Black lines + values = mean sea level pressure isobars each 5 hPa (hectopascal).
Coloured zones + values = windspeed 850 hPa each 5 m/s.
H = high pressure.
L = low pressure. 

Useful for: prognoses for wind speed (tight isobars =  rather windy), direction = clock wise around high pressure and anti clock wise around low pressure, and general type of weather (rather poor in a low, and fair in a high).