March 8, 2011 Chase

The Day Before
A couple days before the event, I noticed that there would be a marginal chance at a severe weather event in North Texas on March 8th.  The NAM continued to show a strong surface low moving E through Central OK that was dragging a dryline east through N TX by 21Z (Tuesday 3/8).  The dryline looked to be from a Sherman-McKinney-Dallas line by 0Z.  Ahead of the dryline, the warm sector was characterized by westerly H50 winds of 50 kts, southwesterly H85 winds of 25-30 kts, and surface winds backing from the south-southeast at 5-15 kts.  These winds provided adequate directional and speed shear for supercells ahead of the dryline.  The 0-6km storm motion vectors were nearly orthoganal to the orientation of the dryline which suggested a potential for discrete supercells!  Storm motions looked to be to the east at 35-40 kts which would be manageable if storms were able to fire along the I-35 corridor and mature before the Sherman-Paris area (areas further east of Paris don't have favorable terrain for viewing storms).  SBCAPE values looked to be around 1000-1500 at 0Z in that same area.  Definitely sufficient enough for vigourous updrafts.  3km SREH values of 150-300 and 1km SREH values of 100-200 indicated a potential for rotating updrafts and tornado potential with strong 0-1km wind shear values.  Moisture didn't look like too much of a problem with 60+ dews spreading N towards a warm front that was draped just south of the Red River by 0Z.  The NAM was showing that CIN would be reduced enough to fire convection along the I-35 corridor by 21Z.  Given these numbers and the fact that there was a pretty decent chance that when convection developed that a tornado threat was possible, I decided to call a sub and take the day off of work.  The first storm chase of the day was less than 24 hours away!!!!

Morning Analysis - Chase Day
When I awoke the morning of the 8th, I looked at the 12Z upper air analysis.

 250mb

100 kt jet max over AZ and NM about to round base of trough and eject into Southern Plains.

 500mb

60kt jet over west TX!

 700mb

45kt over west TX

 850mb

Strong 40kt low level jet.  Didn't like to see winds veering a bit though.  Good fetch of moisture into N and NE TX.

The 12Z FWD observed sounding

Notice the large clockwise curvature of the hodograph. 3-6km lapse rates are pretty steep.  With increased sfc dews and temps, and continued mid-level cooling the cap should be eliminated by early afternoon!

Looking at surface observations:

12Z

Deep moisture in central TX (64 dewpoint).  Strong backing winds.

  Dryline located in eastern TX panhandle.  Very dry air in the Big Bend Country (note the dewpoint of 17).

After checking the morning analysis, I reviewed the RUC and it was in general agreement with the NAM about dryline position and environmental conditions for the afternoon.  It showed convection firing along I-35 corridor between Gainesville and Denton.  The 4km WRF reflectivity image also showed convection firing around the same time and location.  With convection firing pretty early, I knew that I would have to get out of the house around 17Z so that I could make it into the target area early.  I've been burned before by being in position too late.  Best to be early and make decisions from your taget area then to play catch up (especially when you are chasing alone!).  AFter stopping by Best Buy to pick up a 16GB SD card, I made my way out of Fort Worth by 1730Z.

The SPC's 1630 convective outlook showed a pretty large Slight risk area over N and NE TX.  Tornado probabilities were 5% up near the Red River and east of Sherman, TX. 

You can see that the western edge of the Slight risk area is approximately where the SPC forecasters believed convection would fire along the dryline.

Here is the wording from the 1630 outlook:

SPC AC 081625 
DAY 1 CONVECTIVE OUTLOOK 
NWS STORM PREDICTION CENTER NORMAN OK 
1025 AM CST TUE MAR 08 2011 
VALID 081630Z - 091200Z 

...THERE IS A MDT RISK OF SVR TSTMS PARTS OF LA AND SRN MS... 

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF EAST TX/OK 
INTO THE LOWER MS VALLEY... 

