April 14-17th Severe Weather (Day 3 Mod)

[baroclinic_instability]

Random, but from what I've heard from various chasers yesterday (so take that for what it is worth), there were definitely at least a few touchdowns yesterday (Elgin, Lawton, Grandfield, etc) -- how come the SPC page still has nothing? 

I am guessing because Norman did not LSR any tor reports yet. They routinely do that until confirmation.

[Ian]

Extremely disappointing chase day. I missed the tornadoes, but from all indications there wasn't a whole lot to miss. I think the unusually high number of caveats (for a 15% hatched type setup) were well-understood here going into the event, and I can't say I'm shocked by the outcome. Even so, given the ungodly pattern we're now entering and coming on the heels of 2012, this stings quite a bit.

 

No point in dissecting the SPC products ad nauseum, but I would say this: even though I was surprised by and didn't exactly understand the D3 MDT, just because of its rarity and implied significance, I think the D2 MDT yesterday was warranted given the guidance at the time. The ceiling was too high (so it seemed) not to start sounding alarms at that stage. So, if it was eventually going to be MDT anyway, does the D3 really matter in the scheme of things?

I don't think it matters other than the fact that a whole bunch of people compare past instances of D3 mods and what they do on D1 when a moderate risk is fairly subjective to begin with.

 

This might be another negative for social media. Why did Carbin post his tweet about Mar 1990 as the top analog? I don't think the general public understands this stuff enough to realize that you might see that and get a totally different solution. 

 

Everything's a spectator sport these days. Those who do real analysis still rise above in the long run but they get lost in the melee.

[OKpowdah]

7 tornado reports up on SPC

 

http://www.spc.noaa.gov/climo/reports/yesterday.html

 

[brettjrob]

I am guessing because Norman did not LSR any tor reports yet. They routinely do that until confirmation.

 

This. There's been griping about this from chasers and weenies for years and years every time something happens in our CWA. I can even remember looking at the reports page the night after a big outbreak (5/10 or 5/24, maybe?) and seeing no TOR reports in the state, lol.

[Ian]

When should I start worrying about our trip? Mid may thru early June. The chasers on twitter all seem ready to cancel the season lol.

[LocoAko]

When should I start worrying about our trip? Mid may thru early June. The chasers on twitter all seem ready to cancel the season lol.

 

Well, if it makes you feel any better...  

 

http://www.americanwx.com/bb/index.php/topic/39838-mediumlong-range-thread/?p=2262055

[Ian]

Well, if it makes you feel any better...

 

http://www.americanwx.com/bb/index.php/topic/39838-mediumlong-range-thread/?p=2262055

 

I've actually been kind of optimistic.. tho it is disheartening to see Gulf clearing cold fronts in late April. IMO the last two years went too big too soon.. so the reverse might be a positive for later? Much more moisture etc this year as well.  What we've seen and see progged next few weeks one reason why I'm not sure how anyone can do a tour in April. Seems too hit or miss unless you're a local. 

 

At this rate it might be snowing in Nebraska in June though.

[HM]

Today was just a cluster___ of everything going wrong that could, it seems. I understood why the initial storms were messy (VBV), and also why they stayed messy later into the afternoon and evening (frontal orientation and undercutting). But when a new round fired on the DL down south late, I really thought the day would redeem itself, as RAP soundings had shown a markedly different and near-textbook wind profile in that spatiotemporal window. Granted, the Vernon/Oklaunion storm did eventually become the most impressive of the day with a few confirmed touchdowns, but I'd have expected something more earth-shattering given its unimpeded inflow. Given the same setup again, it would be very tough to write it off.

 

I'd be very curious to know whether the outcome would have been drastically different had the warm front lifted about 50-60 mi. farther N (especially W of I-35), or if the environment still would have produced underwhelming results all the same.

