|SKEW-T: A LOOK AT THETA-E
METEOROLOGIST JEFF HABY
1. What is THETA-E?
THETA-E (Equivalent Potential Temperature) is the temperature that results after all
latent heat is released
in a parcel of air and the then brought adiabatically to the 1000 mb level. THETA-E increases as
and/or temperature increases.
2. How is THETA-E determined?
First determine the pressure level of interest. Locate the temperature and dewpoint at that pressure level. Raise
that parcel adiabatically from that pressure level to the 200-mb level. Next, bring the parcel down dry adiabatically
to the 1000 mb level. The temperature once the parcel is at 1000 mb is the THETA-E.
3. Operational significance of THETA-E:
INSTABILITY- A region with a relatively high THETA-E is often the region with the most instability. Warmer low
level temperatures and higher low level dewpoints increase instability.
LOW LEVEL JET- A low level jet from a moisture source will often bring in higher THETA-E values and thus
THETA-E RIDGE- These are regions with higher
THETA-E. They are often the burst point for convective activity.
a. If a strong
cap is in place, convective storms will not occur even if THETA-E is high.