Objectives

The goal of this module is to teach novice forecasters to effectively use the tephigram, a thermodynamic diagram used to evaluate the vertical structure of the atmosphere. After completing the module, they should be able to read and interpret a sounding plotted on a tephigram and apply that information to aid the weather forecasting process.

Specific objectives include the following:

Given a tephigram, identify and describe the various lines.

Given a sounding plotted on a tephigram, read the following properties for a given level:

  • Temperature
  • Dewpoint
  • Mixing ratio
  • Saturation mixing ratio
  • Wind speed
  • Wind direction
  • Dewpoint depression
  • Potential temperature (theta)
  • Equivalent temperature (Te)
  • Equivalent potential temperature (theta-e)
  • Wet-bulb temperature (Tw)
  • Wet-bulb potential temperature (theta-w)
  • Saturation vapor pressure (es)
  • Vapor pressure (e)
  • Convective temperature (Tc)

Given a sounding plotted on a tephigram, calculate the following properties at a given level:

  • Relative humidity (RH)
  • Virtual temperature (Tv)

Given a sounding plotted on a tephigram, determine the following levels:

  • Lifting condensation level (LCL)
  • Convective condensation level (CCL)
  • Level of free convection (LFC)
  • Freezing level
  • Wet-bulb zero level
  • Mixing condensation level (MCL)
  • Tropopause
  • Equilibrium level (EL)
  • Maximum parcel level (MPL)

Given a sounding plotted on a tephigram, determine the following stability indices and use them to assess the potential for severe weather:

  • Lifted index (LI)
  • Showalter stability index (SSI)
  • K index (KI)
  • Total Totals index (TT)
  • Severe Weather Threat (SWEAT) index

Describe how CAPE and CIN are determined.

Comparing 2 soundings, determine which has the larger values of CAPE and CIN.

List and describe the different types of stability and identify them in a sounding plotted on a tephigram.

List and describe the different types of lapse rates.

Given a sounding plotted on a tephigram, characterize the lapse rate of each segment of the sounding.

List and describe processes that alter stability and give examples of common cases where this occurs.

Given a suitable synoptic environment and a sounding plotted on a tephigram, interpret the sounding with regard to the following forecast problems:

  • Air mass thunderstorms
  • Severe thunderstorms
  • Convective wind gusts and microbursts
  • Hail
  • Heavy precipitation
  • Precipitation type
  • Maximum temperature
  • Thermal turbulence
  • Icing