Alerta de tormentas y fenómenos severos

Se vuelve a animar la cosa por el NE



A level 1 was issued for NE Spain mainly for large hail, strong to isolated severe downbursts and heavy rain. An isolated tornado event is possible

DISCUSSION

A weakening upper-level trough approaches N-Spain during the forecast. Attendant minor surface pressure drop assists in a prolonged period with easterly onshore flow towards N-C Spain. A moist air mass is in place east of NE Spain with BL dewpoints in the lower twenties. As this moisture becomes advected beneath 7-8 K/km mid-level lapse rates, 1000 to 2000 J/kg MLCAPE likely evolve. 10-15 m/s DLS will be enough for organized DMC and similar values are forecast temporarily (afternoon/evening hours) in the lowest 3 and 1 km AGL. Expect a rapid upswing in convection between 12-15 Z mainly along the mountains. During the late afternoon and evening hours, this convection moves also off the mountains towards the lower elevations of NE-Spain. During initiation, expect organized multicells and isolated supercells with large hail and strong to severe wind gusts. Betimes, upscale growth into thunderstorm clusters is forecast with heavy rain, strong wind gusts and large hail. With lowering LCLs and enhanced LL shear, an isolated tornado event can't be ruled out. 10-15 kt storm motion vectors and weak forcing indicate slow moving clusters to the E/SE, but think internal dynamics might bring this cluster all the way to the coast. Therefore we expanded the level area further east.

During the night, both, the S-ward sliding forcing and low CIN also allow further convection to fire over C/S/E Spain. Despite modest shear, CAPE remains quite high (around 1000 J/kg ), so a few overnight severe events (large hail, heavy rain and severe downbursts on an isolated scale) can't be ruled out.

Para los expertos....¿Podriamos considerar lo que hay en el NE un SMC?

Yo creo que lo que había entre las 19:00 y las 23:00 horas si era un SCM típico. Un conjunto compuesto por muchas células convectivas, con unas dimensiones horizontales del orden de 100-300km y con una zona extensa con topes nubosos muy elevados. Con el tiempo desarrolló una gran zona de precipitación moderada constante (reflectividades de 30-36dbz), con células convectivas embebidas que incrementaban localmente la intensidad de precipitación y la actividad eléctrica.


Un saludo. 

Yo no estoy muy seguro de que haya sido un SCM porque creo que para ello ha de ser un sistema organizado y único de tormentas cuyos topes nubosos tengan unas dimensiones menores que las correspondientes al hermano mayor, el CCM, y en este caso lo que había eran varios sistemas multicelulares por separado que formaban un techo nuboso común. Ya digo que no estoy seguro, debería informarme más.

Stofex, aemet y meteociel han cambiado sus predicciones de ayer y alertan de tormentas intensas.

De nuevo posibles tormentas interesantes en la zona NE, ya hay varias provincias en aviso...



Y Estofex, animado por granizo grande

Granizada esta tarde en Benasque. Hacía días que no veia una. Las previsiones se han cumplido.

Hoy a partir de la tarde, en el cortísimo plazo, pueden crecer cumulonimbos potentes más o menos aislados en el sur del Sistema Ibérico, interior de la Comunidad Valenciana, La Manchuela y algunos otros puntos del resto de La Mancha oriental, todo ello acompañado por flujo de levante o sureste apreciablemente húmedo, con altos valores de CAPE y de helicidad, ojo con alguna supercélula de tintes severos aislada, las condiciones parecen muy favorables según los modelos. El choque de masas de aire distintas en superficie llegará a ser puntualmente pronunciado.

Ya de cara a la madrugada, no sería extraño con la configuración sinóptica que se presenta, un festival visual-eléctrico por el Golfo de Valencia sobre el mar y que algunas tormentas se puedan generar más al interior peninsular, pues el flujo de levantes profundiza bastante y la inestabilidad tiende a asentarse, según lo que parece intuirse. Ya veremos qué pasa finalmente.

