• What Is an Extended Reflectivity Composite?
• What Is a Snow/Ice/Rain Composite?
• What Is ma Radar/Satellite Composite?
• What Is man Estimated Precipitation Composite?
• Why Does mThe 365-Day Precipitation Estimate Composite Seem Low?
• How Often mAre The Precipitation Estimate Composites Updated?

What Is an Extended Reflectivity Composite?

The default State/Regional/National product from AccuWeather.com is the Extended Reflectivity Composite. This takes the Extended Reflectivity product from all Local Radars and puts them together, so that a more complete picture of the precipitation can be viewed. Using Extended Reflectivity, instead of the default Local product "Base Reflectivity" means that almost 100% of the United States is covered. To read more about the Local Reflectivity Products, click here.

What Is a Snow/Ice/Rain Composite?

The Snow/Ice/Rain (or "SIR") State/Regional/National product from AccuWeather.com tells you not only the precipitation intensity but its type. It is based on the Extended Reflectivity product explained above. The regions which contain Snow, Ice (Freezing Rain), and Rain are determined and colored appropriately. It uses proprietary algorithms that make use of both model and real-time data to determine the type of precipitation.

What Is a Radar/Satellite Composite?

The Radar/Satellite Composite image overlays Extended Reflectivity radar data (explained above) onto the standard Infrared Satellite. This shows not only the precipitation falling, but the clouds surrounding it.

What Is an Estimated Precipitation Composite?

These products take the One-Hour Precipitation product from all Local Radars and puts them together, so that a more complete picture of the fallen precipitation can be viewed. For periods longer than one hour, the total is accumulated from past images. Because the Local One-Hour Precipitation product reaches to a maximum of only 230km in rare instances small areas may seem to be precipitation-free. This is an estimate by the NEXRAD radar and may not match ground truth. To read more about the Local Precipitation Products, click here.

Why Does The 365-Day Precipitation Estimate Seem Low?

Because we came up with the idea of a "365-Day Precipitation Estimate" in late 1999, it will not contain 365 days until late 2000. Until then it will be an estimate of November m1, 1999 to the current date.

How Often Are The Precipitation Estimate Composites Updated?

The 1-Hour, 3-Hour, and 24-Hour Composites are updated hourly. The 7-Day and 30-Day composites are updated daily at 12Z. The 365-Day composite is updated on the 1st, 7th, 14th, 21st, and 28th of each month.