Kans op orkaan boven Middellandse Zee bij Griekenland

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Kans op orkaan boven Middellandse Zee

AMSTERDAM - Ten zuiden van Italië kan komende dagen een heuse orkaan ontstaan. Daarbij is kans op extreem zware windstoten en honderden millimeters regen. Waar de storm precies heen trekt is nog onzeker.

Dat meldt Weeronline. Sommige berekeningen laten de orkaan vol over Griekenland trekken, terwijl in andere weermodellen Sicilië de volle laag krijgt. Er is ook een mogelijkheid dat het helemaal niet tot orkaankracht komt en ‘slechts’ bij zware onweersbuien blijft.

Op dit moment zijn tussen Italië, Griekenland en Libië hevige onweersbuien actief. Volgens de huidige verwachting klonteren deze buien donderdag net voor de Libische kust samen tot een tropische depressie. Vrijdag of zaterdag kan dit systeem uitgroeien tot een orkaan. In het meest extreme scenario komen daarbij windstoten van ruim 200 km/uur voor.

Dit zou overeenkomen met een orkaan van de 2de categorie, op een schaal van 5. Niet alleen de wind kan fel uithalen, ook is kans op veel regen. Lokaal kan in een dag tijd 400 mm vallen. Dat komt overeen met een halve Nederlandse jaarsom.

Medicane
Een orkaan in de Middellandse Zee wordt een ‘medicane’ genoemd. Dit is een samenvoeging van de Engelse term voor orkaan, ‘hurricane’ en ‘mediterranean’, de Middellandse Zee.

Het ‘orkaanseizoen’ boven de Middellandse Zee loopt van september tot en met januari. Op dat moment is het zeewater het warmst. Wanneer koude lucht vanuit het verre noorden over het warme zeewater stroomt ontstaan zware onweersbuien.

twitter:

meteophile twitterde op donderdag 27-09-2018 om 09:16:21 Image satellite #meteo prévue.Un anti-cyclone protecteur sur l'ouest de l'Europe. Creusement en cours d'une dépression au large de la Libye qui pourrait évoluer en #Medicane (Petit #Cyclone) vendredi puis se décaler vers la #Crête et la #Turquie.https://t.co/OppyQMD2sp https://t.co/VAUqzr0WAA reageer retweet

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Op donderdag 27 september 2018 13:59 schreef Infection het volgende:
Is iets vergelijkbaars eerder voorgekomen? Kan het me niet herinneren eigenlijk...

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Extended Forecast
Valid: Fri 28 Sep 2018 06:00 to Sat 29 Sep 2018 06:00 UTC
Issued: Wed 26 Sep 2018 20:13
Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

Thise extended forecast was issued mainly due to the risk of a potential (shallow) warm-core cyclone south of and over the S-Ionian Sea.

On Friday morning, an extensive cut-off will be centered over the Ionian Sea and further south. During the day a gradual turn to the NE is anticipated as this cut-off is forecast to get caught up by another strong upper trough over NE Europe, which approaches SE Europe during the night.

Despite this general agreement regarding the synoptic evolution, global models like IFS, GFS and ICON continue to diverge substantially regarding the exact structure of the deep vortex over the S-Ionian Sea which will be crucial regarding the track forecast of the intensifying LL vortex. ICON breaks the vortex into numerous smaller-scale mid/upper vortices, GFS shows a broadening upper vortex lifting NE towards Greece and IFS expecting an intense/deep vortex E of Sicily with a new upper vortex evolving to its NE (over Greece). Combined with different handling on the intensity of the LL vortex it is not of surprise to see an ongoing substantial model spread regarding the cyclone's track: IFS steering the LL vortex towards Sicily, whereas GFS and ICON indicating a drift to the N and NE (towards Greece), which is in line with the general lifting trend of the upper vortex (all track forecasts until Saturday 06 UTC only).

