Thunderstorm Safety

In the wake of recent tragedies, it's worth a bit of review of flood and lightning safety.  In the case of floods, here's some data from the National Weather Service and their partners:

• More deaths occur due to flooding than any other thunderstorm hazard.
• Over half of all flood-related drownings occur when a vehicle is driven into flood waters.
• The next highest percentage of flood-related deaths is due to walking into or near flood waters.

Source: National Weather Service

A full run-down of National Weather Service flood products, including outlooks, watches, advisories, and warnings is available at https://www.weather.gov/safety/flood-products.  In Utah, the National Weather Service also provides flash flood potential ratings for southern Utah and covering 12 recreation areas at https://www.weather.gov/slc/flashflood.  

As evident in near the Cottonwood Fire and Beaver, fire scars can be especially problematic for flash flooding and debris flows.  

National Weather Service lightning safety tips and resources are available at https://www.weather.gov/safety/lightning.  Lightning kills about 20 people a year nationwide, most commonly in summer, but deaths have occurred in all seasons (and in fact lightning is a threat for skiers in Utah which has a relatively high rate of thundersnow).  If you can hear thunder and are outdoors, you should move indoors or into a hard-topped car if you can.  If you are car camping and are in a tent of soft-sided trailer, move into a vehicle.  If you are at an outdoor sporting event, move indoors or into your car.  

Source: https://www.weather.gov/media/owlie/backcountry_lightning.pdf

In the backcountry, more than 30 minutes from an enclosed modern building or vehicle, lightning safety is about minimizing risk.  The most important thing is to monitor forecasts and time your visit to high-risk areas such as mountain peaks, ridgelines, and open water areas accordingly.  Think of it as being the equivalent of selecting the proper terrain for a given avalanche hazard.  Next is to move to safer terrain, as quickly as safely possible, if you hear thunder or believe the thunderstorm hazard is increasing.  This will not eliminate risk, but strikes are more random in lower elevation areas.  Avoid high trees, open areas, and if you can find a dry, lower elevation area, move there.  Pick tent sites to minimize risk too, but be careful when looking at ravines and other gullies if there is a possibility of flash flood.  

Below is more detailed information from a brochure put together by the National Weather Service and NOLS.  Note that getting into the lightning position is a last resort.  If you can move to a safer location focus on that.  For example, if I was on a ridge, I would move down in elevation as fast as I safely could rather than stay there in the lightning position.  

Source: https://www.weather.gov/media/owlie/backcountry_lightning.pdf

Many of the "FACETS" heuristic traps in avalanche accidents also apply to lightning safety.  

F=Familiarity.  Something that feels familiar feels safer, but just because you've survived lightning storms at high elevations in the past doesn't mean you will today.  

A=Acceptance.  You want to fit in or impress your friends by climbing a line or bagging a peak, which might increase your tendency to push it as weather hazard increases.   

C=Commitment.  You don't want to turn around from the summit when you have invested time and effort and are more likely to to push it as weather hazard increases.

E=Expert Halo.  There's a tendency to defer decisionmaking to others with more experience.  Don't assume your friend with years of mountaineering experience is going to make the right weather-related decisions.

T=Tracks/Scarcity.  This one might be more seasonal, but since there is lightning risk in winter, don't ignore it because you want to get first tracks of the top of Mt. Superior. 

S=Social Facilitation.  This one is actually very valid to lightning safety.  It is much harder to move to a building or car, turn around from high elevations, or get off the lake when noone else is doing it.  However, just because nobody else is doing it doesn't mean you shouldn't be doing something to reduce risk.  

All of that said, I've been there.  In fact, the event that I often think of as pushing me into meteorology happened when I was a teenager backpacking with my Dad and we had to run very rapidly from and Adirondack peak to a lower-elevation pass as a thunderstorm moved in.  I've been pelted by hail and graupel during thunderstorms in the Uintas, keeping to the lowest terrain without flood potential possible.  And I've spent time in the lightning position on backpack trips.  On Saturday, we hiked in the morning because of the increasing thunderstorm hazard during the day, yet were just getting to our car when the thunder started at 11:30.  

