April 24-30th Severe Potential

[jojo762]

What difference does it make, really? 

OUN had a nice thing about stuff like this. 

[wildwestpb]

I know some school districts in Oklahoma have changed their guidelines regarding severe weather and will release children when a PDS tornado watch is issued, so it does matter to parents/guardians so they can come get their children.

[brettjrob]

What difference does it make, really? 

 

So much this.

 

Discussing the outlooks, their history, comparing to previous examples, etc. are all fine. It's just odd, though, that some seem to care as much about that as what happens with the water vapor in the real world.

[jojo762]

I know some school districts in Oklahoma have changed their guidelines regarding severe weather will release children when a PDS tornado watch is issued, so it does matter to parents/guardians so they can come get their children.

Given that storms will probably not form until after 4pm, I don't think it matters. But it however does matter for after-school activities, which knowing how weather aware school districts are, especially in oklahoma, they will be canceled. 

[CryHavoc]

So much this.

 

Discussing the outlooks, their history, comparing to previous examples, etc. are all fine. It's just odd, though, that some seem to care as much about that as what happens with the water vapor in the real world.

It absolutely matters if you live in the area.  The wording issued is the difference between having to sit at work as storms bear down on you and being able to leave to tend to family and pets.  For forecasting purposes it matters too, we want the vernacular we use that's passed to the public to be as concise and informative as possible.

[nwohweather]

You are using an extreme case though, that day had over 6500 J/kg of SB CAPE if I remember correctly.

Conversely though, everyone is focusing on the VBV which would preclude a larger outbreak but that isn't an immediate deal breaker for tornadoes to form and furthermore there will be more than ample bulk shear for severe hail and winds. Also not to mention the wind profiles near the triple point aren't that bad with less VBV.

Yes but the CAPE was not as extreme in other places and I believe there were 3 other violent tornadoes that day

[wildwestpb]

Given that storms will probably not form until after 4pm, I don't think it matters. But it however does matter for after-school activities, which knowing how weather aware school districts are, especially in oklahoma, they will be canceled. 

OUN has issued the following timeline

Looks like they are preparing for the possibility of a more westerly initiation of some storms, while keeping the I-35 corridor in their initial assessment of after 4PM for storms to possibly be in the area. That means that if they have an early issuance of a PDS tornado watch to account for anticipated weather, schools would still be in session when the watch is issued.

Both SPC and NWS OUN has said that storms could be isolated to scattered for some parts of the state, with SPC also stating that they could quickly transition to a more linear storm mode - as has been also hinted at by several of the models.

I hope by tomorrow there is a better grasp of what will happen.

[jojo762]

Not understanding the argument about low-level winds being meager by the SPC, both the NAM and GFS show a strengthening 35-45 knot LLJ at 00Z, and both models show 25-35 knots at 925MB, which isn't too bad either. Main question to me is how far backed are both at 00Z across the dryline.

[KSWx]

18z NAM is rolling in, let's see what we've got. 

[capbreak]

Not understanding the argument about low-level winds being meager by the SPC, both the NAM and GFS show a strengthening 35-45 knot LLJ at 00Z, and both models show 25-35 knots at 925MB, which isn't too bad either. Main question to me is how far backed are both at 00Z across the dryline.

Look at 00z 0-1 SRH from the warm front down to the Red River... it's 150 m2/s2 at best. Off the top of my head, 200 m2/s2 was where the strong tornadoes started being well-represented. Yes, tornadoes are possible, but violent long-track ones typically aren't seen with those values. Probably won't be any OFBs along the dryline to help, either. As you move down the dryline the critical angle also quickly gets into the 60s or lower, which isnt optimal for tornadoes.

[codfishsnowman]

Dr. G beating the big bad weather outbreak drum for parts of Kansas on TWC...numerous long track spinners possible

 

 

what a boring spring so far everywhere except parts of Colorado

[ClicheVortex2014]

[Jim Martin]

At the 2 PM CDT Hazardous Weather Outlook from NWS Wichita...

