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Derived products

A number of derived products are generated from the base products of reflectivity, velocity, and spectrum width.

Echo tops (ET). This displays the highest altitude at which a radar echo exceeds 18.5 dBZ. It is computed to the nearest 5,000 ft up to a maximum height of 70,000 ft. The standard coverage radius is 124 nm with a resolution of 2.2 nm.

Vertically integrated liquid (VIL). Sums the reflectivities above a bin location to provide a measure of the total water load above a given location in kilograms per square meter. It has a direct correlation to severe weather, hail, and flood potential, and is most useful in assessing in an extremely short time which storm cells have the greatest significance. Generally values above 40 kg/m^2 are associated with severe weather. The maximum possible displayable value is 80 kg/m^2. The product has a coverage radius of 124 nm with a resolution of 2.2 nm.

Severe weather probability (SWP). Displays the probability of severe weather, based solely on the VIL algorithm. This product is of extremely limited use for severe weather forecasting and must be used with caution. Values are expressed as a percentage from 0 to 100. The product has a coverage radius of 124 nm with a resolution of 2.2 nm.

Mesocyclone. Shear couplets are resolved vertically and with time to determine the existence of a storm mesocyclone. If one is present, it is displayed as a red circle. The radius of the circle equals the reported radius of the mesocyclone. Mesocyclones are resolved only within 124 nm of the radar.

Hail index. The radar system contains a severe hail index (SHI) algorithm that relates the 45 dBZ level to the -20C height. When the computed probability for hail for each storm cell exceeds a predetermined criteria, it will be displayed as a green isosceles triangle. If the triangle is small, there is a 30% probability of hail (50% if it is filled). If it is large, there is a 30% probability of severe hail (50% if it is filled). The maximum expected hail size (MESH) is displayed in the middle of the symbol, rounded to the nearest whole inch; if less than one inch an asterisk shows. The hail index has a radius of coverage of 124 nm from the radar.

Tornado (TVS). This product uses the Tornado Detection Algorithm (TDA) to resolve velocity signatures that suggest a tornado. The tornado signature is shown as a red filled inverted isosceles triangle. An ETVS may also be displayed, but the NIDS code does not provide for differenting TVS from ETVS signatures, therefore they will appear the same. The radius of coverage is 124 nm, but is rarely detected outside of 60 nm since the algorithm is unable to sample the lower portions of the storm at long ranges.

1-hour precipitation (OHP). Radar reflectivity is summed with time to estimate the rainfall accumulation in the coverage area. This product provides an estimate of how much rain fell during the past hour. The highest reportable total is 8 inches. The radius of coverage is 124 nm with a resolution of 1.1 nm.

3-hour precipitation (THP). Radar reflectivity is summed with time to estimate the rainfall accumulation in the coverage area. This product provides an estimate of how much rain fell during the past three hours. The highest reportable total is 8 inches. The radius of coverage is 124 nm with a resolution of 1.1 nm.

Storm total precipitation (STP). Radar reflectivity is summed with time to estimate the rainfall accumulation in the coverage area. This product provides an estimate of how much rain fell during the past hour. The highest reportable total is 15 inches. The radius of coverage is 124 nm with a resolution of 1.1 nm.

Storm tracking information (STI). This product shows information provided by the radar's Storm Cell Interpretation and Tracking (SCIT) algorithm. It shows past, current, and future location of identified storm cells. Past locations are shown for each volume scan (this is an interval of 5 minutes in VCP11 and 6 minutes in VCP21). Future locations are identified at 15, 30, 45, and 60 minutes in the future; though these intervals are customizable by the radar site operator. Each storm has a unique ID of two characters ranging from A0 to Z9 and is recycled when past A0; when no storms have occurred in a certain number of volume scans the ID is reset to A0. The storm data has a radius of coverage of 248 nm.

Clutter control filter (CFC). Shows the clutter filter notch and bypass maps as a radial image. The levels are coded as follows: 0=disable filter; 1=no clutter filter; 2,5=low clutter filter; 3,6=medium clutter filter; 4,7=high clutter filter. Codes 1 to 4 specify the map is bypassed by CTRL, while 5-7 force the filter to operate. The product has a radius of coverage of 124 nm with a resolution of 1 km and 1.4 deg azimuth.