Central/Western Summer Medium/Long Range Discussions

[andyhb]

After what currently looks quite underwhelming by May standards for 5/7-5/8, the ECMWF continues to advertise another shot just a few days later (5/11-5/12). Its own ensembles are somewhat supportive, while GEFS members are overwhelmingly unsupportive for now.

 

Looking at the means, it appears to be a rather classic case of the GFS being too progressive with the pattern, if this continues to be the idea on the Euro.

[andyhb]

Very substantial signal showing up on the 00z Euro EPS mean for the second system 192 hrs out, despite the lack of intensity/very progressive verbatim from 00z deterministic run. Certainly something to watch given the quality of the moisture return available by this time.

 

[HM]

Good stuff. Your LR expertise is much appreciated, and a lot more valuable than the rest of us just picking at model solutions in the MR!

 

At this point, a two-week period on par with 2013 would be a godsend -- hopefully centered a touch more NW away from populated corridors, of course.

 

Any general thoughts on June and the influence of rapidly-developing Nino conditions? It's remarkable how inactive June has been through the heart of the Plains for three consecutive years now. The most recent ENSO analog, 2009, was quite active and in fact June basically amounted to most of the Plains season. Your last post a couple weeks back mentioned 72, 91 and 97 as the strongest analogs; all had June Plains tornado activity at least within the realm of climo and well above the past couple years (which isn't saying much).

 

At least everyone's expectations are adjusted well given the long-term pattern, drought and building niño. There's no way to sugar-coat a tornado season like this one; but, what last week showed us is that there will be these periods of interest. A total shutout is not the most favored solution but it is more likely than things suddenly going off-the-charts, active, on us. However, I do think years like 1957, 1972, 1991 etc. are good years and, as you indicated, most of them got more active last third of May into mid June.

 

Just focusing on the ENSO signal only, Junes typically see anticyclones from the NE PAC into the Midwest, down through the MS Valley (dry signal is strongest over eastern Plains/Ozarks/MS valley). Year-to-year variability in precipitation/ocean cycles etc. determine if these anticyclones tend to focus more into the Northeast or Northwest US. What can happen is the sub-tropical low, in tandem with monsoonal circulation, can become more assertive into the SW USA, adding some moderate wind shear over the Plains, under anomalous ridges, and increase moisture advection. Some Junes were quite active with legitimate precipitation over your area.

 

It seems to me the MJO should remain active for at least 1 more month. At some point, it will die out as forcing becomes stagnant. Any wave passage through the western hemisphere will help increase mid latitude jet speeds. Notice, currently, the MJO is square over our longitudes while the KW is progressing into the IO...it could be helping out with this week's trough, sort of...but the fact that it is exiting and the Pacific is slowing means, it could also be screwing around things too. 

[HM]

So, factoring in Sam's MQI with the building niño, what do those Junes tend to do more of than the other Junes?

 

List of like MQI years: 2009, 1991, 1986, 1976, 1972, 1965 and 1958

List of opposite years: 2006, 2004, 2002, 1997, 1987, 1982, 1977, 1969 and 1957

Years left-out: 1994, 1968 and 1963 (not on the same wave timing).

 

[HM]

Good discussion by HM, as usual. Models are definitely trending slower with the arrival of a large-scale Western trough pattern.

 

As an aside, the 12Z operational GFS and its ensembles have since 00Z shown a noticeable trend toward a flatter, more zonal/progressive pattern by day six. What seems fairly certain is that we will have a large EML establishing itself over the srn Plains in this time frame, with nice advection of a high-quality warm layer from the Sonoran region of nrn MX. We will probably see good, seasonably deep low-level moisture return from the Gulf at least two days prior to the possible event(s). Big issues continue to be timing and the possibility of capping, but so far the signs look good. In fact we may be looking at multiple events in the srn Plains based on the overall pattern.

 

Thanks. What I'm more unsure of is trying to time quicker KW passages. That doesn't have a lot of skill and their effect is not as pronounce. However, timing a legitimate MJO or a CCKW (convectively-coupled Kelvin Wave) has more skill/effect. Soon, our MJO is going back into the IO. Toward the 20th or so, maybe 5/20-5/25, a CCKW will again cross the dateline/east Pac. It being late May means a slower jet, shorter waves etc. but this force should be enough to add some speed/downstream trough. We'll see...

