2018 severe wx/chase season discussion

[Andy Wehrle]

It's obviously way out in clown land, but there's been a signal for several GFS runs now of another significant system crossing the central CONUS after the first. It's interesting how the 06Z run goes from no CAPE over NW TX/SW OK at 18Z Thursday the 22nd, to almost 2000 j/kg and a PDS TOR hazard type on the soundings valid for 06Z (1AM) Friday the 23rd! That would be a very scary situation if the soundings looked like that at verification hour! By 18Z Friday it bombs the low out to 969 MB over central NE!

 

[Jeff Duda]

There are some signs of an event showing up on the CFS dashboard (reminder URL: http://www.spc.noaa.gov/exper/CFS_Dashboard/) for the 17-18 March period, but only a handful of recent runs are showing it. Also, given the shape of the SCP and precip fields, it's hard to tell whether the model is catching a dryline forced event or more general convection associated with a completely different forecast trough. At that forecast range (day 10-18) there is absolutely no guarantee the model is even forecasting the same synoptic scale evolution.

 

[Jonathan Beeson]

This is the first real "traditional" synoptic look of the spring for a severe weather setup for the plains and points eastward, which gives me a little bit more confidence in the models than this past weekend's NW flow mess.

Also, of interest to me is that both the GFS and the Euro have a weaker primer system traversing the area late this week and into the weekend ahead of the stronger system next week. That may help moisture return get into place considering March usually isn't the most favorable month climatology wise for robust moisture return.

 

[Quincy Vagell]

There are some signs of an event showing up on the CFS dashboard (reminder URL: http://www.spc.noaa.gov/exper/CFS_Dashboard/) for the 17-18 March period, but only a handful of recent runs are showing it. Also, given the shape of the SCP and precip fields, it's hard to tell whether the model is catching a dryline forced event or more general convection associated with a completely different forecast trough. At that forecast range (day 10-18) there is absolutely no guarantee the model is even forecasting the same synoptic scale evolution.

Is it just me, or has that dashboard not updated since March 6th? I realize there are many other places to access CFS data, but I'm just making sure.

To chime in on the "state" of the severe weather season, I'm really not very impressed with progs for this weekend into early next week. The models have been inconsistent and are feeling around for the evolution of the pattern.

Taken literally, the 12z Euro (largely supported by the EPS) shows substantial troughing across eastern North America, which limits moisture return across the central U.S. Combine that with a fast flow, featuring several systems, and there isn't much reason to believe there can be substantial moisture transport, i.e. dew-points over 60F, overlapping with favorable CAPE/shear profiles, much farther north than the Arklatex vicinity. This of course, is unless the evolution drastically changes. Furthermore, the data suggests that troughing over the eastern Pacific is going to throw yet another wrench in this pattern.

It looks to me that several surface lows will quite possibly, if not probably, eject from the Rockies into the Plains over the next 7-10 days, but it does not appear that any of these systems will emerge as a substantive low, capable of producing more than isolated/spotty severe.

I'm not too worried about it, since it's still early in the season. I'd rather see this sort of junky setup in March than April, given the overall lack of moisture, model consistency and perhaps most importantly, lack of ridging across the eastern third of the continental U.S.

Sure, it's possible that one or two of these systems may improve somewhat as time moves on, but I wouldn't start rearranging plans or scheduling any sudden chasecations just yet.

 

[Jeff Duda]

Is it just me, or has that dashboard not updated since March 6th? I realize there are many other places to access CFS data, but I'm just making sure.

Good catch! I did not see that at first. That's unfortunate, as that site offered IMO the best graphical display of CFS uncertainty specifically for severe threats. It is hard to find good CFS data elsewhere. I know http://cfs.hopwrf.info/ still plots CFS graphics, but only starting at week 3 and beyond. Otherwise, COD still plots deterministic CFS runs, but they don't make any TLE products, just their dProg/dt display option.

