Cloud-base estimation from temperature and dewpoint.

• METAR 02/M01 → +2 °C / −1 °C (“M” = minus). Spread = 3 °C.
• Rule of thumb: cloud base (ft AGL) ≈ (T − Td)°C × 400.
• For this example: 3 °C × 400 ≈ 1 200 ft AGL estimated cloud base.
• The slide’s “* 1 000 ft” annotations refer to applying the formula for each cloud layer found in the observation.