Something else to consider was the stability of the inflow parcels. The source region/eastern TX developed a sort of surface ridge with some of the low level moisture being mixed out a bit (950-850mb esp. developing drier pockets). Notice the loss of stability on the FWD sounding from 12z to 18z:

http://www.spc.noaa.gov/exper/soundings/13041712_OBS/FWD.gif

http://www.spc.noaa.gov/exper/soundings/13041718_OBS/FWD.gif

You can also revisit the SPC meso page to see the drier/stable pockets. As the initial thunderstorms took advantage of the deep moisture/instability that pooled near the frontal boundaries, the inflow brought in parcels that were more stable, relatively-speaking.

Finally, the anvil level winds (yeah I like to use these a lot to blame) were not ideal to begin with and grew even worse with time. Over the area of supercell growth, the anvil-level winds increased to 60 KT, mainly easterly. The anvils on the visible loop made it clear into the lower Mississippi Valley. This warming agent (anvil contamination) may have also played a role in the insufficient VPPGF to overcome the negative buoyancy of the high M air of the RFD. Throw in the increasingly poor stability of the source-region inflow, and the negative buoyancy may have won the battle, preventing near-ground parcels from properly lifting near the strongest horizontal vorticity.

[LocoAko]

I've actually been kind of optimistic.. tho it is disheartening to see Gulf clearing cold fronts in late April. IMO the last two years went too big too soon.. 

You're tellin' me. It was in the 30s and windy when I came to work this morning. It just ain't right, I tell ya... 

[brettjrob]

Something else to consider was the stability of the inflow parcels. The source region/eastern TX developed a sort of surface ridge with some of the low level moisture being mixed out a bit (950-850mb esp. developing drier pockets). Notice the loss of stability on the FWD sounding from 12z to 18z:

http://www.spc.noaa.gov/exper/soundings/13041712_OBS/FWD.gif

http://www.spc.noaa.gov/exper/soundings/13041718_OBS/FWD.gif

You can also revisit the SPC meso page to see the drier/stable pockets. As the initial thunderstorms took advantage of the deep moisture/instability that pooled near the frontal boundaries, the inflow brought in parcels that were more stable, relatively-speaking.

Finally, the anvil level winds (yeah I like to use these a lot to blame) were not ideal to begin with and grew even worse with time. Over the area of supercell growth, the anvil-level winds increased to 60 KT, mainly easterly. The anvils on the visible loop made it clear into the lower Mississippi Valley. This warming agent (anvil contamination) may have also played a role in the insufficient VPPGF to overcome the negative buoyancy of the high M air of the RFD. Throw in the increasingly poor stability of the source-region inflow, and the negative buoyancy may have won the battle, preventing near-ground parcels from properly lifting near the strongest horizontal vorticity.

 

Good observations. I hadn't seen the 18z FWD sounding, and that is some rather pronounced low-level drying for a six-hour period.

 

Just to clarify, regarding anvil-level winds: are you theorizing that they were actually too strong, allowing anvils to contaminate the inflow air prematurely?

 

To me, the storm structures as observed by radar were clearly "off" all day, which leads to me suspect the vertical shear profile as a major culprit. Initially, from about 2-4pm, the warm sector storms had trouble even taking on supercell characteristics. But even after they began to do so in the 4-6pm timeframe, the RFDs appeared long and wet, manifesting on reflectivity as nasty appendages rather than classic hook echoes. This was very pronounced on both the initial Lawton storm and the one behind it, near Frederick at the time.

 

The tail-end storm that ramped up near Oklaunion around 7:30pm eventually looked closer to prototypical, but very HP. For that storm, I can imagine some of the issues you raised being the main limiting factors.

 

Revisiting last night's mesoanalyses, the hodograph kink likely never went away, even into the evening. I had a bad feeling about that, even as models insisted it would improve just in the nick of time; I've seen advertised last-minute improvements to veer-back-veer profiles fail to materialize, at great cost, more than once. Even at 01z, H7 winds look to have been slightly more veered than H5. Really, the trough just doesn't look that great, as CoastalWx alluded to. It verified just slightly sharper and slower than most of the guidance, which probably made a critical difference in the geometry of the flow fields.

