Subj : Other Weather News
To : All
From : Daryl Stout
Date : Tue Jul 28 2020 05:51 pm
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_SevereThunderstorm
WarningCategories_2020.pdf
(above URL all on one line)
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/
NNNN
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