Forecast type:

- convective outlook

Dynamic and Thermodynamic analyse:      

... SYNOPSIS ... 

After a trough merging with a downstream wave, a compact, deep, long-wave Rossby wave resides across Europe. It is filled with a cold air at the surface surging from NW with a secondary inner vortex shifting from NNW across the E North Sea into Denmark Tuesday midday. Multiple wave packets pivoting the main trough while the strongest one is drifting downstream around a ridge over the British Isles toward France and it is inducing a momentum advection around a SW periphery of the cold-core disturbance over Denmark. Further IPV elongation and isolation, from the original source region across the Norwegian Sea, continues to closing the isohypses of the aforementioned cold-core vortex which becomes stationary across Denmark for a next couple of days. Two prominent shortwaves are pivoting the longwave trough, one is moving SE across France and the second one, associated with strong dynamics, is moving through the Balkans with an attendant 30m/s mid-level jet-streak. This structure weakens rapidly as the atmosphere quickly adjust to the progressively weakening mid-level horizontal density gradient. 

Ridging remains in place across Anatolia and SW Europe/N Africa while the healthy Levant wind contributes to moisture pooling across the Alboran Sea and Gibraltar vicinity. This LL airmass remains mostly capped due to ample ridging and subtropical airmass present in the boundary layer which cant be heated and destabilized atop the sea surface without an additional ML CAA.

Anyways, a few storms can erupt along the Sierra Nevada in S Spain thank to very strong diurnal heating and a sea breeze front penetrating inland toward the mountain range. If a strong updraft will manage to overcome the capping inversion and mid-level dry entrainment from NW one or two strong downbursts will be possible given an inverted-V profiles.

At the surface, a baroclinic zone follows an eastern flank of the large-scale wave over Europe. It is stretched from Scandinavia into the Baltics and throughout Belarus into Ukraine arcing into the Black Sea and the S Balkans. The zone is expected to shift ENE and become better structured across the Baltics while dissolving across SE Europe. Multiple low-level vortices will undulate this baroclinic boundary and be source for CI during Wednesday. 

... DISCUSSION ...

.. Italy, Denmark, central-W Europe, Corse .. 

A coherent low-level lee troughing behind the Alps will maintain the convergent nature of the surface winds across N Italy and the Ligurian Sea.  A few meso-beta waves/vortices slides SE from the Gulf of Lion partially enhanced by the Mistral wind providing a shear deformation zone SW of Corse. They can partially induce/contribute to moisture pooling within the Ligurian Sea. As the mid-level cold-core shortwave trough overspreads NW Italy Wednesday forenoon increased LL convergence coupled with strong daytime heating allows for a few pockets of MLCAPE in excess of a few hundreds of J/kg. Strongest destabilization (900-1000J/kg MLCAPE) will occur around the sloped terrain and the Po Valley as the sea-breeze and converging winds maximizes. Ample moist profiles across NW Italy combined with missing shear in low-levels and 10-15m/s deep-layer shear (which is situated mostly in mid/upper levels) ensures that the mean wind will be lowish with its vector field oriented SEward. Thus, thunderstorms initiated within this area especially along the Apennine Mountains will have the best chances for cell training over the same location. Isolated flooding perhaps somwehere in the Gulf of Genova costline will be possible. 

More outflow/wind-driven convection is forecast across NE Italy during afternoon hours with a few initial supercells initiated over the Dolomites where shear will be modulated by the orography. Isolated large hail and a few downbursts will be possible within this activity. A few storm clusters will then probably move S into lowlands as the day progresses with an associated wind gust risk. 

A few storms are also possible initiated atop the sloped terrain of Corse. Given a somewhat higher altitude of the area the chances to experience a hailstorm there will be much higher. One or two stronger downdrafts with larger hailstones are possible given copious shear within the hail growth zone despite the surface parcels will not be much buoyant. 

Across central Europe, NE France and Denmark a few stronger low-topped cells beneath the cold-core low are expected to form encouraged by ample surface isolation and local LL convergence boundaries. Steep mid-level lapse rates and higher 0-3km CAPE values will be favorable for vorticity stretching ingested into updrafts. Thus a few landspout tornadoes and funnel clouds within the stronger cells will be possible developed along the surface boundaries. The same in Denmark where a strong stationary cyclonic vorticity field will be present. One or two cold-core tornadoes will be possible within the stronger activity given the well-mixed BL airmass, 60+J/kg 3CAPE and low LCL´s (SE Germany, Czech Republic, W Denmark). 

.. The Baltics, Finland, Ukraine ..

A few small-scale surface cyclones are expected to slide the baroclinic boundary NW through Belarus and the Baltics as diffuse upper-level potential vorticity anomalies couple with the diabatic surface disturbances enhancing LL cyclogenesis through towering of the anomalies. The strongest disturbance is forecast to emerge from Ukraine Tuesday evening and move into Lihuania Wednesday midday. This process linked to the UL anomalies and the surface boundary generates an elongated pressure channel from E Ukraine through Belarus into the main vortex over the S Scandinavian Peninsula and Denmark. Numerous showers and thunderstorms are forecast to develop within this channel and maximized along the disturbance over the Baltics.

Moisture pooling along the boundary especially along the Gulf of Riga and S-CNTRL Ukraine combined with sufficient heating will boost MLCAPE up to 1200J/kg. Plentiful effective bulk shear and very steep low/mid-level lapse rates in Latvia with strong LL instability will be very favorable for a few tornadoes within isolated supercells as the surface winds back around the N sector of the surface low. Large hail and strong wind gusts will also be possible within this activity. A few water-loaded downbursts will also be possible. Given parallel oriented vectors of the bulk-wind difference toward the boundary, storms will be probably clustery and embedded within a large precipitation field.

A couple of strong storms are also forecast within N-CNTRL Ukraine as the upper-level shortwave trough swings throughout the region NE and the surface convergence strengthens (LL cyclogenesis) in response to the passage of a left-exit region of a 35m/s upper-level jet-streak together with strong destabilization. 1300J/kg MLCAPE overlapped by 17m/s DLS will be enough for a few supercells capable of large hail and downbursts. Further clustering is expected given somewhat weaker shear and stronger outflows of the storms. The main risk will then be heavy rain and strong wind gusts.