We began the day in south Oklahoma city (OKC) - in a hotel we would rather forget. The morning was overcast with stratocumulus that was beginning to break under heating by the late morning. A quick look at the forecast for the boundary/trailing front and dryline intersection suggested that the optimal location for the backing of the winds to the southeast and reasonably long hodographs would be somewhere between El Reno and Chickasha, while strong thermodynamics and moderate shear would yield a quite a potent environment. Dynamic models suggested a scenario with several large supercells forming west of OKC in the late afternoon when the environment was primed; what appeared a classic scenario for a regional tornado outbreak. The SPC chose to go with a 15% hatched tornado probability for the area, and a moderate risk, unsure of how widespread the event might be. My choice of an initial target was El Reno - my preferred spot for central Oklahoma dry-lines, with good options north, south and west. I've been burnt before by not waiting for the late initiation in this area, particularly southwest of OKC, and felt this was a good opportunity to turn that around.
As things evolved, the environment became progressively more unstable - with surface observations pushing temperatures of 90F and moisture as high as 77F. The dryline (a moisture gradient) began to surge eastward in response to diurnal heating and the surface cyclone further north, with temperatures exceeding 103F and dew-point temperatures below 40F to the west of the dryline. The environment remained highly capped all afternoon, with towers bubbling against the warm layer of the inversion over the warm sector. A particularly dangerous situation tornado watch (issued to reflect high probabilities of significant tornadoes and thus greater risk to population) was issued at approximately 21:00Z (4pm local), with a 90% probability of two or more tornadoes in the watch area, and a 70% probability of 1 or more significant tornadoes. The risk was also mentioned for hail to 4 inches (though a quick look at the forecast 5000 J/kg CAPE was ringing alarm bells anyway) - so it looked like the core of any storm was going to be a seriously risky prospect.
We met up with Brad, Marko and Valentina at a certain petrol station in El Reno (which seems to be the center of the world), and Rose suggested it would be far nicer to wait out at the lake on the west of town - how right she was. At the lake we ran into Skip Talbot, Nick Nolte, Tony Laubach, Jennifer Brindley and a few others, and enjoyed watching the locals splashing about as the convection bubbled in the oppressive heat. Sure enough, a couple of weak towers made it through shortly after 21Z (4pm), and began to develop into a line of strong storms to our west. Initially, I was concerned by the relative proximity of the three cells, but surprisingly they seemed to suffer little ill effect, probably because of the adequate shear in the 0-3 kilometer layer. We hit the road on our own at around 4:50pm, and decided to drop south out of El Reno and west towards the southernmost storm which was beginning to mature. Yet another cell initiated on its southern flank, but again, the shear and strength of the main cell dominated and simply absorbed it - it looked like we had our storm. We approached into a nice position to the east, and ran into a few Australians on a hill shooting the incredible lightning bolts coming from the cells anvil. At 5:30 (see below) we positioned just north of an east road to watch the cell mature and try to shoot some of the incredible CGs - unfortunately, handheld daytime shots only yielded partial frames, but the GoPro really enjoyed the view (video to come)!
|'Winding Up' - The supercell west of El Reno begins to take shape, with the development of structure while producing large positive lightning strikes. El Reno, OK, 31/5/2013|
The cell began to get serious about inflow and I decided to move us back further east to avoid any issues while it wasn't looking the best. The next view we got in a driveway began to show the storms structure properly as the inflow howled - I could barely stand, and holding the camera steady was incredibly difficult.
