Storm Forecast
Valid: Fri 03 Oct 2025 06:00 to Sat 04 Oct 2025 06:00 UTC
Issued: Thu 02 Oct 2025 10:57
Forecaster: TUSCHY

A level 2 was issued for E/SE Bulgaria mainly for excessive rain.

A level 1 surrounds that level 2 for similar hazards with lowered probabilities. In addition we expect some hail, gusts and an isolated tornado along the coasts.

A level 1 for heavy rain and an isolated tornado was issued for SW Turkey.

SYNOPSIS

Explosive cyclogenesis occurs over NW Europe (named AMY) which emerges from the favorable phasing of residual tropical moisture and a LL positive PV anomaly/diabatic rossby wave of sheared HUMBERTO with a strong/dynamic upper trough. MSLP drops to roughly 950 hPa or less (well clustered in IFS-ENS) and a potent cold jet/sting jet event unlashes hurricane-forced gusts over parts of NW Europe. In addition, a NE-ward pushing dry slot creates a broadening split front event, which could be accompanied by spotty thunderstorm activity.

An extensive upper low over E/SE Europe splits apart with the northern part lifting N into Scandinavia, whereas the southern part brings unsettled conditions to SE Europe. Ridging over SW Europe brings quiet conditions to the Iberian Pensinsula.

DISCUSSION

... NW Europe ...

Severe storm AMY won't be too thundery but could offer two areas with spotty CI.

Sea area W of SW Norway:
One is highlighted with a low-prob. lightning area offshore of SW Norway. All day long intense S-erly winds with hurricane-force gusts seem to peak in strength during the overnight hours during the passage of a split-front. The pressure gradient maxes out between AMY and the orography of SW Norway during that time and offers an extreme background flow event. A vertically stretching mixed low-tropospheric layer may locally approach -10C and an increase of convection along the front is forecast during the night with isolated thunderstorms possible. During that time, BL flow offers gusts well in excess of 150 km/h, so we're not sure about how much rather iffy downdrafts could increase gust magnitude. However onshore moving and then weakening convection could bring extreme gusts to otherwise more sheltered places along coastal areas of SW Norway. Due to the forecast spotty nature of convection no level area was added.

Scotland, N-Ireland into N-England:
Another area of interest will be the periphery of the descending CI/potential sting jet in the SW/S quadrant of AMY. As the surface part of the split flow pushes beneath the dry slot, we could see some LLCAPE for non-electrified activity over Scotland. This activity (late afternoon/evening) probably marks the start of the most extreme onshore gusts, which transitions into the main CJ/SJ event thereafter with gusts in excess of 120 km/h (onshore) and 150 km/h (offshore). This convective uptick during the afternoon could also bring this gust magnitude into far N England.
During the overnight hours, spotty CI is not ruled out over far N Ireland into S Scotland/N England in case we see some regional enhanced BL moisture influx beneath dry slotted airmass. Overall uncertain increase of the already strong to extreme BL flow event with embedded convection and low-end CI probabilities preclude the issuance of any level areas for now. A low-confident lightning area was added however.

Please keep in mind that we just cover the convective input to such an event, which seems to be limited right now. However, this is a serious wind threat for a broad area, so stay informed with your local NMS.

... SE Europe ...

A pronounced upper trough affects SE Europe while drifting towards Bulgaria. It steers a moist airmass into Bulgaria/Romania, where heavy rain/mountain snow is forecast.
Convective-wise the main issue could be training/slow moving convection within the level 2/1 areas of Bulgaria/Romania. NWP guidance indicates a pronounced inflow of 500-1000 J/kg MUCAPE, steered by intense SR flow in the lowest 2 km AGL. Forecast hodographs show strong curvature so expect robust mass flux into surface based coastal convection, which turns elevated more inland. Heavy rain is likely and a few extreme rainfall events along the coasts are possible. Flash flooding cannot be ruled out, especially given some of those places saw very heavy rainfall amounts during the previous night, which could push 36h rainfall amounts in the 200-350 mm range! One or two serious/damaging flash flood events are possible and that's why a level 2 upgrade was performed. In addition, N-ward sliding V-shaped clusters could bring a tornado event or two with some gusts and hail.

Elsewhere, a few waterspouts along the Aegean Sea/Ionian Sea are forecast next to isolated heavy rain over SW Greece. This is not enough for an upgrade right now but a level 1 upgrade as performed over far SW Turkey mainly for heavy to locally excessive rain and a coastal tornado threat.