Enhancements to the text-based NWS Severe Thunderstorm Warning

Updated to reflect the change implementation date of July 28, 2021. The National Weather Service will implement enhanced features in the text products for the Severe Thunderstorm warning (SVR), and the Special Weather Statement(SPS) to address instances of sub-severe weather events.

Enhancements to the text-based NWS Severe Thunderstorm Warning

Although both products have changes that will require different attention from end users, they'll be operationally enabled simultaneously across all NWS Weather Forecast Offices.

SVRs will now have the new damage threat category codes, which are part of the Impact-Based Warning coded tags at the bottom. Based on the hail and wind values specified in the warning, SVRs now have one of three threat-level classifications. The damage threat IBW tag will not be given to the lowest-end category. These coded threat tags will be below the double ampersands (&&) as well as just below the storm motion information and supplemental polygon locations of the alphanumeric/text products.

New criteria and definitions

SVRs will contain the IBW coded tag "THUNDERSTORM DANGER THREAT" for damage threat categories. Based on the hail size and/or wind strength, the tag for the two upper categories of SVRs will be either "CONSIDERABLE", or "DESTRUCTIVE." Even if the hail or wind values are different, the highest-level category will be displayed in the tag line. Base-level SVRs won't invoke the damage threat tags and will display only the hail and wind amounts that are currently in the product. The following trigger criteria would apply to SVRs that include either the damage threat tag or both:CONSIDERABLE...1.75 inches of hail (golfball-sized) and/or 70mph thunderstorm winds.

DESTRUCTIVE...2.75 inches of hail (baseball-sized), and/or 80 mph thunderstorm winds.

All modifications to the SVR will be included in the Severe Weather Statement, (SVS), which acts as an update/follow-up alphanumeric product of SVRs.

SVRs containing "DESTRUCTIVE", will be recommended for activating a Wireless Emergency Alert to mobile devices via the Federal Emergency Management Agency (FEMA) Integrated Public Alert Warning System. This capability allows for immediate and immediate life protection actions in the event of severe hail or wind threats. Any SVR that is issued in its initial form or any update SVS with the "DESTRUCTIVE” tag will have a WEA message activated. The full activation capability must be activated by the July 28th, 2021 implementation of the changes to SVRs. This change to WEA messages will also be sent as a separate Service Change Not (21-23) which describes the different messages regarding hail and wind threats.

The Product Description Document contains minor modifications to IBW tags in SVR, especially for hail and wind tags. These modifications will be made to all relevant tags in the TOR as well as the sub-severe Special Weather Statements (SPS).

Below are examples of the Impact-Based Warning categories (IBW), for the Severe Storm Warning (SVR).

https://nws.weather.gov/products/PDD/PDD_Opl_SevereThunderstormWarningCategories_2021.pdf The Public

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