April 29, 2017 East Texas Tornado Event

A total of 7 tornadoes have been confirmed thus far across Henderson, Hopkins, Rains and Van Zandt counties.

tornadoes have been confirmed thus far across Henderson, Hopkins, Rains and Van Zandt counties. The long track Eustace to West Canton tornado has been rated EF-4 (180 M.P.H. winds).

(180 M.P.H. winds). The EF-4 tornado in Van Zandt County was the highest rated tornado in the county since 1950.

tornado in Van Zandt County was the highest rated tornado in the county since 1950. An additional long track tornado (near Steve Creek in southern Van Zandt County to Canton to Emory) has been rated EF-3 (145 M.P.H. winds)

(145 M.P.H. winds) 4 additional tornadoes occurred in Van Zandt County on this day.

additional tornadoes occurred in Van Zandt County on this day. This results in a total of 6 tornadoes in Van Zandt County which sets a record for most number of tornadoes in a calendar day for Van Zandt since 1950.

tornadoes in Van Zandt County which sets a record for most number of tornadoes in a calendar day for Van Zandt since 1950. 1 brief tornado was observed in Hopkins County near the community of Miller Grove, just south of Cumby.

brief tornado was observed in Hopkins County near the community of Miller Grove, just south of Cumby. There were a total of 4 direct fatalities along with numerous injuries suffered during the April 29, 2017, East Texas Tornado Event.

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NWS Fort Worth, TX, and NWS Shreveport, LA Observed Upper Air Data

Click on any of the above thumbnails for a larger image (opens in new window)

Special and routine upper air observations were taken at National Weather Service (NWS) offices in Fort Worth, TX, and Shreveport, LA, in support of severe weather forecasting operations. The NWS Fort Worth office released a special 1800 UTC (1:00 P.M.) weather balloon as seen in the far left image above. The upper data seen in the far left image above indicated that a capping inversion, while weakening, was still present across North Texas. Instability above this inversion was computed at around 2300 J/kg. Deep layer shear (0 to 6 km) was noted just above 45 knots. The combination of instability and deep layer shear fostered organized storm modes including supercell storm structures. Farther to the east in Shreveport, LA, a special upper air observation was taken at 2000 UTC (3:00 P.M.) as seen in the center figure above. It’s possible that some contamination from nearby storms occurred based on archived radar imagery (not shown) as deep layer shear and instability appear on the low side. The 0000 UTC (7:00 P.M.) routine upper air observation from Shreveport, LA, as seen in the far right image above revealed a good amount of instability coupled with a large amount of deep layer shear. Specifically, a large degree of low level shear, manifest in the large curved hodograph, likely resulted in an environment favorable for rotating storms. Southern Plains Surface Analysis

1000 CDT Regional Surface Analysis

1300 CDT Regional Surface Analysis

1600 CDT Regional Surface Analysis

1900 CDT Regional Surface Analysis Click on any of the above thumbnails for a larger image (opens in new window) Objective surface analysis from the Weather Prediction Center (WPC) indicated that a cold front extended from near the Red River southward along the I-35 corridor down into the Hill Country. With time, this frontal boundary slowly moved eastward through the DFW Metroplex and Waco. Ahead of this boundary, low level moisture, as indicated by the low to mid 70 degree dewpoint air, surged northward. Coincidentally, surface winds across east Texas back towards the southeast near 2100 UTC (4:00 P.M.) as well which likely increased storm relative helicity, another favorable factor for low level storms. Around 0000 UTC (7:00 P.M.), the WPC denoted some sort of mesoscale boundary (perhaps outflow) in the vicinity of the I-20 corridor. This also likely aided in low level mesocyclogenesis and could be a plausible reason for efficient tornadogenesis that was observed during the afternoon and evening hours on April 29, 2017. This was evidenced by the impressive radar signatures that were observed, even at 80-100 nautical miles from both the NWS Fort Worth Radar located at the Fort Worth Spinks Airport and NWS Shreveport Radar located at the Shreveport Municipal Airport.

Storm Prediction Center Day 1 Convective Outlooks

The Storm Prediction Center (SPC) continued to highlight the potential for a good coverage of strong to severe thunderstorms in their Severe Weather Outlooks (SWOs). The eastern half of the NWS Fort Worth County Warning Area (CWA) had been placed beneath an “Enhanced” Risk for severe thunderstorms. The progression of the day 1 severe weather outlook (SWODY1) can be examined in the images above.

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Visible & Infrared Satellite Imagery



Visible Satellite Imagery

Infrared Satellite Imagery Click on any of the above thumbnails for an animated gif of satellite imagery on the afternoon of April 29, 2017

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Satellite imagery on the afternoon of April 29, 2017, indicated that much of North, Central and East TX were all entrenched in widespread cloudiness. This cloudiness gradually decayed through the day as heating occurred. One feature of note was a small cluster of thunderstorms across the Sabine River Valley. While this complex of storms decayed through the afternoon, there appears to be a ring of cumuliform clouds that actually traveled slowly towards the west. Convergence and heating along the front, resulted in the development of deep convection along the I-35 corridor. As the animation plays, however, there appears to be a zone of convergence across East TX. It would appear reasonable that new convection developed quickly. As mentioned above, surface winds were starting to back towards the southeast, and these storms became severe rather quickly.

The IR imagery indicates very cold cloud tops indicative of strong and robust updrafts, which supports severe thunderstorms. Through the evening, convection marches eastward out of the NWS Fort Worth CWA.

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NWS Weather Radar Imagery

A total of 7 tornadoes were confirmed across the NWS Fort Worth County Warning Area during the late afternoon and evening hours on Saturday, April 29, 2017. Below is a summary of various survey teams findings. The map lists tornadoes (1 through 7). The numbers on the map below correspond to radar and photography in the graphics following the map.