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Mediterranean storm kills at least 14 in Greece

A slow-moving storm in the Mediterranean Sea will bring additional rounds of rain to Greece into this weekend. Downpours since Tuesday have already caused deadly flooding and mudslides. The outskirts of Athens have already been hit hard with at least 14 people killed so far, according to the Associated Press.

That number may rise as flooding continues across the region, and additional bouts of heavy rain are forecast in the coming days.

The flooding swamped homes and businesses while also washing out a section of major highway near Athens. The same storm system also produced devastating flooding on the Greek island of Symi earlier this week, which forced a state of emergency to be issued to the popular tourist location. Conditions are not expected to improve across Greece in the coming days as the slow-moving storm over the Mediterranean Sea continues to unleash daily downpours.

The threat for downpours over the same areas that have already been impacted by flooding will result in a high risk for additional flooding and mudslides while also heightening the likelihood for travel disruption. Areas from Thessaloniki south and west will be at highest risk for daily downpours and flooding problems.

Rainfall over these areas will average 50-100 mm (2-4 inches) through Saturday; however, local amounts may exceed 200 mm (8 inches).
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Conditions will begin to improve on Sunday as the storm tracks into western Turkey.
There will be isolated downpours across eastern Greece, but conditions will improve throughout western Greece where the greatest rainfall is expected in the coming days.
A separate storm will threaten Greece with additional rainfall late Sunday into Monday, which could result in some localized flooding.

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Storm Numa May Become a Rare 'Medicane' in the Mediterranean Sea Late This Week

A rare system resembling a tropical storm, known as a "medicane," may develop in the Mediterranean late this week and bring rain and gusty winds to Greece.

An area of low pressure, named Numa by the Free University of Berlin, is currently in the Mediterranean Sea west of Italy and will track south of Italy into Thursday while strengthening. Moisture associated with this system has already brought heavy rainfall and deadly flooding to portions of Greece.

More rainfall is expected in the region through Saturday as this developing area of low pressure is expected to move eastward toward Greece.

During this time, thunderstorm activity will increase, in part due to the contrast of the colder air accompanying the upper-level trough associated with this system and the warmer temperatures to the south. This will result in an increase in instability in the area, aiding further development of this system.

In addition, fairly low wind shear, the changing of wind speed and direction with height, may be in place in the region.

These ingredients may come together and result in the formation of a subtropical cyclone, or possibly a tropical cyclone if the atmosphere warms enough for this system to have a warm core.

These systems resembling tropical cyclones in the Mediterranean Sea have been dubbed medicanes.

In the meteorological community, there is some debate whether past vigorous low-pressure centers over the Mediterranean Sea were truly tropical cyclones, or a combination of a tropical and more typical mid-latitude low-pressure center, known as a subtropical cyclone.

A subtropical storm has characteristics of both tropical and non-tropical systems. This includes a broad wind field and generally low-topped thunderstorms displaced from the center of the system. There also are no cold fronts or warm fronts.

Current indications are that Numa may very well become a warm-core tropical storm, or medicane, Thursday or Friday as it approaches Greece.

Although these storms are rare, fall is a time of year when these type of storms develop.

Unlike in other areas, like the Atlantic and Pacific basins, warm sea-surface temperatures are not necessary for the development of medicanes.

As you can see below, current water temperatures there are below the 26 degrees Celsius (79 degrees Fahrenheit) normally needed to sustain a tropical cyclone in, say, the Atlantic or eastern Pacific basins.

Typically, warmer air temperatures in this region, along with other factors described above, are able to create the necessary conditions for a system to acquire tropical characteristics from time to time.

This Has Happened Before
The area of the Mediterranean Sea is not usually conducive for the development of tropical systems, as it is relatively shallow and there are many land areas that typically hinder tropical development.

However, one such medicane formed just last year on Halloween and was known as Tropical Storm 90M. This storm developed in a similar area over the Ionian Sea, between the west coast of Greece and southern Italy, where potential development will be monitored this week.

Before this low became a tropical storm, it created high surf which resulted in minor damage to the coast of Malta.

Other recent occurrences in November have also been recorded. One such case was in November 2014 when an area of low pressure became tropical-like. This system moved near Malta, where a gust of 95 mph was recorded.