 

Note the 20-30 degree backing over much of OK from the NAM to the analysis:

 

http://www.twisterdata.com/data/models/nam/221/maps/2013/04/17/00/NAM_221_2013041700_F24_WSPD_500_MB.png

http://www.spc.noaa.gov/exper/ma_archive/images_s4/20130418/00_500mb.gif

[HM]

 

Good observations. I hadn't seen the 18z FWD sounding, and that is some rather pronounced low-level drying for a six-hour period.

 

Just to clarify, regarding anvil-level winds: are you theorizing that they were actually too strong, allowing anvils to contaminate the inflow air prematurely?

Yes they could have influenced the "return" inflow but I don't see this being something detrimental to the supercell as much as tornadogensis, given the other parameters. It may have just taken away a little more buoyancy that was needed to make up for the short-comings with the wind shear/mid level wave that you described as the main culprit.

 

To me, the storm structures as observed by radar were clearly "off" all day, which leads to me suspect the vertical shear profile as a major culprit. Initially, from about 2-4pm, the warm sector storms had trouble even taking on supercell characteristics. But even after they began to do so in the 4-6pm timeframe, the RFDs appeared long and wet, manifesting on reflectivity as nasty appendages rather than classic hook echoes. This was very pronounced on both the initial Lawton storm and the one behind it, near Frederick at the time.

 

The tail-end storm that ramped up near Oklaunion around 7:30pm eventually looked closer to prototypical, but very HP. For that storm, I can imagine some of the issues you raised being the main limiting factors.

The wind shear issue you and others raised is valid. Then again, we did manage to get a few right-turning supercells and tornadoes. I think we would have had a few monster tornadoes yesterday if the flow was more southwest at anvil level and the "source" region was equally as unstable/moist as what pooled near the boundaries. So when the right-turning supercells commenced, they would have had the buoyancy they needed to sustain the updraft at the time of maximizing M in the supercell.

 

Revisiting last night's mesoanalyses, the hodograph kink likely never went away, even into the evening. I had a bad feeling about that, even as models insisted it would improve just in the nick of time; I've seen advertised last-minute improvements to veer-back-veer profiles fail to materialize, at great cost, more than once. Even at 01z, H7 winds look to have been slightly more veered than H5. Really, the trough just doesn't look that great, as CoastalWx alluded to. It verified just slightly sharper and slower than most of the guidance, which probably made a critical difference in the geometry of the flow fields.

 

Note the 20-30 degree backing over much of OK from the NAM to the analysis:

 

http://www.twisterdata.com/data/models/nam/221/maps/2013/04/17/00/NAM_221_2013041700_F24_WSPD_500_MB.png

http://www.spc.noaa.gov/exper/ma_archive/images_s4/20130418/00_500mb.gif

Definitely agree that VBV profiles can and have been detrimental (we may have seen that with the high risk episode in 2009 that didn't deliver). That certainly was one of the factors that limited a potential major tornado outbreak.

The h5 trough was definitely slower and the speeds were too, when compared with the NWP. But there still was a vort that traveled right through N TX-OK ahead of the main trough last night.

I default to you guys as far as what you think was the main culprit. Every year I learn something new, at the very least, from you guys.  

[OKpowdah]

One thing that we observed yesterday with three supercells that passed near / north of FDR, were very similar evolutions, with the rear flanks becoming elongated and then racing eastward, quickly occluding. I could see that mid level weakness in the hodograph encouraging this to some extent.

 

We saw a lot of lowerings, and lots of rotation in the clouds. Low level shear was fantastic.

[a mighty wind]

I don't think it matters other than the fact that a whole bunch of people compare past instances of D3 mods and what they do on D1 when a moderate risk is fairly subjective to begin with.

 

This might be another negative for social media. Why did Carbin post his tweet about Mar 1990 as the top analog? I don't think the general public understands this stuff enough to realize that you might see that and get a totally different solution. 

 

Everything's a spectator sport these days. Those who do real analysis still rise above in the long run but they get lost in the melee.

Hey Amin...Pro Forcaster...you seem to rely on SPC, then critique...

