Sterling, VA sounding

KIAD · 00Z Oct 7 launch · 84 m elevation

The 00Z Oct 7 launch on a Skew-T log-p, the key drawn on it. The hodograph is the wind through the lowest six kilometres, coloured by height: red near the ground, amber to three kilometres, green above. The 12Z Oct 6 launch is the faint trace behind it.

No instability. The freezing level is about 12,200 ft up.

CAPE: 0 J/kg · none
CIN: -71 J/kg · moderate cap
LCL: 880 hPa · 2.9°C
Lifted index: 18 · very stable
K index: -45.5
Precipitable water: 10.2 mm

Reading a sounding

A radiosonde goes up on a balloon twice a day and reports temperature, humidity and wind all the way through the atmosphere. On a Skew-T the temperature axis leans right as you go up, so a parcel of air rising without exchanging heat - the faint purple lines - runs nearly straight up the page, and the gap between the red temperature trace and the green dewpoint trace is how dry each layer is.

CAPE is the energy a surface parcel would pick up rising through the profile: the area where the dashed parcel path sits to the right of the red trace. CIN is the energy holding it down first - the cap. The hodograph is the wind with height; a curve that turns clockwise with height is what rotating storms are made of.

Nearby launches

Wallops Island, VA Pittsburgh, PA Blacksburg, VA Greensboro, NC Upton, NY Buffalo, NY

Source: National Weather Service radiosonde observations for KIAD, via the Iowa Environmental Mesonet RAOB archive. Indices are computed here from the surface parcel and can differ from SPC’s.