April 24-30th Severe Potential

[FHSC Sam]

Quick side note, does anyone know if SPC has ever issued a "Day 8" risk before this week?

Not sure, although I dont remember ever seeing one

[brettjrob]

Unfortunately this is going to happen with every event going forward. Not only because those events are fresh in our minds but social media blows everything up and compared to years past there is so much information out there now that the general public gets to see stuff that leads to fear and worry.

 

Yep. Social science is an increasingly large focus of research in meteorology of late, and I have to admit I don't keep up with that aspect closely, so my comments here are more offhand. But to me, there's never going to be a perfect balance between POD and FAR that makes everyone happy. This is true from the storm scale 30 minutes out all the way to the synoptic scale a week out.

 

I think there are absolutely some scenarios where it's appropriate to start raising the threat level 5-7 days in advance, given the current state of our NWP. In my mind, this one is pretty borderline - but only because, in my opinion, there are nontrivial flies in the ointment on the synoptic scale. If the trough looked similar but there were broad ridging extending all the way to the east coast ahead of it, then it would definitely be one of those cases. In some regimes and given enough consensus between models and ensemble members, we can say "tornadoes are likely 5 days from now within this general section of the country" with confidence.

 

The real challenge lies in how that threat is communicated to the public by NOAA and, even moreso, the media. But generally speaking, I don't support withholding information that we have reasonable confidence in simply due to the "potential for panic" among the grossly uninformed. If this morning's SWODY7 induced panic in some scattered areas of social media, that's something that needs to be addressed somewhere further down the information pipeline than SPC.

[IllinoisWedges]

Quick side note, does anyone know if SPC has ever issued a "Day 8" risk before this week?

Yes. One in 2008 and one in 2012. 

[capbreak]

But generally speaking, I don't support withholding information that we have reasonable confidence in simply due to the "potential for panic" among the grossly uninformed. If this morning's SWODY7 induced panic in some scattered areas of social media, that's something that needs to be addressed somewhere further down the information pipeline than SPC.

Completely agree. It's not the SPC's job to account for when their products are blindly regurgitated onto social media to a very small portion of the public. 99% of the hype I've seen so far has been by weather enthusiasts to an audience of weather enthusiasts - they feed off the hype to an extent.

Broyles gets dumped on a lot, but there is certainly good potential for an outbreak on Tuesday, regardless of how well/poorly the parameters stack up to historical analogues.

edit: I see nothing wrong with the wording from their latest Facebook post, a place where they are trying to interact with the public more (opposed to the outlook text product):

"A pattern change will bring increasing severe weather chances to parts of the Plains and middle Mississippi Valley next week. The greatest threat at this time appears to be on Tuesday, April 26 across parts of Kansas, Oklahoma and Texas, where a severe weather outbreak will be possible. Stay tuned for updated outlooks and information. The most recent and up-to-date info can be found on our webpage: www.spc.noaa.gov"

[Stebo]

Completely agree. It's not the SPC's job to account for when their products are blindly regurgitated onto social media to a very small portion of the public. 99% of the hype I've seen so far has been by weather enthusiasts to an audience of weather enthusiasts - they feed off the hype to an extent.

Broyles gets dumped on a lot, but there is certainly good potential for an outbreak on Tuesday, regardless of how well/poorly the parameters stack up to historical analogues.

Yeah I am also against withholding information as well but it is misinformation from bad sources that session to get the most hits on social media which is the biggest issue. That said I'll stop sidetracking the thread here .

[JoMo]

OUN

 

 

That's from Tulsa. 

[Quincy]

I think most here are aware, but many on social media aren't. A 15% risk shading for days 6-8 is not really that crazy. Back when SPC only issued medium range convective outlooks for 30% probabilities, even those did happen occasionally. (There was one example of a D8 outlook for the Great Lakes, and that was 30%, not 15%)

[ClicheVortex2014]

That's from Tulsa. 

 

It's the week before finals. I get a free pass, right?

[ClicheVortex2014]

ICT

 

