Weather Photos blog

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.

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.

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!

I am in time shortage today, so this will only be a quick update/outlook for tomorrow. Winter period is returning into Alpine region again, as the blocking pattern has established over western Europe with strong ridge forming. This will allow polar/arctic airmass to blast into central Europe and Mediterranean and lead into colder than average temperatures during the next 5-7 days at least. First, some snowing is expected tonight and tomorrow as the surface depression approaches from the SW. Light to moderate snowing is likely over most of Slovenian inland areas, except the lowlands in SW Slovenia. Only 5-10mm are forecasted by the models, with snow mixing down to near 300m or slightly lower. Ground accumulations are quite questionable given the warm period in the last days, so the ground has temperatures several degrees above zero. However, up to 15cm is still possible locally, especially a bit higher, above 500m or so. Lower places might have only few cm deck according to the most optimistic scenarios.

Additionally, very strong to extreme Bora is forecasted along the whole eastern Adriatic coast as well, as tightening gradient and increasing temperature difference along the Dynaric mountain range creates perfect conditions for strong gusts. Locally, gusts will be reaching above 150km/h (e.g. Vipavska valley).

I hope I’ll find some time tomorrow afternoon to edit this post and atttach some of the interesting model maps for this event. Stay tuned for future updates!

After a devastating and powerful deadly extra-tropical storm Xynthia crossing WNW-ern Europe during the last weekend, cooler conditions prevail over Europe. Over Alpine region, a not very interesting and quite stable conditions prevail with weak disturbances crossing every few days as the zonal flow established about a week ago. Such pattern seems likely for few more days when large ridge will again form over western Europe and blocking pattern will then favour polar airmass to blast into central Europe again. Winter days will be back, possibly also with extreme Bora wind days and quite cold period for a couple of days. As regarding the snow chances, it all depends where secondary cyclogenesis will take place along the wavy polar front/trough pushing towards the west-central Mediterranean. As for now, the highest chances seem over weekend, but thats too far in advance to make it sure. Please, stay tuned for possible future updates on this changing pattern.

On the other hand, its hard to hide that I, as being the summer perido fan, am hardly waiting for the new storm season to begin. Then, also forecasting will be much more interesting than it is now during these cold winter days. However, during my official shifts at ESTOFEX project, which are now during Mondays, I do regularly issue convective outlooks for the Tuesdays each week. Here is one interesting setup over Europe for tomorrow when an intense upper vortex approaches SW Iberia with some severe storms possible. Pretty impressive satellite presentations should be available as the strong advection from NW-ern Africa pushes warm airmass into SW-ern Mediterranean. More details can be found below.

Storm Forecast
Valid: Tue 02 Mar 2010 06:00 to Wed 03 Mar 2010 06:00 UTC
Issued: Mon 01 Mar 2010 22:42
Forecaster: KOROSEC

A level 1 was issued for southern Portugal and extreme SW Spain mainly for large hail, excessive convective rainfall and lesser extent for tornadoes and strong winds.

SYNOPSIS

Two disturbances affect parts of Europe during the forecast period. First, a short-wave trough with a developing weak surface low over SE Balkans and northern Turkey. An attendant cold front will be a focus for convective development. Another trough/low, more pronounced disturbance takes place over SW-ern Iberian Peninsula as the intense vortex/upper low approaches from the west. Deep surface low with strong cold front is pushed towards southern Spain while strong subtropical airmass/warm front advects into the SW Mediterranean.

DISCUSSION

… SW Iberian Peninsula …

Another surface depression takes place over the Iberian Peninsula during the day. Ahead of this low, strong subtropical airmass is advected northwards towards southern Portugal and SW Spain. Once the cool midlevels/steepening lapse rates overspread the warm sector, large scale lifting and marginal instability will lead into scattered convective development. However, a forced line of storms is as well possible just ahead/along the cold front. Shear up to 30m/s in the 0-6km layer and up to 20m/s in the lowest layers will favor organized storms. Locally, threat for excessive rainfall and large hail will exist. Given the easterly LL winds, enhanced SREH could yield in tornadogenesis, especially along the Iberian coast, but threat seems quite low attm.

Overnight on Wednesday, when vort-max moves more to the east, another surface depression forms in the left exit jet region over SW Mediterranean and a few storms will result. But given the uncertainities about the timing of this formation, a threat level was not extended more to the east. Although conditions may favour organized storms as well.

… SE Balkans towards NW Turkey …

Models do agree in convective development along the SE-wards moving surface cold front during the first half of the forecast period, as the large scale ascent ahead of the trough overspreads the region. Weak instability signals but deep layer shear near 20m/s could be supportive for some stronger and organized storms, but both severity and coverage seem limited to warrant a threat level. However, locally excessive convective rainfall event with small hail cannot be completely ruled out.

Source: ESTOFEX outlooks