Use the tips above to adventure at the safest times and to know what to do to minimize risk when you are caught out.  

Stadium Safety

Tonight is the opener for the University of Utah football team.  Masks aren't required, but clear bags are.  Plan accordingly!

Have you bought your clear bag yet? As a reminder, Rice Eccles Stadium only allows clear bags! Make sure you're ready for tomorrow's game with one of your own.

Buy one here: https://t.co/iwvOOuwtuP pic.twitter.com/RV0XzSTrLi

— Utah Red Zone (@UtahRedZone) September 1, 2021

The Storm Prediction Center has us in the marginal risk category, meaning that isolated severe thunderstorms are possible.

Source: SPC

If I were attending the game, I would keep this in mind.  Things could work out just fine, but if there is a thunderstorm in the vicinity, it is best to take appropriate measures, which likely means moving to a hard-topped vehicle such as your car.  Stadiums are generally not safe from lightning, even in covered open-air areas.  I always get a pit in my stomach when a thunderstorm is near Rice-Eccles stadium, most recently in September 2019 when there was lightning near the stadium, the camera people left due to lightning concerns, but the game went on (for more see https://wasatchweatherweenies.blogspot.com/2019/09/concerns-about-lightning-safety-at-rice.html).  

Hopefully the storms say away and the Utes win convincingly.  

Concerns about Lightning Safety at Rice-Eccles Stadium

Readers of this blog know that I frequently discuss issues with lightning safety at outdoor stadiums.  Prior to yesterday's game, I discussed the difficulties of the game-day forecast and the potential for thunderstorms during the game (see prior post Difficult Game Day Forecast). 

I did not catch the start of the game as we were out with friends, but when I turned on the game at some point into the first half, I heard some discussion about their camera people leaving for safety.  Nevertheless, the game was going on.  I thought this was quite odd.  They returned to the field at some point and the game went on, with the Utes achieving a convincing victory.

This morning I decided to look into things.  Information on lightning strikes is available at lightningmaps.org.  According to their site, there was a lightning strike 4.3 km (2.7 miles) from Rice-Eccles stadium at 2:49 UTC/8:49 PM MDT during the game. 

The NCAA Sports Medicine Handbook (available here) has an entire section on lightning safety.  To quote, "lightning is the most consistent and significant weather hazard that may affect intercollegiate athletics."  In it, they note that NOAA estimates that 62% of lightning strike fatalities occur during outdoor organized sport activities.  During this season's Utah-BYU game there was a delay due to a nearby lightning strike.  Nobody likes these delays, but they are important for participant safety.  Further, they are also important for spectator safety.  The American Meteorological Society Statement on Weather Safety at Venues and Public Gatherings (available here) provides some examples of lightning and other severe weather fatalities and injuries at outdoor events.

I don't know why last night's game was not stopped.  I do believe the U and whoever they have monitoring the weather should review their protocols. 

Holy War Fireworks?

I had to spend a few hours in Utah County last night.  My skin began to crawl as I passed south across the county line and my stomach churned when I saw the white letter of the school down south on the hill.  There are places where one should not linger, and Utah County is one of them.  It is best to go down there, kick butt, shut people up, and get out, as the Utes will do tonight.

The Holy War kickoff is scheduled for 8:15 PM MDT.  There is a chance of thunderstorms later this afternoon and evening.  These storms are expected to be scattered, so the pre-game festivities, game itself, post-event celebration by Ute fans, and whining by Cougar fans could go off without a hitch.  On the other hand, the potential for a thunderstorm and related impacts is there should they be in the wrong place at the wrong time. 

Chances are you have noticed the increase in humidity since yesterday.  At the Salt Lake City Airport, dewpoints yesterday were in the high 30s in the morning and near or below 30 in the afternoon.  The have, however, climbed overnight and have been hanging in the mid 40s today.  Similarly, at the Provo Airport, they are running in the upper 40s. 

It's not a juicy airmass, but it may be enough for some action to get going this afternoon.  The High Resolution Rapid Refresh (HRRR) forecast model, for example, shows some convective storms firing up in western Utah and moving into the Wasatch Front around 0000-0100 UTC (6-7 PM), with scattered storms for a few hours thereafter. 

