Proposed tweaks to severe thunderstorm warnings

The National Weather Service (NWS) is collecting public comment on some proposed changes to severe thunderstorm warnings. These changes would add damage threat labels for wind and hail threats. The three tiers are (no label), considerable, and destructive.

(no label)> 60 mph> 1.0″
Considerable> 70 mph> 1.75″
Destructive> 80 mph> 2.75″

As part of the proposal, the NWS says, they will recommend that destructive severe thunderstorms trigger a wireless emergency alert (WEA) message. This means most modern cell phones will receive an alert for the highest-end storms. According to an analysis by Joseph Patton, this would apply to just over 1% of severe thunderstorm warnings. (This percentage will vary by time and location.)

I am 100% on board with this proposal. Let’s be honest with ourselves: most people ignore severe thunderstorm warnings. I’ll be the first to admit that I do. Once I’m inside, I’m safe enough without taking extra precautions. But those top-end storms can do damage similar to tornadoes. Being able to distinguish between “get inside” and “get to the basement” severe storms is helpful.

Now I’ve suggested before that tornado and severe thunderstorm warnings should be combined into a single product. I still hold that opinion. Intensity of the threat matters more than the specific mechanics of the threat. But I very much doubt the NWS will implement that idea any time soon. This proposal at least allows for cleaner communication of the most life-threatening thunderstorms.

You can give the NWS your own opinion via online survey before July 30, 2020.

2013 severe weather watches

Greg Carbin, Warning Coordination Meteorologist at the Storm Prediction Center, recently updated his website to include maps of 2013 severe thunderstorm and tornado watches. I always like looking at these, because they highlight areas of increased and diminished severe weather threat. It’s important to not read too much into them though. As with hurricanes, it’s not always the frequency of events that makes a year memorable. 2013 was a below- or near-normal year for watches in the areas of Illinois and Indiana that were hit by a major tornado outbreak on November 17.

Tornado (left) and severe thunderstorm (right) watch count (top) and difference from 20 year average (bottom) by county. Maps are by the NOAA Storm Prediction Center and in the public domain.

Speaking of hurricanes, the quietness of the 2013 Atlantic hurricane season is evident in the below-average tornado watch count along the entire Gulf coast. Landfalling hurricanes are a major source of tornado watches for coastal states, so an anomaly in watches is often reflective of an anomaly in tropical activity. Preliminary tornado counts for 2013 are the lowest (detrended) on record. It’s not surprising, then, that the combined severe thunderstorm and tornado watch counts are generally below normal.

Severe weather watches (left) and departure from normal (right) by county. Maps are by the NOAA Storm Prediction Center and are in the public domain.

As you’d expect, Oklahoma and Kansas had the largest number of watches. What’s really interesting about the above map is the anomalously large number of watches in western South Dakota, western Montana, and Maine. Indeed, western South Dakota counties are comparable to Kansas in terms of raw watch count. Of course, that doesn’t mean the watches verified, but it’s an interesting note. Looking back through past years, the last 4 years have been anomalously high in western South Dakota. Is this an indication of a population increase, forecaster bias, or a change in severe weather climatology?

Increased complacency about severe weather benefits no one

The number of meteorologists in the United States is very small.  According to the Bureau of Labor Statistics, less than 10,000 people are employed as atmospheric scientists in non-faculty positions (anecdotal evidence suggests that the number of people holding meteorology degrees is significantly higher. To wit: of the 12 people in my graduating class, four are meteorologists).  With such a tiny fraction of the population trained in atmospheric science generally, and severe storm meteorology specifically, it should come as no surprise that the public knows relatively little about severe weather.  With the small number of meteorologists, a heavy reliance is placed upon the media and local officials to convey information.

However, while the media and local officials may get more exposure to weather information, they do not necessarily understand it any better than the rest of the general public.  This leads to newspapers reporting that a “local tornado warning was issued” (only the National Weather Service issues tornado warnings officially, and causing confusion about this does not help the public interest) after a “funnel cloud on the ground” was sighted (a “funnel cloud on the ground” is more properly known as a “tornado”, but in this case it was more likely a mere “scary-looking cloud”). It leads to emergency managers sounding warning sirens when the greatest threat is heavy rain and sub-severe winds.  And it leads to confusion and eventual complacency for the public.

Meteorologists have enough trouble fighting complacency as it is.  The most recent data from the National Weather Service indicates that 76% of tornado warnings are false alarms.  This is not because of incompetent meteorologists.  It is a limitation of available observation systems (radar), of the understanding of tornadogenesis, and of the (quite reasonable) belief that it’s better to overwarn than to miss a tornado.  Additionally, since tornadoes are often relatively small and short-lived events, it may be that some of these false alarms are not so, but there are no reports thus the warning remains unverified.  The upshot of all of this is that it’s very easy for the public to not take warnings seriously.

I can, perhaps, understand the reason the Tippecanoe County Emergency Management Agency (TEMA) decided to sound the sirens last Saturday.  A street festival was about to begin in downtown Lafayette, and many people were moseying down Main Street.  The wind and rain had already begun clearing the streets before the sirens sounded, and no one seemed to be in any additional hurry when they heard the beautiful wail.  It can argued that the sirens were sounded appropriately in that case, but the public mindset is that the sirens are “tornado sirens”, so sounding them for non-tornadic events (especially events that posed such a dubious threat) does a disservice to the public because it increases complacency.  In this specific case, the sirens added nothing helpful, and thus should have remained silent.

Were this an isolated incident, I would not have felt compelled to write this post, but TEMA during the Mark Kirby era has been quick to sound the sirens.  In my circle of meteorological friends, there are two common consequences to rainfall: 1) the Indianapolis radar goes out of service, and 2) the tornado sirens are sounded in Tippecanoe County.  If I’ve associated the sirens with rainfall, surely there are others in the county who have done so as well.  So who benefits from sounding the sirens so much? No one.