Types of rainfall: Frontal, orographic and convective

Rain is generally classified into three main types, based on how it is generated. Do you know them?

After a quiet start to the week it's all change with spells of rain expected to frequent from the west. Rainfall can be classified into frontal, orographic and convective, and today, we are experiencing frontal rain.

Frontal rain occurs when colder air meets warmer air in a weather front. The warm air is then forced to rise over the cooler air leading to clouds and rain.

This type of rainfall happens everywhere in the UK and Ireland and tends to bring overcast skies and persistent rainfall.

Orographic rainfall is most commonly found in hilly regions, and also explains why places in the west tend to be wetter. As air reaches land - or mountains - it is forced to rise.

This leads to the formation of clouds and then rainfall on the mountain, but often leaves the leeside (downwind) dry. When that happens it is called the "rain shadow effect".

For convective rain, or showers, the sun needs to shine on the ground and heat a layer of air close to Earth's surface. When the air close to the surface gets warm enough - and warmer than the air above it - it begins to rise up into the atmosphere.

The higher the air rises, the colder the atmosphere gets. At a certain level, the warm air will begin to cool and as a result the water vapour in the air condenses, forms a cloud and then we see rain.

On hot days, the warm air is able to move higher and faster into the atmosphere which sometimes can lead to the production of thunderstorms, which becomes more common as we head through the spring and summer months.

It is also the trickiest type of rain to forecast because showers can be so spatially and temporally variable.