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
| 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.
|
| 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.
|
| 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.
|
| <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.
