Central/Western Summer Medium/Long Range Discussions

[HM]

It's the first run we've seen this but the new 12z ECMWF does the following key things in the extended range:

 

1. Jet energy kicks out cold air, allows next wave day 7-10 to close off more east.

2. Gulf of Alaskan Low retrogrades to Aleutians, pumps NE PAC ridge and gets some legit s/w action into the West by day 10.

3. A monster -NAO develops at the end of the run (hasn't shown this yet but I brought up this potential while speculating yesterday).

 

While the first and last point seem like new developments, the second one is not despite the smaller details. The ECMWF has trended progressively more semi-zonal 5/15-20, unlike the GFS family.

 

The GGEM is sort of a compromise solution between the extreme/more westward closing off low of the GFS and quick moving / semi-zonal ECMWF. I'm sure all ensemble means will follow their operational model's general depiction but I'm interested to see if the EPS looks like the op EC. Clearly, the GFS ensemble memebers/mean is following the GFS op closely.

 

No matter the outcome, it seems the Gulf opens up for business during that time...especially on the GGEM and ECMWF.

[HM]

not really ideal with some 500 ridging mainly over the mtns but probably still works by late May for activity in the high plains at least at times with any little ripple. tho probably better to have a zonal look at range than some sort of highly convoluted blocky crap or something.  still seems to be a tendancy for lower than normal heights in the NE or the Gulf area .. tho the GFS has been showing little trouble with moisture as we head into later May. capping might be a problem tho.

 

This next Canadian-northern CONUS wave early next week could break more west like the GFS and keep a similar pattern going. The new ECMWF is more progressive/further east with it while the GGEM is sort of a compromise (with slight hedge toward the ECMWF). This wave seems a bit important for the overall evolution of 5/15-5/25. I would go even as far as saying the ECMWF and GGEM suggest some actual potential in two weekends, but way too early.  

 

 

In fact, the ECMWF's solution is so drastic that it shows a full -NAO pattern developing now where it hasn't previously. We'll see if this is a new development or some erroneous run in the coming days.

[Ian]

I want to be positive but recent models look pretty meh. At least my focus is still 10+ days out.

[Dsnowx53]

I want to be positive but recent models look pretty meh. At least my focus is still 10+ days out.

 

 

It does seem, though, that even at the longer range, there is great ensemble agreement for a very tight gradient/active PAC Jet. Along with a relatively zonal flow across the CONUS -- any shortwave can hopefully pump the heights out ahead of it enough to make the GOM available for access...it's not like there is a huge GOM trough, so a shortwave should be enough to help orient the heights somewhat favorably.

 

As you said, capping could be an issue due to EML advection and the fact that you are only relying on a shortwave and thermodynamics for lift, rather than dynamics, since the main energy is still to the north and there are no true longwave troughs. With the main energy to the north, you also get relatively slow mid and upper level winds, as well. But an active train of shortwaves in a zonal regime is not terrible. 

[Dsnowx53]

This next Canadian-northern CONUS wave early next week could break more west like the GFS and keep a similar pattern going. The new ECMWF is more progressive/further east with it while the GGEM is sort of a compromise (with slight hedge toward the ECMWF). This wave seems a bit important for the overall evolution of 5/15-5/25. I would go even as far as saying the ECMWF and GGEM suggest some actual potential in two weekends, but way too early.  

 

 

In fact, the ECMWF's solution is so drastic that it shows a full -NAO pattern developing now where it hasn't previously. We'll see if this is a new development or some erroneous run in the coming days.

 

 

00z Euro doesn't have quite the Greenland block that the 12z Euro had, but it does have a small west-based block. 

 

Looks like it also likes a nice little shortwave in a pesudo downstream zonal/split flow regime for an okay setup on the 19th or so. 

 

It's also not as zonal as the previous run -- the previous run looked better for a more active train of shortwaves, whereas the energy was a lot more consolidated and convoluted out in the PAC on the 00z run. I'd still say though that shortwaves would have to eject out from that monster Aleutians Low and eject eastward. Hopefully the gradient can "re-retreat" back southward enough where we can get shortwaves interacting with the STJ instead of staying north and riding the Canadian rollercoaster. 