Latest WV data highlights a significant tropopause fault with the intrusion of very dry mid/upper air along the W/NW fringe of the cut-off (sampled well by Brindisi, 26th September at 12 UTC). Until Friday this dry air and attendant upper level jet maximum are forecast to circle the deep vortex and both will push NE towards Crete and the Aegean Sea, cutting off a pool of warm/moist and unstable air to the west (beneath the mid/upper vortex). SBCAPE will be in the 500-1000 J/kg range and supportive for vigorous convective activity. However, upper divergence starts to weaken over the S-Ionian Sea as the upper jet pushes NE and away from the main vortex. With decreasing baroclinicity and shear, the main driver of the LL vortex strength becomes the convection, which starts to organize during the forecast period (here organized convection means convective banding and not rotating updrafts!). Abating divergence could be a crucial point regarding a slow-down of convective activity and attendant organization into convective bands.

Latest phase diagrams remain somehow reluctant regarding the speed of the transformation of the thermal structure, but still indicate a shallow warm-core structure (excluding IFS, which continues to advertise a deeper warm-core anomaly). Uncertainties regarding the intensifiaction rate and strength of the LL vortex depend on:

- the potential of better upper-level ventilation to the NE into the upper jet which also depends on the final structure of the upper level vortex

- how broad the LL vortex will be with a smaller vortex susceptible to more rapid intensity changes (up and down)

The first point is not yet supported by all global models due to the different geometry of the geopotential height fields. The second point seems to be crucial as ICON and GFS prefer a broader LL circulation which would need more time for intensification, whereas IFS already starts the forecast with a compact vortex which could intensify much faster. ASCAT data will give more and helpful input into that topic as the vortex forms but for now we lean more towards ICON/GFS (slower intensification rate) given the large nature of the upper vortex and the persistent forecasts of both models during the past few days regarding the size of the LL vortex (plus abating divergence).

Otherwise the background environment remains favorable with SSTs of 26-28C (above climatology), weak DLS next to the evolving LL vortex and deep moist profiles with elongated thin CAPE profiles.

Mentioned uncertainties preclude confined areas with higher probabilities for now but the main risk will be excessive rain, severe wind gusts (mainly driven by the ageostrophic response to the deepening depression) and isolated tornadoes. Further model data will be evaluated to determine certain areas with an higher severe risk, especially if a potential landfall becomes clearer.

Aside from that cyclone two more areas with organized convection exist over:

Crete and the Aegean Sea:
A northward surging upper jet and PVA ahead of the upper trough create supportive conditions for lift over a broad area. Low-tropospheric moisture increases from the south with MLCAPE aoa 1kJ/kg affecting the highlighted area. Straight and elongated hodographs indiacte a risk of organized and splitting multicells/supercells with DLS in excess of 20 m/s and enhanced SRH-3. A broad level 1 was issued for this area due to ongoing uncertainties (e.g. where DMC could be suppressed by the deep dry slot).

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Mesoscale Discussion
Valid: Thu 27 Sep 2018 21:00 to Fri 28 Sep 2018 09:00 UTC
Issued: Thu 27 Sep 2018 20:35
Forecaster: ESTOFEX

This is the first of a series of Mesoscale Discussions issued for a cyclone that is primarily driven by convection. They will be issued twice daily before 9, and 21 UTC until the cyclone dissipates or becomes extratropical. This Mesocale Discussion is not an official product and does not substitute any warnings from National Meteorological Services. We welcome any feedback at inflow@estofex.org.

System: 2018M02
At 27 SEP 18 UTC the centre was located near 32.8N and 18.7E
Estimated minimum pressure: 1004 mb.
Maximum sustained winds: 20 m/s (40 kt, 70 km/h).
Maximum gusts: 25 m/s (50 kt, 90 km/h).

ANALYSIS

A closed low-level circulation has formed near 32.8N and 18.7E, as predicted by most of the global model guidance. The system bears subtropical characteristics as the low-level circulation is exposed and convection is occurring in a band NW and one located 5-8 degrees east of the low-level centre. Furthermore, strong baroclinity is present associated with a southwesterly mid-/upper-level jet to the SW of the centre. The minimum pressure is estimated from a combination of the higher resolution models and the Hebert-Poteat method yielding an ST number between 2.5 and 3.0. The maximum winds occur in the northern hemicircle and are estimated to be near 20 m/s (40 kts) gusting to 25 m/s (50 kts).