The storms are not widespread, but they will be around.  They could kick off some microburst winds and potentially produce a little lightning.  Precipitation will probably be limited.  Hopefully all will go off without incident, but there is a low but non-zero threat of thunderstorm impacts.  Should a thunderstorm approach, don't linger in the open or other lightning exposed areas, even if precipitation is scant.  Stadiums are not safe during thunderstorms.  Heed the advice of stadium officials, even if those officials are from that school down south.

Convection over the Uintas

During periods of weak large-scale forcing in the summer, the mountains play an important role in the initiation of convective clouds and thunderstorms.  Nowhere is this more apparent in our region than over the Uinta Mountains where a visit sometimes makes one feel like they've traveled to another planet.

The photo below was taken from the Gobblers Knob summit at about 10 AM this morning looking east toward the Uintas.  As is often the case, one can see the first cumulus clouds of the day forming over the Uintas.  Often, these clouds grow in depth, producing showers or thunderstorms later in the day. 

I don't know of a study that has specifically examined the influence of the Uintas on convective cloud initiation and evolution, as well as growth into thunderstorms, but I'll speculate here on one of the reasons why the Uintas are so active: their scale.  They are quite high and broad with large expanses of lower elevation terrain to the north and south of their west-to-east oriented spine.  This favors the development of a robust "mountain-plain circulation" which during the day features upslope flow with convergence over the Uintas, as depicted schematically above.  This convergence leads to ascent, which not only helps to trigger cumulus clouds, but also creates a moist environment in which those clouds are not as easily destroyed as they mix with the ambient air through a process known as entrainment. 

The "smoothness" of the Uintas might also help since the large-scale mountain-plain circulation is not strongly disrupted by deep, incised topography, although even in the Alps, the influence of the mountain-plain circulation is often apparent. 

Constrasts between the evolution of convection today over the Wasatch and Uintas are apparent in MODIS imagery from NASA's Terra and Aqua satellites.  The Terra overpass at approximately 11:30 MDT shows extensive cumulus clouds over the Uintas.  In contrast, cumulus over the Wasatch was confined primarily to the central Wasatch, especially the high terrain between Snyderville Basin and Alta. 

Source: NASA

The Aqua overpass at 2:30, shows that the convective clouds became much deeper over the Uintas than the Wasatch.  Note the extensive and continuous anvil associated with a storm over the central and eastern Uintas in the image below, with a cloud free area near the Uinta crest to the east, likely associated with a local cold pool in its wake. 

Source: NASA

Radar coverage in the Uintas is so-so at best, but imagery at the time shows a that precipitaiton was likely falling in the Kings Peak area.

Source: NCAR/RAL

Data from lightningmaps.org shows numerous lightning strikes today in the Uintas.  

lightningmaps.org

It's best not to assume that the forecast you hear on TV applies to the Uintas.  It's a better option to check the National Weather Service site for a Uinta-specific forecast and take low probabilities of thunderstorms seriously.  Review National Weather Service recommendations for backcountry lightning safety at https://www.weather.gov/media/safety/backcountry_lightning.pdf. 

Lessons in Lightning Safety from Yesterday

Yesterday afternoon, a series of convective storms formed over or near the central Wasatch and moved northwestward toward Bountiful and portions of the Salt Lake Valley.

The first of these storms was near Parley's Canyon at 2059 UTC (1459 MDT) and organized in a line. It looked like a close call for the University of Utah to receive rain, as well as thunder and lightning.

Over the next 13 minutes, the storm shifted northward and became more cellular in structure.  By that time, it was northeast of campus and we had missed out on any significant precipitation.

However, it is important to realize that threats from lightning can often extend many miles from the rain shaft and indeed, that was the case yesterday.  I was taking the occasional glance at the wonderful lightning products at lightningmaps.org and noticed a strike not only on Little Black Mountain close to the storm, but also in the mouth of City Creek Canyon, not far from downtown.

That strike illustrates that lightning can strike outside of the rain shaft, sometimes 10 miles (or in some instances more) from the storm.