...SYNOPSIS... 
LARGE SCALE TROUGH SHIFTS EWD ACROSS PLAINS THRU THE FORECAST 
PERIOD. ONE S/WV NOW ROTATING NEWD THRU KS/NRN OK WHILE UPSTREAM 
VORT MAX CENTRAL NM MOVES EWD ACROSS SRN PLAINS TO LOWER MS VALLEY 
12Z WED. 
IMPRESSIVE MOISTURE STREAMING NWD FROM WRN GULF INTO SRN PLAINS AND 
LOWER MS VALLEY THRU THIS EVENING AS A WARM FRONT DEVELOPS INLAND 
ACROSS SERN TX EWD INTO SRN MS BY LATER THIS AFTERNOON. STEEP MID 
LEVEL LAPSE RATES HAVE SPREAD EWD ACROSS SRN PLAINS INTO LOWER MS 
VALLEY THIS MORNING ATOP THE DEEPENING LOW LEVEL MOISTURE AS 
DEWPOINTS RISE THRU THE 60S BY THIS AFTERNOON ACROSS LWR MS VALLEY. 
..LA/MS LATER THIS AFTERNOON AND TONIGHT... 
THE FOCUSING MECHANISMS FOR CONVECTIVE DEVELOPMENT REMAIN A QUESTION 
ATTM HOWEVER A WEAK CAPPING INVERSION AND INCREASING LARGE SCALE 
FORCING ARE EXPECTED TO RESULT IN SCATTERED DISCRETE THUNDERSTORM 
DEVELOPMENT IN A RATHER STRONGLY SHEARED ENVIRONMENT. FORECAST 
SOUNDINGS SUGGEST EFFECTIVE SHEAR VALUES OF 40-50 KNOTS AND 0-3KM 
SRH OF 250-350 M2/S2. WITH LARGE SCALE ASCENT INCREASING BOTH DUE TO 
CONTINUED WARM ADVECTION AND APPROACH OF THE NM IMPULSE AND 
MID/UPPER LEVEL WIND MAX... DISCRETE THUNDERSTORM DEVELOPMENT 
APPEARS LIKELY BY LATER THIS AFTERNOON AND EVENING VICINITY OF THE 
WARM FRONT MOVING INLAND ACROSS LA AND SRN MS. GIVEN THAT MLCAPES 
INCREASE TO 1500 J/KG AND FAVORABLE SHEAR ENVIRONMENT NOW IN PLACE 
WILL JUST IMPROVE THRU THE AFTERNOON...THE THREAT OF SUPERCELLS 
DEVELOPING INCLUDING TORNADOES ARE LIKELY BEGINNING BY LATE THIS 
AFTERNOON AND CONTINUING TONIGHT ACROSS LA INTO SRN MS. THERE IS 
THE RISK OF STRONG TORNADOES. UPSCALE ORGANIZATION INTO BOWS/LEWPS 
IS POSSIBLE OVERNIGHT WITH THE POTENTIAL FOR DAMAGING WINDS 
SPREADING EWD INTO WRN AL. 
PORTION OF THIS AREA HAS BEEN UPGRADED TO A MDT RISK DUE TO THE 
GREATER CONFIDENCE OF THE POTENTIAL FOR STRONG TORNADOS. 

...OK/TX/AR/LA... 
BY LATER THIS AFTERNOON...THE SURFACE DRYLINE WILL SURGE EASTWARD 
INTO EAST-CENTRAL OK AND CENTRAL TX. MODELS STILL DIFFER ON THE 
EXTENT OF CONVECTIVE DEVELOPMENT ALONG THE BOUNDARY...BUT SUFFICIENT 
RISK IS PRESENT TO MAINTAIN SLIGHT RISK ALONG THIS CORRIDOR. THOSE 
STORMS THAT DO DEVELOP WILL POSE A THREAT OF LARGE HAIL... DAMAGING 
WINDS...AND EVEN ISOLATED TORNADOES. IT APPEARS THE MOST LIKELY 
AREA FOR THUNDERSTORMS ALONG THE DRYLINE WILL BE ALONG AND 
IMMEDIATELY SOUTH OF THE RED RIVER LATER TODAY. THESE STORMS WILL 
SPREAD EASTWARD INTO PORTIONS OF AR/LA THIS EVENING WITH A CONTINUED 
SEVERE THREAT. 
..HALES/GRAMS.. 03/08/2011

The Chase

On my way to Gainesville, I noticed several updrafts that were struggling with the strong speed shear and what was left of the cap. 

At 1930Z, the first storm became visible on radar.

By 2117Z, one storm became dominant and had developed mid-level rotation. 

Dominant storm near Whitewright, TX

Storm just beginning to develop an inflow notch.

This storm would track east along and just north of Highway 82.  It was HP for all of it's life.  As the storm moved toward Sherman, I made the biggest mistake of the chase.  I traveled south of Highway 75 to meet up with the updraft of the not-yet severe warned storm.  At the time, the storms were semi-discrete but were forming into line segments.  Remember, always stay well east of these storms and let them come to you.  I was a over-anxious and wanted to be near the updraft early in the storm's development.  Will try not to make that mistake again this season!  Anyways, I headed south to Highway 11 and made my way towards the city of Randolph, TX.  Then I headed NE on Highway 121 towards Bonham in hopes of getting out in front of the core of the main storm.



Video of 1st bad decision of the day

Video of that updraft (got blasted by RFD after updraft moved past me)  Quite intense!