In early November 2011, another area of low pressure transitioned to a subtropical storm, if not a tropical storm. NOAA/NESDIS designated this system 01M, and the Free University of Berlin gave it the name Rolf. This system made landfall in southeastern France.

Up to 2 feet of rain was reported with this system, which resulted in landslides and flooding in portions of France, Spain and Italy and the deaths of 12 people.

twitter:

wxjerdman twitterde op donderdag 16-11-2017 om 11:38:19 Quite a change in Storm #Numa over the past 24 hours. Already taking on a more "subtropical" look SE of #Sicily. Ph… https://t.co/GPNiQvDUk3 reageer retweet

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The cut-off low in Central Mediterranean is gradually weakening and mid-levels are warming due to the ongoing marine DMC. At the surface below, a warm-core vortex has formed just SE from Italy, verified by Suomi NPP/ATMS (ch8) brightness temperature, with high low-level PV values. Models predict that SBCAPE will remain in the range of 600-1200 J/kg over Ionian Sea, and thunderstorms will continue to develop near the center of the system. Even though global NWP models show the SLP dropping near 1010 hPa, LAMs forecast a more vigorous system with a core pressure even below 990 hPa, but it will be extremely difficult to verify the actual values since the vortex will remain away from the coast and surface observations are limited to cargo ships. The latest GFS run shows the system approaching SE Italy in the morning of Friday, where severe convective and non-convective wind gusts will be the main threat (25  30 m/s). Moreover, thunderstorms will be able to produce flash floods near the coast, due to the slow motion and saturated vertical profiles.
Since the strength of this vortex is directly linked to the latent heat release processes associated with DMC and sea-surface fluxes, LAMs suggest very different solutions, even those using the same initial and boundary conditions. So, the final track of the vortex remains unknown, probably approaching Greece in the morning of Saturday, after the end period of this outlook. Nevertheless, wind speeds at the range of 30  50 m/s pose a serious threat for ships and marine infrastructures.

More to the east of the aforementioned cyclone, very humid masses exist over Greece, overlapping with steep lapse rates over the Aegean Sea where local large hail events may verify. SBCAPE in the range of 1000-1600 J/kg and 15-20 m/s DLS create a favorable environment for hail up to 3 cm in diameter. In north parts of Greece, a strong convergence zone is placed for the third consecutive day (already 250-300 mm of rainfall), where we forecast flash floods due to training convection, but with limited lightning activity. During the night of Friday and morning of Saturday, only marine thunderstorms should be found over our domain, in NE Aegean and Ionian Seas.

Finally, waterspouts can form in Ionian and Aegean Seas. In SE Italy, strong vorticity near the coasts as the cyclone approaches, increase the probability of tornadoes. In Aegean Sea, weakening low-level wind field and strong instability also increases the chances for waterspout develoment.

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A level 1 was issued for SE Italy, Greece and W Turkey mainly for large hail, severe wind gusts and excessive precipitation. Waterspouts are expected in Ionian and Aegean Seas.

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16 killed, six missing in devasting Greek floods
Rescue crews were searching Friday for six people missing from deadly flash floods that killed at least 16 near Athens, as new storms hit the Greek capital.

The fire department, which had been searching since Thursday for four missing people, said two more people were reported missing Friday in the district of Mandra, on the western outskirts of Athens.

Wednesday's flash floods, which came after an overnight storm, turned roads into raging torrents of mud that flung cars against buildings, inundated homes and businesses and submerged part of a major highway.

The flooding is one of the worst disasters to have hit the Athens area in decades. More bad weather, with heavy rainfall and storms, lashed the capital Friday, flooding a central road in the Keratsini area west of Athens, cutting off traffic.

The fire department said it had received 910 calls for help in the western areas of the capital since Wednesday morning to pump water from flooded buildings and transport people to safety. It said its crews rescued 96 people trapped in vehicles and homes.

The repeated storms led to another 70 calls for help to the fire department in other areas of the Greek capital and the nearby island of Aegina on Friday, and hundreds more from towns in northern Greece.

twitter:

weermanreinier twitterde op zaterdag 18-11-2017 om 10:16:57 #Medicane #Numa, pracht van een circulatie. Zo zie je ze niet vaak op de Europese kaart. https://t.co/dvmNFXmxeC reageer retweet