[Ian]

It does seem, though, that even at the longer range, there is great ensemble agreement for a very tight gradient/active PAC Jet. Along with a relatively zonal flow across the CONUS -- any shortwave can hopefully pump the heights out ahead of it enough to make the GOM available for access...it's not like there is a huge GOM trough, so a shortwave should be enough to help orient the heights somewhat favorably.

 

As you said, capping could be an issue due to EML advection and the fact that you are only relying on a shortwave and thermodynamics for lift, rather than dynamics, since the main energy is still to the north and there are no true longwave troughs. With the main energy to the north, you also get relatively slow mid and upper level winds, as well. But an active train of shortwaves in a zonal regime is not terrible. 

 

Well the good news is even the bad runs have moisture generally and there is qpf etc. Just not sure the shear will be there always but by late May daily storms are more  norm than not somewhere out there.  Good upslope days often have a ridge axis somewhere in that 100-110W area.. just not sure we're late enough into the season for that but I guess we're close at least. 

 

I do think the changeability in the long range is still a signal something might shift toward more troughiness in the west but who knows. I think one way or another it'll be fine.. but the way this year has gone doesn't help with the optimism lol.

 

The last 1 to 2 weeks of waiting is awful generally.

[icebreaker5221]

Well the good news is even the bad runs have moisture generally and there is qpf etc. Just not sure the shear will be there always but by late May daily storms are more  norm than not somewhere out there.  Good upslope days often have a ridge axis somewhere in that 100-110W area.. just not sure we're late enough into the season for that but I guess we're close at least. 

 

I do think the changeability in the long range is still a signal something might shift toward more troughiness in the west but who knows. I think one way or another it'll be fine.. but the way this year has gone doesn't help with the optimism lol.

 

The last 1 to 2 weeks of waiting is awful generally.

 

 

 

I think at this point that's pretty unlikely that you see any large-scale troughiness in the west, at least throught the 20th.  Your best best before then will probably be if a split flow develops, and either chasing shortwaves that go up and over the crest of the trough in the northern high plains (better dynamics), or further south where a potentially active subtropical jet with a few sneaky shortwaves in the better thermodynamics. 

 

FWIW the CPC 11-day multi-model analogue best match right now is 05-02-2006.  In an otherwise crappy year for chasing, that week wasn't horrible, with several sneaky shortwaves embedded in an active STJ making things interesting for TX.  05-06-1992, the 2nd best analogue, was quiet for a few days but followed by a respectable tornado event in OK on the 11th. 

[Ian]

I think at this point that's pretty unlikely that you see any large-scale troughiness in the west, at least throught the 20th.  Your best best before then will probably be if a split flow develops, and either chasing shortwaves that go up and over the crest of the trough in the northern high plains (better dynamics), or further south where a potentially active subtropical jet with a few sneaky shortwaves in the better thermodynamics. 

 

FWIW the CPC 11-day multi-model analogue best match right now is 05-02-2006.  In an otherwise crappy year for chasing, that week wasn't horrible, with several sneaky shortwaves embedded in an active STJ making things interesting for TX.  05-06-1992, the 2nd best analogue, was quiet for a few days but followed by a respectable tornado event in OK on the 11th. 

 

Yeah, I agree on the troughing.. honestly don't even care that much about anything before then. The earliest we'll be on the Plains is afternoon/evening of the 19th if we really book it west.

 

I wouldn't necessarily expect any large-scale troughing after either but it's possible.  The 6z GFS offered up some nice late run eye candy but not anything to get excited about at this point.

[HM]

The thing that was the "take-away" with the overnight/morning data is the modeling trending toward the ECMWF's idea. We'll see if the 12z runs hold, but the idea of a second "cutoff low" that holds the PNA pattern in place just went out the door on the GFS.

