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The Papal Front of 3 May 1987: A remarkable example of frontogenesis near the Alps
Author(s) -
Volkert Hans,
Weickmann Ludwig,
Tafferner Arnold
Publication year - 1991
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711749707
Subject(s) - geology , frontogenesis , orography , mesoscale meteorology , climatology , front (military) , orographic lift , foreland basin , squall line , potential vorticity , cold front , vorticity , meteorology , precipitation , seismology , geography , vortex , oceanography , tectonics
All available, routinely collected surface data are used to document the development of the ‘Papal Front’, which crossed southern Germany on 3 May 1987 causing casualities and damage. Objective analyses on isentropic surfaces, initialized with the European aerological data, indicate that the development of the violent mesoscale front, which exhibited squall‐line characteristics, began when a distinct mid‐troposopheric anomaly of potential vorticity reached the north‐western rim of the Alpine arc. The forced uplift ahead of the associated shortwave trough combined with ageostrophic motions due to a jet streak at higher levels apparently provided a trigger for deep convection as was observed over the Alpine foreland. Numerical simulations with a dry hydrostatic model indicate the relative importance of the synoptic‐scale forcing and the Alpine orography for the generation of the ‘Papal Front’. A westerly ‘orographic jet’ over the foreland below crest height only develops in the simulation with full Alps and is corroborated by the few mountain wind observations that are available. A comparison with studies of frontal propagation along other mountain ranges reveals that the routine network in the Alpine region and its surroundings is at least of similar density, but so far hardly used for frontal case‐studies. It is concluded that a series of ‘routine‐data case‐studies’ could help to determine the variability of frontal progression along the Alps and, thus, provide guidance when assessing the significance of single events, particularly those sampled during special observation programmes.