|'Rapid Development' - The supercell takes a classical, though slightly high precipitation morphology, with an impressive barrelled structure and inflow that made it hard to stand. Near El Reno, OK, 5/31/2013.|
The structure of the storm at this stage was also a sight to behold and probably the highlight, as it began to really spin up to drop a tornado:
|Oklahoma Scissor-tail- Like the state bird of Oklahoma, scissor-tailed inflow stretches into the strengthening mesocyclone as a tornado begins to develop. Near El Reno, OK, 5/31/2013.|
|'Sculpted Above and Below' - The tornado begins to develop, with an inflow tail visible under the incredibly sculpted barrel mesocyclone. Near El Reno, OK, 5/31/2013.|
|'Fields of Gold' - The clouds contort as the supercell focuses its energy to the central circulation, as vortices begin to periodically extend from the ground to cloud. El Reno, OK, 5/31/2013|
Even though I was disorganized, the photos really captured the moment of the storms peak organisation:
|'Multivortex Majesty' - The tornado touches down with multiple vortex tendrils extending from the supercells base and a strong inflow tail.|
|'Layered Twins' - The spectrum of colour stretches from bottom to top with twin vortices, from the verdant fields and into the clouds. El Reno, OK, 5/31/2013|
|'The Beast Retreats' - The tornado darkens and grows in size, though little would suggest that soon this monster would stretch to over two miles. El Reno, OK, 5/31/2013.|
|'Under the Meso' - As the mesocyclone approaches, the dark tornado and rapid rotation stretch to our west. The time to run from the storm is at hand. El Reno, OK, 5/31/2013|
|'The El Reno Wedge' - A large EF-5 wedge tornado under an enormous HP/Classic supercell observed from southeast of El Reno/Union City, 5/31/2013.|
Looking back on the day, there are a few things I would have perhaps done slightly differently. The first relates to being prepared with the video camera gear - or at least remembering that the D800 has a video setting. I had a great opportunity to record the tornado and at the same time shoot photos - but instead wasted time stuffing around with a video tripod mount. Not my proudest moment right there, and reflects being out of practice and adjusting to a new chase partner (Brad and I had this down pat). The second relates to wishing that I had set up a rearward facing GoPro mount, as the results would have been stunning running away from the storm. The third relates to the poor decision I made in over-ruling my navigator - she was damn right and would have got us out of there no problem, and probably kept us further from the 2nd tornado (there were other small tornadoes but only talking longer ones here). I think its unfortunate the storm occurred where it did - as I had planned several ways to skirt the OKC metro to the south, but hadn't considered a track like the storm produced (I thought things might set up further SW of the city and move NE initally and then E). In future I think I will be steering well clear of the Oklahoma City metro area on big days, and city areas in general - especially if mass panic evacuations induced by the media are going to become a recurrent feature.
|'A Glimpse Below' - The dark wedge tornado is spread beneath the enormous mesocyclone, at this stage, likely at its widest. Difficult to really comprehend the size or intensity of the storm. Shot taken SE of El Reno, 5/31/2013.|
One thing that concerns me greatly is the growing number of locals and amateur chasers that have absolutely no idea what they are doing close to the storm and are recording it on whatever device that happens to be close at hand. As the impacts of this storm revealed, even experienced chasers can be caught unaware by a sudden change in storm behavior, and putting yourself in danger for something to talk about at the bar is probably not the smartest decision. If you are truly interested in chasing or severe thunderstorms - educate yourself. Try talking to someone who you have seen that chases regularly and asking them for places to look. Try joining stormtrack.org and learning from the extensive archive of knowledge that can be found there. And if you still can't find the information or where to look, please contact me - I would be happy to help point you in the right direction. As you can read in my previous post, alot of things were happening in the environmental characteristics that lead to it producing this tornado - and at least at a basic level this information can give us ideas about how we chase any storms that form. To find the way to best stay safe - do not put yourself in the tornado's path unless you are very aware of the potential consequences and behavior of the storm - and even then, think about what the storm might do in a worst case scenario and decide if you would still like to find yourself in that position. Forward thinking is essential to chasing storms - always plan your escape and re-plan it as the situation evolves; then, when the unexpected occurs, at least you have a way out to somewhere safe. Just don't leave it too late.
|'Golden Wrapping' - Over gold wheat, the mesocyclone and the large tornado begin to rapidly wrap in rain, shifting northeastward before occluding. SE of El Reno, OK, 5/31/2013.|