Wave Depression Watch 16th/17th November - Low Risk of Intense Storm

Storm Forecast
Valid: Tue 16 Nov 2010 06:00 to Wed 17 Nov 2010 06:00 UTC
Issued: Mon 15 Nov 2010 19:58
Forecaster: KOROSEC


A level 1 was issued for Ireland and areas towards extreme NW Iberia mainly for strong/severe wind gusts and brief tornadoes.

A level 1 was issued for much of central Mediterranean mainly for strong winds, excessive convective rainfall as well as a couple of waterspouts.

SYNOPSIS

A well defined upper cut-off low over northern Mediterranean slowly makes its SE-ward progress. Associated with this upper low, a frontal system will be the focus for convective activity along the surface cold front across Italy and surrounding areas.

Another feature of interest will be rapidly deepening surface low beneath the robust slowly negative tilting upper trough west of UK. Strong surface cyclone moves towards NE just west/near Ireland during the forecast period.

Upper ridging builds up over North and East Europe and western Russia.

DISCUSSION

... Ireland ...

During the morning hours, rapid cyclogenesis takes place just west of Ireland and moves towards NE during the day. A strong cold front extends from its center towards SW and will be moving east towards UK, France and NW Iberia. With rather strong WAA ahead of the front and coming steep lapse rates aloft, some destabilization and convective cells/line is likely to occur along the surface frontal convergence. Mostly, strong to severe wind gusts will be the primary threat. Closer to the low, better veering profiles suggest enhanced SR helicity which could bring some organized rotating convective cells as well. A couple of funnel clouds or brief tornadoes cannot be excluded there either. Behind the front, strong CAA moves towards the continent with numerous shallow convective cells.

... central Mediterranean ...

Beneath the rather well organized upper low, surface cold front moves across Italy during the forecast period. Well mixed BL airmass ahead of it suggest that at least marginal instability will be available and some hundreds of MLCAPE should release. At mid-levels, moderately strong jet wraps around the vort-max with 20-25 m/s of deep-layer shear, which will be favorable enough for locally organized storms. Current thinking is that organized convection will be more likely over open seas and affect coastal areas with some strong winds and intense rain. Excessive (partly convective) rainfall is also expected around northern Adriatic sea where again a rather high precipitation sums are suggested by the models.

In the wake of the core, cold air advection will overspread the Tyrrhenian sea and where quite high LL buoyancy enhances threat for a couple of waterspouts, as wind field will be rather weak.