"Destructive" severe thunderstorms to trigger wireless alerts

You are probably familiar with Wireless Emergency Alerts (WEA), the push notification-based alert you receive on your smartphone when a Tornado or Flash Flood Warning has been issued in your area. These alerts are defaulted on from the cell phone companies, but can be disabled in your phone's alert settings if you wish. They are triggered from cell towers to those within their broadcast area whenever the tower's coverage area (roughly) overlaps the weather-warned area. Thus, they are a little more precise than county-based alerts (like those from NOAA Weather Radio), but not quite as precise as a well-designed weather alert app that pinpoints your specific location. 

A sample WEA for a "destructive" Severe Thunderstorm Warning.

Beginning Monday, August 2, the National Weather Service will make a nationwide change to "tag" Severe Thunderstorm Warnings into one of three categories based on expected impact. The highest of these alert levels will also be sent to smartphones via the WEA system. All three categories will continue to be called "Severe Thunderstorm Warnings," but there will be additional information in the warning as to their degree of severity. The three categories are:

1. Base (or baseline) - These warnings follow the existing criteria for a severe thunderstorm: 1.00 inch (quarter-sized) hail and/or 58 mph thunderstorm winds are expected. These are the lowest level of severe thunderstorm and are a threat to those not properly sheltered and will not trigger a WEA.

2. Considerable - Warnings tagged as having the potential to cause considerable damage are expected to contain at least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. These also will not trigger a WEA, but pose a higher level threat.

3. Destructive - Storms that pose a threat of destructive damage will be tagged as such and will trigger WEA alerts. The threshold for a destructive storm is at least 2.75 inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. These storms are estimated to comprise less than 10% of all severe thunderstorms. Extra precaution is warranted (similar to actions taken during a Tornado Warning) given the level of damage they can cause - similar to a low-end tornado, particularly to weak structures.

So while additional alerts will be generated to your smart device, the number will be small and they will be high-end storms capable of significant damage. As a rough measure of their frequency, the NWS office in Memphis issued 223 Severe Thunderstorm Warnings in 2020. If ten percent of those were for "destructive" storms, that would be 22 warnings. And remember that is for all of west TN, north MS, east AR and the Missouri Bootheel! For your location, perhaps you could expect to receive ONE of these warnings per year. And remember that they are in essence based on your neighborhood - based on a cell tower location - not your county. This move by the National Weather Service and Federal Communications Commission is a good one and will hopefully draw more public attention to, and therefore result in a better rate of taking action, for the most destructive storms.

Want even more precise alerts and more control over those alerts you receive? Those that ONLY alert when your specific location is expected to be impacted by the type of alerts you select? Then StormWatch+ Alerts is for you! Add this upgrade to your MemphisWeather.net app and take control over which alerts you receive and for where (select multiple locations anywhere in the U.S.).

Erik Proseus
MWN Meteorologist

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Comparing Wireless Emergency Alerts (WEA) and StormWatch+ Alerts

The wireless industry, Federal Communications Commission (FCC), and Federal Emergency Management Agency (FEMA) now disseminate Wireless Emergency Alerts (WEA) to cell phone users across the nation.  The National Weather Service (NWS) utilizes WEA to push select extreme weather bulletins using this platform.  WEA, also known as Commercial Mobile Alert System (CMAS) or Personal Localized Alerting Network (PLAN), is a national emergency alert system to send concise, text-like messages to users’ WEA-capable mobile devices.  Along with severe weather alerts, other messages that will be sent as Imminent Threat Alerts include natural disaster notices, such as in the event of an earthquake.  In addition to Imminent Threat Alerts, AMBER Alerts will be sent via WEA, as well as Presidential Alerts.

WEA Basics

• Users are automatically enrolled in the program, but can opt out of all alerts except Presidential Alerts
• Alerts will only be sent to WEA-capable devices (most phones released in the past few years)
• Carriers representing more than 97% of cell phone users are represented
• Mobile users are NOT charged to receive these messages
• Message will appear similar to text messages, though they utilize more robust delivery technology than traditional text messages that is not susceptible to network congestion
• Alerts will arrive on your device with a distinct tone and vibration which is different from a standard text message
• Alert messages will be sent to those within a targeted area (individual cell towers can be programmed to send a specific alert), unlike text messages which are not location aware
• Though the messages are targeted, your location is not "tracked." An alert to a particular area will be delivered to all capable devices within that area, regardless of where the device originates or it's "home" area (i.e., someone from Boston traveling in Dallas will receive any severe weather alerts for Dallas while he is in the affected area)
• Messages will be limited to 90 characters (though an expansion is planned in early 2020)

Weather alerts sent via WEA (may vary by area)

• Tsunami Warning
• Tornado Warning
• Extreme Wind Warning
• Flash Flood Warning
• Hurricane Warning
• Typhoon Warning
• Blizzard Warning
• Ice Storm Warning
• Lake Effect Snow Warning
• Dust Storm Warning

While this sounds like a direct (and free) competitor to Cirrus Weather Solutions, LLC's SW+ Alerts service, SW+ Alerts actually has several distinct and important advantages over the WEA system.  These are outlined below.

Benefits of StormWatch+ over WEA

• Delivery method
• WEA - SMS-like text message
• SW+ Alerts - Push notification with link to full-featured content in app
• Weather alert types
• WEA - Limited set of high-end warnings, no watches
• SW+ Alerts - Expanded list of warnings, advisories, and watches
• User selection of alerts
• WEA - All on/off (except Presidential alerts)
• SW+ Alerts - User controls individual alert types, quiet time, and vacation stop
• Location(s) monitored
• WEA - current location only
• SW+ Alerts - 5 user-defined locations anywhere in the U.S., as well as GPS-based location alerts for use while traveling
• Area warned
• WEA - entire county + "bleed over" if cell tower near county line
• SW+ Alerts - Only within NWS warning polygon
• Reliability
• WEA - fairly reliable but statistics not available
• SW+ Alerts - proven based on extensive use in all weather types (well above 99% reliability)
• Availability
• WEA - all recent iOS/Android smartphones
• SW+ Alerts - all iOS/Android smartphones and tablets
• Additional content
• WEA - none
• SW+ Alerts - local radar, forecast, current conditions, graphical depiction of warning + full text of the alert

For more information on SW+ Alerts+ please visit www.StormWatchPlus.com

For more information on Wireless Emergency Alerts, refer to these sources:

• CTIA - The Wireless Association (includes links to WEA info for specific carriers)
• NWS Central Region WEA page (with more information on how the NWS plans to use WEA)
• FCC website on CMAS
• FEMA website on CMAS

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Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

MWN is a NOAA Weather Ready Nation Ambassador

Meteorologist Erik Proseus is an NWA Digital Seal Holder