Quasi-Stationary Fronts

1) Cold frontal systems tend to become quasi-stationary through central Mississippi, southeastern Louisiana, and southeastern Texas when the air mass behind the system has a trajectory down the Mississippi Valley to central Kansas, and then eastward. The Bermuda Ridge has pushed westward.  Another indication that a frontal system is going to become stationary west of the local area is digging of the jet stream westward along the West Coast, which produces a cut-off low or a retrograding trough along the California coast. 

Prolonged quasi-stationary frontal systems in the local area have a similar pattern.  A continental polar/arctic air mass moves down the Mississippi Valley to northern Arkansas and then east-southeast into western Georgia and becomes stationary. The cold frontal system moves into the Gulf where the front then becomes stationary. At the same time, a westward extension of the Bermuda High moves into the north central Gulf. 

  2) The atmospheric conditions are similar to that of a cold frontal passage with prolonged postfrontal cloudiness.  However, wiith a quasi-stationary front, short waves move eastward through the axis of the long wave trough. They continue eastward and produce open waves along the front. Close monitoring is needed to detect low pressure development so that timely warnings and forecasts can be made. 

About 24 hours after the front becomes stationary, weak short waves at the 700/500 mb level begin to move along the frontal system.  This produces stable waves on the surface that ripple along the frontal zone.  

The open waves that ripple along the surface frontal system produce an increase in rain showers at and northward of the frontal wave.  Radar is helpful in detecting the associated shower activity. 

Severe weather is often associated with the development of an unstable wave or closed low on the frontal system. A strong short wave trough with associated positive vorticity advection moving off the Texas coast just south of Galveston will trigger a closed surface wave development on the quasi-stationary front. 

Depending on the upper-air pattern, this wave may continue to develop as it moves east and northeast, producing thunderstorm activity that has a high potential of being severe as it passes through KNPA's area of  responsibility. 

Concept Mapping Toolkit
Insitute for Human and Machine Cognition
The University of West Florida