Understanding Accumulation Weather Parameters: Rain, Snow, Sleet

Welcome to our guide on weather parameter accumulation. Here, we break down the specifics of snow and ice accumulation, helping you accurately interpret and use this data in your applications.

Precipitation Accumulation

• Overview: Precipitation is categorized into four types: rain, freezing rain, ice pellets, and snow. Accumulation data is updated frequently and calculated differently for past, present, and future time frames to ensure the most accurate forecasts.
• Calculation: Accumulation is measured hourly. Past data is derived from observations, while present and future forecasts come from predictive models. Each precipitation type is accumulated separately to maintain clarity and accuracy in forecasts.

Liquid Equivalent: 

At Tomorrow, we use liquid equivalent measurements to evaluate precipitation intensity because it provides a consistent and accurate way to quantify all types of precipitation, including rain, snow, sleet, and hail. This approach is widely regarded as the industry standard and is used by most leading weather providers and meteorological services globally.

• Precipitation Intensity: Represents the liquid equivalent for rain, snow, sleet, and freezing rain.
• Precipitation Accumulation: Represents the liquid equivalent for rain, ice accretion for sleet/freezing rain, and solid accumulation for snow.
• Snow Accumulation: Refers to the frozen equivalent accumulation, representing how much snow accumulates as a solid. Accumulation uses a 10:1 solid-to-liquid ratio to depict snowfall accumulation. For example, a liquid equivalent precipitation rate of 1 in/hr snow intensity corresponds to a solid snow equivalent of 10 inches of snow accumulation over one hour. 

Snow Accumulation

Definition: Snow Accumulation refers specifically to the amount of solid snow falling within a specific time frame. It excludes sleet, freezing rain, and ice pellets, ensuring precise and actionable information. Different precipitation types have distinct safety implications and physical properties, which are vital for accurate data usage.

Best Practice: Use the Snow Accumulation field to display predicted snowfall amounts. This ensures users are informed about snow-specific forecasts without the confusion of including other precipitation types.

Snow Depth

Definition: Snow Depth measures the current depth of snow on the ground, considering various factors like compaction, temperature changes, and new snowfall. This dynamically calculated variable provides insight into the existing snowpack's state rather than the amount of falling snow.

Usage: Relevant for both current conditions and forecasts, the Snow Depth field helps predict how accumulated snow will impact ground conditions over time. For daily forecasts, it indicates the maximum expected snow depth within a 24-hour period.

Displaying Snowfall in the Platform

Hourly and Daily Snowfall: For applications aiming to show comprehensive snowfall predictions (including all solid precipitation types), focus on using the Snow Accumulation field. Remember, incorporating ice pellets or freezing rain with snow accumulation might not always provide a clear picture due to their distinct impacts.

Daily Snowfall Accumulation: To display daily snowfall totals, use the Snow Accumulation parameter. This reflects the sum of snowfall over the day and is distinct from the Snow Depth measurement, which indicates how much snow is present on the ground. Read more about the benefits of displaying accumulation map tiles here.

Handling Multiple Precipitation Types

While it's rare, there can be instances where more than one precipitation type is recorded in the same hour. However, for clarity and user safety, it's recommended to treat each type separately rather than combining them into a single insight or alert. Check out our API documentations for more information.

Recommendations

For the most accurate and user-friendly display of weather information, it's advisable to:

• Use Snow Accumulation for forecasts specific to snow.
• Keep Ice Accumulation and Snow Accumulation separate to accurately represent their differing effects.
• Employ Snow Depth data to convey how long snow might remain on the ground.

Need more info or assistance with weather data integration? Contact support@tomorrow.io or your account team.