Storm Forecast
Valid: Mon 09 May 2011 06:00 to Tue 10 May 2011 06:00 UTC
Issued: Mon 09 May 2011 08:12
Forecaster: DAHL

A level 1 threat has been issued across a narrow strip from N
France into the Benelux countries mainly for marginally severe
hail/wind as well as for excessive convective rainfall.

... SYNOPSIS ...

Omega-type upper pattern exists over Europe with a deep
eastern-Atlantic trough over the British Isles that will make
slow eastward progress. East of this feature, an upper
ridge stretches across the central portions of Europe into
Scandinavia. An upper low is present over the Balkans/SE
Europe, which will drop southwestward into the Tyrrhenian/
Ionian regions.

... DISCUSSION ...

... France into Benelux ...

Scattered mainly diurnally-driven storms should develop from
the Iberian Peninsula across France into the Benelux countries.
There will be some 15 - 20 m/s DLS in the very northwestern
part of the area where storms are expected, suggesting that an
isolated severe hail/wind event cannot be excluded. Especially
over the Benelux, local excessive rainfall cannot be ruled out.
GFS suggests that the best chances for severe weather will
exist over extreme NW Netherlands into the NW portions of
central France.

... south-central Mediterranean ...

CAPE should increase SE of the Mediterranean upper low,
with the bulk of the region with instability being unsheared, and
shear of 15 - 20 m/s existing only at the southern fringes of this
region. Scattered storms should form and increase in coverage
throughout the period, with a slight chance of marginally severe
winds and hail. Marginal LLS will also be in place, suggesting
that non-zero but rather low probabilities exist also for a brief
tornado or two. However, the overall setup is too weak to
warrant a LVL1 threat area.

... British Isles ...

Diurnally-enhanced cellular polar-air convection should develop over the British Isles. It looks like LLS will increase in the early evening hours ... and although DLS should remain quite weak, a brief funnel or two cannot be discounted. However the loss of daytime heating should limit the duration of the severe threat. A LVL1 does not seem to be warranted.