Skew T Diagrams

K Index (KI)

A measurement used to predict potential air mass of thunderstorms by looking at mid level lapse rates and low level moisture. If this number is/or above 36, there is an 80% to near 100% probability for severe weather.

Lifted Index (LI)

A product of air parcel's buoyancy at 500 mb. If this number is negative, there is instability.

Convective available potential energy (CAPE)

Value that determines the possibility of severe weather. Positive area of a Skew T. The air parcel line is warmer than the surrounding temperature. A value of more than 1500 J/kg is large.

Level of Free Convection (LFC)

Level at which the hypothetical air parcel warms and rises all by itself. The lower the level, the more explosive the weather. If it is 745 mb or below, potential is strong. 1. Find the LCL 2. Draw air parcel line up moist adabatically until it intersects with the air temperature. 3. Intersection is the _______.

saturation mixing ratio

Maximum mass of water vapor (g) that can exist in a mass of dry air (kg). Where the TEMPERATURE and mixing ratio lines meet.

Showalter Index (SI)

Number assigned to the environment to determine overall stability. Starting point is at 850 mb. If this value is negative, there is instability.

Total totals index (TT)

Number that represents potential for convective weather. If it is 52 or above, there is a very high chance for thunderstorms.

relative humidity

Ratio of the mixing ratio to the saturation mixing ratio.

mixing ratio

Ratio of water vapor mass (g) to mass of dry air (kg). Where the DEW POINT and mixing ratio lines meet.

Equilibrium Level (EL)

Represents level at which the temperature of an unstable (positive buoyancy) air parcel drops below surrounding air and becomes stable again. This is almost always very high in the atmosphere. 1. Start at the LFC 2. Follow moist adiabat line up until it intersects with the temperature sounding. 3. Intersection is the _______.

Convective Condensation Level (CCL)

The altitude (pressure level) to which an air parcel, if heated at the surface, will rise dry adiabatcally until it becomes saturated. (This is generally higher than the LCL) 1. Find the surface dew point temp 2. Draw parallel line up along the mixing ratios until it intersects with the temperature sounding.

Convective inhibition (CIN)

The amount of negative area on the sounding which measures the amount of energy needed to get buoyancy forces to accelerate the air parcel upwards. If this value is high, there is stability in the atmosphere.

Lifting Condensation Level (LCL)

The level at which a parcel of air, when lifted dry adiabatically, would become saturated. This rising is not caused by heat. 1. Look at temp and dew point approx. 50 mb above the surface. 2. From temp, draw line parallel to dry adiabatic lines up 3. From dew point, draw line parallel to mixing ratios up. 4. Intersection of those two lines is the _____.

wet bulb temperature

The lowest temperature that can be reached by evaporating water into the air/ the temperature to which air will drop if/when it becomes saturated. 1. Start at LCL for height that you want 2. Draw line DOWN moist adiabatically to pressure level you want. 3. Read temp from temperature axis.

surface

The place where the temperature and dew point profile start (not necessary the X-axis)

temperature inversion

The temperature profile line is "skewed" more than the isotherms.