Sunday, May 16, 2010

Tulsa Metro Tornado & Wind Damage of May 13, 2010 - Part I

I was born and spent the first 12 or so years of my life in Tulsa, so I naturally have a fondness for the city.  I haven't been back in awhile (seems like family and friends always come to us rather than the other way around), and I'm sure there are parts of town I wouldn't even recognize since the last time I was there.  Unfortunately, there may be a few spots in town that some current residents don't even recognize after last Thursday morning's storms.

From a local warning standpoint, the time of day of this event couldn't have been worse. Most folks were in bed asleep and had little knowledge of what was about to happen.

The storms rolled through (and I mean rolled through) between 4:45 and 5:05 a.m.  The line, with embedded rotating comma heads, literally crossed the entire city from west to East during that short period of time!

Below is an image depicting storm reports received by the NWS in Tulsa for this event.  Text details of the more significant reports are also shown:

At first glance of the radar (see reflectivity image below), a bow echo/wind damage event was about to take place as the line approached the Tulsa area from the West at nearly 60 mph, and gaining:

As the event unfolded, however, several rotating "comma heads" began to develop within the line, which resulted in a couple of short to moderate track tornadoes, as well as other isolated (though equally significant) touchdowns:

The above track estimates are based on a combination of the NWS Tulsa preliminary ground survey information and doppler radar circulation signatures (see images later on in this post).  The time estimates along the tracks are based on radar signatures, as ground report times often lag the actual event times (for obvious reasons).

For purposes of brevity throughout the remainder of this post, I'll refer to the southern track as the "Kiefer" tornado and the northern track as the "Sapulpa" tornado (please note that the "Sapulpa" tornado actually began about 3 miles Northeast of that city).

The shorter, Kiefer, tornado track began between 4:41 and 4:46 a.m.  The first ground truth report came from just East of Glenpool (estimated by radar to have occurred about 4:48 am) where "large tree limbs" were reported down, along with "large trees snapped at their bases".  Below are the reflectivity and storm-relative velocity images taken at 4:46 a.m. (0946Z) from the Inola (INX) radar:

The circulation then continued to intensify as it moved NE across southern Tulsa county.  Below are the reflectivity and storm relative velocity images from 4:50 and 4:54 a.m.:

According to the NWS Tulsa preliminary ground survey, the ground-based circulation lifted near 111th Street and Garnett Road.  According to the proximity of the corresponding radar signature, this probably occurred at around 4:55 a.m.  Damage was estimated at EF0-EF1 (winds of 65-110 mph) along the broken path of this circulation.

Radar continued to track a low-level circulation on to the Northeast, passing to the southwest of Broken Arrow at around 4:58 a.m. as seen on the images below:

At this time it appears that no more ground-truth tornadoes were generated by this particular circulation after this time.  However, you can see by the last several sequences of images that numerous "comma heads" were evolving and cycling through within the leading bow echo signature throughout the entire line of storms.  You can even see hints of smaller, weaker circulations on some of the velocity images at times (though none were as well developed nor as pronounced as those being pointed out specifically).

Immediately to the Southeast of the track of the circulation we've been examining, a brief but possibly significant tornado touchdown was reported shortly after 5am.  The report was 1 mile Northeast of Oneta along highway 51.  The NWS Tulsa preliminary survey has estimated damage at EF2 intensity (winds of 111-135 mph) by a "250-300 yard wide" tornado.

Below are the 5:03 a.m. Inola (INX) reflectivity and storm relative velocity images corresponding to this circulation.  The white circle denotes a pronounced "comma head" signature on the radar.  The location of the damage report is highlighted by the arrow and pink text box.  I would estimate these images were taken about 2 minutes before the damage took place:

Below are the radar images of the same storm taken at about 5:07 am, or roughly 2-3 minutes after the damage was reported:

Once this comma head cycled through, no additional reports of damage were received from this particular part of the storm.  It is very interesting to me (and fortunate for Tulsa, in hindsight) that this particular circulation produced such a wide and strong damage path, though extremely brief, while the circulations that passed directly through South Tulsa were much weaker, less wide and at the same time equally short lived!

In Part II we'll examine the tornado track that initiated near Sapulpa...

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