 

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

 

A SIGNIFICANT SEVERE WEATHER OUTBREAK REMAINS POSSIBLE ON 

TUESDAY INTO TUESDAY NIGHT ACROSS THE ENTIRE AREA. SUPERCELL

STORMS WITH THE POTENTIAL FOR VERY LARGE DESTRUCTIVE HAIL AND

STRONG LONG TRACK TORNADOES WILL BE POSSIBLE...MAINLY FROM 

LATE AFTERNOON THROUGH AROUND MIDNIGHT. DETAILS WILL CONTINUE TO

BE REFINED.

[ClicheVortex2014]

OUN showing some skepticism with the evolving storm mode. But it just takes one ridiculous supercell to make it a noteworthy event.

 

BETTER HEIGHT FALLS WILL OVERSPREAD THE SOUTHERN AND CENTRAL PLAINS
TUESDAY AFTERNOON/EVENING...AS THE UPPER LOW/TROUGH MOVES ACROSS
THE SOUTHERN PART OF THE GREAT PLAINS. A RATHER UNSTABLE AIRMASS
WILL BE IN PLACE BY AFTERNOON WITH CAPE VALUES AROUND 3500-4000
J/KG PER 12Z NAM12. DANGEROUS STORMS ARE POSSIBLE...ESPECIALLY IF
STORM DEVELOPMENT REMAINS ISOLATED TO WIDELY SCATTERED DURING THE
LATE AFTERNOON-EARLY EVENING. IT`S POSSIBLE STORM MODE MAY BECOME
QUICKLY LINEAR GIVEN THE TIMING OF THE WAVE AND LARGE-SCALE
ASCENT. STORMS MAY FIRST DEVELOP TO THE WEST OF INTERSTATE 35
MAINLY ALONG AND EAST OF A CHEROKEE TO ANADARKO AND LAWTON LINE.
STORM DEVELOP FARTHER WEST OR EAST IS CERTAINLY POSSIBLE. BOTTOM
LINE...DANGEROUS STORMS ARE LIKELY TUESDAY AFTERNOON/EVENING...SO
PLAN AHEAD.

 

 

[jojo762]

18Z NAM showing impressive 0-1KM and 0-3KM helicity at 03Z with a bit lesser SRH at 00z. VBV is pretty prominent, which will obviously complicate forecasting storm mode.

[ClicheVortex2014]

Parameters really look good at 03z... but by then, storm mode might be an inhibiting factor

 

 

[wildwestpb]

Parameters really look good at 03z... but by then, storm mode might be an inhibiting factor

Reflectivity of the NAM at that time for your sounding in eastern Oklahoma County

[nwburbschaser]

Just a reminder that posting 03z forecast soundings or talking about parameters from that time is usually pointless, especially with Plains setups.

[jojo762]

Just a reminder that posting 03z forecast soundings or talking about parameters from that time is usually pointless, especially with Plains setups.

Not true, at all really. The point of it is to gain a better understanding of what the environment will look like after the LLJ kicks in-- usually when the tornado threat is at its pinnacle. 

[ClicheVortex2014]

Reflectivity of the NAM at that time for your sounding in eastern Oklahoma County

Yeah, well I thought NAM isn't good at handling convective initiation... but I thought the thinking was that the peak for that area is around that time. It's not - OUN has it 1-3 hours earlier.

 

 

Not true, at all really. The point of it is to gain a better understanding of what the environment will look like after the LLJ kicks in-- usually when the tornado threat is at its pinnacle. 

 

Exactly. The question is how many storms are still supercells by that time. But if there are any, they're gonna have a really nasty environment to roll in.

[chase_stormz]

Yeah, tell that to Greensburg.

Yea no kidding...

[nwburbschaser]

Not true, at all really. The point of it is to gain a better understanding of what the environment will look like after the LLJ kicks in-- usually when the tornado threat is at its pinnacle.

Sorry, but I have to disagree with the relevance of 03z forecast soundings for the vast majority of Plains tornado events.

[ClicheVortex2014]

ICT put out a good AFD especially for the recent conversations.