 

We are having issues in the tropical forcing department, mainly in terms of speed (already flying into phase 3) and tropical cyclones. There is "tropical cyclone 24" battling f-->0 and meandering about. The exact timing/strength of this along with the general superclusters that make up the "MJO" wave are going to skew the subtropical anticyclones and jet placements in the NH.

 

The situation east of the MJO is more inhospitable for its maintenance but we will see a stagnant / Walker Cell-related area of tropical forcing get a boost in uplift from this wave. This should promote quicker changes than what the GFS was portraying over the last few days, so I'm glad to see it move toward the ECMWF.

[HM]

The new 12z GFS continues the trend of keeping the next low north of the US-Canadian border with a warmer/more zonal flow for the CONUS. It becomes more and more threatening starting in two weekends/beyond (where two potent Pacific waves come crashing into the West Coast).

[Thundersnow12]

The 12z GFS continues it's trend and IMO looks even better than the Euro for chasing and actually pretty nice heading into 17-19th with with some decent little setups as early as next Tues in TX. Probably it's best run in at least the last 3-4 days.

[HM]

The last of these miserable Canadian Highs drops southeastward next week, positioning nicely for return flow into the Plains. The dewpoints will actually be respectable for a change, lol.

[Chrisrotary12]

Hi everyone.  Chris from New England. I will be heading your way on the 16th and will be out there until the 26th.  

 

I must say that the trend in the GFS has been nice.  I was actually a little excited when I saw this mornings GFS run.  

 

Let us all hope that this continues.

[Chicago Storm]

The 12z GFS continues it's trend and IMO looks even better than the Euro for chasing and actually pretty nice heading into 17-19th with with some decent little setups as early as next Tues in TX. Probably it's best run in at least the last 3-4 days.

You're really grasping straws now...

[andyhb]

This doesn't look like a bad pattern on the GFS ensemble mean heading into truncation.

 

[Ian]

This doesn't look like a bad pattern on the GFS ensemble mean heading into truncation.

 

something's gotta give at some pt.

 

edit: actually, looking over the 12z ensemble.. pretty decent run of recent.

[HM]

The MJO database is pretty limited; but, I thought I would mention that this month's wave is one of the strongest orbits through the Indian Ocean.

 

Here is a list of other years where their May RMM data was quite strong in phase 2:

 

2010
2005* 5/3 2.607186
1995
1993
1991
1990* 5/10 2.423260

1987
1982
1981

1979

1978

 

This year will not get a MAY RMM value in phase 2 as high as 2005 and 1990 but its orbit through the Indian Ocean is easily one of the strongest as a whole of the years above.

 

[HM]

I am bringing up phase 2 because of the paper(s) posted a while back where there was apparently some correlation with phase 2 and tornadic activity. Clearly, it is dangerous using the MJO to forecast tornadic activity alone, especially with some specific "phase 2" correlation (or any phase).

 

Larger scale patterns in the air/ocean, ENSO, stratosphere, general Walker/Hadley Cell behavior, QBO, solar activity etc. all play a role in spring circulation. This can change/alter the "meaning" of the MJO correlations of each phase as circumstances change. As we've seen this year and in some of the past years on the list, Indian Ocean forcing can combine with these major players in circulation to produce a rather horrible pattern for tornadoes.

[andyhb]

something's gotta give at some pt.

 

The Euro doesn't look bad either through 168, already has a s/w moving across the central CONUS (which develops from the Baja ULL) with a broad trough in the Pacific NW in behind.

[Ian]

The MJO database is pretty limited; but, I thought I would mention that this month's wave is one of the strongest orbits through the Indian Ocean.

 

Here is a list of other years where their May RMM data was quite strong in phase 2:

 

2010

2005* 5/3 2.607186

1995

1993

1991

1990* 5/10 2.423260

1987

1982

1981

1979

1978

 

This year will not get a MAY RMM value in phase 2 as high as 2005 and 1990 but its orbit through the Indian Ocean is easily one of the strongest as a whole of the years above.

 

lol.. some weenie years at least up top.