As I made my way into Bonham, I found myself on the back side of the storm in the RFD.  I jumped onto Highway 82 and did my best to get out in front of the storm.  Strong north winds around 50 miles per hour, extremely heavy rain, and pea to quarter size hail were pounding the driver's side of my car until I was able to break free into the clear slot near the city of Toco, TX.  At one point during this venture, I was afraid that I would drive into the back side of a rain-wrapped tornado.  When I made it into Paris, TX I headed south on loop 286 and after traveling a mile or so I noticed what looked like a small area along the RFD front that exhibited strong rising motion (almost like a weak funnel).  It lasted about 20 seconds.  Don't know if it was a gustnado or maybe the roping out of a tornado.  SPC reported damage from a weak tornado near the city of Brookston, TX.  This would have been near the location that I was looking at.  Very interesting to say the least.  Here is a radar grab at the time I saw the feature:

Reflectivity

Storm is 100 miles from radar and the 0.5 tilt is displaying reflectivity at about 11000 ft.

Storm-Relative Velocity

I sat at the intersection of loop 286 and Farm to Market Road 137 for a few minutes and faced north to get video of strong inflow into the meso of the storm.  Here is what I saw:



I continued along loop 286 till I reached the intersection of Highway 271.  I stopped to get video.  The storm was tornado warned at this point and about to make it's way into the city of Paris.  Siren's were blaring in the city.  Rapidly moving cloud tags (assuming this was the tail cloud) were streaming into the meso at this time.  Here is a video of what I saw at the time:



This is the point where I made my second bad decision of the chase and that was to sit too long at that intersection instead of heading north to Highway 82 and get east of this storm.  For some reason I was afraid that I would move north onto 82 and get hit by the 2-3 inch hail that this baby was dropping.  The storm was turning right and heading slightly south across 82 and I thought I wouldn't get to the highway by the time the soon to be tornado would drop out of this storm.  The storm was still HP and the meso was wrapped  with rain.  The tornado would have been difficult to see if it had dropped near Paris.  So, I decided to head SE on 271 to Airport Road and then head east a mile or so to get back to 82.  Big mistake!  The storm caught up to me and I decided to allow the RFD to blast through.  After that, I was on the back side of the storm and didn't have a good east road option to get out ahead of the storm again.  Plus, now the storm was about to put down a tornado and I didn't want to take the risk being by myself.  So, I ended the chase near the airport. 

As the storm continued to head east, it did drop two other tornadoes.  One developed into a wedge near the city of Clarksville, TX and traveled into the north side of the city.  I believe that it did F1 damage.  A few chasers got some great video of this wedge.

So, I ended my chase around 5pm and began my way home.  I am pretty satisfied with my chase overall.  I forecasted the area of initiation well and was able to get out ahead of this HP.  For being by myself, I thought I made pretty good road decisions except for the two that I discussed earlier.  I didn't get video of the rotating feature near Bonham, but I have a feeling that I may have seen the ending of that tornado. 

Lessons learned today.............Stay well out ahead of the storm and let it move toward you.  If you are chasing alone, be more aware of your road options before you make a rash decision to move.  Stay near any warm front if storms are moving near it.

Here are the SPC reports for the day.  Note the cluster of reports from the storm I was on in NE TX.



Tornado Reports (CSV) (Raw Tornado CSV)(?)
Time		Location	County	State	Lat	Lon	Comments
2215		BROOKSTON	LAMAR	TX	3362	9570	AT LEAST TWO LAW ENFORCEMENT OFFICIALS REPORTED A BRIEF TORNADO TOUCHDOWN SOUTHWEST OF BROOKSTON. AT LEAST ONE BARN WAS DAMAGED. TIME WAS BETWEEN 410 PM AND 415 PM. (FWD)
2315		8 W CLARKSVILLE	RED RIVER	TX	3361	9519	AN EF1 TORNADO TOUCHED DOWN ABOUT 8 MILES WEST OF CLARKSVILLE TEXAS ... AND MOVED EAST NORTHEAST TO A POINT ABOUT 3 MILES EAST NORTHEAST OF CLARKSVILLE. DAMAGE PATH WAS 1 (SHV)
2320		4 E DETROIT	RED RIVER	TX	3366	9520	CHASERS CONFIRMED RAIN WRAPPED TORNADO ON THE GROUND NEAR BAGWELL..EAST OF DETROIT ALONG US 82 (SHV)
2330		2 N CLARKSVILLE	RED RIVER	TX	3364	9506	CHASERS AND SPOTTERS CONFIRM TORNADO ON THE GROUND ... RAIN WRAPPED. SEMI ON A CAR ... TRAILERS FLIPPED ... POWERLINES DOWN ... MANY ROOFS DAMAGED TO HOMES. (SHV)