A level 2 was issued for E Spain, including the Balearic Islands mainly for excessive rain.
A level 1 surrounds the level 2 for similar hazards but with lower probabilities. Coastal convection could also produce a few tornado events.
SYNOPSIS
A warm/blocking anticyclone over NW Europe with an amplified downstream trough (including embedded stronger low-amplitude impulses) over Scandinavia/E/SE Europe keep the overall thunderstorm risk rather low.
The main focus for DMC activity remains along the S periphery of that anticyclone over the E-Iberian Peninsula/far W Mediterranean. A zonally aligned upper trough interacts with a marine/unstable airmass and results in an active day for thunderstorms over this area.
Some deterministic outputs favor a more focused area of lowered MSLP over the Alboran Sea/Strait of Gibraltar and hence a bit E of the typical benchmark, wereas others like IFS-ENS are more in favor with weak/transient vortices E of Spain. Hence the QPF distribution in this less dynamic pattern, although favorable regarding pattern recoginition, will be more driven on the mesoscale.
DISCUSSION
E Spain, the Balearic Islands and surrounding offshore areas
A more dominant mid/upper vortex resides S of the Balearic Isands (atop the Algerian Basin). A tongue of enhanced mid/upper-level moisture (emenating partially from the W-African ITCZ and from the subtropical NE Atlantic) wraps around this circulation with TPW anomalies in our area of interest approaching locally 200% (blended Hydro PCT Anomaly) or effective TPWs of 30 mm to (probably contaminated) near 40 mm (sampled by latest sounding data).
Along the surface, mass response towards lowering MSLP over the Alboran Sea and surroundings induces a NE-erly flow regime with mixed BL mixing ratios in the 10-12 g/kg range. SSTs in the area still run 2-3K higher than the climatology.
Offshore CAPE increases with a more dominant southerly wind direction from the Atlas Mountains/N Africa. A northward fanning EML atop the mentioned marine airmass assists in offshore CAPE between 1000-2000 J/kg with increasing (but more capped) magnitude towards the N African coast. Latest soundings partially support these numbers.
Placed beneath the broad/weak upper trough with marginal mass response in this weakly dynamic setup cause very weak shear conditions - mostly in the 5 m/s range for DLS/0-3 km shear with even weaker 0-1 km shear. However, shear at lowst 3 km could locally increase in excess to 10 m/s within orographically influenced (coastal) areas.
The main concern for sure will be heavy to excessive rain but the final focus for any peak rainfall maxima remains rather nebulous. Convection, probably ongoing from the previous night, will be in a self-sustaining mode. Weak/moist lower levels preclude disruptive cold pools, so it takes some time and longer-lived thunderstorm activity to induce some cold pool dynamics/cluster motion. Any mesoscale convergence zone, laid out either by ongoing thunderstorms or the orography (e.g. Islands), could become a focus for back-building convection. The warm cloud layer depth remains aoa 3km and forecast synthetic satellite data show a lingering wedge of moist air, framed by more dry slotted air to the N/S. Another uncertainty is, if already ongoing convection can induce a latent driven positive PV anomaly with more focused areas of convergence along its periphery.
The latest idea is to place two foci for excessive rain.
One is along the E coast of Spain, from N Alicante to Castellon/S Tarragona, where embedded convection in the E/NE-erly flow regime moves ashore all day long. Any more focused LL convergence could spark a training cluster with sub 6-hourly rainfall amounts in excess of 100 l/qm and a few significant flash flood events are possible. The stronger any offshore positive PV anomaly evolves, the more to the north any rainfall peak will be displaced. Hence a very N-S elongated level 2 was added, although not all places will see level 2 rainfall conditions.
The second area of interest could evolve near/atop the Balearic Islands. Any clustering convection will be fed from the S with strongly unstable and moist air, while 850 hPa winds in the 15-30 kt range turn more to the E. This could result in S/SE-ward backbuilding and W-ward venting convection. Probabilities for CI near the Islands are enhanced by better coastal convergence, so confidence in excessive rain for parts of the Islands is increasing. Flash flooding (with a few significant events not ruled out) is possible.
Coastal/offhore convection can produce numerous tornado/waterspout events especially near the Islands, where LLCAPE peaks in the 300-400 J/kg range.
Other lightning areas
No severe thunderstorm risk is forecast for the rest of the lightning areas.
However we could see a temporarily increasing risk for a few better organized nocturnal thunderstorms near the Gulf of Alexandretta with isolated strong gusts, heavy rain and a tornado or two. This risk however should stay below a level 1 threshold.
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- Niveau 2 Waarschuwing: Uitgegeven voor Oost-Spanje, inclusief de Balearen, voornamelijk vanwege overmatige regen.
- Niveau 1 Waarschuwing: Omvat het niveau 2 gebied voor vergelijkbare gevaren, maar met lagere waarschijnlijkheden. Kustconvectie kan ook enkele tornado-evenementen opleveren.
SYNTHESE
- Een warm/blokkerend hogedrukgebied over NW Europa houdt samen met een trog boven Scandinavië/E/SE Europa het risico op onweersbuien laag.
- De focus voor DMC-activiteit ligt langs de zuidelijke rand van het hogedrukgebied over het oostelijke Iberisch schiereiland en het westelijke Middellandse Zeegebied.
- Een oost-west georiënteerde boventrog beïnvloedt een maritiem/instabiel luchtmassa en leidt tot een actieve dag voor onweersbuien.
- Verschillende voorspellingsmodellen wijzen op variaties in het gebied met verlaagde MSLP, wat de QPF-verdeling beïnvloedt op mesoschaalniveau.
DISCUSSIE
- Oost-Spanje, de Balearen en omliggende zeegebieden
- Een dominante midden-/bovenluchtvortex bevindt zich ten zuiden van de Balearen en beïnvloedt vochtstromen in de regio.
- Oppervlakte-eigenschappen omvatten een NE-windregime met hoge SST's, wat de CAPE-waarden offshore verhoogt.
- Er is zwakke windschering, maar lokaal kan deze toenemen in kustgebieden.
- Belangrijkste zorg is zware regenval, vooral langs de oostkust van Spanje en mogelijk op de Balearen.
- Convergentiezones kunnen aanleiding geven tot stationaire en terugkerende onweersbuien, met kans op flitsvloeden.
- Kust- en offshore convectie kan talrijke tornado/waterspout-evenementen veroorzaken, vooral nabij de eilanden.
- Andere bliksemgebieden
- Er is geen risico op ernstige onweersbuien in andere gebieden.
- Er kan een tijdelijk verhoogd risico zijn op enkele goed georganiseerde nachtelijke onweersbuien nabij de Golf van Alexandretta.