THE GFS MODEL WOULD PLACE MUCH OF OUR FORECAST AREA IN THE WARM
SECTOR BY MIDDAY TUESDAY...WITH A SURFACE LOW NEAR CENTRAL
KANSAS...A WARM FRONT EXTENDING EASTWARD TO CENTRAL
MISSOURI...AND A DRYLINE TRAILING SOUTHWARD FROM THE LOW INTO
WESTERN OKLAHOMA. WITH THE MID-LEVEL TROUGH TAKING ON A NEGATIVE
TILT AS IT EJECTS NORTHEASTWARD TUESDAY-TUESDAY NIGHT...A 70 KT
MID-LEVEL JET STREAK WILL BE NOSING INTO THE VERY UNSTABLE WARM
SECTOR (MLCAPES 2500-3500 J/KG). THIS WILL RESULT IN STRONG DEEP-
LAYER SHEAR FAVORING HIGHER-END SUPERCELL STORMS WITH ALL FACETS
OF SEVERE WEATHER POSSIBLE. LCL HEIGHTS ARE PROGGED TO BE LOW
GIVEN RECENT WIDESPREAD SIGNIFICANT RAINFALL AMOUNTS OVER THE PAST
WEEK. THE SLOWER GFS SOLUTION ALSO IS IN AGREEMENT WITH THE STORM
PREDICTION CENTER DAY 6 SEVERE WEATHER OUTLOOK FOR TUESDAY. SEVERE
STORMS WILL LIKELY CONTINUE OVER MUCH OF EASTERN KANSAS TUESDAY
NIGHT...FED BY A 50 KNOT SOUTH-SOUTHWESTERLY LOW-LEVEL JET AND
STRONG MOISTURE TRANSPORT. ALTHOUGH THERE ARE STILL SOME MODEL
DISCREPANCIES AND UNCERTANTIES ON EXACT TIMING AND AREAL PLACEMENT
OF SEVERE STORMS...STAY TUNED TO LATER FORECASTS AND OUTLOOKS AS
TUESDAY PRESENTS THE POSSIBILITY OF HIGH-END SEVERE WEATHER FROM
CENTRAL/EASTERN KANSAS SOUTHWARD THROUGH OKLAHOMA.

 

 

 

DDC

 

.LONG TERM...(Friday night through Thursday)
Issued at 234 PM CDT Thu Apr 21 2016

There will be a few bouts of convection through the long term domain.
The first is across west-central Kansas, where the 4 km NAM breaks
out storms Saturday evening. MUCAPE is moderate, but shear is particularly
weak. Forecast soundings show a mixed profile, so the main threat would
be sub severe microbursts. Only have slight to low chance pops here
as the upper level trough is still located well to the west. The next
chance for storms comes Sunday evening. This would be mainly across
the SE zones, perhaps extending northward if upscale growth developed.
Both CAPE and shear are stronger, so there is a more robust threat of
severe. Of the most concern of severe storms is on Tuesday. Pattern
recognition screams tornadic storms somewhere across Kansas or Oklahoma.
See two areas of tornadic concern... along and east of the dryline and
along the warm front. Where will these boundaries be located? You got
me. Mesoscale details like this cannot be resolved this far out. But
with a jet coming out, a dryline, low level shear along a warm front,
and abundant low level moisture... all the "math" (aka svr wx parameters)
are adding up for supercells. The bottom line, pay attention to future
forecasts as a high impact event is certainly within the realm of possibility.

 

 

[brettjrob]

I will say that the Euro ensemble mean is certainly slower than the control run, which isn't surprising. Also less aggressive with Great Lakes/Northeast troughing later in the week.

 

http://www.ecmwf.int/en/forecasts/charts/medium/ensemble-mean-and-spread-four-standard-parameters?time=2016042112,120,2016042612&parameter=Geopotential%20at%20500hPa&area=North%20America

 

My suspicion is that the 12z ECMWF was onto something, but that it hopefully went too far in that direction and we will start settling toward a compromise that's closer to the GFS.

[Stebo]

18z GFS holds serve, if anything the wind fields inched up a bit.

[thewxmann]

I will say that the Euro ensemble mean is certainly slower than the control run, which isn't surprising. Also less aggressive with Great Lakes/Northeast troughing later in the week.

 

http://www.ecmwf.int/en/forecasts/charts/medium/ensemble-mean-and-spread-four-standard-parameters?time=2016042112,120,2016042612&parameter=Geopotential%20at%20500hPa&area=North%20America

 

My suspicion is that the 12z ECMWF was onto something, but that it hopefully went too far in that direction and we will start settling toward a compromise that's closer to the GFS.

 

A compromise might be the worst case scenario for population centers along I-35.

 

Either way, one additional thing to consider is that high soil moistures in the area will slow down how fast the dryline mixes eastward, all other factors held steady.

[jojo762]

What is perhaps most dangerous about tuesday is that storms will likely stay discrete well into the night, LLVL wind fields will increase, Mid-Level wind fields will increase, and we will still have 2000-3000J/KG MUCAPE until roughly 06Z. 

[brettjrob]

A compromise might be the worst case scenario for population centers along I-35.

 

Yeah, that may be true. Although I don't see it backing up so much that OKC/ICT are east of the main bullseye, so a progressive trend may be their best hope. Of course, a ECMWF-like solution just puts KC and Tulsa in the crosshairs, so it's hard to win. It's probably fair to say that Tuesday will be suboptimal for chasing and high-impact for the public, assuming the threat magnitude stays about how it looks.

 

Either way, one additional thing to consider is that high soil moistures in the area will slow down how fast the dryline mixes eastward, all other factors held steady.

 

This is definitely worth considering, too. With such a dynamic, progressive wave, it might not make a massive difference, but it doesn't take much to matter a lot for the I-35 corridor.

