The origin of western European warm-season prefrontal convergence lines

Johannes M.L. Dahl, Jannick Fischer

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The authors investigate the origin of prefrontal, warm-season convergence lines over western Europe using the Weather Research and Forecasting Model. These lines form east of the cold front in the warm sector of an extratropical cyclone, and they are frequently the focus for convective development. It is shown that these lines are related to a low-level thermal ridge that accompanies the base of an elevated mixed layer (EML) plume generated over the Iberian Peninsula and northern Africa. Using Q-vector diagnostics, including the components that describe scalar and rotational quasigeostrophic frontogenesis, it is shown that the convergence line is associated with the rearrangement of the isentropes especially at the western periphery of the EML plume. The ascending branch of the resulting ageostrophic circulation coincides with the surface velocity convergence. The modeling results are supported by a 3-yr composite analysis of cold fronts with and without preceding convergence lines using NCEP-NCAR Reanalysis-1 data.

Original languageEnglish
Pages (from-to)1417-1431
Number of pages15
JournalWeather and Forecasting
Issue number5
StatePublished - 2016


  • Ageostrophic circulations
  • Circulation/Dynamics
  • Convergence/divergence
  • Europe
  • Frontogenesis/frontolysis
  • Geographic location/entity
  • Mesoscale models
  • Models and modeling


Dive into the research topics of 'The origin of western European warm-season prefrontal convergence lines'. Together they form a unique fingerprint.

Cite this