Support updated IBW Tags

[akrherz]

The PNS below details some significant chances to the IBW tags found in SVR and even TOR warnings. Will have to watch for an announcement after the comment period ends.

NOUS41 KWBC 301500
PNSWSH

Public Information Statement 20-49
National Weather Service Headquarters Silver Spring, MD
1000 AM EDT Tue Jun 30 2020

To:      Subscribers:
         -NOAA Weather Wire Service
         -Emergency Managers Weather Information Network
         -NOAAPORT
         Other NWS Partners and NWS Employees

From:    Michelle Hawkins, Chief
Severe, Fire, Public, and Winter Weather Services Branch

Subject: Seeking Public Comment through July 30, 2020 on the
Proposed Use of Impact-Based Damage Threat Categories in NWS
Severe Thunderstorm Warnings

The National Weather Service (NWS) is collecting comments
through July 30, 2020 on the proposed addition of Impact-Based
Warning (IBW) damage threat categories in Severe Thunderstorm
Warnings (SVR).  The proposed changes are similar to the current
operational format for Tornado Warnings (TOR) and Flash Flood
Warnings (FFW).  In the case of SVRs, machine-readable IBW coded
damage threat tags would be assigned one of two threat-level
categories.  Each category would be associated with a minimum
threshold of either hail and/or thunderstorm wind.  These coded
threat tags would appear below the double ampersand (&&) and
just below the supplemental polygon location and storm motion
information portion of the alphanumeric/text product.

The container in SVRs for these proposed damage threat
categories is the "THUNDERSTORM DAMAGE THREAT" IBW coded tag.
This tag mirrors the "TORNADO DAMAGE THREAT" within TORs and
would be set to either "CONSIDERABLE" or "DESTRUCTIVE",
depending on hail size and/or wind magnitude.  The highest-level
category would appear in the tag line, even if both categories
are reached.

Similar to TORs, the base-level SVRs have the lowest tier
hail/wind criteria and will not invoke these categories or the
damage threat tag.  Base-level SVRs will only provide the wind
and hail amounts as they appear in the current operational
product.  SVRs that contain either of the proposed damage threat
tags would be based on the following minimum trigger criteria:

- CONSIDERABLE...1.75 inch diameter hail (golf ball-sized)
and/or 70 mph thunderstorm winds.
- DESTRUCTIVE...2.75 inch diameter hail (baseball-sized)
and/or 80 mph thunderstorm winds.

These proposed changes would also be incorporated into the
Severe Weather Statement (SVS), which serves as the official
update/follow-up alphanumeric product for SVRs.

Warnings with the "DESTRUCTIVE" tag would be recommended to
activate a Wireless Emergency Alert (WEA) to mobile devices
through the Federal Emergency Management Agency's (FEMA's)
Integrated Public Alert Warning System (IPAWS).  This added
capability is aimed at promoting instant and immediate life
preservation actions for this level of hail and/or wind threat.
If added into the FEMA IPAWS suite of NWS warnings, a WEA would
be activated for any SVR or update SVS that carries the
"DESTRUCTIVE" tag.

Other changes to the SVR IBW tags include the renaming of the
hail and thunderstorm wind gust speed IBW coded tags (HAIL and
WIND) to "MAX HAIL SIZE" and "MAX WIND GUST".  Also, two new
coded tags have been added that will appear in each issuance of
the SVR and its updates.  These are the "HAIL THREAT" and "WIND
THREAT" tags, which will display either "RADAR INDICATED" or
"OBSERVED", depending on that selection, linking to the amount
in the maximum (MAX) wind/hail tag.  No changes will be made to
Tornado Warnings with these proposed changes except the tag for
"HAIL" being changed to "MAX HAIL SIZE", along with SVRs.

Examples of the proposed Impact-Based Warning (IBW) categories
for the Severe Thunderstorm Warning (SVR) are contained document
in the link below:

https://nws.weather.gov/products/PDD/PDD_Proposed_SevereThunderstormWarningCategories_2020.pdf

Comments and feedback on these proposed changes may be directed
to the NWS via an online survey form at:

https://www.surveymonkey.com/r/ProposedSvrTSWarningCategories

Please send feedback/comments on this proposed change to Severe
Thunderstorm Warnings to [email protected], NWS Severe
Weather Services Program Leader, by July 30, 2020.

National Public Information Statements are online at:

https://www.weather.gov/notification/