Pick an example atmosphere, then change its temperature, moisture and wind to see how the Skew-T, the hodograph and the storm parameters respond.
Helicity, EHI and storm-relative winds use the storm motion chosen on the hodograph. Winds are shown as direction/speed in knots. A dash means the value does not exist for this sounding.
| Pressure (hPa) | Height above ground (m) | Temperature (°C) | Dewpoint (°C) | Wind from (°) | Wind speed (kt) |
|---|
Paste a sounding below and choose Load. The page reads University of Wyoming “Text: List” soundings (copy the whole page of text) and SHARPpy files. Plain rows of pressure, temperature, dewpoint, wind direction and wind speed in knots also work.
You can get soundings from the University of Wyoming upper-air sounding archive. Pick a date, time and station there, choose the text list output, then copy everything on the page that opens.
The sounding is thinned to about 50 significant levels and added to the example list as “Your pasted sounding”. It stays only until you close or reload the page, and nothing is sent anywhere.
CAPE is the fuel available to a rising parcel of air. More CAPE means stronger updrafts. CIN is the cap: energy a parcel has to overcome before it can rise freely.
LCL is roughly the cloud base. LFC is the height where the parcel becomes warmer than its surroundings and rises on its own. EL is where it stops, near the storm top.
Bulk shear is the change in wind between two heights. Around 35 to 40 kt or more from the ground to 6 km supports supercells.
Storm-relative helicity (SRH) measures how much low-level spin a storm can draw in. On the hodograph it is the shaded area between the storm motion and the wind trace. A critical angle near 90° means that spin is fed almost directly into the updraft.
The supercell composite and significant tornado parameter (STP) blend instability, shear and helicity into one number. Values above 1 favor supercells and significant tornadoes respectively. SHIP does the same for significant hail.
The effective inflow layer is the layer of air near the ground that is buoyant enough to feed a storm. Effective SRH and effective shear (EBWD) are measured from that layer instead of from fixed heights.
EHI combines CAPE and helicity. PW is the depth of water you would get by wringing out all the moisture above you. DCAPE is the energy available to downdrafts, and the downdraft temperature estimates how cold the outflow reaches the ground.
The freezing level is the height where the air reaches 0°C, and the wet-bulb zero height is where falling hail and rain stop cooling the air below freezing. Wet-bulb zero heights of roughly 2 to 3.5 km are typical of large-hail days.
Hail growth zone CAPE is the buoyancy between −10 and −30°C, where hailstones grow fastest. Warm cloud depth is the distance from the cloud base up to the freezing level. A deep warm cloud, about 3 km or more, makes rain very efficiently.
Corfidi vectors estimate the motion of a storm complex: upshear for back-building storms, downshear for forward-moving lines.
The idealized examples are teaching profiles, not observations or forecasts. The historical soundings are real weather balloon observations, thinned to about 40 to 50 significant levels for this page. Each was launched some distance and time away from the tornado, as its description notes, so it only approximates the air the storm formed in. The “What storms would likely do” summary applies simple rules of thumb to the numbers; it is a teaching aid, not a forecast. Historical data come from the Storm Prediction Center’s SARS proximity sounding database (Jewell, R., 2010: The Sounding Analog Retrieval System (SARS). Preprints, 25th Conf. Severe Local Storms, Denver CO) and the SHARPpy sample data. Parameters follow the standard SPC and SHARPpy definitions where practical, but they are calculated on a coarser set of levels, so expect small differences from Pivotal Weather or SPC values. Do not use this page for real-time safety decisions.
Set the wind at the surface, at 850 mb and at 500 mb, then see how the three levels cross over and what that says about wind shear.
Winds are shown as direction/speed in knots. Storm-relative values and helicity use the right-mover estimate. A dash means a level is calm, so the value has no meaning.
The crossover lab is separate from the sounding lab above: changing one does not change the other. It uses only three winds, so it cannot see anything that happens between those levels, and it knows nothing about temperature or moisture. Strong shear here does not mean storms will form.
Bulk shear, turning and speed change are exact for the winds you set. Everything under Estimates is a rough stand-in. It assumes the wind changes in a straight line between levels, with 850 mb about 1.2 km above the ground and 500 mb about 5.4 km. Over high terrain such as the High Plains, 850 mb sits at or below the ground and the low-level values do not apply. Storm motion is a simplified Bunkers-style estimate, and real storms often move differently. Winds near the ground veer with height partly because of friction, so the temperature advection reading for the lowest layer is only a hint. Do not use this page for real-time safety decisions. This page was created by Claude AI at the direction of Clarence Smith. Updated November 12, 2026