University of Illinois

> online guides
  educational cd-rom
  current weather
  about ww2010

Online Guides
> meteorology
  remote sensing
  reading maps
  projects, activities

  air masses, fronts
  clouds, precipitation
  el nino
  forces, winds
  hydrologic cycle
  light, optics
  midlatitude cyclones
  severe storms
> weather forecasting

Weather Forecasting
> surface features

Surface Features
  cold fronts
  warm fronts
  stationary fronts
> occluded fronts
  dry lines

User Interface
> text

Occluded Fronts
when a cold front catches a warm front

An occluded front develops when a cold front catches a warm front. For a maturing cyclone, a warm front is progressing northward ahead of the storm center while a cold front is sweeping southeastward. The cool air mass north of the warm front is already in place.


Ahead of the occluded front, temperatures were reported in the low 40's, while temperaturesbehind the front were in the 20's and 30's. The air mass behind the front is also drier as shown by the lower dew points. Wind direction reports to the east of the front are from the east or southeast, while winds behind the front are from the west or southwest. Convergence of the easterly winds ahead of the occluded front and the westerly winds behind it can result in showers of rain or snow.

[Image: occluded front on weather map (26K)]
Image by: WXP Purdue

With the passage of an occluded front, weather conditions will likely turn from cool to cold. Winds will swing around from easterly to westerly or southwesterly with rain or snow showers possible, (depending upon how cold the temperatures are).

stationary fronts
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

dry lines