Small Town News


Microburst wreaks havoc in Big Horn Mountains

The Lovell Chronicle of Lovell, Wyoming

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A microburst with winds estimated by the National Weather Service in the 90 to 100 mph range cut a path a quarter mile wide and two miles long snapping trees, crushing camp trailers and sending people running for cover on Monday evening. The event took place at around 5 p.m. in a popular camping area in the Big Horn Mountains near Little Horn and Dayton Gulch Roads.

Big Horn County Sheriff's deputies were the first on the scene after receiving a call at around 5:30 p.m. reporting that an extreme weather event, possibly a tornado, had occurred, causing extensive damage in the popular recreation area.

"It appears that it started on top of Bald Mountain," said Big Horn County Sheriff Ken Blackburn. "You can see the swath (of downed timber) where it came down, crossing Highway 14A proceeding north, where it looks like it settled into the Little Horn drainage."

Blackburn noted that it is a popular camping area, where multiple campers often pull off the road to set up camp.

"Our first report was there were campers destroyed and timber down in the area," said Blackburn. "As deputies responded to the area, there were additional reports of severe damage and stranded campers. Trees had fallen across the road and some of the campers could not get out. Fortunately, there were no injuries reported and very few people were actually in the path of this (microburst).

"Some people who were in its path reported that it hit so fast that they just got down into the creek banks and hid in culverts and cuts in the bank as it passed over them. They said it sounded like jet engines or freight trains as it passed over them."

The Lovell Fire Dept. received the call at about the same time and responded with six men wielding chainsaws.

"We went ahead and starting cutting trees (on Little Horn Road) at about six o'clock and kept cutting until after 9," said Lovell Fire Chief Jim Minchow. "In some places trees were pulled up by the roots, in other places they were snapped off. We cut some in chunks and rolled them off the road. We cut at least 40 or more trees for about three hours straight to clear the road, so stranded campers could get out."

Search and rescue teams from both the South and North ends of the county were the next to arrive on the scene and immediately began systematically checking the area for injured or trapped individuals.

Blackburn said he only had contact with about 15 or 20 campers during the period of time he was on the scene. Had it been a weekend, he said there would have been hundreds in the area.

"We immediately spread people throughout the area, especially in the affected zone, to make sure no one was in there needing help," said Blackburn. "We assessed the damage and determined that it was fairly isolated to the Little Horn and Dayton Gulch roads."

He said golf ball sized hail had literally wiped the roads clean of any tracks from vehicles. He said he saw cows "bunched up and looking afraid" and wild animals that looked "spooked." He described the scene as eerie, where something big and very frightening had obviously happened.

"The power of Mother Nature was obvious," said Blackburn. "It was pretty impressive."

He said deputies proceeded immediately down Little Horn Road on foot to check on campers. He said they moved as fast as they could, with downed trees impeding their movement along the way. He said more than 40 vehicles were methodically checked to make sure no was inside needing assistance.

"SAR systematically cleared those areas and found no injuries," said Blackburn. "We were concerned that with significant damage like this, someone could have been in the trees or trapped somewhere needing help. People could have been anywhere.

"Between the hail, wind and downed trees we saw a significant amount of property damage. I recognized many of the people, many of those people I recognized from Big Horn County.

"Fortunately, the damage was to equipment, not to people. We can always replace equipment, not people. I am still amazed that we did not see significant injury or loss of life as a result of this event."

Meteorologist Chris Jones of the National Weather Service toured the area with Big Horn County Emergency Management Coordinator Jason Beal on Tuesday. Jones said based on what he saw, the damage was caused by a microburst with estimated winds up to 100 mph.

Jones explained that micro-burst is created by the winds surfacing as a result of a downdraft created by a storm. The down-draft not only carries wind but it also can carry rain and hail. He said in this case, there was both rain and hail, including hail up to Wi inches in diameter. He said the high winds often create a roar, like the sound described by eyewitnesses at the scene.

