The Jarrell, TX Tornado:May 27, 1997

Karin Swanson

AOS 453

May 11, 2000

What happened?

May 27, 1997-huge tornado outbreak 24 tornadoes were sighted throughout Texas Tornadoes ranged from F0 to F5. They were

just funnel clouds in some areas, and huge causes of destruction in others

Jarrell, Texas

F5 on the Fujita scale Touched down at 2:40 pm CST Vortex 1/2 mile wide Property damage $40.0 million Crop damage $100,000 27 deaths in Jarrell alone

What made the Jarrell tornado occur?

Synoptic overview Mesoscale analysis

– satellites– sounding– indices for the area

Mean Sea Level Pressure Analysis

What is needed for a tornado?

Dry area to west of tornado area Vertical wind shear Latent instability Middle level jet Moist air at surface Dry air aloft

Miller diagram

Conceptual Model

Probabilities

Helicity=56.0 m^2/s^2 (12Z)

+ CAPE=3447 J/kg

=

Good Chance for Tornado

Indices (from 12Z)

Lifted Index=-9.59C > Probable T-storm Showalter=3.77C >No chance Total Totals=43.60C >No chance K Index=21.10 >20-40% chance Sweat Index=45.50 > No chance BRN=152.20 CAP=4.8

Conclusion

Several things happened on May 27, 1997 in Texas to make tornadic activity possible. – Large CAPE coupled with a lower helicity and

a strong cap– Moist air was present at lower levels, while dry

air was present aloft – Supercell progression through Texas

Questions?