Now there is some possibility that there is an inaccuracy in the data, but lightning studies have shown that strikes up to 10 miles from the rain shaft in the absence of rain happen.  If you can hear thunder, even if it isn't raining at your location, you should move indoors.  If you are at a sporting event, move into your car.  In the United States from 2006 to 2016, there were 31 lightning fatalities during sports-related activities, with the most at soccer events, followed by golf.  Many more are injured.

Source: Jensenius (2017)

Note that picnic shelters, dugouts, and porches are not considered lightning safe.  Move to a substantial building or a hard-topped automobile if you are at an outdoors sporting event, rock concert, whatever.

For outdoors oriented people like myself, it's best if you can rearrange your schedule to recreate when lightning is not a concern.  We did this yesterday as we waited until late evening to hike in the Avenues foothills.  There are times, however, when you can't wait or find shelter.  I've had some miserable and scary experiences hiking and backpacking during thunderstorms.  In fact, I became a meteorologist in part because of a miserable storm night my dad and I had in the Adirondacks when I was a teenager.  In these instances, the goal is to reduce the threat.  This involves:

• Moving from a tent to a car if possible
• Avoiding open areas, ridge lines, and mountain tops.  
• Moving to lower elevation (Note: Avoid washes and other areas if flash-flooding is a concern)
• Staying away from tall, isolated trees and objects.  Find lower tree stands if possible.
• Spreading out if you are in a group
• Avoiding open water
• Avoiding laying on the ground.  Minimize contact with the ground. 

Now I'm no "angel" when it comes to lightning safety.  I've sat too long on my porch or have tried to squeeze in a workout when I shouldn't on several occasions.  Being human is hard.  Nevertheless, it's a good idea though to practice good lightning safety practices and minimize risk as much as possible.

Lightning Safety Lessons

I need to pick on myself today for poor lightning safety practices.  Much like avalanche accidents, human factors often come to play in lightning accidents.

As I was heading out for a quick mountain bike, a cell was popping over the Oquirrhs.  It wasn't much to be concerned with at the time, but I made a mental note to keep an eye on it.  Plus, I needed to be somewhere later and had to get my ride in.

The climb from the valley to the ridge was uneventful, other than running into this not-so-friendly fellow.

I know little about snakes, but I come across one about once a month in the warm season.  Usually they are gopher snakes.  I'm not sure what this one was.  It was fairly non-aggressive and wasn't rattling, but a close look at the tail suggested it may have been a rattlesnake that had lost the rattle.  I watched him slither into the grass and kept my distance.

Getting back to lightning safety, I didn't hear any thunder on the climb, but on the summit, although the main cell was in the distance, it was clear that the anvil had overspread me.

Anvils are capable of producing lightning, so being somewhat removed from the main cell is no guarantee of safety.  As I rode along the trail at elevation, I heard thunder, which was a tell-tale sign that I should have turned around earlier.

I made it home safely and a quick look at lightningmaps.org showed now cloud-to-ground strikes anywhere near my ride.  However, a post-ride assessment show it would have been best to wait.

Graduation Rumblings

Although the University of Utah general commencement was last night, most college convocations are today, ensuring that campus is bustling with activity.  The morning dawned, however, with thunderstorms and rain on campus, which surely sent a shiver down the spine of Deans, Administrators, and campus planners.

Thunderstorm over the University of Utah campus around 7:05 AM MDT this morning.

Radar imagery at 1333 UTC (7:33 AM MDT) showed stronger returns just west of the Wasatch spine east of campus, with two cells further west, including one over campus.

These storms were moving northward and as I write this at 7:50 AM MDT, rain has stopped.

Graduation day was always stressful for me back in the day.  We used to have our college reception outdoors, and the dean would always want to know if he needed a tent and would call me for a forecast starting days in advance.

Today, we have a new building and enough room to hold the reception indoors, so I'm off the hook.  Nevertheless, nobody likes rain and thunder on campus for graduation.

Despite the early action, I don't think today will be a washout.  Showers and thunderstorms will be scattered today, so lets just hope the activity is well timed to allow for dry walks around campus.  If thunder roars, head indoors. 

