April 24-30th Severe Potential

[ClicheVortex2014]

Hmm. I'm sure it overestimates 2 m dew points in some cases, mainly outside of peak heating or when there's cloud cover/precip during peak heating. But in a typical Plains environment with a moist PBL beneath a dry EML and under full afternoon sun, my observation for the past 3 years has been that it ends up mixing out moisture far too aggressively. The drought conditions in 2013-2014 masked the problem somewhat, since the LSM scheme was probably being too generous with ET (therefore offsetting some of the bias). And then last year, on a lot of the days where you had massive morning MCSs, it also masked the problem because there wasn't vigorous mixing going on in the wake of those complexes.

 

Here's a cherry-picked example from yesterday's 10z HRRR (first image) and HRRRx (second image) valid at 20z. Moisture was underwhelming yesterday, but nowhere as bad as the HRRR predicted over C and E KS:

 

http://rapidrefresh.noaa.gov/HRRR/for_web/hrrr_ncep_jet/2016042410/t5/dewp_t52m_f10.png

 

http://rapidrefresh.noaa.gov/HRRR/for_web/hrrr_jet/2016042410/t5/dewp_t52m_f10.png

 

Sometimes it can be entertaining in situations like the above to do a dProg/dt loop in the afternoon. It takes a few hours for the PBL scheme to mix out all the moisture, so I've found it's not uncommon for the 2m dew point forecasts for, say, 21z to rise by a couple degrees each hour around lunchtime, and then skyrocket even further by the time the 19-20z HRRR comes out.

Mesoanalysis also shows no cap in that part of Oklahoma, as well as in Texas where HRRR shows storms popping there, forming a cluster, and trekking northeast through the night.

[Smokey_mountain_vols]

Forget a cap bust. Something like this is more what I'm worried about.

If this happens Tulsa will be fine.

That would be more of what I'd expect in my area. We typically get an intense squall line with embedded tornadoes with storms that initiate in central KS/OK. The GFS positioning of the dryline being farther east into SE KS was worrying me a bit, but it looks like it's moved back west.

The UH for (almost) the entire run sure is a mess though.

If this happens Tulsa will be fine.

I shall be happy with either.

Sent from my HTC6525LVW using Tapatalk

[thewxmann]

Hmm. I'm sure it overestimates 2 m dew points in some cases, mainly outside of peak heating or when there's cloud cover/precip during peak heating. But in a typical Plains environment with a moist PBL beneath a dry EML and under full afternoon sun, my observation for the past 3 years has been that it ends up mixing out moisture far too aggressively. The drought conditions in 2013-2014 masked the problem somewhat, since the LSM scheme was probably being too generous with ET (therefore offsetting some of the bias). And then last year, on a lot of the days where you had massive morning MCSs, it also masked the problem because there wasn't vigorous mixing going on in the wake of those complexes.

 

Here's a cherry-picked example from yesterday's 10z HRRR (first image) and HRRRx (second image) valid at 20z. Moisture was underwhelming yesterday, but nowhere as bad as the HRRR predicted over C and E KS:

 

http://rapidrefresh.noaa.gov/HRRR/for_web/hrrr_ncep_jet/2016042410/t5/dewp_t52m_f10.png

 

http://rapidrefresh.noaa.gov/HRRR/for_web/hrrr_jet/2016042410/t5/dewp_t52m_f10.png

 

Sometimes it can be entertaining in situations like the above to do a dProg/dt loop in the afternoon. It takes a few hours for the PBL scheme to mix out all the moisture, so I've found it's not uncommon for the 2m dew point forecasts for, say, 21z to rise by a couple degrees each hour around lunchtime, and then skyrocket even further by the time the 19-20z HRRR comes out.

 

Thanks Brett. I suppose in cases where moisture quality is not very good, it will overforecast Td's, whereas when the moisture quality is solid, it will underforecast them. I only recalled the instances when moisture was questionable (for example, yesterday).

 

Remember the ol' RUC which overmixed dewpoints in almost all situations? I wonder if that used a similar PBL scheme.

[jojo762]

Thanks Brett. I suppose in cases where moisture quality is not very good, it will overforecast Td's, whereas when the moisture quality is solid, it will underforecast them. I only recalled the instances when moisture was questionable (for example, yesterday).