 

Mike's Components Graphic:

[Ian]

If we have a 2011 redux this might be my last chasecation. Esp if we don't get any Big Texan thanks to the drought. 

[LocoAko]

If we have a 2011 redux this might be my last chasecation. Esp if we don't get any Big Texan thanks to the drought. 

 

 

Could always go get Big Texan and hike Palo Duro Canyon if there is truly nothing to see anywhere. 

[HM]

If we have a 2011 redux this might be my last chasecation. Esp if we don't get any Big Texan thanks to the drought. 

 

It looks pretty wet in the northern Plains on the June composites. You'll head up that way, right (should it look favorable)?

[Ian]

It looks pretty wet in the northern Plains on the June composites. You'll head up that way, right (should it look favorable)?

We'll go wherever we have to. But we are locked in as usual which can be stressful. Not sure there are any years with no good chase days last two weeks of May. Just need a little shear and moisture by then. Honestly the pattern doesn't look great at least to start but the ensembles don't suggest a shutout either.

[Ian]

Could always go get Big Texan and hike Palo Duro Canyon if there is truly nothing to see anywhere.

Might be an option. we've managed to make it to the PH every year so it could still happen.

[HM]

We'll go wherever we have to. But we are locked in as usual which can be stressful. Not sure there are any years with no good chase days last two weeks of May. Just need a little shear and moisture by then. Honestly the pattern doesn't look great at least to start but the ensembles don't suggest a shutout either.

 

Yeah, the NWP right now doesn't look too good mid-month (I know we've been talking about the cold shot mid-month on Twitter with Pacific jet extension). It seems like this next KW passage may not be enough to provide a threat. I wouldn't give up on the beginning, yet, because sometimes the models adjust as the wave's effects become realized.

 

I still like late May. Everything that has brought something significant this season, should repeat again late month:

 

1. Rise in AAM/tendency

2. CCKW/MJO passage through Tropical C-E PAC

3. Temporary drop in the AO.

[HM]

It does appear that the GFS is seeing the KW but, as usual, it is a weak signature. Perhaps trends will grow more favorably 5/15-5/20 as we get closer. Regardless, the last third of May should be...gulp..a lot better.

[Ian]

Yeah, the NWP right now doesn't look too good mid-month (I know we've been talking about the cold shot mid-month on Twitter with Pacific jet extension). It seems like this next KW passage may not be enough to provide a threat. I wouldn't give up on the beginning, yet, because sometimes the models adjust as the wave's effects become realized.

 

I still like late May. Everything that has brought something significant this season, should repeat again late month:

 

1. Rise in AAM/tendency

2. CCKW/MJO passage through Tropical C-E PAC

3. Temporary drop in the AO.

Having a quiet start wouldn't be the worst thing ever. We always are racing out for a threat the next day -- meandering out over two days might be a nice change of pace.  Last yr was such a chasing high anything might seem lesser this go.. as long as we see at least one or two somethings it's a success though. From my weenie perspective the shift into the end of the mo looks decent for now..

[HM]

Hi HM. Great information!

 

Any thoughts on how things might end up here on the southern Prairies of Canada (AB/SK/MB). We've had quite a bit of moisture going all the way back to the winter and look to be in a favorable spot for more in the weeks to come. My concern, severe-wise, is the strength of northern high pressure which has been an issue, at times. If this continues, it may not allow much for convection north of the border in the next month or so.

 

I've got to think that the final third of May throughout June should be good. It's a climo signal, I know, but the pattern from the data above looks fine. Things at some point may go in an unfavorable direction for you, esp. by July. It seems a trough may get anchored over your area or just east of you. This could limit convection but I do not have a lot of information about Canada's severe weather in these patterns.

[HM]

Having a quiet start wouldn't be the worst thing ever. We always are racing out for a threat the next day -- meandering out over two days might be a nice change of pace.  Last yr was such a chasing high anything might seem lesser this go.. as long as we see at least one or two somethings it's a success though. From my weenie perspective the shift into the end of the mo looks decent for now..