FORECAST

Models predict a north-northwestward motion during the first 12 hours and later slow the cyclone down over the Central Ionean sea. After 24 hours an eastward motion should commence that bring it near the Peloponnese Saturday evening. Model consensus slows down the cyclone a bit as it moves over or just south of Peloponnese, producing very heavy rainfall there. After 48 hours, ECMWF accelerates the cyclone ENEwards towards Turkey, whereas ICON and GFS predict slower motion. The track forecast is a consensus of these models.

The intensity of the cyclone is modelled quite differently by various models during previous days. UKMO deepends the cyclone to below 985 before landfall in the Peloponnese while ECMWF, ARPEGE and ICON are less intense. GFS forecasts reintensification after 48 hours over the Aegean, and other models keep the intensity steady, except for ECWMF that weakens it as it accelerates it east-northeastward. The ultimate intensity after 48 hours will depend strongly on the amount of interaction with the mountains of the Peloponnese. The intensity forecast is a blend of the models.

Impacts from strong storm force winds are expected when the cyclone makes landfall on the Peloponnese. Rainfall, however is the biggest threat. Amounts of 200-300 mm can be expected on Saturday and Sunday across the Peloponnese, 125-250 mm over Attica, Eastern Central Greece and the Cyclades, and 50-125 mm over southern Crete. Given that enhanced low-level shear, a few tornadoes may occur over the Greek mainland and the Cyclades on Saturday and Sunday. After Sunday, hazards related to the storm, especially extreme precipitation, could affect western Turkey.

Forecast:
FH DATE & TIME LOCATION PRESS WIND GUSTS
00 27 SEP 1800 UTC 33.0N 18.7E 1003 mb 20 m/s 25 m/s
12 28 SEP 0600 UTC 34.8N 18.2E 996 mb 25 m/s 30 m/s
24 28 SEP 1800 UTC 35.3N 18.5E 994 mb 25 m/s 30 m/s
36 29 SEP 0600 UTC 36.2N 20.8E 992 mb 30 m/s 40 m/s
48 29 SEP 1800 UTC 37.1N 23.2E 996 mb 25 m/s 30 m/s
60 30 SEP 0600 UTC 37.5N 25.2E 997 mb 25 m/s 30 m/s
72 30 SEP 1800 UTC 38.0N 26.0E 999 mb 25 m/s 30 m/s

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Op vrijdag 28 september 2018 10:16 schreef Dven het volgende:

[..]

Arpege laat hem nu via de Egeïsche zee over de Dardanellen Strandzha (Bulgarije/Turkije) overtrekken

[ afbeelding ]

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Schade en overlast door 'Zorbas' op Griekenland

Het lijkt erop dat de gevolgen van de subtropische storm Zorbas, die vanmiddag aan land kwam in Griekenland, meevallen. De afgelopen dagen leek het erop dat Zorbas zou uitgroeien tot een 'medicane', een orkaan in het Middellandse Zeegebied, maar dat is niet gebeurd. De storm verloor eenmaal boven land snel aan kracht. Wel is er veel overlast.

Sommige delen van het land zitten zonder stroom en de brandweer moest tientallen mensen uit hun huis halen omdat ze door het water niet meer uit hun woning konden komen.

Ook het verkeer heeft veel last van overstromingen. Sommige automobilisten kwamen vast te zitten in hun auto's en moesten worden bevrijd. Rederijen hebben hun schepen in de havens aan de ketting gelegd.

Modderstromen
Vooral op het zuidelijke schiereiland Peloponnesos zijn de gevolgen van Zorbas goed te merken. Op beelden op sociale media en op de Griekse tv is te zien dat straten door de enorme hoeveelheid regen blank staan. Er zijn windstoten gemeld van zo'n 100 kilometer per uur.

Volgens de gouverneur van het schiereiland hebben huizen, de landbouw en infrastructuur schade opgelopen. Hij heeft voor delen van het schiereiland de noodtoestand uitgeroepen en de Griekse hulpdiensten hebben bewoners opgeroepen waakzaam te zijn. Het lijkt erop dat het vliegverkeer weinig hinder heeft van de storm.

Zorbas trekt vannacht langzaam richting Turkije. Mogelijk worden ook de eilanden Lesbos en Chios getroffen. De gouverneur van die regio heeft plannen klaarliggen om de duizenden migranten die in tentenkampen op die eiland zitten te verhuizen, maar waarheen precies is niet bekend.