 

Remember the ol' RUC which overmixed dewpoints in almost all situations? I wonder if that used a similar PBL scheme.

Thinking of the RUC... Its predecessor-- the RAP-- is still terrible with moisture, just not quite as bad as the RUC was.

[jojo762]

I have a question - one of the local OkC head weathermen just claimed the surface low will be in SW or West Central Oklahoma tomorrow.

Now, I don't have access to all the models, but the ones I do all show the low in Kansas or Nebraska.

Is there any models showing the surface low in Oklahoma?

I haven't seen any model that shows that as of now, that wont happen... Most models show the SFC-low across NW/NC KS or SC NE at 00z tomorrow.

[OUGrad05]

I have a question - one of the local OkC head weathermen just claimed the surface low will be in SW or West Central Oklahoma tomorrow.

Now, I don't have access to all the models, but the ones I do all show the low in Kansas or Nebraska.

Is there any models showing the surface low in Oklahoma?

Is the second letter of their call sign an F?

Does anyone happen to know what SRH was on May 3rd 1999?  A friend of mine brought it up earlier today on the phone saying it had low helicity values.  I was thinking I read a white paper years ago that had SRH for 350-500 m2/s2 depending where you were in the outbreak area.  I did a quick google search only turned up one piece of data that wasn't very conclusive...

[andyhb]

Not exactly promising coming from the best: https://twitter.com/akracki/status/724752424091578369

[1900hurricane]

Is the second letter of their call sign an F?

Does anyone happen to know what SRH was on May 3rd 1999?  A friend of mine brought it up earlier today on the phone saying it had low helicity values.  I was thinking I read a white paper years ago that had SRH for 350-500 m2/s2 depending where you were in the outbreak area.  I did a quick google search only turned up one piece of data that wasn't very conclusive...

 

You can check out some of the parameters for that outbreak (and many others) on the SPC Violent Tornadoes page. I was able to pull the 990504 00Z OUN sounding from there:

 

[jojo762]

Is the second letter of their call sign an F?

Does anyone happen to know what SRH was on May 3rd 1999?  A friend of mine brought it up earlier today on the phone saying it had low helicity values.  I was thinking I read a white paper years ago that had SRH for 350-500 m2/s2 depending where you were in the outbreak area.  I did a quick google search only turned up one piece of data that wasn't very conclusive...

http://www.spc.noaa.gov/publications/thompson/3may99/waf.htm

 

Here is the SPC publication and study into the environmental conditions of that day. It indicates that 0-3KM SRH of 300-400m2/s2 was prevalent that day.

[brettjrob]

Is the second letter of their call sign an F?

Does anyone happen to know what SRH was on May 3rd 1999?  A friend of mine brought it up earlier today on the phone saying it had low helicity values.  I was thinking I read a white paper years ago that had SRH for 350-500 m2/s2 depending where you were in the outbreak area.  I did a quick google search only turned up one piece of data that wasn't very conclusive...

 

Here's the 00z OUN sounding for that event: http://journals.ametsoc.org/na101/home/literatum/publisher/ams/journals/content/wefo/2000/15200434-15.6/1520-0434%282000%29015%3C0682%3Aaooeca%3E2.0.co%3B2/production/images/large/i1520-0434-15-6-682-f05.jpeg

 

The sicle-shaped hodographs from that day have come to be regarded as the signature for major Plains tornado outbreaks. IIRC, the 0-1 km SRH for his hodograph is somewhere around 200 m2/s2. (EDIT: 263 m2/s2, see the SHARP-style sounding posted by 1900hurricane above).

 

The hodographs forecast tomorrow don't resemble this at all, for better or worse. The magnitude of 0-1 km SRH might reach 200 m2/s2 in some spots, but the overall shape is much less favorable. Recall about 5-6 days ago when 3 May 1999 appeared on many of the SARS sounding analog lists. We've come a long way from that scenario. I expect most storms tomorrow will be quite messy, and a decent number of them will probably be nontornadic or weakly tornadic. At least a few will likely be strongly tornadic (for a period), but picking them out ahead of time is going to be quite a formidable challenge.

[jojo762]

Not exactly promising coming from the best: https://twitter.com/akracki/status/724752424091578369

Looks like that kid had some fun listening to Rich Thompson and Ariel Cohen tonight. Good insight into what SPC is thinking. Best guess is, unless there is some dramatic change in the 00Z models, we will see nearly no changes to the outlook. Wouldn't be too surprised to see a 60% hail probability  tomorrow somewhere, if the hires models zone in on an area for legit CI.

