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1KM Visible MPEG
27 May 97

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Texas
Tornadoes


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Introduction

Violent thunderstorms erupted over central and south central Texas during the afternoon of May 27, 1997. They produced at least six tornadoes which decimated parts of four central Texas counties from Waco to Austin. One tornado destroyed an entire subdivision in Jarrell, Texas in Williamson County where at least 27 people died and dozens more were hurt. Also, 2 people were killed in Austin (one by flash flooding), bringing the overall death toll to 29. A tornado warning for Williamson County was issued by the National Weather Service 35 minutes before the tornado struck Jarrell. Damage estimates are in the $50-$100 million range. Other locations receiving very high winds associated with the thunderstorms included: Austin--71 mph, Kelly AFB--122 mph.

The Jarrell tornado was probably a Fujita scale F-5 tornado according to National Weather Service officials who surveyed the area. Less than 1% of all tornadoes are rated that severe. Last year's only F-5 hit Oakfield, WI on July 18. As of May 28th this year, 67 tornado-related deaths have been reported for 1997 vs. 24 for all of 1996. All 67 of the tornado deaths for 1997 have occurred in tornado watch areas (i.e., watch active at the time).

Previous tornadoes in Texas which were even more deadly include:

Saragosa - May 1987 - 30 killed.
Wichita Falls - April 1979 - 42 killed.
Waco - May 1953 - 114 killed.

For further information, see the NCDC Storm Data publication for May 97.


Satellite And Radar Images

Figures 2-4 are infrared (IR) satellite photos taken during this event. They show the development and growth of violent thunderstorms over central and south central Texas. The IR spectrum senses thermal radiation of wavelengths longer than visible light. In these IR photos the strongest thunderstorms appear as dark red to black. Unstable conditions were in place aloft as an upper level system moved over Texas from the west. At the surface, a cool front moving south was intersected by an outflow boundary from a thunderstorm moving southwest in central Texas. Conditions in this part of Texas were warm and humid with a southerly flow and dew points in the mid to upper 70's. The explosive growth of the complex is seen over the 6 hour intervals shown in Figures 2,3, and 4.

The Jarrell, Texas tornado of May 27, 1997 was detected by the Austin Texas WSR-88D radar site. Figure 5 is a NEXRAD Base Velocity image at 20:43Z on May 28, 1997. Figure 6 is a loop of NEXRAD Base Velocity images, beginning at 20:14Z on May 28 and sequenced every six minutes until 21:18Z. Doppler radar has "tunnel vision" and can detect only motion toward or away from it. The color green has been assigned to the winds moving toward the radar, and red for winds moving away. The more intense the colors, the greater the wind velocity. Cyclonic rotation occurs when the maximum inbound wind is to the left, as seen from the radar, the maximum outbound to the right and they are equidistant from the radar. Note the intense gate to gate (side-by-side) azimuthal shear indicated by the arrow. These images were obtained from level II data.

Figure 7 is a Base Reflectivity image of the May 1997 Jarrell, TX tornado event taken from level II data provided by the Austin, TX WSR-88D radar site. The Base Reflectivity MPEG movie loop (Figure 8) depicts the volume scans recorded as the storm moved across the area.

Warning to modem users: Image files larger than 50KB are indicated showing approximate size of the file.

Click on each of the following to view full size satellite images.

Figure 1

1KM Visible
27 May 97 20:45Z
(3:45PM CDT)
(300KB)

Figure 2

4KM Enhanced IR
27 May 97 20:45Z
(3:45PM CDT)
(237KB)

Figure 3

4KM Enhanced IR
27 May 97 23:45Z
(6:45PM CDT)
(237KB)

Figure 4

4KM Enhanced IR
28 May 97 02:45Z
27 May (9:45PM CDT)
(228KB)

Figure 5

NEXRAD Base Velocity
28 May 97 20:43Z
(260KB)

Figure 6

NEXRAD Base Velocity Movie
(Animated GIF-260KB)

Figure 7

NEXRAD Base Reflectivity
28 May 97 20:43Z
(260KB)

Figure 8

NEXRAD Base Reflectivity Movie
(Animated GIF-260KB)

Additional Resources and Links

Weather Events of 1993-1998

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http://www.ncdc.noaa.gov/oa/reports/txtornadoes/texastornadoes.html
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Last Updated Wednesday, 20-Aug-2008 11:47:28 EDT by Neal.Lott@noaa.gov, Mark.Lackey@noaa.gov
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