Your forecasts are wrong too, hmmmmm.

[Ian]

Hey Amin...Pro Forcaster...you seem to rely on SPC, then critique...

Your forecasts are wrong too, hmmmmm.

I don't think I made a forecast.

[a mighty wind]

I don't think I made a forecast.

So...as the ADMIN of this site, you had no opinion of this potential outbreak? Really???

Dude, step down.

[SmokeEater]

I don't think I made a forecast.

So...as the ADMIN of this site, you had no opinion of this potential outbreak? Really???

Dude, step down.

So being an admin of this forum requires him to issue a forecast? He's a respected member of this forum, you have 8 posts in 2 years, calm yourself. Or in fact, don't, you won't last long here. And where were you when this event was going on? Nowhere to be found. You only showed up to attack him.

[a mighty wind]

WOW, thanks mr. respected member...

So being an admin of this forum requires him to issue a forecast? He's a respected member of this forum, you have 8 posts in 2 years, calm yourself. Or in fact, don't, you won't last long here. And where were you when this event was going on? Nowhere to be found. You only showed up to attack him.

I will be sure to take your valued opinion into consideration, SmokeEater, because 7,000 meaningless posts is so credible at 21 years old. HA!

[Ian]

So...as the ADMIN of this site, you had no opinion of this potential outbreak? Really???

Dude, step down.

 

i had opinions. they just weren't that critical to the situation. 

[SmokeEater]

WOW, thanks mr. respected member...

So being an admin of this forum requires him to issue a forecast? He's a respected member of this forum, you have 8 posts in 2 years, calm yourself. Or in fact, don't, you won't last long here. And where were you when this event was going on? Nowhere to be found. You only showed up to attack him.

I will be sure to take your valued opinion into consideration, SmokeEater, because 7,000 meaningless posts is so credible at 21 years old. HA!

Keep going, you'll be banned shortly, lol.

[JoMo]

EF-1 in  Spavinaw  and they haven't surveyed the Grove or Tulsa area ones yet I don't think.

 

http://www.srh.noaa.gov/tsa/?n=weather-event_2013april17

[David Reimer]

WOW, thanks mr. respected member...

So being an admin of this forum requires him to issue a forecast? He's a respected member of this forum, you have 8 posts in 2 years, calm yourself. Or in fact, don't, you won't last long here. And where were you when this event was going on? Nowhere to be found. You only showed up to attack him.

I will be sure to take your valued opinion into consideration, SmokeEater, because 7,000 meaningless posts is so credible at 21 years old. HA!

 

Take it from a fellow 21 year old, you're acting like a 14 year old. You must not have taught etiquette. 

[CoastalWx]

Something else to consider was the stability of the inflow parcels. The source region/eastern TX developed a sort of surface ridge with some of the low level moisture being mixed out a bit (950-850mb esp. developing drier pockets). Notice the loss of stability on the FWD sounding from 12z to 18z:

http://www.spc.noaa.gov/exper/soundings/13041712_OBS/FWD.gif

http://www.spc.noaa.gov/exper/soundings/13041718_OBS/FWD.gif

You can also revisit the SPC meso page to see the drier/stable pockets. As the initial thunderstorms took advantage of the deep moisture/instability that pooled near the frontal boundaries, the inflow brought in parcels that were more stable, relatively-speaking.

Finally, the anvil level winds (yeah I like to use these a lot to blame) were not ideal to begin with and grew even worse with time. Over the area of supercell growth, the anvil-level winds increased to 60 KT, mainly easterly. The anvils on the visible loop made it clear into the lower Mississippi Valley. This warming agent (anvil contamination) may have also played a role in the insufficient VPPGF to overcome the negative buoyancy of the high M air of the RFD. Throw in the increasingly poor stability of the source-region inflow, and the negative buoyancy may have won the battle, preventing near-ground parcels from properly lifting near the strongest horizontal vorticity.

 

It all ties into the basics HM, which is why I had a few flags up, although I just ,mentioned it in the SNE forum.