[ClicheVortex2014]

Looking at the 00z soundings... so good to see legit EMLs in the spring again.

 

OUN is only slightly capped. Guess HRRR wasn't as wrong as I thought it was.

[OUGrad05]

You can check out some of the parameters for that outbreak (and many others) on the SPC Violent Tornadoes page. I was able to pull the 990504 00Z OUN sounding from there:

 

Thats the famous truncated sounding.  Other soundings in the area had SRH values up closer to 400-450...I just found one from Purcell at 411

 

http://www.spc.noaa.gov/publications/thompson/3may99/waf.htm

 

Here is the SPC publication and study into the environmental conditions of that day. It indicates that 0-3KM SRH of 300-400m2/s2 was prevalent that day.

Thats what I thought.

[wildwestpb]

Is the second letter of their call sign an F?

It is indeed an F.

He's been using the worst case scenarios that the models have been showing, since last week when they started warning the public about this upcoming storm. Don't know why he does it, but he is.

[MattPetrulli]

Thinking they'll go High risk at triple point at 06z or 13z. Hard to say for OK/KS. 

[jojo762]

This dude...  From Mike Morgan at KFOR. I understand that the graphic is just for the risk of one tornado in the KFOR viewing area, but they probably should just get rid of either 1. that broad criteria, or 2. this graphic.

[capbreak]

The hodographs forecast tomorrow don't resemble this at all, for better or worse. The magnitude of 0-1 km SRH might reach 200 m2/s2 in some spots, but the overall shape is much less favorable.

IE. critical angle. I seem to remember 5/3/99 was mentioned in the critical angle paper as having an almost perfect 90 degree critical angle. Everything I've seen tomorrow down the dryline is in the 60s.

[OUGrad05]

IE. critical angle. I seem to remember 5/3/99 was mentioned in the critical angle paper as having an almost perfect 90 degree critical angle. Everything I've seen tomorrow down the dryline is in the 60s.

Yea, we're not in the same ballpark, that was the point I made to him.  

I'm leaning towards chasing though...

[jojo762]

Thinking they'll go High risk at triple point at 06z or 13z. Hard to say for OK/KS. 

Besides better low-level directional shear--when compared to further south-- the triple point also suffers from the same wind-profile VBV problems. Also the triple-point appears that it might get kind of messy.

[wildwestpb]

This dude...  From Mike Morgan at KFOR. I understand that the graphic is just for the risk of one tornado in the KFOR viewing area, but they probably should just get rid of either 1. that broad criteria, or 2. this graphic.

He is also predicting EF4 tornadoes tomorrow from about Custer county eastern county line (north to Kansas and south to Texas) to Okmulgee county western county line (also north and south to borders).

Here is for central OK tomorrow according to him -

Here is the post showing he believes the surface low will be in Oklahoma.

https://www.facebook.com/MikeMorganKFOR/photos/a.426268834243032.1073741828.293952280808022/488306148039300/?type=3&theater

[OUGrad05]

Besides better low-level directional shear--when compared to further south-- the triple point also suffers from the same wind-profile VBV problems. Also the triple-point appears that it might get kind of messy.

I think everything could get messy tomorrow relatively early.  Things that pop between 4pm and 7pm will have a real shot at producing but as the cap erodes it becomes a mess...things may line out pretty early...

[NorthArlington101]

He is also predicting EF4 tornadoes tomorrow from about Custer county eastern county line (north to Kansas and south to Texas) to Okmulgee county western county line (also north and south to borders).

Here is for central OK tomorrow according to him -

Here is the post showing he believes the surface low will be in Oklahoma.

https://www.facebook.com/MikeMorganKFOR/photos/a.426268834243032.1073741828.293952280808022/488306148039300/?type=3&theater

I don't read that as him saying there will be an EF-4 tornado, rather that he sees an EF-4 's wind speed as the maximum possible in this outbreak.

[jojo762]

00Z RAP looking as though things could pop pretty early. Already has the jetcore overspreading the warm sector at 15Z in OK. 

[wildwestpb]

I don't read that as him saying there will be an EF-4 tornado, rather that he sees an EF-4 's wind speed as the maximum possible in this outbreak.

