27-07-2013 KNMI waarschuwt voor zware windstoten
Het KNMI verwacht vandaag zware regen en onweersbuien. Voor een groot deel van Nederland geldt code geel maar voor het zuidelijke deel code oranje. Het zijn plaatselijke buien dus grote verschillen van plaats tot plaats
Estofex meldt onder andere het volgende
Synopsis...
Between a deep trough over the Altantic and a ridge over central Europe, a strong southwesterly flow is present over western parts of the continent. A shortwave trough over the Bay of Biscay should move northeastward during the forecast period.
An area with steep mid-level lapse rates has advected northward off the Spanish Plateau across much of France and Germany. To the west and north of this warm air mass, convergence is located in a frontal zone with high low level moisture.
During the day, a beginning wave in this front will become more pronounced in response to the approaching trough. An associated low-pressure area is expected to move northward ahead of this system across France, reaching southeastern England during the evening.
Discussion...
...North and Northwest France, Benelux, northwest Germany...
Widespread elevated convection is expected to be ongoing across northwestern France and the Benelux during the morning, the remnants of overnight convective activity.
In response to pressure falls, surface winds are expected to retain an easterly component north of a boundary seperating humid air to its northwest and dry, hot air to its southeast. This boundary is visible in several NWP models and because of its temperature and moisture gradient may be interpreted either as a warm front or as a dry line.
Strong 20-25 m/s deep-layer (0-6 km) shear is forecast north of this boundary where high amounts of storm-relative helicity are forecast of 200-300 m2/s2, suggesting a high threat that any initiating storms in that environment will quickly acquire rotation and become supercells. With dew point temperatures of 20-22 C forecast, and steep lapse rates present, sizable CAPE of about 2000 J/kg should be available.
It seems likely that a number of supercell storms will form near the boundary during the afternoon and evening. Any supercell storm will be able of producing large hail and damaging wind gusts. In addition, strong low level (0-1 km wind shear) indicates that a risk of tornadoes will exist, some of which may be significant tornadoes (F2 or stronger).
The storms will likely cluster overtime and may well evolve into a bowing systems producing swaths of damaging winds.
Bron KNMI en ESTOFEX