 

Hey, any seasoned chasers have just as good of a perspective as anyone trying to figure out long range tornado probabilities. There clearly are no "hard rules" with using tropical forcing-->severe weather outbreaks. I think it depends on the background state of a season. I know there was a paper floating out there about phase 2 of the MJO being correlated, but last year is a great example of that failing (and having to adjust to the mean background state to be more accurate).

 

So, as usual, I'm eager to be taught again this year.

[andyhb]

Great discussion in here HM.

 

12z Euro coming back with a much larger/stronger trough in the 5/10 and beyond period this run, which isn't too surprising considering the 00z run looked to be a heavy outlier from it's ensemble mean.

[HM]

Great discussion in here HM.

 

12z Euro coming back with a much larger/stronger trough in the 5/10 and beyond period this run, which isn't too surprising considering the 00z run looked to be a heavy outlier from it's ensemble mean.

 

Thanks man. Yeah that Euro run today is a big improvement in the extended range. The extreme North Pacific blocking is likely causing some havoc out there in the medium range.

 

Oh, BTW, If you are using the MJO octant graphs to plot when tropical forcing may favor a big outbreak, I'm thinking it will be when it orbits through 5-6-7. It will likely cut into the circle and head for phase 8-1-2, after doing this. Regardless if it is coherent or not, this will be when things may get interesting in Tornado Alley. The true MJO will be in the W. PAC but a CCKW will come through western hemisphere then.

 

For an analog to see a great example of this, look up 1977. 1977 is a pretty okay analog from a SST / MJO standpoint.

[brettjrob]

At least everyone's expectations are adjusted well given the long-term pattern, drought and building niño. There's no way to sugar-coat a tornado season like this one; but, what last week showed us is that there will be these periods of interest. A total shutout is not the most favored solution but it is more likely than things suddenly going off-the-charts, active, on us. However, I do think years like 1957, 1972, 1991 etc. are good years and, as you indicated, most of them got more active last third of May into mid June.

 

Just focusing on the ENSO signal only, Junes typically see anticyclones from the NE PAC into the Midwest, down through the MS Valley (dry signal is strongest over eastern Plains/Ozarks/MS valley). Year-to-year variability in precipitation/ocean cycles etc. determine if these anticyclones tend to focus more into the Northeast or Northwest US. What can happen is the sub-tropical low, in tandem with monsoonal circulation, can become more assertive into the SW USA, adding some moderate wind shear over the Plains, under anomalous ridges, and increase moisture advection. Some Junes were quite active with legitimate precipitation over your area.

 

It seems to me the MJO should remain active for at least 1 more month. At some point, it will die out as forcing becomes stagnant. Any wave passage through the western hemisphere will help increase mid latitude jet speeds. Notice, currently, the MJO is square over our longitudes while the KW is progressing into the IO...it could be helping out with this week's trough, sort of...but the fact that it is exiting and the Pacific is slowing means, it could also be screwing around things too. 

 

Great discussion. A relatively/seasonably active central/northern Plains pattern in June would be welcome, after the past few years.

 

Great discussion in here HM.

 

12z Euro coming back with a much larger/stronger trough in the 5/10 and beyond period this run, which isn't too surprising considering the 00z run looked to be a heavy outlier from it's ensemble mean.

 

That's a rather phenomenal difference between the NCEP and ECMWF guidance between 144-192 hrs. A glance at the 12z CMC shows it's leaning more toward the Euro, thankfully. The pattern progged by both around Sun-Mon is impressive, to say the least. Granted, the ECMWF explicit 2m dew point forecast is gut wrenching for Sunday, but we'll worry about crossing that bridge if/when we get there.

[andyhb]

That's a rather phenomenal difference between the NCEP and ECMWF guidance between 144-192 hrs. A glance at the 12z CMC shows it's leaning more toward the Euro, thankfully. The pattern progged by both around Sun-Mon is impressive, to say the least. Granted, the ECMWF explicit 2m dew point forecast is gut wrenching for Sunday, but we'll worry about crossing that bridge if/when we get there.

