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April 26th-30th, 2014 Major Tornado Outbreak


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Just curious, something I might want to post on FB, is there a website for 4 km NAM forecast skew-Ts?

 

Not that I know of...would be very helpful

 

 

Their label for the '4km NAM' is actually the SPC-WRF

 

 

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15z SREF now has two areas of extreme tornado potential tomorrow evening:

 

 

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The environment on the 18z NAM over MS and spreading into AL at 15z on Monday is insane.  Just insane.  With convection already ongoing, I would imagine we'd be off and running.  It's conceivable that strong-violent tornadoes may be ongoing from 21z tomorrow afternoon all the way until predawn Tuesday morning.  And after that, we have to tackle Tuesday.

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The environment on the 18z NAM over MS and spreading into AL at 15z on Monday is insane.  Just insane.  With convection already ongoing, I would imagine we'd be off and running.  It's conceivable that strong-violent tornadoes may be ongoing from 21z tomorrow afternoon all the way until predawn Tuesday morning.  And after that, we have to tackle Tuesday.

 

A lot of the forecast soundings try and stabilize the boundary layer tomorrow night, but not so much so that a well rooted supercell couldn't remain surface based.

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FWIW almost all the severe parameters are maxed out or close to it on the 18z 4km NAM..

 

Fixed-layer STP is pushing 10 at points

0-3KM EHI is completely maxed out for several frames

Supercell composite is also maxed out in several frames

 

..and the list goes on.

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FWIW almost all the severe parameters are maxed out or close to it on the 18z 4km NAM..

 

Fixed-layer STP is pushing 10 at points

0-3KM EHI is completely maxed out for several frames

Supercell composite is also maxed out in several frames

 

..and the list goes on.

 

Do you expect a high risk to come from the SPC for both Sunday and Monday?

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The 00z UKMET incidentally also shows the same vorticity lobe swinging around the base of the trough during the day Monday, resulting in the strengthening of the low-level jet.  The GFS has slowly trended towards showing this subtle vorticity lobe, but still hasn't caught up with the ECMWF/UKMET camp.  I suspect it will as we get closer to the event.

Taking Sunday and Monday together, I think that this is the most substantial large-scale tornado outbreak threat that we have seen since 2011.  This is definitely not a garden variety spring tornado setup we're dealing with here...

I heard similar several days ago from Reed. So more widespread and numerous in terms of tornadoes than March 2, 2012 and April 14, 2012? If all these days together is what is being pointed at, then that makes sense.

 

The environment on the 18z NAM over MS and spreading into AL at 15z on Monday is insane.  Just insane.  With convection already ongoing, I would imagine we'd be off and running.  It's conceivable that strong-violent tornadoes may be ongoing from 21z tomorrow afternoon all the way until predawn Tuesday morning.  And after that, we have to tackle Tuesday.

The only nocturnal tornado outbreak that stands out to me is the Leap Day one just before March 2, 2012. However rare those are, what is unheard of is a tornado outbreak being continuous from one day into the other, at least not from the 2 worst outbreaks in history which I think had some minor incidents IIRC joining days. It would truly be insane if that did occur.

 

About tomorrow, what is the earliest possible time for storms to initiate without previous convection that might turn up overnight? We haven't see a before noon initiation for a while.

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About tomorrow, what is the earliest possible time for storms to initiate without previous convection that might turn up overnight? We haven't see a before noon initiation for a while.

 

It's not that overnight convection could prevent initiation, it's that overnight convection will stabilize the atmosphere and narrow the threat area for tomorrow late afternoon/evening severe convection.

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It's not that overnight convection could prevent initiation, it's that overnight convection will stabilize the atmosphere and narrow the threat area for tomorrow late afternoon/evening severe convection.

Yeah a whole lot depends on overnight convection.  If no convection overnight we could see early initiation on the dryline which would push the moderate risk back to the west but doesn't do anything to minimize the issues Arkansas is going to face tomorrow.

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I would not be at all surprised to see this be issued at some point for both days given the intensity of this system with parameters nearly off the charts.

 

I agree, but you won't see a day 2 high risk because of the question regarding overnight evolution of convection.

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I heard similar several days ago from Reed. So more widespread and numerous in terms of tornadoes than March 2, 2012 and April 14, 2012? If all these days together is what is being pointed at, then that makes sense.

 

Actually Sunday and Monday as individual days may exceed the magnitude of the events you mentioned, both in numbers of significant/violent tornadoes and in terms of human impact given the higher population density of the areas affected.  I don't think any of the upcoming individual days look quite as impressive as 4/27/11, but on the other hand we have several days to get through.  Comparisons aside, it's a very dangerous setup over a lot of real estate.

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one thing I am noticing on the 18Z NAM bufkit profiles, and yes I know it's the 18Z NAM to take it as a grain of salt.

 

but if you look monday morning for areas like BNA, LIT, STL, MEM, etc; there's a ton of elevated cape (1500-2500 J/kg) that can spark off at a fairly reachable height between 800 and 900hpa. that's not exactly good comfort if you have all types of convection coming from the west, as gust fronts and other meso-boundaries can get to that height rather easily.

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one thing I am noticing on the 18Z NAM bufkit profiles, and yes I know it's the 18Z NAM to take it as a grain of salt.

 

but if you look monday morning for areas like BNA, LIT, STL, MEM, etc; there's a ton of elevated cape (1500-2500 J/kg) that can spark off at a fairly reachable height between 800 and 900hpa. that's not exactly good comfort if you have all types of convection coming from the west, as gust fronts and other meso-boundaries can get to that height rather easily.

The 0-1km SRH should allow for dynamic enhancement of updrafts through any shallow, weak stable layer and allow storms to become sfc-based.

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