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Central/Western Medium-Long Range Discussion


andyhb
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If the lower analog domain is used for Saturday, it shows one of those high-end matches that we saw last week. Either way, a consistent signal of significant potential, if the red flags and limiting factors don't win out.

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12z GFS certainly appears to show a fairly healthy EML being advected over the warm sector Friday night looking at 700 mb RH. Significant increases in instability through the day Saturday as opposed to previous runs (18z/00z/06z) despite some early convection still being there. Also appears to show stronger wind fields.

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Regarding the subtropical jet and its effect on the EML in recent events, where should I look to find the STJ? Is it at 200 mb, 500 mb, 700 mb? Didn’t major Plains events like 4 May 2003 feature a STJ influence? Also, if the EML is at 700 mb and comes from the Sonoran region of northern Mexico, then why is a STJ coming from N Mexico a problem? Is the STJ within the same level as the EML or not? Can, say, a 500-mb STJ affect the quality of the EML at lower levels? If so, how? Maybe I am totally wrong, but I would like to gain some meteorological understanding.

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The 0z Euro itself for Saturday does look pretty ominous even though it has the morning round convection, destabilizes behind into across north TX into western/sw OK with 4000 j/kg and dew points in the low 70's as that jet comes across. 

 

Our trip is probably going to leave very early Friday morning if something like the NAM ends up verifying for that afternoon/evening. 

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Models seem to be moving the next weekend trough forward. Meh. Worried about the period right after as some hints of jet being pinched. Now I remember why I mock the long range model watchers in winter.

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Models seem to be moving the next weekend trough forward. Meh. Worried about the period right after as some hints of jet being pinched. Now I remember why I mock the long range model watchers in winter.

 

Yeah GFS ensembles are trying to latch onto the next weekend trough, maybe Thur-Sat or Fri-Sun before Memorial day and the 12z op Euro has it too. 

 

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Yes all 3 ensemble suites hint at a less meridonal upper level jet ahead of Memorial Day. They also show LLJ responses. This coming weekend of May 15-16 will be great; but, if you can't make it the lead-up to Memorial Day looks good too. Why do I have faith in a 10 day forecast? It is late May in the Plains. If all else fails and/or the trough teardrops again, upslope would verify. This is not like forecasting snow in the South. This is peak tornado season in the Plains.

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Looking at the ECMWF and its ensembles, and considering what's already in the books and about to occur this week, this will easily rank up there with 2008 and 2010 as among the most active May months on the Plains over the past decade. It could easily surpass those, too, since neither had much of anything during the first 10 days. (Speaking of which, since around April 10, there's been no extended downtime lasting more than 5-7 days really... it's been a long while since that's happened, too).

 

Unfortunately, I'm speaking in terms of the broad continental pattern, rather than the results. Last week was something akin to having a 980 mb low pass just SE of Cape Cod in January and Boston only picking up 3-4". "Oh well, there'll be more" -- except we'd been waiting years to see a trough like that in May or June, especially without extreme PBL mixing over the High Plains. We'll see about this Fri-Sat.

 

Even as it stands, and assuming this week falls short of its potential, the "results" for May should be better than all but 2013 out of the past four years. Still, you can go quite a few years without an optimally-timed pattern like this, and it would be nice to cash in finally...

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Still no major sign of it ending. Deeper into the ensembles show less in the way of big trough activity but fairly normal heights across the SW into the Plains. Gotta think one will get it done high end. 

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Still no major sign of it ending. Deeper into the ensembles show less in the way of big trough activity but fairly normal heights across the SW into the Plains. Gotta think one will get it done high end. 

One thing I've noticed too, is that in the long range, particularly >15 days out, the ensembles have consistently "changed" the pattern too quick. First we were supposed to get into ridging in the East in April. Eventually it did happen, but it kept getting pushed back. Now we're been seeing this "death ridge" keep getting pushed back further and further. Question is, when does the pattern give away to climo? We won't see these deep troughs in the West last forever.

 

It looks like most, if not all of the rest of May holds potential with the overall, larger-scale pattern.

