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SEVERE ADRIATIC BORA STORMS IN RELATION TO SYNOPTIC DEVELOPMENTS
Vesna Jurčec
; Hydrometeorogical lnstitute of Croatia, Zagreb
Sažetak
Five typical north Adriatic bora storms are presented from the period 1957-1986. lt is shown that severe bora is caused by a very cold air outbreak in a deep upper tropospheric trough which usually develops into a cut-off low in the Mediterranean. This process is often accompanied by a cut-off high in the norheastern Atlantic. Such a blocking type circulation prevents the warmer air from the Atlantic to invade the European continent which is occupied by a broad cold surface anticyclone. The latter builds up a large pressure gradient toward the Mediterranean cyclone which is particularly strong at the northern Adriatic coast. This pressure difference is calculated from the mountain drag according to Smith's (1985) hydraulic model and the results are mainly in good agreement with the observations.
Fast upper level development causes changes in the wind direction above the bora layer. Strongest bora occurs with the reversed upper air flow regardless of the wind intensity, whereas bora ceases under strong unidirectional (NE) current, unless there is a strong temperature inversion in the lower troposphere.
Ključne riječi
Adriatic bora; severe downslope wind; blocking type circulation; hydraulic parameters
Hrčak ID:
69265
URI
Datum izdavanja:
15.12.1989.
Posjeta: 1.026 *