Total Totals
Total Totals is an index used to determine storm strength.
Total Totals may not detect cap, and will not detect CAPE and shear.
<43
Convection Unlikely
44-50 Thunderstorms
Likely
51-52 Isolated
Severe Thunderstorms, Isolated Tornadoes
53-56 Widely Scattered
Severe Thunderstorms, Scattered Tornadoes
>56
Severe Thunderstorms and Tornadoes Likely
EHI (Energy Helicity Index)
A combination of CAPE and Helicity. Possibly the best
index for forecasting tornadoes.
<2
Supercells Unlikely
2.0-2.4 Supercells Possible
2.5-2.9 Supercells
Likely, Tornadoes Possible
3.0-3.9 Tornadoes Likely
>4.0
Multiple Strong Tornadoes Likely
CAPE (Convective Available Potential Energy)
<300
Very Weak CAPE
300-1000 Weak CAPE
1000-2500 Moderate CAPE
2500-3000 Strong CAPE
>3000 Extreme CAPE
LI (Lifted Index)
Lifted Index is used to determine thunderstorm potential,
taking into account low-level moisture availabilty. CAPE is better for determining instability in the entire troposphere.
-1 to -2 Minimal Instability,
Thunderstorms Possible
-3 to -5 Marginal Instablility,
Thunderstorms Likely
-5 to -7 Large Instability,
Severe Thunderstorme Likely, Tornadoes Possible
-8 or Less Extreme Instability, Tornadoes Likely
BRN (Bulk Richardson Number) Shear
The balance between CAPE and Wind Shear.
<10
Too Much Shear-Thunderstorms Not Likely
11-49
Moderate Potential For Thuderstorms
>50
Supercells Favorable
SRH (Storm Relative Helicity)
A combination of speed shear, directional shear, and the strength
of low-level winds.
150-300 Supercells Possible
300-400 Supercells Favorable
400+
Tornadoes Possible
K Index
K Index assesses convective potential.
0-14
Thunderstorms Unlikely
15-25
Little Convective Potential
26-39
Moderate Convective Potential
40+
High Convective Potential
SWEAT (Severe Weather Threat Index)
SWEAT Index uses several variable to determine the likelihood
of severe weather and tornadoes.
<272
Thunderstorms Unlikely
273-300 Slight Severe Potential
301-400 Severe Storms Possible
401-600 Isolated Tornadoes
Possible
601-800 Scattered Severe Thunderstorms
and Tornadoes Likely
>801 High
Wind Damage, But Not Favorable For Severe Weather
TEI (Theta-E Index)
Potential for elevated convection. An area with high Theta-E is
usually an area with high instability.
<5
Not Favorable
5-9
Potential Elevated Convection
>9
Very High Potential Of Elevated Convection
LCL (Lifted Condensation Level)
An LCL closer to the surface is more supportive of tornadoes in a severe
thunderstorm environment.
Cap (Capping Inversion)
A layer of warm air aloft that prevents the rising of warm
moist air. Prevents thunderstorms.
0
No Cap
1-2 Weak
Cap
3-4
Moderate Cap
>4
Strong Cap
CINH (Convective Inhibition)
Anti-CAPE or capping layer.
0-50
Weak Cap
51-199 Moderate Cap
200+ Strong
Cap
Heights
1000 mb = near surface
850 mb = about 5000 feet
700 mb = about 10,000 feet
500 mb = about 18,000 feet
300 mb = about 30,000 feet
