘nice’!; at day 9 - actually properly nice ; at day 15 - ‘nice’ again! 

  

Yes, the 12z GFS operational run has something for everyone. For those in the south craving a bit of warmth, there’s 18 degrees in London on the 30th, 16 degrees widely across the English south and Midlands. Dry away from Scotland and the northern half of Ireland. 28 degrees in March in southern Spain. The warmth from the March ‘plumette’ works further north on the last day of the month, with spots in Northern England reaching 18 degrees. 

    

A slightly different feel to things by day 15 with the return of some snow to Scotland, Ireland and the Welsh hills, the warmth by then over Eastern Europe.

 

The real action of course, the wholesale defection of the PV from the Siberian side to the North American / Greenland side of the Arctic - just in time for the Easter holidays. ‘Nice’. 

Meanwhile, 12z ECM operational run is firming up the cold for Sunday / Monday, -8 uppers through the south coast, snow for many parts of Scotland, northern and eastern England, including Kent, by Sunday evening, and transitional snow into the north Midlands and Wales by a week today. 

   

And quite a transition it is too, as following that, like with the GFS, mid to high teens for southern England and the Midlands by day 9.

That said the 12z is missing the two things that would get me interested for spring: a) several consecutive days of fine weather, or b) cold locked-in for a few days, enough to give some snow in the south.

Seriously hoping that run does not verify for early April.

 

Edited March 21, 2023 by Summer8906

[Rain All Night]

I just noticed that the ECM op 12z shows next Tuesday as being even colder than Monday! No support from any other sources though...