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One thing I've noticed too, is that in the long range, particularly >15 days out, the ensembles have consistently "changed" the pattern too quick. First we were supposed to get into ridging in the East in April. Eventually it did happen, but it kept getting pushed back. Now we're been seeing this "death ridge" keep getting pushed back further and further. Question is, when does the pattern give away to climo? We won't see these deep troughs in the West last forever.

 

It looks like most, if not all of the rest of May holds potential with the overall, larger-scale pattern.

I think that's rather typical. Know at least in winter it seems to always take a week or two longer than expected to get a pattern change. Some is the natural smoothing of ensembles at range probably too... as you close in it becomes more "interesting." I'm certainly no long-range guy -- usually lean heavily on persistence. Add that to the look of the ensembles and it's a pretty safe bet it'll be more active than not for probably most of May and seemingly beyond for now.  Even the looks that are quieter after keep fairly persistent SW flow over the Plains. A lot of Nino years have decent Junes.. or at least a bigger event or two. The big NE Pac ridge and the wave disruption from the typhoons are something of wild cards I suppose.. but most other things still seem positive to keep it active it not "perfect." I still tend to think most chasers will be pretty happy with the season once it's over.

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It's interesting that when you look at the large scale pattern that the NPAC Ridge that we have been dealing with for the last few years is still there (although its a bit weaker now it will strengthen towards next week), but the enhanced southerly jet has obviously become important. General pattern looks to remain locked in with a rex block setting up over the west next week. Probably will continue to see a strong jet into the southern plains, and so I would expect at a minimum, more severe weather than average for the next 2-3 weeks.

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Long range more muddled than it's looked for sure. Right on time for the trip! Doesn't seem to go worse than zonal which is likely to have some little waves embedded though I'm sure we are trending toward a NE trough... ;) lol.

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Long range more muddled than it's looked for sure. Right on time for the trip! Doesn't seem to go worse than zonal which is likely to have some little waves embedded though I'm sure we are trending toward a NE trough... ;) lol.

 

Gonna need a pretty deep eastern trough to have any appreciable affect on the Plains this time of year.

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Gonna need a pretty deep eastern trough to have any appreciable affect on the Plains this time of year.

As long as it doesn't set up over the lakes or similar that far west it would probably not be the hugest issue but it wouldn't be the best either. Haven't quite gotten there yet anyway.. Maybe it won't happen.
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Might want to mention that there is a very nice W TX/E NM setup showing up next week (5/19) on the 12z GFS.

Kinda have liked that little trough. Not a huge area of coverage but could be a good day for sure. 

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Regarding the subtropical jet and its effect on the EML in recent events, where should I look to find the STJ? Is it at 200 mb, 500 mb, 700 mb? Didn’t major Plains events like 4 May 2003 feature a STJ influence? Also, if the EML is at 700 mb and comes from the Sonoran region of northern Mexico, then why is a STJ coming from N Mexico a problem? Is the STJ within the same level as the EML or not? Can, say, a 500-mb STJ affect the quality of the EML at lower levels? If so, how? Maybe I am totally wrong, but I would like to gain some meteorological understanding.

An easier way around that is to look at dynamic tropopause maps. The tropopause elevation depends on the airmass and so it tends to be higher in the tropics and lower in the polar regions. At any rate the jet stream (whether polar or subtropical) will show up on this map.

That said the subtropical jet is normally higher but its not always at the same altitude. Even so it will normally be visible on the 200 or 300mb maps.

 

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I wouldn't worry about an op run especially at a 15 day range...

Yeah.. I lose all rationality before chase trips. I'd argue I should be banned if I was a n00b and someone else.

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Yeah.. I lose all rationality before chase trips. I'd argue I should be banned if I was a n00b and someone else.

I understand the worry, you don't want to have to spend money going all the way out there to see nothing. However, we both know you always see stuff out there, the outcome is always the same year to year, it is just the difference is in the details.

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I understand the worry, you don't want to have to spend money going all the way out there to see nothing. However, we both know you always see stuff out there, the outcome is always the same year to year, it is just the difference is in the details.

Yeah that's true. After a bunch of maybenadoes last year I have somewhat high standards for success this go. Waiting is the worst.
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