Insanely extreme Bora and heavy snowfalls on Wednesday’s night
An extremely dangerous setup is shaping up for northern Adriatic sea due to high potential for hurricane force Bora winds during the next 48 hours period. Tightening pressure and temperature gradient will create conditions for very extreme wind gusts, locally exceeding 220km/h.
Not so unusual situation for Europe for the last winter decade, but quite rare setup if looking more into the details. A large ridge is placed over west-central Europe while a deepening surface low is located over western Mediterranean and moving NE-wards towards the northern Adriatic sea. As can be seen on the latest satellite image (see the Water Vapour image below), the surface low is quite impressive while forming a nice cyclonic shape just NE of Balearic islands.

Image copyright: © EUMETSAT (2010)
The following maps show this surface low pushing NE-wards towards the large high pressure area and resulting in tightening pressure gradient all the way from central Italy towards the northern Balkans. Ahead of this system, a warm front will be pushed northwards and rapid moisture return with strong WAA from the south will be on going.



Its expected that snowing will arrive later in the evening tomorrow and night on Wednesday until Thursday’s night will be quite snowy over Slovenia and surrounding areas. Depends how north the surface low will be pushed, the snow accumulations will be likely from 10-30cm. More likely even higher in southern Slovenia on the eastern side of Dynaric mountain range (SE Slovenia) where strong SE-erly winds will be favorable for strong orographic lifting with persisting flow. There, accumulations even higher than 40cm until Thursday noon cannot be completely ruled out. But once again, all depends how north the surface low will be. Only minor changes could have big effect on evolution of extreme Bora as well as snow accumulations. Given the very cold temperatures at all levels, it will be snowing also along the seaside and probably also over the sea towards Venice and Istria. The extreme winds will be creating snow drifts and will be pushing the driving conditions to very unfriedly, as zero visibility will be locally possible.



But what is the most impressive with this setup is, as already said, an extremely dangerous potential for very strong to hurricane force Bora winds. Such model simulations that can be found today were surprisedly never seen before, as especially local ALADIN model has 850mb and 925mb level average wind speed as high as 35 to more than 40m/s along the Dynaric mountain range. Sometimes values up to 35m/s can be seen on the maps, but this time it seems like a record breaking values!



At surface level winds are also incredibly impressive with values even above 30-35m/s average speeds locally, which becomes extremely dangerous for lowlands where people live. A special ALADIN products for simulated wind gusts at 10m heights are predicting gusts near or above 180km/h in SW Slovenia and Trieste gulf, while Kvarner area has values near 220km/h. This has never been seen before! And what is even more impressive is the fact, that even a very good models like ALADIN for wind speed simulations are usually underestimating values for max gusts possible, so its is quite likely that is this setup realizes like it shows now, gusts could be even 15-20% higher than currently forecasted.




For this reason of expected very extreme winds gusts, our national meteorlogical agency ARSO has issued a Red Alert for SW Slovenia and Primorska region.

valid from 09.03.2010 15:00 CET Until 10.03.2010 CET
Wind Awareness Level: Red
maximum-wind-speed > 140.0 km/h
Slovenia / South-West : maximum wind speed - more than 140 km/h.
Slovenija / jugozahod : maksimalna hitrost vetra - vec kot 140 km/h.
It has to be noted that as can be seen on the maps above, the wind direction will be mostly from the east, which is usually very favorable for extreme gusts over Karst region into Trieste gulf, along with classic well known Bora places. I do believe that record breaking wind gusts could occur locally, if not over mostly all places.
To repeat once more; issued Red Alert for SW Slovenia tomorrow and day after means that this will be extremely dangerous and life threatening situation where a lot of damage could be done on buildings as well as to people lives. When such winds are blowing, a lot of rocks, trees and other objects are flying in the air and can kill people, so be prepared for such dangerous events during the next 48 hours.
And stay tuned for possible updates or analysis later!



