Weather Photos blog

A warm period continues as large ridge and high pressure area expands over the most of Europe. Here is a convective outlook across Europe tomorrow. Some severe weather seem likely over Iberian Peninsula as large trough digs in, while the rest of continent remains stable or only affected by diurnal driven thunderstorms. Additional warming will be on going this week, before a large trough blasts into central Europe after May 1st. But its too far away for any details about it yet.

Storm Forecast
Valid: Wed 28 Apr 2010 06:00 to Thu 29 Apr 2010 06:00 UTC
Issued: Tue 27 Apr 2010 19:48
Forecaster: KOROSEC

SYNOPSIS

An omega like ridge pattern with large high pressure area builds over Europe. On its eastern side, weak geopetential falls within the large but weak upper low will persist and will be moving southwards into SE Europe. On the western side of the ridge, a large trough with an attendant surface front digs into western Europe and Iberian Peninsula.

DISCUSSION

… NW Iberian Peninsula …

Ahead of an approaching trough/front, moist and warmer airmass advects across the Iberian Peninsula. It seems that destabilization is likely in the afternoon hours as the mid-level lapse rates become steeper. Both QG forcing ahead of the trough and strong diurnal heating should be enough to overcome the weak capping inversion and convective initiation is likely just ahead and along the surface convergence/cold front. About 500-800 J/kg of MLCAPE seem reasonable to release and overlap with moderate deep layer shear in range of 15-25m/s. Therefore, some organized multicells or even supercells can be expected with the main threat for large hail and strong wind gusts.

Due to simulated quite limited coverage of convective activity on today’s model runs, a severe threat level has not been issued at this moment. But situation will be closely monitored for a possible upgrade tomorrow if coverage will be more widespread than currently anticipated.

…highlighted areas in southern Italy, the central Balkans and eastern Europe…

Some areas will again see mostly diurnal driven convective activity as cold mid-levels still persist within the large but constantly weakening upper-level depression. Still healthy BL moisture and good temperature insolation should yield several hundreds J/kg of MLCAPE and locally, again most likely along the complex terrain, showers and thunderstorms will initiate. The strongest cells could pose a threat for marginally large hail and intense convective rainfalls due to weak wind profiles and mostly pulsating nature convective cells.

Source: ESTOFEX convective outlook for Europe – Apr 28th 06 UTC until Apr 29th 06 UTC

Here is a convective outlook across Europe tomorrow I made. Some severe weather action seem likely ahead of the deep trough over SE-ern Europe while the rest of continent remains stable or only affected by diurnal driven convection. Nice warming is on going this week, finally!

Storm Forecast
Valid: Tue 20 Apr 2010 06:00 to Wed 21 Apr 2010 06:00 UTC
Issued: Mon 19 Apr 2010 22:37
Forecaster: KOROSEC
A level 1 was issued for western Turkey mainly for large hail, strong winds and lesser extent for excessive rainfall.

SYNOPSIS

A large trough over eastern half of Europe shifts eastwards while deepening towards the SE Europe on Tuesday. At surface, an attendant surface depression moves ahead of it towards the Black sea. Embedded in this large main European trough, another trough/upper low moves from North Sea into southern Scandinavia.

A new trough/upper low approaches Iberia towards the Wednesday morning hours. The rest of Europe, except the Alpine region and most of Italy which again becomes unstable during the day, will remain stable.

DISCUSSION

… Western Turkey …

The deepening trough will affects Aegean Sea and western Turkey during the first half of the period before shifting further east and outside our forecast area. A strong WAA spreads NE-wards ahead of this trough where destabilization continues across the warm sector ahead of the surface front. Several hundreds J/kg of MLCAPE seem reasonable to result in environment with steep lapse rates, while well overlaping with moderate shear. Therefore, an organized convection seem likely to occur, posing a threat for large hail and strong winds. Especially over the western Turkish complex terrain, longer lasting convection may enhance excessive convective rainfall/flash flood threat as well. It seems that surface based convection may occur as well, then a 10-15m/s of 0-3km layer shear seem favorable also for a few LL mesocyclones and enhanced threat for tornadogenesis. But with only marginal SREH, this threat seem quite limited attm.

… central Italy and Alpine region …

Diurnal driven showers and thundertorms are again forecasted as warm/moist airmass becomes weakly unstable with daytime heating. The higher probabilites seem confined mostly to the complex topography of central Italy and across the Alps. Given the only weak shear in place, no severe weather is expected.

… North sea towards Denmark …

With an approaching upper low/trough and surface front across the North sea, a forced line of convection is possible. GFS model agrees in minor instability and some electrified convection could occur. A strong wind gusts seem to be the main threat, but staying below the severe criteria.

Source: Convective outlook for Europe – Apr 20th 06 UTC until Apr 21st 06 UTC

The main problem remains to be a Icelandic volcanic ash, but thats another story. I might have some time to update some information about it tomorrow, however the eruption is still on going and much of Europe’s airspace remains closed. Stay tuned!

Some relief for an airline companies at least over the Alpine region today it seems. A weak upper low is crossing the Alps today and some precipitation will at least partly wipe out the volcanic ash from the air. Actually this upper low is the remnant of the long lasting big upper cold core low wobbling across much of central Europe during the last week. GFS has it perfectly shifting across the Alps during the day today, bringing 10-20mm of rainfall across Slovenia. weak forcing and DCVA associated ascent should maintain weakly organized convective line of showers while moving eastwards during the day. With a steepening lapse rates behind the core, uncapped convection will be occuring with mostly showers and isolated storms possible as well. Nothing severe though, a marginal April’s day with showers.

This upper low is nicely visible on the WV satellite imagery…

Check also the visible satellite animation where vort-max centered over central Alps and western Austria slowly shifting NE-wards. A marginal convective line of showers is spreading across Slovenia.

As it can be seen on the long-range maps, it seems that significant warming is finally coming in the coming two weeks. Models are finally changing the April’s pattern and cooler weather as upper lows are filling out while the Azoric high is pushed towards central Europe and Mediterranean. Hopefully something similar as ECMWF model today shows, will happen next week. This would finally mean above normal temps and some much needed warming if we want to have an interesting month of May. Given the Adriatic sea only having near 13°C of sea surface temps, thats almost 2 degrees colder than average!

Now, few days of relatively calm days with NW flow are foreseen, however another trough seem to be crossing our region in the second half of the week. Stay tuned for any future updates.