This kind of forecast indicates that periods of intense rainfall are expected intermittently throughout a given time period. It suggests that there will be intervals of heavy rain alternating with periods of lighter rainfall or even temporary breaks in precipitation. These variations in rainfall can be attributed to atmospheric conditions and meteorological phenomena. Here are a few possible causes:
- Weather Fronts: Rainfall is often associated with the passage of weather fronts, such as cold fronts, warm fronts, or stationary fronts. As these fronts move through an area, they can trigger rain showers or storms.
- Convection: Convective activity, driven by temperature and moisture differentials in the atmosphere, can lead to localized rain showers or thunderstorms. These convective cells can be relatively small and move relatively quickly. As they pass over a specific location, they can bring rain, followed by a temporary break until the next cell arrives.
- Topography: The geographical features of an area, such as mountains or valleys, can influence rainfall patterns. Orographic lifting occurs when moist air is forced to rise over elevated terrain, leading to enhanced precipitation on the windward side of the mountains. In such cases atmospheric conditions interact with the topography.
- Atmospheric Instability: Instability in the atmosphere, often associated with the presence of warm and moist air, can contribute to the development of showers or thunderstorms. These convective systems can be sporadic and result in intermittent rainfall.
- Mesoscale Weather Systems: Localized weather systems, such as mesoscale convective systems or mesoscale rainbands, can produce variable rainfall patterns in specific areas. These systems are typically smaller in scale and can bring localized bursts of rain followed by lulls before the next round of precipitation.