 

The southern stream leftovers from Thursday's system appear to be the main problem for Sunday.

[hm8]

FWIW: The 2014 HWT Spring Forecast Experiment began today...not much has rolled out yet but at http://hwt.nssl.noaa...vrforecasts.php you'll be able to find all of the juicy hi-res models they'll be running. If you're into that kinda thing.

[blizzardof96]

Hey, any seasoned chasers have just as good of a perspective as anyone trying to figure out long range tornado probabilities. There clearly are no "hard rules" with using tropical forcing-->severe weather outbreaks. I think it depends on the background state of a season. I know there was a paper floating out there about phase 2 of the MJO being correlated, but last year is a great example of that failing (and having to adjust to the mean background state to be more accurate).

 

So, as usual, I'm eager to be taught again this year.

Really interesting discussion, as always. Are you suggesting that IO forcing is more favourable for plains severe wx in nina springs while 180-100W forcing w/ +AAM is more favourable in nino springs? I believe that this is the paper you were referring too from roundy and thompson: http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-12-00173.1

[nwburbschaser]

I would be all for something along the lines of the 18z GFS solution for the weekend and early next week.

[Ground Scouring]

I'll bet that the 00Z GFS will make some big shifts toward the ECMWF's solution re: Sunday's system. GFS 18Z has already made big changes vs. 12Z.

[brettjrob]

I'll bet that the 00Z GFS will make some big shifts toward the ECMWF's solution re: Sunday's system. GFS 18Z has already made big changes vs. 12Z.

 

Run is coming in and that doesn't look to be the case at all... there's broad western CONUS ridging Sun-Mon. Even with the clear ECMWF superior performance this spring, watch it cave to the GFS this time. I'm on the verge of abandoning all rationality and just assuming the worst-case scenario for everything at this point.

[andyhb]

Run is coming in and that doesn't look to be the case at all... there's broad western CONUS ridging Sun-Mon. Even with the clear ECMWF superior performance this spring, watch it cave to the GFS this time. I'm on the verge of abandoning all rationality and just assuming the worst-case scenario for everything at this point.

 

Nevermind the fact that the GFS has had terrible run to run consistency (not to mention rather poor verification) with practically anything outside of 96-120 hrs all year long.

 

[nwburbschaser]

Run is coming in and that doesn't look to be the case at all... there's broad western CONUS ridging Sun-Mon. Even with the clear ECMWF superior performance this spring, watch it cave to the GFS this time. I'm on the verge of abandoning all rationality and just assuming the worst-case scenario for everything at this point.

For the most part, the ECMWF has been showing potential during that period for a few days now so I would be very surprised if it goes towards that particular GFS solution.  I won't count it out though. 

[andyhb]

I'll mention the crazy 2013-style anafront the 00z Euro shows at 168 for the sake of argument, although the 500 mb evolution is still a world away from the GFS.

[brettjrob]

I'll mention the crazy 2013-style anafront the 00z Euro shows at 168 for the sake of argument, although the 500 mb evolution is still a world away from the GFS.

 

I don't think I've ever seen anything like that this far south in mid May, but the 12z Euro is similar with a crashing front Monday. As for Sunday, moisture quality along the dryline would be mediocre for a late March event, nevermind mid May.

 

Something I know for sure I've never seen: two consecutive high-amplitude western troughs in May that don't warrant any serious tornado threat in the Plains. But that looks like exactly what we have on tap for the next seven days.

[soonertrey]

I don't think I've ever seen anything like that this far south in mid May, but the 12z Euro is similar with a crashing front Monday. As for Sunday, moisture quality along the dryline would be mediocre for a late March event, nevermind mid May.

 

Something I know for sure I've never seen: two consecutive high-amplitude western troughs in May that don't warrant any serious tornado threat in the Plains. But that looks like exactly what we have on tap for the next seven days.

 

I agree....I don't ever remember it happening either.

[Ian]

D10+ ops are all over the place a should be expected I suppose tho even the Euro has a totally different pattern at d10 than it did at 0z. Waiting is the worst.