US and Vicinity Sounding Data: SKEWT, STUVE, HODO, and Text Info
These pages made possible in part by systems from the Unidata Program

Sites in Darker Blue are standard radiosonde sites which launch balloons every day at 12Z and 00Z.

Sites in Lighter Blue are supplemental radiosonde sites which launch balloons at various times and days.


Key Indices

CAPE
1 - 1,500 Positive
1,500 - 2,500 Large
2,500+ Extreme
High CAPE (Convective Available Potential Energy) means storms will build vertically very quickly. The updraft speed depends on the CAPE environment. Hail: As CAPE increases (especially above 2,500 J/kg) the hail potential increases. Large hail requires very large CAPE values. Lightning: Large and extreme CAPE will produce storms with abundant lightning. Storms will only form and the CAPE actualized if the low level capping inversion is broken.

CAP
0 No Cap
0.1 - 1.9 Weak Cap
2.0 - 4.0 Moderate Cap
4.1+ Strong Cap
CAP is a stable region of the lower troposphere that impedes convection. When the CAP is less than 2.0, storms are likely to develop shortly when the only parameter holding back convection is the CAP. When the CAP is greater than 4, help will be needed over the next few hours to break it.

K INDEX
15-25 Small convective potential
26-39 Moderate convective potential
40+ High convective potential
K Index is used to assess convective potential. This index should not be used to determine severity of storms. Works best for flat areas in low to moderate elevations. Does not work for high elevations.

TOTAL TOTALS
<44 Convection not likely
44-50 Likely thunderstorms
51-52 Isolated severe storms
53-56 Widely scattered severe
>56 Scattered severe storms
The TT (Total Totals) is used to assess storm strength. This index works best for flat areas in low to moderate elevations. It does not work for high elevations. Index will be too stable if a layer of moisture is just under the 850 mb level.

NOTES Tornado: In a supercell thunderstorm situation, a low LCL (closer to surface) increases the likelihood of tornadogenesis since the region of CAPE will be closer to the surface.


Resources

Breaking down the SkewT PART I
Breaking down the SkewT PART II

Notes about SkewT by Meteorologist Jeff Haby: Getting to Know SkewT Parameters.

SkewT Boot-Camp.

Learn about Atmospheric Stability.

Thanks: Sacrey Weather.

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