Severe Weather Discussion > General Weather - all topics not current severe weather.
Conditions Resulting in Thunderstorms
orage:
On this site, and in other places, I have seen terms such as CAPE, lifted index and wind shear etc.
Firstly, could anyone tell me whether there are any other measures of conditions which may effect the potential for a severe storm, and what do they mean.
Secondly, does anyone know how I might be able to find current figures, what charts I could use to use to work it out (and possibly how they should be read), or how I can observe it myself?
David Brodrick:
Nice post thanks John.
I've got a GFS forecast table on our weather site that attempts to show the convection around my home town, eg 'isolated showers' 'severe thunderstorms' etc, but at the moment it only looks at CAPE, so it is obviously somewhat deficient.
Does anyone have suggestions on combining some of these other parameters, such as shear and maybe LI, CIN, cloud cover, to come up with a useful forecast of the storm activity?
Best wishes,
Dave
Jimmy Deguara:
Hi David,
Hopefully there is something you are able to find.
I guess though that is the fun of forecasting - to combine your own experiences as well as current conditions and compare with forecast models. Even if there was something that combined all parameters, how accurate are they?
This year, more than any other recent years at least, the models have on the whole been disappointing in pinpointing where the best area of convection will occur. Success at forecasting and storm chasing has been attributed to past experiences in my case at least.
Regards,
Jimmy Deguara
David Brodrick:
Cheers Jimmy. I guess my question was more on the best way to interpret the models rather than the usefulness of the models themselves.
I was thinking of something grossly along the lines of:
potential=CAPE/500
if ( shear(850,600) > 20 ) potential=potential + 1
if ( CIN > 200 ) potential=potential - 1
etc.
While no algorithm will encapsulate what's really happen, at the moment I rely on CAPE alone and there has to be something better than that. Maybe I should just use SWEAT instead?
Cheers,
Dave
Jimmy Deguara:
Hi David,
I appreciate what you are saying and had thought about this concept about 2 years ago. If only I was a good programmer, I would have come up with a solution years back.
When I came across the GFS (I guess then the AVN models) back in 1998, it was a gold mine. With these models alone we were able to confidently expand our storm chasing beyond the horizon.
CAPE is a pretty useful variable as well as is surface lifted index. The sensitivity of CAPE though with only slight changes in temperature and moisture should not be underestimated. But using it as a guide is still helpful.
So any programmers?
Regards,
Jimmy Deguara
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