Lightning and Topography

Given that this is lightning week, it seems quite appropriate that a paper examining the influence of topography on lightning strikes came out this week in Monthly Weather Review (Vogt and Hodanish 2014; paywalled, but I'll hit the highlights).

Specifically, they used data from the North American Lightning Detection Network (NLDN) operated by Vaisala to document the characteristics of 12.5 million cloud-to-ground lightning strikes over Colorado from 2003–12.  The topographic map below highlights some of the key topographic features that influence lightning strikes within the state.

Source: Vogt and Hodanish (2014)

The map below shows the stroke density during the warm season (1 April to 31 October).  One can clearly see the influence of elevation, but also some important geographic effects.  Stroke densities are highest in the high terrain encompassing Pikes Peak, the southern Front Range, and along the Palmer Divide east of east of Pikes Peak.  High densities are also found in the high terrain near the southern Sangre de Cristos and along Raton Mesa.  Low densities are found in the San Luis Valley, as well as lower elevations regions along the Gunnison and Uncompahgre Rivers near and southeast of Grand Junction (not shown in the above map), far northwest Colorado, and along the I-25 corridor in northern Colorado. One can clearly see the influence of local terrain throughout the western half of the state, but with this color scale it is especially apparent in the San Juan Mountains.

The influence of elevation and topography is summarized nicely in the graph below, which shows the stroke density as a function of elevation. There is a peak at 5500–6000 ft that reflects the high stroke density of the Palmer Divide and Raton Mesa (point D), a minimum at 7500–8000 ft that reflects the low stroke density of the San Luis Valley (point D), and then a very clear increase above 10,500 feet reflecting the increasing stroke density in the high mountains of the state.

Source: Vogt and Hodanish (2014)

Now is a good time to mention that low stroke density doesn't mean no stroke density. Climatological stroke densities may be lower along the northern I-25 corridor than in the Front Range to the west, but you wouldn't catch me golfing or mowing the lawn there if there was a storm nearby.  Ditto in the San Luis Valley and other broad lowland regions.  If you are in the mountains, you can minimize risk by moving to lower elevations, but if you can, it's still best to seek shelter in an enclosed building or hard-topped vehicle.  If you are car camping in a valley and you hear thunder, best to be in the car than your tent.

It would be great to see a product like this produced for Utah.  For you atmospheric sciences undergraduates out there, producing such a map would make a great senior capstone project.

Storms Provide Relief, Floods, and Learning Opportunities

With temperatures in the 60s, dewpoints near 60, and rain falling steadily from the sky, I slept like a baby last night.  I can't even remember the last time we had a long period of steady rain like this and it seems like a gift from heaven, although yesterday's stronger downpours unfortunately caused some flooding and debris-flow problems in wildfire-scared areas such as near Alpine.  Further, the delay of the Texas–BYU football game is a prime example of why major stadiums need to prepare and have a plan for participant and spectator safety during severe weather (as does the Broncos–Ravens game on Thursday night).  Even if the U is prepared, the BYU experience provides a learning opportunity to see what worked effectively and what didn't.  U officials should also have a look at Gratz and Noble (2006), who provide a summary of lightning safety guidelines for large groups.  It's not a matter of if but when there is a thunderstorm, possibly severe, that impacts a U football game.

Electrifying!

I don't know about you, but I thoroughly enjoyed last night's thunderstorms.  We had a BBQ in the evening and followed by the thunderstorms as they moved across the Oquirrh Mountains and towards Salt Lake City.  

A crowded porch examines the approaching thunderstorms.
Photo: Trevor Alcott

Wasatch Weather Weenies BBQs never disappoint in August.  We're always able to conjure up some action.  Our resident photographer snapped this photo.  Fantastic!

Photo: Trevor Alcott

Classes start here at the University of Utah on Monday.  Readers of this blog who are U of U students might want to consider taking Atmos 1010: Severe and Unusual Weather and learn about storms like the one above.  

Daytime Destabilization

In Colorado, where thunderstorms are pretty much a daily occurrence during the summer, the rule of thumb is to be back down to timberline by 1 PM.  Here in northern Utah, thunderstorms are not always a daily occurrence, but that rule of thumb turned out to be quite useful today.

