Sunday, June 02, 2013

El Reno Tornado - May 31, 2013

After working a midnight shift, I slept 3-4 hours, woke up at 130 pm, did a data check, dropped off a rent check, and then headed north on I-35 into OKC, then west on I-40.  I reached El Reno, OK by 4 pm, headed south and west a bit from that town, and then waited patiently for thunderstorm initiation.  Turkey towers would morph into orphan anvils during the next hour, and then a clump/cluster of cumulus broke through the cap and developed into three different cells.  The southern most cell quickly strengthened into a supercell, with a long expansive anvil spreading downstream across my location.  I slowly moved west and found a viewpoint looking across a large wheat field.  A shower eventually merged with the developing supercell, and rain briefly blocked my view of the base.  However, updraft structure dramatically improved, with inflow bands rapidly developing along the southern flank and eastern portion of the storm.  During the 530-600 pm time period, surface inflow strengthened and backed out of the east.  I moved west and south again, located in the vicinity of the El Reno Air Park.

By 600 pm, the updraft base came into clear view, and at this time I had my first glimpse of a tornado, which appeared to me as a white-ish cone that quickly morphed into other shapes (likely multiple vortices).  Since I was viewing the tornado from the east-southeast, contrast was not great, and none of my pictures turned out initially.  Soon after, the appendage/hook echo accelerated east-southeastward, and I had to retreat fast.  I would pull over on occasion, and saw a large barrel shaped tornado surrounded by sheets of rain wrapping around the circulation...this time one of my pictures turned out reasonably well.  The tornado was directly across a wheat field from me, approximately 1-2 miles.

I was still in danger of being overtaken, so I raced east to highway 81, at which point the human drama aspect of the chase began.  The highway was filled with hundreds of chasers and local observers heading south away from the approaching tornado.  Traffic slowed down to a standstill by the time I entered Union City.  I decided to continue following the storm east into Oklahoma City, so I headed down highway 152 at Union City, and actually managed to stay ahead of the potentially tornadic portion of the storm all the way past Will Rogers World Airport.  However, by the time I reached southern OKC, traffic jams developed on every major road, highway, and interstate, with traffic backed up for miles.  Apparently a local TV meteorologist advised residents to flee the city.  This is obviously stupid can a metro area with a population of 1 million people be evacuated in such a short amount of time?  Easy answer, it can't, and the result was thousands of people driving into the path of a tornadic HP supercell.  Luckily a significant tornado didn't develop after the El Reno event, but the potential was there for a much bigger tragedy with substantial loss of life as cars filled with people sat idle in the path of the storm.

Sadly, people did die near El Reno as the tornado accelerated northeast toward I-40...including three well respected storm chasers.  The combination of strong-extreme CAPE, a supercell shear profile, and storm mergers led to a rapidly evolving tornadic thunderstorm that began to behave in a way that was not anticipated by other chasers as the tornado approached highway 81 and then coiled northeast toward I-40.  The erratic behavior caused many chasers to retreat as the tornado enlarged to over 2 miles in diameter, with multiple vortices (with embedded wind speeds over 250 mph based on mobile radar) racing around the primary vortex.  Some chasers were overtaken, most survived, but a few did not.

Initial cumulus towers near El Reno, OK.
Shower merging with the El Reno supercell from the south.
Supercell southwest of El Reno.
Turbulent updraft base and wall cloud.
El Reno tornado surrounded by rain curtains as it approaches highway 81.
Surface observations valid at 23Z 31 May 2013.
850 mb chart valid 00Z 1 June 2013.
500 mb chart valid 00Z 1 June 2013.
250 mb chart valid 00Z 1 June 2013.
OUN RAOB valid 00Z 1 June 2013.
Visible satellite image valid 23Z 31 May 2013.
Base reflectivity valid 2310Z 31 May 2013.
Base reflectivity valid 2314Z 31 May 2013.
Base reflectivity valid 2328Z 31 May 2013.
Storm relative velocity valid 2310Z 31 May 2013.
Storm relative velocity valid 2314Z 31 May 2013.
Storm relative velocity valid 2328Z 31 May 2013.

Saturday, June 01, 2013

Central Oklahoma - Supercell - 5/30/2013

I chased a supercell that moved from Chickasha to east of Purcell with Sharon Austin on May 30th.  This storm displayed interesting structure throughout its lifespan, but it failed to produce a tornado multiple times during the chase. Things got really interesting as the supercell moved over Purcell.  A big wall cloud developed underneath the base, and midlevel updraft rotation intensified greatly as the cell drifted east of I-35.  The structure was at its best during this time, but similar to every other meso cycle, low-level rotation wasn't sustained and the storm weakened.  We were contemplating dropping south to another supercell near Pauls Valley, but decided we were too far out of position to make that happen.  Sharon's brother in law did make the jog south, and his car was nearly totaled by giant hail (last picture)...we probably made the right decision not to core punch.