 

H5 was a stinker..mentioned why earlier. Srfc low pressure was never really text book and followed the warm fron so to speak...crappy way to get severe. There are a few examples...and your anvil winds would not be an issue with a nice ejecting s/w. Sometimes it's good to go back to the basics.

[FSMweather]

WOW, thanks mr. respected member...

So being an admin of this forum requires him to issue a forecast? He's a respected member of this forum, you have 8 posts in 2 years, calm yourself. Or in fact, don't, you won't last long here. And where were you when this event was going on? Nowhere to be found. You only showed up to attack him.

I will be sure to take your valued opinion into consideration, SmokeEater, because 7,000 meaningless posts is so credible at 21 years old. HA!

I wouldn't call Smokeeater's posts pointless at all. He is always the first one in these forums to post storm reports or scanner reports. That is pretty significant in my book, and especially helpful if you have family members that you can't contact in a area that a bad storm hit.

[andyhb]

I wouldn't call Smokeeater's posts pointless at all. He is always the first one in these forums to post storm reports or scanner reports. That is pretty significant in my book, and especially helpful if you have family members that you can't contact in a area that a bad storm hit.

 

Meh, I wouldn't pay attention to him, don't have a clue where he came from but he seems like another mongoose/reber (or w/e that guy's name was) on the loose.

[andyhb]

Wxmann brought up some good points over the past few days and I'm glad BI actually agreed. Just like weenies in the east when it comes to a snowstorm..sometimes people push back and bash someone who brings up red flags. There were a few big flags here, but such is the nature of convection. Some of the more mundane setups spit out supercells and TORs like nothing, while other setups that seem to have the big calling cards are just missing one small detail..and that's all it takes to keep activity down. To me H5 was one of the flags. + titled trough and no good S/W ejecting out and tilting the trough -. When you have a s/w kick out and eject from the Rockies like that, the divergence, shear, windfields  heightfalls, and rapid intensification of the low all  contribute to a big outbreak.  It doesn't always have to happen like that, but I certainly was not impressed with the H5 setup, despite the shear looking good.

 

Yes, ala 5/24/11, I believe you posted a graphic of the H5 pattern with that low amp s/w and it had that SW "kick" at H5 that you mentioned ramping up the low level flow fields and increasing diffluence aloft.

 

That's actually a feature I now look more for especially with neutral/negatively tilted troughs, the Christmas storm had it in the Deep South.

[OKpowdah]

Wxmann brought up some good points over the past few days and I'm glad BI actually agreed. Just like weenies in the east when it comes to a snowstorm..sometimes people push back and bash someone who brings up red flags. There were a few big flags here, but such is the nature of convection. Some of the more mundane setups spit out supercells and TORs like nothing, while other setups that seem to have the big calling cards are just missing one small detail..and that's all it takes to keep activity down. To me H5 was one of the flags. + titled trough and no good S/W ejecting out and tilting the trough -. When you have a s/w kick out and eject from the Rockies like that, the divergence, shear, windfields  heightfalls, and rapid intensification of the low all  contribute to a big outbreak.  It doesn't always have to happen like that, but I certainly was not impressed with the H5 setup, despite the shear looking good.

 

Yeah, you can also see how the jet streaks aren't quite perfectly coupled. There was a bit of a battle between the ridging over the Midwest and the trough axis extending from Montana northeastward.

 

One of the things I mentioned a few days ago was looking at the extent to which convection along the warm front extending into the Midwest could pump up ridging to the north and west, helping to anchor the northern section of the trough axis further west, and the polar jet streak to the west. Not quite enough.

 

The result was the more elongated area of lift oriented SW-NE which kind of left part of the Great Plains down into the panhandles "exposed" to cold high pressure pushing southward.

 

 

But that's some pretty impressive upper level divergence to be seen on a synoptic chart ... in the equatorward entrance of the jet over eastern KS and eastern NE ... 80kt perpendicular to 55kt. If we could've had that shifted west/southwest, synoptically at least, it would've been a different story

[HM]

 

It all ties into the basics HM, which is why I had a few flags up, although I just ,mentioned it in the SNE forum.

