Synoptic Scale Factors of Significant Tornadoes

in the Mid-South

Thomas Salem, NWS Memphis,

Heather Hyre, Miss. St. Univ.,

Janice Maldonado and Alina Nieves, Univ. of Puerto Rico Mayaguez

From Rose et. al, 2004 WAF

10 year Study of Tornadoes and Jets

• 97% of tornadoes associated with jets

• Dominate quadrant was left exit

Total Ent. Exit

Left 9% 37%

Right 20% 25%

Outbreaks Ent. Exit

Left 7% 44%

Right 16% 28%

Mid-South Sig.Tornadoes (79-06)

250 mb

Winter Ent. Exit

Left 0 % 21 %

Right 8 % 71 %

Spring Ent. Exit

Left 2 % 28 %

Right 35 % 35 %

Fall Ent. Exit

Left 0 % 32 %

Right 37 % 32 %

EF2+ Ent. Exit

Left 1 % 27 %

Right 28 % 44 %

Parameters Slight Moderate High

MSLP >1010 mb 1010-1005 mb <1005 mb

2m Dewpoint <55 °F 55-64 °F >65 °F

Dewpoint 850mb <8 °C 8-12 °C >12 °C

Isotachs 850mb ≤30 kts 30-40 kts >40 kts

Temp 700mb >11 °C 8-11 °C <8 °C

Isotachs 500mb ≤35 kts 36-49 kts >50 kts

Isotachs 250mb ≤65 kts 66-85 kts >85 kts

850-500 Wind Shear ≤25 kts 26-35 kts >35 kts

SBCAPE <1500 J/kg 1500-2500 J/kg >2500 J/kg

0-3 km Helicity <300 m²/s² 300-450 m²/s² >450 m²/s²

Lifted Index ≥-2 °C -3 to -5 °C <-6 °C

Parameters High Moderate Slight

MSLP 48.51% 30.69% 20.80%

2m Dewpoint 28.71% 68.32% 2.97%

Dewpoint 850mb 18.81% 62.38% 18.81%

Isotachs 850mb 50.50% 31.68% 17.82%

Temp 700mb 98.02% 1.98% 0.00%

Isotachs 500mb 77.23% 15.84% 6.93%

Isotachs 250mb 41.58% 26.73% 31.68%850-500 Wind

Shear 3.96% 8.91% 87.13%

SBCAPE 15.84% 18.81% 65.35%

0-3 km Helicity 14.85% 24.75% 60.40%

Lifted Index 29.70% 28.71% 41.58%

Parameters High Moderate Slight

MSLP 42.31% 38.46% 19.23%

2m Dewpoint 46.15% 53.85% 0.00%

Dewpoint 850mb 25.00% 71.15% 3.85%

Isotachs 850mb 30.77% 44.23% 25.00%

Temp 700mb 98.08% 1.92% 0.00%

Isotachs 500mb 71.15% 19.23% 9.62%

Isotachs 250mb 34.62% 32.69% 32.69%

850-500 Wind Shear 5.77% 11.54% 82.69%

SBCAPE 26.92% 26.92% 46.15%

0-3 km Helicity 13.46% 15.38% 71.15%

Lifted Index 50.00% 21.15% 28.85%

Parameters High Moderate Slight

MSLP 68.42% 10.53% 21.05%

2m Dewpoint 15.79% 73.68% 10.53%

Dewpoint 850mb 15.79% 84.21% 0.00%

Isotachs 850mb 68.42% 21.05% 10.53%

Temp 700mb 100.00% 0.00% 0.00%

Isotachs 500mb 73.68% 26.32% 0.00%

Isotachs 250mb 42.12% 21.05% 36.84%

850-500 Wind Shear 0.00% 5.26% 94.74%

SBCAPE 5.26% 15.79% 78.95%

0-3 km Helicity 21.05% 31.58% 47.37%

Lifted Index 15.79% 31.58% 52.63%

Parameters High Moderate Slight

MSLP 51.85% 33.33% 14.81%

2m Dewpoint 0.00% 96.30% 3.70%

Dewpoint 850mb 3.70% 33.33% 62.96%

Isotachs 850mb 81.48% 18.52% 0.00%

Temp 700mb 100.00% 0.00% 0.00%

Isotachs 500mb 100.00% 0.00% 0.00%

Isotachs 250mb 59.30% 22.22% 18.52%

850-500 Wind Shear 3.70% 7.41% 88.89%

SBCAPE 0.00% 3.70% 96.30%

0-3 km Helicity 14.81% 40.74% 44.44%

Lifted Index 0.00% 40.74% 59.26%

Parameters High Moderate Slight

MSLP <1005 mb 1010-1005 mb >1010 mb

2m Dewpoint >65 °F 55-64 °F W,F <55 °F

Dewpoint 850mb >12 °C 8-12 °C F, Sp <8 °C

Isotachs 850mb >40 kts W 30-40 kts ≤30 kts

Temp 700mb <8 °C W,F, Sp 8-11 °C >11 °C

Isotachs 500mb >50 kts W,F, Sp 36-49 kts ≤35 kts

Isotachs 250mb >85 kts 66-85 kts ≤65 kts

850-500 Wind Shear >35 kts 26-35 kts ≤25 kts W,F,Sp

SBCAPE >2500 J/kg 1500-2500 J/kg <1500 J/kg W,F

0-3 km Helicity >450 m²/s² 300-450 m²/s² <300 m²/s² Sp

Lifted Index <-6 °C -3 to -5 °C ≥-2 °C