Archive for August 4, 2017

Very warm Mediterranean sea – and what that means for severe weather in the autumn

Posted in 2017, Extreme Weather, Uncategorized with tags , , on August 4, 2017 by theboldcorsicanflame

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Take a short look at the weather patterns across the Mediterranean in the autumn that produce severe weather and how high sea surface temperatures may affect them.
There are several weather patterns that generate particularly severe thunderstorms across the Mediterranean, particularly the N-CNTRL part. As summer progresses into autumn increasingly deep troughs enter the Mediterranean region, producing severe weather setups.

Major flooding – particularly along the Ligurian coast (NW Italy) and north Adriatic region (NE Italy, W Slovenia, NW Croatia)

Increasingly deep troughs over the northern Mediterranean with secondary cyclogenesis frequently establish slow moving strong surface wind convergences over the Ligurian sea. Lifting along the convergence and strong jetstream aloft produce long convective lines of training thunderstorms, that produce persistent torrential rainfall along the Ligurian coast. Cumulatives of 200-400 mm / 24h are not unusual. Along the northern Adriatic sea, training cells usually form in the Friuli region (Italy) and Kvarner (Croatia), where upslope flow and forced lift occurs along the slopes of the Alps and Dinarides. These persistent setups often produce rainfall episodes lasting 24-48 hours, with cumulatives 200-400 mm / 24h not unusual. Particularly high sea surface temperatures may result in a more moist airmass advected into these setups and higher amounts of rainfall. See some examples of these intense autumn flash flooding events in the northern Mediterranean region.

Tornadoes – particularly along the Ligurian coast (NW Italy), Tyyrhenian sea coast and central Mediterranean

In November 2011

Higher sea surface temperatures and moister airmass combine with deep troughs to produce very unstable environments. Additionally, the deep troughs are rounded by strong jetstreams providing strong winds aloft. Secondary cyclogenesis over the northern Mediterranean often results in very strong low level / surface southerlies, providing strong vertical veering wind profiles, conductive for supercells and tornadoes.

In particular, the same setups that produce training cell convective lines in Liguria also tend to produce tornadoes.

Also, as autumn progresses and deep troughs reach further into the central Mediterranean. With remaining high instability in place (2000+ J/kg MLCAPE not unusual in November in S Tyrrhenian sea and central Mediterranean) and very strong deep layer shear, wedge tornadoes do occur.

Check their articles on tornadoes in Italy and Croatia too.<

MORE VIDEOS ON SEVERE WEATHER EUROPE

http://www.severe-weather.eu/theory/very-warm-mediterranean-sea-and-what-that-means-for-severe-weather-in-the-autumn/

ROME- Italy’s heatwave is not expected to end soon and will even get hotter

Posted in 2017, Extreme Weather, Uncategorized with tags , , on August 4, 2017 by theboldcorsicanflame

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A heatwave that has left Italy sweltering in record temperatures sparked wildfires Thursday which claimed the life of one elderly woman and forced the closure of a major highway. The 79-year-old woman was found dead in a field next to her home in Sant’Omero in the central region of Abruzzo, having apparently been overcome by flames that engulfed two hectares of surrounding farmland.

A section of the Via Aurelia coastal motorway that runs northwards from Rome to the Riviera had to be closed for several hours because of a major fire near Grosseto in Tuscany. The region’s celebrated landscape is usually baked to a rich golden colour by the end of the summer: this year it resembles burnt toast with August barely underway. With peak temperatures topping 40 degrees Celsius (104 degrees Fahrenheit) in much of the country, a total of 26 major towns and cities were on the health ministry’s maximum heat alert.

In many cities, record highs have already been overtaken by recent temperatures, according to statistics from Centro Epson Meteo. In Alghero, the record of 40.4 degrees in August 2003 has been beaten by 42 degrees. On Tuesday in Florence, temperatures reached 41.3 degrees which is the highest temperature the Tuscan capital has seen since its hot summer of 2013.  A new all-time record was made in Perugia and L’Aquila on Tuesday, with temperatures rising to 40 degrees and 38 degrees respectively. Being 700 metres above sea level, L’Aquila’s hot Tuesday was especially unusual for the capital of the southern Abruzzo region. Another Tuesday record was seen in Potenza at 37 degrees. 

 August’s heatwave is the result of the anticyclone coming from North Africa and the hot air it is carrying from Western Sahara, the press office for meteo.it reported. It is the fifth heatwave to hit Italy this summer and expects to be the most intense one, due to its long duration of a week, temperature peaks and its territorial spread. 

Admissions to hospital emergency units have spiked 15 percent in recent days and forecasters see no respite coming before early next week. High humidity in the north and hot winds from Africa in the south are making the perceived temperatures seem even hotter for Italians longing for the beach.

The heatwave has come on the back of a prolonged drought that is set to cost Italy’s large agricultural sector billions with 11 regions facing critical water shortages. Olive yields in parts of the country are forecast to be 50 percent lower than normal this autumn and the scarcity of water has cut sheep’s milk production by 30 percent in others, with knock-on effects for the production of one of Italy’s most popular cheeses, pecorino.

http://hisz.rsoe.hu/alertmap/database/index.php

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