 

H5 was a stinker..mentioned why earlier. Srfc low pressure was never really text book and followed the warm fron so to speak...crappy way to get severe. There are a few examples...and your anvil winds would not be an issue with a nice ejecting s/w. Sometimes it's good to go back to the basics.

 

You are right that things all tie into each other. But who's to say that a more classic, ejecting s/w would have produced a more substantial outbreak/stronger tornadoes? While improving the shear profiles, it could have easily ingested more of those stable profiles downstream or perhaps promoted a linear system much earlier in the day. There are a number of reasons it could have made things better or worse.

Even with an improved h5, you still would have had the westerly upper level jet and strong anvil level winds. They would not have matter as much I'm sure if the hodos were better but...

If a strong, classic s/w would have ejected and promoted a quick linear response or simply frontal convection, the anvil winds would have still mattered (even if slightly).

I guess it doesn't matter. In the end, we did get awesome supercells to form so it wasn't like the shear vector or h5 wave was that ineffective. I suppose my perspective was coming from the moment of truth where we needed a sufficient updraft to influence the horizontal vorticity. So my instincts were to look at the lowest level buoyancy, tendency of parcel stability and environmental temperature.

[HM]

 

Well, if it makes you feel any better...  

 

http://www.americanwx.com/bb/index.php/topic/39838-mediumlong-range-thread/?p=2262055

I guess I'm funny.  

 

I've actually been kind of optimistic.. tho it is disheartening to see Gulf clearing cold fronts in late April. IMO the last two years went too big too soon.. so the reverse might be a positive for later? Much more moisture etc this year as well.  What we've seen and see progged next few weeks one reason why I'm not sure how anyone can do a tour in April. Seems too hit or miss unless you're a local. 

 

At this rate it might be snowing in Nebraska in June though.

I'm in your camp. Despite winter not wanting to let go, you know this kind of thing of delivering Canadian Cold into the Gulf/southern Plains can't go on forever. Logically, the next period for a favorable pattern can only be warmer / less influenced from Canada.

Of course, now that I've said that, a volcano will erupt tomorrow that prevents summer from ever coming!

[OKpowdah]

 

 

You are right that things all tie into each other. But who's to say that a more classic, ejecting s/w would have produced a more substantial outbreak/stronger tornadoes? While improving the shear profiles, it could have easily ingested more of those stable profiles downstream or perhaps promoted a linear system much earlier in the day. There are a number of reasons it could have made things better or worse.

Even with an improved h5, you still would have had the westerly upper level jet and strong anvil level winds. They would not have matter as much I'm sure if the hodos were better but...

If a strong, classic s/w would have ejected and promoted a quick linear response or simply frontal convection, the anvil winds would have still mattered (even if slightly).

I guess it doesn't matter. In the end, we did get awesome supercells to form so it wasn't like the shear vector or h5 wave was that ineffective. I suppose my perspective was coming from the moment of truth where we needed a sufficient updraft to influence the horizontal vorticity. So my instincts were to look at the lowest level buoyancy, tendency of parcel stability and environmental temperature.

 

I do think that at the very least, a more neutrally tilted trough and coupled jet streak would've opened the door to higher potential. With the setup that I discussed above, this would've kept the front from punching south, with more activity staying discrete along the dryline (e.g. one of the best supercells of the day was Grandfield) into and across western OK. This could've been a much more disastrous nocturnal event.

 

The evolution of all of the storms from FDR to LAW was for a rapid elongation of the rear flank that raced eastward, followed by the storm cutting across to the cold side of the front, and then it was over.

 

This difference is pretty clear in the NAM vs. GFS 48hr forecasts too. In the GFS the s/w impulse had rotated further around the base of the trough, with the overall orientation more neutral vs. positive, and the jet streaks are much better coupled. And of course we saw how this manifested itself in the model differences ... major outbreak vs. well, what we saw.

 

 

[OKpowdah]

By the way, here's the event page from the Norman NWS

 

http://www.srh.noaa.gov/oun/?n=events-20130417