Mediterranean Winds
Meteorology
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The Bora Wind of Trieste

Let us examine a little closer the phenomenon of the bora in Trieste. This wind is created at the meeting point of two climatic zones: the Northern and the Mediterranean. Like any wind, it is  caused by movement of air induced by different atmospheric pressures.Trieste is situated at the extremity of a warm sea extending deeple into the continent and in the proximity of a cold hinterland. The jumps in temperature and pressure cause the influx of cold air from the centre of Europe towards the sea.

The bora is a low altitude wind (it is not felt at high altitudes) from a constant north easterly origin. At Trieste it rushes in from the pass of Postumia and it acquires more strength in the maze of the city buildings. Its only positive side is that it purifies the air and it restores a clear sky. But when it blows, roof tiles are unseated, it may even upturn cars, ships strengthen their moorings to prevent being pushed out at sea, people that dare to brave the streets must cling to ropes and railings installed in the more exposed locations. 

Bora winds are common in Trieste during wintertime. Winds of 50 knots with occasional gusts to 80 knot are not uncommon. In 1956 a gust of 125 knots was recorded, but in more recent years the highest gust has been 95 knots. On January 12, 2001 the wind was reported to have reached 144 kilometers per hour (89.5 mi/hr) - see news article. The peak month for bora occurrence is February while strong winds associated with the bora can occur in any month. The strong bora episodes usually end by April, but milder boras can occur in any month of the year. The wind has been known to last for up to 30 days at Trieste without a significant lull. 

Other strong winds, usually from the south, can occur prior to cold frontal passage associated with a transitory low pressure system from the Gulf of Genoa referred to as "Genoa lows".

Below freezing temperatures are common during winter. Wind chill factors can be dangerous when cold temperatures occur with high winds, quite common in a bora outbreak. Early spring resembles winter and as spring progresses some summer like days are noted.  Wind chill is still a factor during early spring. 

Trieste normally experiences good visibility year-round. However, one or two days per year, usually in November, expect visibility to be near zero in dense fog. The fog is associated with a west wind and can last the entire day. On another two or three days of the year, visibility will be in the 1 to 3 mile range, again associated with fog and a west wind. Some visibility restrictions can occur with fog in the early spring. This is usually due to a fog laden west wind and can last for a day or more. 

The bora announces itself with long and threatening hisses called refoli. In the most severe winters, the Triestini say: 

Tre giorni la nassi,
Tre giorni la cressi,
Tre giorni la crepa
Three days to be born, 
Three days to grow, 
Three days to die

(T) evidencing with an old proverb a wind that blows by the rhythm of perfect numbers.

From Il Resto del Carlino, 13 gennaio 2001:

TEMPESTA DI BORA A TRIESTE: 144 CHILOMETRI ORARI

TRIESTE, 13 GENNAIO - Ha raggiunto i 144 chilometri orari la bora che soffia con intensitą dalla scorsa notte su Trieste. Due raffiche di tale intensitą sono state infatti registrate, alle 8.55 e alle 9.50 della mattinata, dall' Ufficio previsioni meteo dell' Istituto Tecnico Nautico del capoluogo giuliano.

La tempesta di bora - rileva lo stesso Istituto in un comunicato - č stata determinata «dall' irruzione di aria polare, cominciata nel pomeriggio di ieri e determinata da una cellula anticiclonica di blocco, posto sul centro-nord Europa». 

Le forti raffiche di vento, per il momento, stanno continuando a creare disagi: si sono avute centinaia di richieste d' intervento ai vigili del fuoco per alberi caduti, cornicioni pericolanti e vetri in frantumi e le navi in rada hanno dovuto rinforzare gli ormeggi. Non sono per il momento segnalati, comunque, danni di rilievo o gravi conseguenze per le persone.

Tratto da:

  • IlRestoDelCarlino.it, Tespesta di bora a Trieste: 144 chilometri orari - http://ilrestodelcarlino.monrif.net/art/2001/01/13/1708763
  • Cartoons - http://utenti.tripod.it/caia/trieste.htm#bora
  • Photographs by Corrado Ballarin (Trieste) - courtesy of Italo Cunei and Mario Majarich.

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This page compliments of Marisa Ciceran

Created: Thursday, June 20, 2001; Last updated: Tuesday, October 16, 2012
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