0-3KM CAPE

[RMacDonald]

Hello,

Trying to build my SmartModel for severe weather season, had a few questions. Love to hear thoughts on the 0-3 KM CAPE. Did a bit of reading on around the net, looking for what kind of threshold values you need for aiding a severe weather environment. Any thoughts or resources would be greatly appreciated.

 

[Jeff Duda]

There really isn't any well established threshold for 0-3 km CAPE that I'm aware of. In general, the more, the better. You generally won't see more than 250 - 300 J/kg even during the most unstable days, and you can get supercell thunderstorms and storms that produce severe hail, wind, and tornadoes with little to no 0-3 km CAPE.

 

[J Allen]

Should have looked at more of Davies stuff.

 

[Scott Weberpal]

Jon Davies has a few good papers describing the importance of 0-3km CAPE in regard to supercell tornado development...

http://www.jondavies.net/LLthermo.PDF

and a great paper showing a direct correlation between 0-3km CAPE and tornadoes from supercells in a low-CAPE (<1000 j/kg MLCAPE) environment.

http://ams.confex.com/ams/pdfpapers/115477.pdf

This image, from the paper, shows the correlation:

 

[RMacDonald]

Awesome, thanks for the information, this will help out so much. Trying to use threshold values are tough, because they can vary by location and by synoptic conditions.

 

[Bob Hartig]

I've been using 0-3 km CAPE for a while now, having been made aware of its value in Davies' paper on cold core tornadoes. I noted with interest that the New Years Eve tornadic storms in Missouri formed along a forecasted axis of 50-75 J/kg 0-3 km CAPE. It makes sense that low-level CAPE would play a significant role in low-top supercells. You can't expect a lengthy CAPE profile; what you need is enough CAPE down low to create rapid parcel acceleration.

 

[Darren Addy]

Jon Davies also mentioned at ChaserCon that the 0-3km CAPE is a big player in nighttime tornadoes.

 

[RMacDonald]

Thanks for the resources, I played with the thresholds based on the climatology and informative reading. This will help wrap up my convection tables for my SmartModel, looking to push this out starting tommorrow. Again thanks for the information.

 

[Ryan Wichman]

To piggy back on what Bob said a few posts ago:

Following the New Years Eve tornado outbreak, I did a case study which showed the relationship of 0-1 and 0-3 VGP. The parameter takes into account not only low level instability but also low level wind shear. Through quick glances of big warm sector set-ups this previous year, the VGP parameter did NOT do a great job in general of showing one favorable target over another. But on days where there is a more concentrated set-up region the VGP and to a lesser extent 0-3 CAPE has been shown to exhibit some promise.

http://convectiveaddiction.com/2011/01/04/mesoscale-overview-of-new-years-eve-tornado-outbreak/

Hope this helps.