As to what Brandon and Quincy have discussed, I have seen a persistent trend for negative 500 mb height anomalies dominating western North America through the 6-14 day range, which implies a lot of western US troughing. And this is not just one wave, either, but rather a succession of troughs coming out across the southwest and west central US. If it was late April or May I would be very excited about the prospect of an extended period of severe weather. But the last few troughs that have affected the central/eastern US have done their part to mostly clean out the Gulf of good moisture, and moisture return is not going to be as rapid at this time of year as it will be two months from now, so that's one of many ingredients that will probably not be in place to make any of these troughs particularly threatening for good severe weather.

 

[Brandon Centeno]

It is rather disappointing to see the recent trends in model guidance. To me, the killer isn’t quite the eastern trough. While having a stouter ridge in place would certainly help, sustained vort maxima traversing the plains actually seems to be distorting the surface pattern and really veering the flow such that moisture return is being significantly impeded compared to earlier runs.

I’ve seen a lot of “too bad this pattern is happening now and not later.” Friendly reminder that patterns are not used up! There’s no magical well the atmosphere goes digging through until it runs dry in June. For all we know, April and May could be dominated by a central US ridge like last season. It could also be dominated by western troughing. Sure seems like we are headed for an active base state similar to one of the more active seasons in recent history. GWO forecasts show no sign of slowing down, granted there is a bit of noise at the week 3 range leading to uncertainty. Inevitably a quiet stretch will come by, but it could simply be an active year for us in the plains. This is suggested by research focusing on declining Nina years. We will see what that holds; but I believe there is reason to be quite optimistic about plains chasing this year.

 

[Tim Paitz]

I'm being St. Louis-centric with this, but what about St. Louis?

I mean, March is pretty much shot, Intellicast is showing chilly weather for some time, and there hasn't been much severe weather in the spring here for the past few years. We already had the best severe weather at this point last year.


I've been thinking about buying a couple dashcams for my car in the miraculous event there is chaseable severe weather around here.

 

[DNewman]

Now that we are in mid March. I'd like to see and hear the latest thoughts regarding the severe weather season. Especially seeing drastically increased rainfall across areas near and east of I-35 during mid to late February, which significantly put a dent in ongoing drought conditions or eliminated them completely. I have been monitoring low level features and upper level patterns over the last several weeks since late February. And I've noticed strikingly similar setups to 2011 with the dryline surging much farther east past the I-35 corridor in the last couple of weeks here in Texas. When the dryline doesn't mix out west of I-35 and continues into deep east Texas during the spring , this more often times than not means significant drought and or very dry soil, vegetation conditions across western areas of the state of Texas. Which is why we saw repeated events either east of Texas from 2011-2014 or in a handful of cases from near I-35 and points east from March through April, with reduced events in May. Being in Texas all my life and studying state weather anomolies and climate patterns (being no expert however). I'd be willing to put money on a more active Spring severe weather season due to a lingering very weak La Nina affect that will continue into the upcoming months, before turning more neutral by June. Areas along and east of I-35 have a higher chance at seeing above average severe weather this season from Texas to Kansas primarily, with the farther east you are, the better your chances of seeing more tornadoes from my experience. The entirety of the panhandles of Ok/Tx into western Kansas and into west Texas and areas nearby have yet to see any meaningful precip, and this will not get any better this spring.

 

[Warren Faidley]

I have no reason to think the spring SVR regions for 2018 will be any different than recent drought years. The western regions of Texas, Oklahoma and Kansas are still suffering from drought conditions with almost weekly extreme fire risks. Soil moisture content is something I always consider as the season progresses. The current soil moisture map (link below) is hauntingly similar to where the true DL has been setting up on average since the drought began, with the exception of course for late season RH which generally remains undisturbed. It would be interesting to overlay severe weather events on these maps over a course of months / years. (Map source: https://www.drought.gov/drought/data-maps-tools/soil-moisture)

 

[Jeff House]

Believe it will be difficult to get a true trough west ridge east pattern while the atmosphere works through the sudden stratospheric warming SSW hangover and continued blocking. Early in the season one really needs a ridge back East to help moisture return. Rest of March I predict BN activity but that does not mean no activity.

