Tasmania and Hobart just had one of their wettest Octobers on record as prolific mid-spring rainfall soaked southeastern Australia.

An unusual patter of air pressure near southeastern Australia saw frequent and heavy rain hitting Tasmania during October.

The map below shows the monthly average mean sea level pressure anomaly in the Australian region last month.

Image: Mean sea level pressure (MSLP) anomaly during October 2021. Source: Bureau of Meteorology.

The blue areas on the map above show areas that had abnormally low air pressure near the ground, while yellow areas saw higher-than-normal pressure during the month.

During October, Tasmania was sandwiched between an area of abnormally low pressure over the Tasman Sea and a region of unusually high pressure to the south of Australia.

In the Southern Hemisphere, wind flows clockwise around low pressure and anti-clockwise around high pressure. As a result of this, Tasmania was buffeted by rain-bearing easterly winds on a regular basis throughout October.

These abnormally strong easterlies are revealed in the map below, which shows the 850 hPa horizontal wind anomaly during October.

Image: 850 hPa horizontal wind anomalies during October 2021. Source: Bureau of Meteorology.

Hobart collected 160.4 mm of rain last month, which is the city's third wettest October in records dating back to 1882. The only wetter Octobers were 1906 (173.0 mm) and 1947 (193.1 mm).

Some areas in eastern Tasmania had their wettest October on record. Orford's 229.8mm beat the previous record of 175.4mm from 1952.

Image: Observed rainfall deciles during October 2021. Source: Bureau of Meteorology.

More broadly, Tasmania registered its 10th wettest October in 121 years of records and its 2nd wettest October in the last 30 years.