Turbulence & icing

What it shows

Clear-air turbulence at cruise and airframe icing lower down, from the NOAA GFS model. The field is the Ellrod index, vertical wind shear times deformation plus convergence, between 300 and 200 hPa (about FL300 to FL390), the worse of the two layers. The readout adds the icing risk where air close to saturation sits between -20 and 0 °C at 700 or 500 hPa (about FL100 and FL180). Planning guidance, not an official briefing.

Where the data comes from

NOAA GFS 1° isobaric winds, temperature and humidity, derived every run; 3-hourly from 24 hours back to 48 hours ahead.

Reading the map

Colour runs from dark blue (smooth air) through green (light) and amber (moderate) to red and purple (severe).

Units Ellrod turbulence index in 1e-7 s^-2 (4 light, 8 moderate, 12 severe); icing risk in percent.

One page for each

See the list: every item this layer shows has its own page, with facts, source and a map

Other layers in air

• GPS interference
• Winds aloft
• SIGMET & AIRMET
• PIREP