Seibert Spouts

28 May 2018

Today was the first day of our season so far with a 10% risk of tornadoes. We had previously felt ourselves lucky to be chasing in 2% risk areas, so this was quite an upgrade. There were 2 potential mechanisms in play - upslope flow across the foothills of the Front Range in Colorado or lift from an outflow boundary in place from earlier convection. These boundaries, similar in effect to a cold front can often act as a focus point for convection later on in the day.

We headed from Sidney a couple of hours south to Limon, Colorado. We weren’t far from town when the first tornado warning of the day was issued, covering the outflow boundary off to our east and a large area north of it. We held fire in Limon for a while bet hedging to see if anything tempting rolled off the hills. But nothing was really happening. Meanwhile, a few cells were starting to initiate along the boundary. We could see their tops and watch them pulsing from outside the gassy in Limon. We decided to head east toward the main storm cell.

When storms fire on the boundary, they tend to become anchored and it was clear this storm wasn’t going anywhere in a hurry. Before long we had sight of it and Timbo noticed what looked like a faint lowering from the base. Shortly after noticing this, a landspout tornado was reported by another chaser who was about 15 miles to our north. We took the next north and headed towards the storm.

As we got closer, the cloud bases became noticeably lower and before long we were driving through very murky eerie low hanging cloud. Not sure how far to go in these conditions with very little sight, we hung back for a while. It was at this point we noticed to our southwest an amazing landspout. It was close enough for us to see the detailed vortices dancing and churning away in the distance. We grabbed our cameras and whilst shooting noticed another, this time even closer. We got a couple more shots before jumping back into the car to try to get closer.

Hatchwork

Funnel And Cloud

Growing Spout

Landspout tornadoes are somewhat different to the more traditional tornadoes that develop from supercell storms. They don't need the storm to as yet be rotating and can develop under strong updrafts where boundary layer vorticity (spin) is stretched and pulled up into the base of the storm.

We took the dirt roads to try to get closer and we were starting to see two separate areas of rotation. Before long there were two tornadoes on the ground at the same time. We watched these until they blew themselves out in huge clouds of dust.

Two From Rogue

Twins And Updraft

Landspout Deaths

Shortly after this, we caught another one in a slightly different area of the storm. We couldn’t believe this was happening.

Thin Spout

Once this new one had dissipated, we took somet ime to take in the sight of the amazing updraft from which these landpots had originated. The rotation was now clearly visible by eye and the power of the storm was incredible.

Updraft

We tracked with the storm to Burlington, 30 or so miles further east, all the time with it hugging the boundary but the tornado show seemed to be over for the day. We found a great motel in Burlington and a Safeway to pick up some cold beer and sat in the last bit of sun which had crept out from under the base of the storm - a perfect end to am amazing chase day.

Afterglory

SPC Day 1 Weather Outlook as at 06:00UTC (01:00 Central Time the night before)

SPC 01:00UTC day 1 forecast for Mon May 2018

SPC Day 1 Weather Reports for the day.

SPC storm reports for Mon May 2018

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