On air he said we will likely have 1-2 EF4 tornadoes in the state tomorrow, with the highest chances located in the graphic show, or NC Oklahoma, where everything is a 9 out of 10 on his scale.

https://www.facebook.com/MikeMorganKFOR/photos/a.426268834243032.1073741828.293952280808022/488288888041026/?type=3&theater

[ClicheVortex2014]

Y'all are talking about SRH being an issue... I agree. But if there's any supercells remaining after ~00z, the nocturnal LLJ should kick in and increase the SRH as CAPE decreases. The way I see it is the supercells will start out with a threat for giant hail, but the tornado threat increases as the sun sets and the nocturnal LLJ kicks in and elongates the hodograph. The significant tornado threat persists until everything grows into a line.

 

2 caveats that throws a wrench into the whole "plan" is 

1) Supercells become elevated quickly after sunset (don't know if that's gonna happen; I don't think so)

2) If the storms form a line quicker than ICT's thinking of after 03z.

 

That's my novice thinking. I think the potential for high risk is there in that window between the nocturnal LLJ and the evolution of the squall... but it'll have to wait until specifics become clear. If they become clear.

 

 

00Z RAP looking as though things could pop pretty early. Already has the jetcore overspreading the warm sector at 15Z in OK. 

It and HRRR don't seem to be handling the very near-term very well.

 

At all.

[NorthArlington101]

On air he said we will likely have 1-2 EF4 tornadoes in the state tomorrow, with the highest chances located in the graphic show, or NC Oklahoma, where everything is a 9 out of 10 on his scale.

https://www.facebook.com/MikeMorganKFOR/photos/a.426268834243032.1073741828.293952280808022/488288888041026/?type=3&theater

Ah, I gotcha now. Bold prediction, we'll see if it pays off for him.

[jojo762]

Not sure if Mike Morgan is just always overly optimistic, stupid, or both. Needs to stop with the incessant use of the EF scale on air and on graphics.

[jojo762]

 

Y'all are talking about SRH being an issue... I agree. But if there's any supercells remaining after ~00z, the nocturnal LLJ should kick in and increase the SRH as CAPE decreases. The way I see it is the supercells will start out with a threat for giant hail, but the tornado threat increases as the sun sets and the nocturnal LLJ kicks in and elongates the hodograph. The significant tornado threat persists until everything grows into a line.

 

2 caveats that throws a wrench into the whole "plan" is 

1) Supercells become elevated quickly after sunset (don't know if that's gonna happen; I don't think so)

2) If the storms form a line quicker than ICT's thinking of after 03z.

 

That's my novice thinking

 

 

It and HRRR don't seem to be handling the very near-term very well.

 

At all.

 

I wasn't saying that because of the cap, I was saying that because it has the H5 jetcore overspreading the warm sector so early... But that is a good point and something to pay attention too... Also, I do not think that supercells inside the warm sector would become elevated at all after sunset, the BL will not decouple until well into the night, and the air parcel will be highly instability until about 4-5Z. 

[ClicheVortex2014]

I wasn't saying that because of the cap, I was saying that because it has the H5 jetcore overspreading the warm sector so early... But that is a good point and something to pay attention too... Also, I do not think that supercells inside the warm sector would become elevated at all after sunset, the BL will not decouple until well into the night, and the air parcel will be highly instability until about 4-5Z. 

Oh yeah I know. The very end of RAP/HRRR seem to be as accurate as hour 84 NAM. I recall one time over this winter, one of the two put the low pressure in Alabama while the rest of the models put it in the Ohio Valley. Guess which verified.

 

Yeah I really doubt they'll become elevated quickly. I don't think that's a real worry.

 

New day 1 outlook puts 15% hatched hail in NE KS/N MO for the warm frontal supercells.

[KSWx]

This dude... From Mike Morgan at KFOR. I understand that the graphic is just for the risk of one tornado in the KFOR viewing area, but they probably should just get rid of either 1. that broad criteria, or 2. this graphic.

The graphics coming out of KFOR never fail to piss me off. So unbelievably stupid and and do nothing but scare their viewing area. It's one thing to get people prepared, it's something entirely different to act like you can predict the EF rating of a tornado before it occurs. The people of Oklahoma do not need these dopey graphics to know tornadoes are dangerous.

Let me hop off my soap box now.