 

THE INITIAL STORM MODE STILL APPEARS TO FAVOR DISCRETE SUPERCELL
STORMS GIVEN THE MODERATE TO EXTREME INSTABILITY & ORIENTATION OF
THE DEEPER LAYER (0-6KM/0-8KM) SHEAR (40-50 KTS) VECTORS IN RELATION
TO THE DRYLINE. LATEST HI-RES SOLUTIONS SUGGEST THE DISCRETE
SUPERCELLS MAY BE DELAYED UNTIL THE DRYLINE BEGINS TO RETREAT BACK
THE WEST SOME (WITH INCREASING BACKED WINDS/CONVERGENCE)...BETWEEN
22-00Z. THIS WOULD FAVOR A MORE WESTERLY POSITION OF THE DRYLINE. SO
WOULD PREFER TO GO WITH THE FURTHER WEST MODEL POSITION FOR ANY KIND
OF STORM INITIATION. NOT EXPECTING NUMEROUS CLOSELY SPACED
SUPERCELLS (THUS SPC`S RELUCTANCE TO GO WITH A HIGH RISK)...BUT A
FEW HIGH END SUPERCELLS WITH ALL FACETS OF SEVERE WEATHER STILL LOOK
POSSIBLE...INCLUDING VERY LARGE/GIANT HAIL AND A FEW STRONG...LONG
TRACK TORNADOES CONTINUES ACROSS MUCH OF THE AREA INTO TUE EVENING.
INCREASING MLCAPE CAPES INTO THE EVENING HOURS...SUGGEST A THREAT OF
TORNADOES WELL INTO THE EVENING HOURS.

AFTER 03Z/TUE...SHEAR VECTORS BECOME MORE UNIDIRECTIONAL WHICH WOULD
SUGGEST A RAPID TRANSITION TO A LINEAR CONVECTIVE MODE...WHICH WOULD
SUGGEST MORE OF AN EMBEDDED SUPERCELL THREAT WITHIN A CONVECTIVE
CLUSTER OF STORMS FOR THE LATE EVENING HOURS AND POTENTIALLY
TORNADOES WELL AFTER DARK.

 

 

 

[jojo762]

Sorry, but I have to disagree with the relevance of 03z forecast soundings for the vast majority of Plains tornado events.

there are plenty of events that lasted overnight. I'd have to research a little more to tell you all of them exactly, but just look at 4/14/12, that lasted until 6Z. Plus for this event, the SPC and numerous related WFOs expect a tornado threat to last well into the night--even with the linear mode-- given that instability will last well into the night, and the BL won't decouple for quite a while.

[nwburbschaser]

there are plenty of events that lasted overnight. I'd have to research a little more to tell you all for them exactly, but just look at 4/14/12, that lasted until 6Z.

Please do. My point is that Plains tornado events that last into the night are the exception to the rule and not the norm so in most cases posting those 03z amped up soundings will be pointless.

[jpeters3]

Please do. My point is that Plains tornado events that last into the night are the exception to the rule and not the norm so in most cases posting those 03z amped up soundings will be pointless.

 

I'm currently doing a study on this, and you are incorrect.  More often than not, tornado events that produce EF-1 or greater tornadoes during the spring last into the night.

 

Edit: The question of whether chasing is very relevant after 03Z depends on who you are asking ;-)

[nwburbschaser]

I'm currently doing a study on this, and you are incorrect. More often than not, tornado events that produce EF-1 or greater tornadoes during the spring last into the night.

Edit: The question of whether chasing is very relevant after 03Z depends on who you are asking ;-)

I'll take your word for that then.

[jpeters3]

I'll take your word for that then.

 

Result was actually kind of a surprise to me.  I would have agreed with you prior to seeing the data.

[KSWx]

Anyone still targeting the triple point tomorrow?

[1900hurricane]

As someone who is coming from pretty far south, I think I might end up trying to play the dryline near the exit region of the 850 mb jet in north Texas. It's far from a guarantee, but if a storm that fires off the dryline can stay isolated for just a little while, better low level shear should exist just to the east. Instability and lapse rates should be more than sufficient, and deep layer shear looks adequate. Guidance has also been consistent with convective initiation in the area (maybe too much so even). Concerns with backing in the vicinity of 700 mb still exist, and shear vectors off the drylline aren't ideal, but hopefully being further south (where the flow is somewhat less meridional) and the quantity of instability will help take some of the edge off these concerns. Besides, these same concerns exist pretty much along the length of the dryline, and potential targets still in my driving range further north honestly don't look too much better to me.