Storm Forecast

Storm Forecast
Valid: Fri 29 Jan 2016 06:00 to Sat 30 Jan 2016 06:00 UTC
Issued: Thu 28 Jan 2016 23:49
Forecaster: TUSCHY


Quiescent conditions (convective-wise) continue for most parts of Europe, as zonal flow pattern persists.

One exception will be parts of Scotland and areas further north/east. Impressive cyclogenesis will be underway during the start of the forecast period. At mid-levels, compact short-wave turns negative throughout the forecast period while crossing the aforementioned areas. Q-vectors indicate intense/deep lift which accompanies eastbound moving and rapidly deepening surface cyclogenesis (some models bring the pressure down to 950 hPa or less). Main focus for enhanced convection will be eastbound racing cold front, which should cross Scotland and parts of the N-North Sea between 06-12 UTC from W to E. Separation of modest prefrontal boundary layer moisture and steeper mid-level lapse rates behind the front keep confidence in robust CAPE build-up on the low-end side. However, dry intrusion spreads rapidly east and both GFS and EZ show marginal instability along that front. Combined with intense lift, a forced line of convection could accompany that front - also proposed by some numerical outputs. Any deeper updraft could bring 30-35 m/s 850 hPa winds to the surface with a substantial damaging wind gust threat. SRH-1 of up to 250 m^2/s^2 also inidcates a chance for an isolated tornado. The severe risk (induced by enhanced convection) rapidly vanishes from W to E, but intense gradient flow keeps overall damaging wind gust risk elevated until the early afternoon. The risk and cold front spread east but somewhat weaker gradient flow lowers the overall damaging wind gust threat. However, due to ongoing model discrepancies, the level 2 was expanded all the way to the coast of Norway. The southern end of the level 2 was kept north of the mid-level jet core (500 hPa with 65 m/s).

Warm seclusion - well reflected in phase diagrams with good warm core signals - moves in from the NW around noon, but stays further north during the past few runs. This would bring the strongest winds to the Shetland Islands and thereafter to the SW coast of Norway. Near BL flow in excess of 45 m/s and enhanced LL lapse rates/LL CAPE point to a BL wind gust threat of that magnitude. However, this type of event won't be accompanied by DMC and will not be reflected in our warning scheme.

During the overnight hours, very cold mid-levels and 30 m/s near boundary layer flow support enhanced convection with an ongoing severe wind gust risk for areas north of Ireland and N-UK. Shallow nature of somewhat better BL moisture should see a rapid mixing onshore with limited onshore convection expected. A broad level-1 will cover that risk.

... Spain ...

Beneath a SE-ward moving cut-off, a few thunderstorms develop during the forecast. Nothing severe occurs although graupel and gusty winds accompany stronger cells.

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