Analyzing shear when forecasting

[Devin Pitts]

I've been playing around with pivotalweather for a few months and I think I've got an ok grasp on utilizing models now despite very little field experience to test it on (outside of a single weak supercell back in February, thanks California).

The thing I'm having trouble grasping is shear when looking at Skew-T and Hodographs, along with actual observations. I understand what the wind barbs are showing on Skew-T as far as speed and direction go, it's more about the actual speed differentials and what constitutes "good" shear when forecasting that I'm a little lost on.

Sent from my Nexus 5X using Stormtrack mobile app

 

[kevin-palmer]

This Severe Weather Forecasting Tip Sheet from the NWS has a lot of good information about the ingredients needed for a tornado and other types of severe weather: http://www.weather.gov/media/lmk/soo/SvrWx_Fcstg_TipSheet.pdf

A 0-6km bulk shear of 40 knots or greater seems to be the dividing line between supercells and other types of storms (assuming the other ingredients are there).

This article shows an example of a favorable, veering wind profile: http://www.ustornadoes.com/2015/01/...ying-and-understanding-the-basic-ingredients/

 

[Randy Jennings]

It is important to understand the difference between deep layer shear and low level shear. Strong deep layer shear (0-6km) will get you a mesocyclone, but you also need low level shear (0-2km) for tornadoes. A week ago on Monday 4/11 I told my chase partner that there wasn’t enough low level shear and I wasn’t going to take the day off work just to chase hail. That turned out to be a good call, as there were no tornadoes in North Texas that day. We did go out late in the day and got some great shots of a supercell and very large hail.

Another key difference is directional vs speed shear. Too much speed shear just blows the tops off the storms. Directional shear is what you want for rotating storms.

Another good resource about shear and SRH (storm relative helicity) is http://www.spc.noaa.gov/exper/mesoanalysis/help/sfcoa.html

 

[Jessie Schafer]

This Severe Weather Forecasting Tip Sheet from the NWS has a lot of good information about the ingredients needed for a tornado and other types of severe weather: http://www.weather.gov/media/lmk/soo/SvrWx_Fcstg_TipSheet.pdf

A 0-6km bulk shear of 40 knots or greater seems to be the dividing line between supercells and other types of storms (assuming the other ingredients are there).

This article shows an example of a favorable, veering wind profile: http://www.ustornadoes.com/2015/01/...ying-and-understanding-the-basic-ingredients/

Thank you for this!!!! super helpful for a beginner.