If the La Nina breaks down correctly, anomalies warming in 1-2 before 3-4, the TNI could set up bullish. Subsurface right now is not pointing that way, but much can change before the April predictability barrier. Either way I expect closer to normal activity in April as the SSW hangover ends.

 

[Michael Snyder]

It's going to be like most other years, good for some, junk for others, periods of inactivity, periods of higher activity.

It is rather disappointing to see the recent trends in model guidance. To me, the killer isn’t quite the eastern trough. While having a stouter ridge in place would certainly help, sustained vort maxima traversing the plains actually seems to be distorting the surface pattern and really veering the flow such that moisture return is being significantly impeded compared to earlier runs.

I’ve seen a lot of “too bad this pattern is happening now and not later.” Friendly reminder that patterns are not used up! There’s no magical well the atmosphere goes digging through until it runs dry in June. For all we know, April and May could be dominated by a central US ridge like last season. It could also be dominated by western troughing. Sure seems like we are headed for an active base state similar to one of the more active seasons in recent history. GWO forecasts show no sign of slowing down, granted there is a bit of noise at the week 3 range leading to uncertainty. Inevitably a quiet stretch will come by, but it could simply be an active year for us in the plains. This is suggested by research focusing on declining Nina years. We will see what that holds; but I believe there is reason to be quite optimistic about plains chasing this year.

 

[Tim Paitz]

This cold, rainy November-like weather needs to GTF outta here. Now.

 

[Quincy Vagell]

March will likely end as another below average month in terms of tornadoes across the U.S.

There is at least some potential for spotty severe from Sunday through Tuesday, but none of those days particularly stands out, despite having a slow-moving trough moving from the Southwest into the southern Rockies. It's a case of being early in the season and nearly constant troughing over the eastern U.S.

Sunday's threat is quite conditional, but there does appear to be a narrow corridor from North Texas into the Red River Valley region that could support an isolated supercell threat. Forcing, both large scale and mesoscale, appears limited, but model forecast soundings have trended toward better boundary layer heating than previous days. This may be enough to erode surface-based convective inhibition.

Monday could be a bigger day, if it was not for messy looking wind profiles. There is a veer-back-veer signature in almost all forecast soundings, and hodographs are not impressive at all, especially in the 0-3km layer. Mesoscale details could augment some of the kinematic issues, but I doubt this will be a significant or widespread severe day.

Tuesday's threat pushes south across Texas and the lower Mississippi Valley region. Wind profiles become worse, largely unidirectional as a sagging frontal boundary becomes increasingly parallel to the deep layer shear vectors. A squall line with thunder and locally excessive rainfall will likely evolve.

There is not much hope for substantial rainfall over the High Plains in the days ahead, but areas from I-35 and points east will see several opportunities for heavy rain over the next 3-5 days.

Once the trough moves east, the pattern looks relatively quiet through the end of March, with a generally WNW flow aloft and no notable areas of low pressure across the Plains. This will probably result in a continued threat of fire weather from the southern Rockies into the High Plains.

 

[TJ Schulte]

I’ll tell you what guys this has been one long winter. December was brutally cold, and here we are in late March with still the same pattern. Even today in Toledo, it’s a high of 38 with pure sunshine.

I will say the jet has been pretty active (just look at the amount of nor easters) so when the pattern shifts I’d look for it to be active in the severe season. Last year we saw an incredibly active early severe season just shut down by the time May rolled around, a reverse of that would be nice and I’d expect it honestly

 

[Ethan Lang]

I have had only one chaseable setup in my area and it was on the one night of that week where I was busy and unable to chase