ESTOFEX dice esto para hoy, válido desde las 06 h. de hoy 25 hasta las 06 h. de mañana 26:

...eastern Spain...

A chance of large hail exists due to moderate deep layer shear combined with CAPE and triggering by higher terrain. SREH ranges around 150 m²/s² allowing supercell mode (although there may just be 1 storm). Cap will initially be strong. During the evening and night it weakens over sea, activating convection while effective shear will still be 20 m/s. It is doubtful that updrafts with such low LCL (500-1000m at night) are effective producing hail, though.

 

ESTOFEX dice esto para mañana:

...eastern Spain...

A chance of large hail exists due to moderate deep layer shear combined with CAPE and triggering by higher terrain. SREH ranges around 150 m²/s² allowing supercell mode (although there may just be 1 storm). Cap will initially be strong. During the evening and night it weakens over sea, activating convection while effective shear will still be 20 m/s. It is doubtful that updrafts with such low LCL (500-1000m at night) are effective producing hail, though.

 

Es para hoy Evein

DISCUSSION

...E-Spain towards the Balearic Islands, Sardinia, Italy and parts of the Adriatic Sea ...

With the synoptic feature showing marginal to no net-motion through the forecast, numerous weak impulses dictate DMC chances during the forecast, as they eject out of the base of this main upper low. The strongest wave will leave NE Spain during the morning hours to the NE. It should affect NE Italy during the first part of the night, before weakening while moving into a meso-beta ridge to its east. Also, numerous impulses, which are embedded along the far N-fringe of the subtropical jet cross Algeria/Tunisia to the NE during the forecast. Hence, CI will be likely over a broad area, but different in regional coverage and intensity.

South of and along the quasi-stationary front, which runs from the Balearic Islands to S-Sardinia to C-Italy, thermodynamics will be good, given a very moist marine BL (dewpoints in the mid twenties) and steep mid-level lapse rates on the order of 7 to 8 K/km atop. TPW anomalies run between 100 to 150% with readings between 30-40 mm, so this moisture is also well shared in the lower to mid-troposphere. 1000 to 2000 J/kg MLCAPE is forecast along and south of that boundary. The Tyrrhenian Sea could see even higher values during the night, when BL moisture continues to increase/pool along the stationary front.

A brisk W/SW-erly flow keeps shear profiles high with 0-6 km bulk shear up to 25 m/s and 15 to 20 m/s shear in the lowest 3 km AGL. While shear gradually weakens over the Balearic Islands during the night, it even increases slightly over the Tyrrhenian Sea and adjacent areas.

Thunderstorms will already go on over the Balearic Islands and the coastal areas of E-Spain with the influence of the departing short-wave and weak capping. Soon, thunderstorms also initiate over SE to NE Spain with only some additional heating needed. This activity will continue well into the night ... probably all night long. Well organized multicells and supercells with large to very large hail, severe wind gusts and excessive rain are forecast. A concern is that 15 kt easterly winds over the Balearic Islands could offset 15-20 kt NW-erly storm motions with a long-lasting and repeatedly regenerating thunderstorm cluster sitting between València, Barcelona and the Balearic Islands. PWs in excess of 40 mm indicate an enhanced risk of damaging flash flooding both along the E-coast of Spain but also over the Islands. Other than that, an isolated tornado event is possible with mature supercells along the coast, where sea-breeze interaction and enhanced LL CAPE increase a spin-up.

From Sardinia to the east, CI probably awaits the mid-level impulse at 18 Z onwards. Isolated to scattered CI is forecast although models differ regarding strength of cap and the path of further and weaker impulses. Hence a broad level 1 area was issued with the lack of confidence in any CI bullseye precluding a level 2 for now. Shear and CAPE both support severe multicell/supercell events with all facets of severe. An update and upgrade might be needed if models have converged a bit regarding magnitude and placement of CI. The same applies to N-Algeria/Tunisia.

Pregunto para los expertos, lo que está afectando ahora mismo a las Baleares es un SCM?? igual meto la pata que no domino la materia