[jojo762]

Yeah, that may be true. Although I don't see it backing up so much that OKC/ICT are east of the main bullseye, so a progressive trend may be their best hope. Of course, a ECMWF-like solution just puts KC and Tulsa in the crosshairs, so it's hard to win. It's probably fair to say that Tuesday will be suboptimal for chasing and high-impact for the public, assuming the threat magnitude stays about how it looks.

 

 

This is definitely worth considering, too. With such a dynamic, progressive wave, it might not make a massive difference, but it doesn't take much to matter a lot for the I-35 corridor.

Any chance that this could result in multiple waves of supercells, especially as the main core starts to overspread the warm-sector?

 

Also, TWC really hyping Tuesday up on their Weather Underground show. Carl Parker mentioned long-track, strong, and possibly violent tornadoes... Not that he'll be wrong, but just seems so odd to see something so hyped already being 5-6 days out.

[Thundersnow12]

18z GFS holds serve, if anything the wind fields inched up a bit.

 

The dryline had a better look to it and was tighter with a little more backing thanks to the strong p-falls 

[ClicheVortex2014]

Reed Timmers' thoughts FWIW https://warningaware.com/blog/2016/04/21/outlook/

 

 

18z GFS holds serve, if anything the wind fields inched up a bit.

Yeah. The sounding in north-central OK is almost perfect. Boundary layer's a bit dry, but it's not a deal breaker for sure.

 

[jojo762]

Seems like Reed had matured some recently as it relates to not over exaggerating threats or getting too hyped too quick. While his idea of a large tornado may still be a bit off...

[nwohweather]

A compromise might be the worst case scenario for population centers along I-35.

Either way, one additional thing to consider is that high soil moistures in the area will slow down how fast the dryline mixes eastward, all other factors held steady.

That also however will contribute in lower LCL's

[JasonOH]

I would like to add that moisture return will be better the stronger this initial trough becomes. Also, looking at trajectories and upstream soundings, it appears that our airmass is coming directly out of the Carribean. This leads me to believe that the dews will at least be in the upper 60's to low 70's by Tuesday.

[rolltide_130]

Reed Timmers' thoughts FWIW https://warningaware.com/blog/2016/04/21/outlook/

 

 

Yeah. The sounding in north-central OK is almost perfect. Boundary layer's a bit dry, but it's not a deal breaker for sure.

 

For some reason, the GFS just cannot handle the decoupling of the boundary layer at all. Likely won't be quite like that come Tuesday. 

[OUGrad05]

Man I almost started this thread last night, glad someone else did.  

Next week is looking like a multi day plains outbreak.  I'm curious to see how the runs hold up as we move forward.  Moisture return seems to be adequate.  I wouldn't worry too much about boundary layer issues in the GFS until we're within 48 - 60hrs.

[andyhb]

I wouldn't worry too much about boundary layer issues in the GFS until we're within 48 - 60hrs.

 

FYP.

 

It does this every time.

[ClicheVortex2014]

Out of all the ways I thought this could bust, JB pulls this out

 

 

Rare time when he's posted Euro graphics publicly from Weatherbell

 

 

No idea what he's talking about here. 

Not saying there is not potential Meets PSU Meteo 434 long range criteria from 1970s Pressure below 1008 Wet bulb above 65

 

[Radtechwxman]

I never take what he says seriously. If anything that extra ground moisture will be beneficial for dews not mixing out which has been a problem in the Plains prior to these drought busting rains

[ClicheVortex2014]

00z not as robust with STP as 18z, but not as weak as 12z. Boundary layer is looking better and dew point depression is 4 degrees lower

 

 

For reference, here's 12z

 

[brettjrob]

Severe weather forecasting is a whole different ballgame. Plenty of great synopticians and east coast snowstorm experts (even professional) are fairly clueless about the intricacies, just as the converse is also true. I'm not really sure what "Soggy Plains may inhibit potential" is supposed to mean, but if it relates to the rain we got last week, I can't imagine any scenario where that hurts us. In summary, I'd disregard.

 

00z GFS has somewhat caved to the eastern dryline placement. I think any hope for a true chaser-friendly outcome where mature storms are rolling across wheat fields in Harper Co. KS and Major Co. OK at 00z Wed is close to being out the window. The big question will be the magnitude of the I-35 threat, as things stand.

[andyhb]

00z not as robust with STP as 18z, but not as weak as 12z. Boundary layer is looking better and dew point depression is 4 degrees lower

 

The subtle hint of a VBV there is something to watch in the 700-500 mb layer.

 

That CAPE profile is just nasty though, would be even more impressive if there was a bigger surface wind response (i.e. more towards the SE, which may very well still be in the cards considering the GFS' problems with this type of thing).

[Chicago Storm]

00z not as robust with STP as 18z, but not as weak as 12z. Boundary layer is looking better and dew point depression is 4 degrees lower

For reference, here's 12z

A 12F spread like on the 12z was fine.

[ClicheVortex2014]

A 12F spread like on the 12z was fine.

8F spread is even better