"As anyone across Wyoming could attest, we had plenty of wind on that day from the cold front," said Jones. "Greybull had gusts of up to 74 mph and the air-port at Cowley had gusts of up to 63 mph. So, we already had strong winds with the thunderstorm itself, then we added to that taking the wind up to 90 or 95 or 100. It's common to have a micro-burst in those conditions but that speed is the highest I've seen. Usually microbursts are in the 60 to 70 mph. This is definitely the strongest I've seen since I've been here (in Wyoming), which is since 2002."

Jones said the biggest difference between a micro-burst and a tornado is that during a microburst high winds come down from the storm above in the form of a downdraft, similar to pouring a bucket of water from above. He said the air comes down similar to the motion of water with great force, spreading as it hits the ground. He explained that it is at the impact point where most damage occurs. He said the power decreases as it spreads, ending up weaker and weaker until it reaches its outer edges. He noted that in a situation like the one experienced on Monday, where the force of the downdraft combines with already existing high winds below, a situation is created where the speed of the wind increases dramatically.

He said a tornado is associated with an updraft, creating the exact opposite effect with wind moving upward in a sucking motion. He said it actually draws air in and up into the storm. During his tour of the area in the aftermath of the storm he said he did not see evidence of that sucking motion. He said it appeared to him that trees and camp vehicles were hit from more of a side motion, which in some cases must have happened with such force as to make them airborne for a brief period of time.

He said especially in the Bald Mountain area, the trees appeared to have been pushed down from the side rather than lifted and scattered the way they would have been by tornado activity.

"The one thing about tornados and microbursts, they can be similar in speed," said Jones. "A weak tornado is 65 to 85 mph, so we were certainly in that range and actually exceeded that with this microburst. Both can do a lot of damage."

Jones said he didn't see campers that had been impaled by trees, as reported by other emergency re-sponders. He noted that since camp vehicles often are made of lightweight materials and have a broad surface area, it can make them similar to a sail when hit by a strong wind.

"You're dealing with a broadsided sail, basically, similar to a trampoline that gets tipped on its side; it will fly," said Jones.

Jones said it was extremely fortunate that the event occurred on a Monday, when most of the camp trailers were empty.

"Had this happened on a Saturday, when a lot more people were involved, I think we may have seen more injuries because the natural instinct for most people would be to go inside their camper when the hail and rain started to come down. Winds of 90 to 100 mph are a rare event and people would not be expecting that."

Jones said it's not uncommon for the wind to suddenly pick up during a microburst.

"It's not a gradual thing," he explained. "There's a demarcation. When it hits it will be stronger at the point of impact and when it spreads out it will dissipate until it reaches the end. We saw that when we looked at the area. Usually when it's spreading out like that you don't feel it until it hits you."

He noted that witnesses did not report seeing a tornado. He said they reported that it became dark.

The national weather service issued a severe thunderstorm warning about 4 p.m. on the same day, but since microbursts can only be predicted moments be-fore they occur, there was no way to issue a warning further in advance.

He said the weather service received reports of snow at 10,000 feet with 90-de-gree temperatures ahead of it. By late afternoon, many mountain areas reported sudden temperature drops into the 30s, including drops of 40 to 50 degrees in some cases. He said those conditions set up a pressure gradient to already breezy conditions, creating a "convection" effect that added to what happened in the Big Horn Mountains on Monday.

"It's one of those things that can happen at any time," said Jones. "We've seen them happen in June, we've seen them happen in July and August. It's not unheard of to have them throughout the summer, but to this extreme is a rare event. Is it the kind of thing we can predict a week out? No, we can't do that. So, we couldn't have predicted what happened on Monday.

"The thing to remember is that when you are outdoors, trees get toppled, lightning strikes. Mother Nature can do that, so it's important to stay alert to current conditions and to check on weather conditions before you go out camping."

Jones agreed with Blackburn that the timing of the event reduced the potential for injuries.

"It could have been a very different outcome had it occurred on a Saturday afternoon," said Jones. "I'm sure people would have got hurt. It's pretty miraculous really that no one got hurt."

Blackburn described the timing of the event as nothing short of a miracle.

"This was either a divine intervention or some sort of miracle," said Blackburn. "If this would have happened on a weekend or at night, there is no doubt in my mind there would have been fatalities and injuries."

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Original Publication Date: July 30, 2015

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