UNDERSTANDING BARROMETRIC PRESSURE AND TERMINOLOGY

Reading in Millibars (mb)

Reading Rising Steady Falling

1032mb and above Settled, Fine Settled, Fine Fine, outlook less settled

1023mb Fine Fine Probably fine with possibility of rain

1015.9mb Probably Fine, Outlook Favourable Probably Fine Changeable, Showers likely

1007.4mb Rain at times, improving Changeable Rain, dry intervals likely

999.0mb Rain Likely Rain Rain

990.0mb and below Heavy Rain Heavy Rain Heavy Rain – Storms

PRESSURE TENDENCY IN STATION REPORTS

Rising or Falling more slowly

Pressure rising (or falling) at a progressively slower rate through the preceding three hours

Rising or Falling slowly

Pressure change of 0.1 to 1.5 mb in the preceding three hours

Rising or Falling

Pressure change of 1.6 to 3.5 mb in the preceding three hours

Rising or Falling quickly

Pressure change of 3.6 to 6.0 mb in the preceding three hours

Rising or Falling very rapidly

Pressure change of more than 6.0 mb in the preceding three hours