Entry 6 - A Kansas Classic
So, finally, I was looking at a day with a decent chance at tornadoes, a bit surprising even for the alley.
A triple point (the intersection between a warm front and the dryline in this case) was poised to form in northern Kansas, with very potent rotation possible provided storms could make it through the inversion and explode into the unstable air. The Storm Prediction Centre stuck to a 5% tornado risk, but noted the probability was much higher in the vicinity of the triple point. The target was Great Bend, Kansas with an expectation that storms would form slightly to the northwest.
As other chasers struggled to make it back from chasing Wisconsin the day before, for us it was a leisurely breakfast and a short drive west to Great Bend from Ottawa. Then we waited, chatting to other chasers who had begun to converge on the sweet spot.
It took some time for storms to form, but around 5pm local time the first cell popped into existence from an average looking convective field and then exploded, hitting 42,000 feet in less than 5 minutes in an environment of 4000 Jkg-1 of CAPE. It took some time to form up and push even higher into the mid-50 thousands, but by the time we had closed on the cell it had rapidly developed.
The cell seemed to struggle to really get going in the lower levels, with strong mid-level mesocyclone rotation, but many small points of rotation in the lower part of the cell. It also produced a very interesting outflow surge that kicked up tall jets of dust into the inflow and produced a number of strong gustnadoes (similar in mechanism to a dust-devil that occur on the gust front of a thunderstorm but do not originate from the storm itself), with a possible tornado reported at this time.
Giant gustnadoes kick out from the base of the storm behind us. Photo: John Allen
An unusual feature that was reported as a tornado by other chasers, but may have been a stretching of the spin-up vorticity, illustrated by the vortices within the dust. Photo: John Allen
Although the cell was looking nice in terms of structure and putting on a dust show like no other, it didn't quite look like it was going to produce a tornado at this point as the it had crossed the warm front and lost its energy and connection to the surface.
Meanwhile, two other cells had formed to the southwest and we decided to drop onto the next cell and its accompanying wall cloud.
We quickly closed again as there were reports of a tornado (unconfirmed) and were treated to a barrage of lightning strikes from the anvil (including one that hit the powerlines 15m away) as the cell intensified before wrapping its wall cloud into the precipitation. Interestingly, the bolts were completely without branching, which suggests that they were of positive polarity. This apparently arose from the production of hail within the storm that flipped the charge of the storm, resulting in the production of dozens of these deadly bolts (a positive strike is far more likely to kill a human, with a current 10 times that of the more common negative strikes).
A quick reposition onto the next storm and we watched as it began to strongly rotate, dropping an impressive cone that quickly became a beautiful tall elephant trunk tornado, back-lit by the setting sun.
A tornadic tail: The tornado extends down from the mesocyclone with a long tailcloud extending to the right. Picture: John Allen
The tornado develops an interesting phase with a thick moisture sheath extending high into the storm while pushing southwards. Photo: John Allen
After shedding its sheath of fractus, the tornado elongates taking on a classic elephant trunk structure. Photo: John Allen
The tornado transitioned towards a long horizontal rope phase and pushed southwards from the circulation, and appeared to weaken and begin to disappate, only to suddenly re-intensify and extend even further while drilling into the ground.
The tornado begins to rope out and drill into the surface, or does it? Photo: John Allen
This show went on for several more minutes as the tornado eventually roped out and our attention turned to a new wall cloud in front of us that would go on to produce several tornadoes after dark including one that would hit part of the town of Russell. As is typical in the Great Plains, just because someone turns natures’ lights off does not mean that the show stops, and the low level jet (warm moist flow near the surface from the Gulf of Mexico that rushes towards the surface cyclone) ramped up on dark.
It is not often that you have a (relatively) safe situation to chase tornadic storms in the dark. But with the storms moving very slowly in a single direction, the opportunity presented itself and we decided to drop south after a second tornado near Russell, to a cyclic (producing one meso-cyclone after another like a hand-off) supercell near La Crosse, KS.
Initially, we were hoping to get lightning illuminated structure, but it quickly became clear that the tornadoes were also revealing themselves periodically under the storm structure. The lightning frequency wasn't perfect for getting pictures but the experience was incredible!
While we could have gone closer, for safety sake and to keep us out of danger we stayed a reasonable distance from the storm - but what a show. As we arrived the storm already had two tornadoes in progress, a 45° stovepipe/rope, and a weaker tornado from the new wall cloud. It wasn't long before a new circulation really got going and the storm began to produce a classic cone tornado that later transitioned into a stout stovepipe.
The cone tightens in shape under the structure. Note the new wallcloud and mesocyclone to the right of the cone and closer to us, which is the area of next development. The beaver tail extends to the right of frame. Photo: John Allen
A stovepipe tornado northeast of La Crosse, Kansas. Photo: John Allen
Dust swirls rise from weak vortices under the wallcloud on the left, while a trunk kicks up a large amount of dust on the right hand side. Photo: John Allen
The storm continued to produce tornado after tornado for hour after hour, finally deciding that it had done enough by midnight. Fortunately for the majority of its life it stayed away from populated areas, with only relatively minor damage.
It definitely goes down as one of the more unique experiences I have had while chasing, though it was disappointing that the structure of the storms and at least a few more of the tornadoes couldn't occur during the day - imagine what they would have looked like!