 

funny when i saw the 6z gfs this moring i thought june 1995.. of course i was looking at high plains upslope setups last night (there was one a few days later in CO) and caught that evolution. side note on 95 .. it had some sort of EC low at the same time as the big chaser events. gom up the coast, tropical?

[Ian]

The Euro doesn't look bad either through 168, already has a s/w moving across the central CONUS (which develops from the Baja ULL) with a broad trough in the Pacific NW in behind.

 

euro looks very solid. two in a row with some hope. 228 500 anomalies might be the best map i've seen in weeks.

[andyhb]

euro looks very solid. two in a row with some hope.

 

The Pacific NW trough deepens substantially at 192, with an axis in Central/Southern CA (i.e. a historically consistent pattern).

[HM]

The ECMWF clearly shows, again, the retrograding N PAC low which means the western ridge retrogrades. This allows the next set of troughs to dive into the West as the MJO orbit through 4-5 would indicate. Suddenly, things are beginning to line up for a change (which calms my nerves lol).

 

In terms of the wave next week, the ECMWF/GGEM look similar with the "west -NAO domain" but only the GGEM ends up looking poor over the CONUS for tornadoes. I think it went way overboard with the idea where the ECMWF/GFS look more reasonable.

[andyhb]

The ECMWF clearly shows, again, the retrograding N PAC low which means the western ridge retrogrades. This allows the next set of troughs to dive into the West as the MJO orbit through 4-5 would indicate. Suddenly, things are beginning to line up for a change (which calms my nerves lol).

 

In terms of the wave next week, the ECMWF/GGEM look similar with the "west -NAO domain" but only the GGEM ends up looking poor over the CONUS for tornadoes. I think it went way overboard with the idea where the ECMWF/GFS look more reasonable.

 

I like the consistency that the Euro has been showing with this feature over the past number of runs, both in timing and position.

[Dsnowx53]

euro looks very solid. two in a row with some hope. 228 500 anomalies might be the best map i've seen in weeks.

 

 

I really liked last night's Euro ensembles, too. 

[HM]

lol.. some weenie years at least up top.

 

funny when i saw the 6z gfs this moring i thought june 1995.. of course i was looking at high plains upslope setups last night (there was one a few days later in CO) and caught that evolution. side note on 95 .. it had some sort of EC low at the same time as the big chaser events. gom up the coast, tropical?

 

lol

 

Interesting. I haven't gone through all of the data but it would appear in May that once the MJO gets out of the IO, severe thunderstorm activity starts to increase in the mid-section of the US.

 

Sounds like you are talking about Allison:

http://en.wikipedia.org/wiki/Hurricane_Allison_(1995)

[HM]

I like the consistency that the Euro has been showing with this feature over the past number of runs, both in timing and position.

 

Yes, definitely liking the trends. I think the the models, especially the GFS, were suffering with the complicated IO setup in the last few days. These strong MJO waves can and usually do set off cyclones in the IO, which can tamper with the subtropical to mid latitude circulation. Because we sorted through the mess and found legitimate signals, we anticipated the potential for these changes. But we can't get comfortable now because there are likely more changes ahead.

 

The wave next week interacting with all the features in the NAO domain is a situation that can easily change drastically. Also, the MJO may not be done yet giving us headaches as it begins to settle into the climo walker cell region. How quickly will it bounce out of there and head for the Atlantic again? Could there be an "Allison" again this year, like in 1995 as the MJO returns to the Atlantic in June? The PDO continues to trend more positive and has definitely impressed me. It will take a hit with this new pattern though.

[Dsnowx53]

12z Euro Ensembles look great post May 20. Looks like a split flow regime. Blocking in NW Canada forces energy to slide underneath, and there is a bit of troughing in a relatively zonal regime out west. Very active PAC Jet as well. 

[Ian]

18z op GFS has a nice look LR. Eventually the trough is pretty east for the Plains with a big ridge behind but days of action first and with an EC ridge probably stuff with NW flow.

Definitely a more positive look last several runs.

[wxmeddler]

Zonal with small shortwaves is better than anything else we've had this season. Take what we can get at this point.