June 4th 2015 Simla, CO Tornadoes

Storm Prediction Center’s Day 1 Outlook for June 4th 2015

June 4th 2015 in northeast Colorado will be a day that a lot of chasers remember OR regret for many years to come. The Storm Prediction Center (SPC) had issued their outlook, with an ENHANCED risk for severe storms for parts of Kansas/Nebraska. Very rarely do I disagree with an outlook issued by the SPC, but on this day, I did not agree with this 2% tornado risk in northeast Colorado.

My Forecast

We began our day in Limon, CO. Limon is a little community on Interstate 70 (I-70). After looking at forecast models and surface observations, I could not understand why most chasers were heading east into Kansas. Per my analysis, Kansas was more of a late-evening threat and Colorado was the place to be.

Surface Analysis at 1917Z by National Weather Service. Arrows edited by me.

The surface analysis above depicts a classic storm setup for Colorado, often referred to as the “Denver Cyclone”, which is when a Low pressure sets up shop near the Kansas/Colorado border and funnels warm/moist air from the Gulf of Mexico east of the Rocky Mountains (depicted by the green arrows). After seeing this being depicted by forecast models, I figured I was in the perfect place for some pretty significant supercells later in the day. Orographic lift should provide the necessary “kick” in the atmosphere east of Denver for some robust storms.

MLCAPE//MLCIN at 1900Z by Storm Prediction Center on June 4th 2019

At roughly 2pm CDT (or 1pm local time), surface analysis depicted an uncapped atmosphere in northeast Colorado and parts of Kansas. We knew storms were going to initiate within the next hour. With an environment around Limon, CO of ~3000J/kg of MLCAPE and 4500J/kg of SBCAPE, robust updrafts were expected.

The Chase

Radar screenshot and location at 3:13pm local time

At roughly ~3pm local time, a massive storm exploded just west of Limon (depicted above/below). This storm was nearly stationary and gave quite a sight:

First supercell along I-70 around 3pm MDT

This storm started dying as another massive supercell developed south of Limon:

4:50pm MDT radar screenshot

We headed towards this storm as it quickly became a “right-mover”. Right moving supercells are not fully understood, but are believed to be a product of the coriolis force and terrain influences. This storm intensified and began dropping tornadoes just outside of Simla:

Textbook mesocyclone, wall cloud and tornado near Simla, CO

At roughly 5pm MDT, the National Weather Service issued a tornado warning on our storm.

As we headed towards Simla to get a better look, the storm dropped a long-track cone tornado:

Massive mesocyclone and tornado near Simla, CO

The storm then began to turn right even more and intensified substantially over Simla, dropping baseball-sized hail while recycling:

Baseball-sized hail in Simla, CO on June 4th 2015

As we were getting pounded by hail in Simla, we witnessed something rarely seen in storm chasing, a massive “bell-shaped” mesocyclone:

Third tornado of the day just outside of Simla, CO on June 4th 2015

This storm just kept on giving. We proceeded to follow the storm outside of Simla and witnessed something we will never forget. The storm intensified further and dropped sister tornadoes, one being anticyclonic.

Radar velocity at 6:16pm MDT showing anticyclonic tornadoes
Bell-shaped mesocyclone depicting tornado damage and two tornadoes

The picture above went viral overnight for a reason. This depicts a “textbook” supercell mesocyclone, an anticyclonic tornado on the left and a cone tornado on the right. After witnessing this, we proceeded to get even closer, where we got a closer look at another tornado:

Tornado behind a house. The tornado did some damage to the roof of this house.

The storm dropped one final tornado (the 7th of the day):

Tornado number 7 on June 4th 2015

The storm began to loose strength near dark and became more high-based. We ended our chase by witnessing the death of the storm:

June 4th 2015 dying “corkscrew” updraft

We headed back to Limon for the night and enjoyed our victory steak after seeing a total of 7 tornadoes and a once in a lifetime storm structure. While the NWS only confirmed 6 tornadoes, we believe that the tornado outside of Simla (third tornado) and the sister tornado lifted and dropped again. However, there is little evidence of this. To this day, the Simla, CO chase remains one of our proudest forecasting and chasing moment. Out of the 8 tornadoes reported in North America that day, 6 were confirmed near Simla, CO. However, we counted 7 for that day based on our pictures and videos.

Storm Prediction Center preliminary storm reports

According to the National Weather Service storm survey, “The Elbert county tornadoes that affected the Simla area and southeast Elbert county have been rated an EF1.  There were a total of 6 tornadoes over Elbert County.  3 of the tornadoes were anti-cyclonic. Below is a map of the Elbert/El Paso county damage points.” -NWS Denver/Boulder, CO

Tornado intensity (EF-scale). Map by the NWS Denver/Boulder, CO


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