The following are some images from the chase as well as some radar images, etc. Everything is in sequential order (well, should be anyway).
Towers began to fire along the dryline around 21z.
Just after, storms began to organize visually and on radar. One of the main ingredients was visible on radar as well, backing surface winds and horizontal convective rolls that were running parallel with the winds. This signified enhanced streamwise vorticity available to the storms if they push east of the dryline.
Eventually the storm south of I-40 began to organize and we moved NW into position and saw a very mature and distinct base.
The storm was strengthening very fast and many, many intense cloud-to-ground lightning was occurring near it.
At about 15 min till 23z, the storm really started looking good with a very large base evident.
The mesocyclone moved just to our north and took on very rapid and broad rotation before our very eyes. The white clouds are the outer edge and closest to us moving from left to right, while the darker clouds (lower in appearance) were the inflow condensing with air parcels moving from right to left.
Then at just about 23z we had first touchdown to our north.
From this point, things escalated quickly. The tornado immediately grew to a multi-vortex tornado. We drove north towards it and to our good paved road east option.
We came to about a mile from it and went east. It was moving at a pretty good clip and had numerous condensation funnels that made it a wonder to see in person.
From here the tornado took a turn to the south and became wrapped in rain. You can barely make out the edges looking west into the rain curtains. This is when things got a bit tense as the strong RFD winds were wrapping in front of us and trees were leaning pretty good. My guess is we were encountering winds near 70mph.
Now the last image was taken at about 23:17z so the tornado has been on the ground for a little less than 20 minutes and has become an absolute monster, likely a mile wide in the above image. Just after that image, approximately 5 minutes later, it appeared as if the tornado had broken away from the main updraft and surged to the east and eventually north becoming extremely wide (to 2.6 miles wide) and reached speeds in excess of 295mph (EF-5 strength). The following picture shows the disconnect either due to the RFD or the tornado making it's own environment.
From this point we realized the tornado was moving north and away from us so we held tight and took video and stills for awhile until the RFD caught up to us. This tornado was amazingly large. No doubt the largest I have seen to date and the motions were insane. Here is a final shot of the tor, likely still at EF-5 strength.
Here is the video of the chase to this point. The movement of the multiple vorticies were absolutely insane!
[Correction, it appears this "second" circulation was indeed a anticyclonic that formed off the southern side of the RFD from the El Reno tornado] A second circulation developed on the western side of the supercell and tracked over nearly the same exact area. We were very close to it and observed a quick spin up tornado from a very large wall cloud. Here is the condensation funnel reaching the ground.
Though there wasn't a condensation funnel a few seconds later, it was obviously still on the ground as we observed power flashes.
After that, a third circulation [really the second], weaker than the previous two nearly over ran us and definitely put us in a hard place as we were trying to bail on the storm. Traffic was a mess because the TV meteorologist for a particular station had told people to get in their car and flee south. DON'T EVER DO THAT! Always shelter in place and put as many walls between you and the outside. These people not only put their lives at risk, but ours too! It was worse than rush hour in any large city, at 8pm at night!
All in all, a good chase day for us. We had one motto going into the day, "always, always stay in front of other chasers and be a step ahead!" We stuck to it and it benefited us greatly because we were safe and avoided possible massive chaser convergence. It is too bad people had to be killed in this tornado and definitely took the fun out of this day. As I mentioned earlier, the loss in the chaser community on this day is tragic and will never be forgotten.
As for me, I don't see any changes needed in how I chase. We did it smart and safe. We stayed far enough from the tornado and were never in imminent danger. The traffic is a third concept that we thought of originally with other chasers, but never considered on a magnitude of 1000s fleeing the city. Therefore, I must say, I will not be chasing in Oklahoma anytime soon, but I will be chasing again, very soon most likely as the northern Plains should pick up in activity!
Stay safe everyone!