Given the forecast, I opted for a mid-morning hike up Patsey Marley.  I awoke to just a few shallow cumulus clouds over the mountains, and kept an eye on things during the ascent, which proved uneventful.  On top at about 11:45, the sky was filled with cumulus, which were growing in depth, but hadn't yet become deep enough to glaciate (i.e., develop ice crystals), which is essential for the electrification.  Rather than push it, I enjoyed lunch on top and decided to head down.

Subsequently, surface heating continued to destabilize the atmosphere, resulting in increasingly deep convective clouds and eventually the development of thunderstorms over the Oquirrh Mountains and portions of the Salt Lake Valley.  The growth of the convective clouds was well captured by George Wilkerson's Cove Cam, which looks westward toward the Oquirrhs from Olympus Cove.

The spotty nature of convection is such that you can get lucky and not be in it, but it's better to finish early and enjoy a cold drink at home than to be cowering on a high ridge.  In addition, I can't sprint downhill to safety as easily as I could a few years ago!

Spring Rumblings

For the second day in a row we are being treated to flashes of lightning and rumblings of thunder on the University of Utah campus.  In both instances, the thunder and lightning are being produced by storms that moved in from the east or southeast.  Here's the latest showing the thunderstorms that are moving across the Wasatch and towards campus at about 2:15 PM today.

The culprit in driving these storms westward is of course the huge split flow that is present over North America along with an embedded upper-level trough that is stretched out like a rubber band from southern California to Colorado and driving easterly flow across northern Utah at 700 mb.

Given all these thunderstorms, now is a good time to remind everyone that when thunder roars, head indoors.   As discussed in today's Salt Lake Tribune, lightning yesterday damaged an Air National Guard plane and struck a house in West Jordan.  Take a few minutes to read our post Lightning Safety and take steps to minimize your exposure to lightning.

Bryce Canyon Lightning Death

A man from Hamm, Germany was tragically killed by a lightning strike while hiking the Rim Trail near Sunset Point at Bryce Canyon Thursday afternoon.  

We have discussed lightning safety in a previous post, but we didn't discuss a human element that sometimes plays a role at National Parks and other outdoor areas where there are larger concentrations of people.  In particular, we all have a false sense of security when others are around and tend to go with the crowd when it comes to decision making.  Don't let a crowd opting to stay outside dissuade you from taking safety measures if you hear thunder or lightning is nearby.  

Lightning Safety

Photo: John R. Southern/Wikipedia Commons

As reported in today's Salt Lake Tribune, there have been two tragic lightning deaths in Utah this week.  On Monday, a man was struck and killed near the Wedge Overlook in the San Rafael Swell, and yesterday a Boy Scout was killed while camping at Scofield Reservoir.  Apparently, the Boy Scout was moving to shelter when he was struck.  What a tragedy.

Perhaps today is a good day to discuss lightning safety and what you can do to minimize lightning hazard.  The NWS has a brochure on lightning safety available here.  The bottom line is that there is no outdoor place that is safe during a thunderstorm.  Head indoors or get in your car.  When car camping, move from your tent into your car.

Many readers of this blog spend considerable time in the backcountry where one can take steps to minimize (but not eliminate) lightning hazard.  Plan ahead.  Know the forecast.  The rule of thumb to be off high ridges in the afternoons is just that...a rule of thumb.  There are certain situations when this applies and when it doesn't.   Keep an eye to the sky.  When thunderstorms are near, stay away from open areas where you are the highest object and away from tall isolated obstacles.

Keep in mind that many people are struck either before or after it rains.   Don't wait to find shelter or minimize exposure, and linger a bit longer as the storm moves out.

Although there is a tendency for lightning-strike frequency to be higher on ridges and mountains, this does not mean that lightning cannot strike in lowlands or valleys.  For example, a few years ago after a thunderstorm in the Oregon Cascades, we observed a lightning-induced spot-fire at Crater Lake, well below the surrounding rim and nearby mountain.

You can minimize the odds of being struck by going low, but not eliminate it.  If you can get indoors or in a car, do so.