It was great, but only for 4 hours…

Over Blister – Range, Thursday morning

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It’s one of those marks everywhere that it is difficult to explain to someone who fell asleep before 2 and woke up after 8, while the house is at an altitude below 250 m. But those who lived in this 4-hour period, on the substance, snowball, in the morning on Thursday 29/12, from 3 to 7 roughly, will have to remember some impressive things. He, the snow had the makings of a “great”, if someone think that the intensity of the snowfall was such that it paved as well as 10 points in the central neighbourhoods of Athens with positive temperatures! You will see in the pictures below, that this volume with negative temperatures, it would have been comfortable as a half measure.

It just so happens that it’s snowing with positive temperatures and with such high temperatures in the level of 850 hPa for? For the record, the temperature at 850 hPa, in accordance withthe ραδιοβόληση the Greek at 2 in the morning of 29/12, a little before it starts, the snow that is, was once -5.7!

However, the northwest wind in the lower tropospheric layers and up to the surface, being dry, reduced satisfactorily moisture. It is characteristic that the dew point in the above ραδιοβόληση is -4. This is shown in the μετεώγραμμα.

Source: Wetterzentrale

In such cases, the flake survives until the ground thanks to a phenomenon called evaporative cooling (cooling exhaust). In a nutshell the flakes that fall to a warmer environment, take heat from this and melt. Thus, the environment is gradually cooled. If an environment with positive temperature, has a large amount of water vapor (high rates of humidity), then the flake’t bear to reach the ground, as although it receives heat from the environment (and melts), but the environment is cooled slightly because the water vapor (the water practically) have a high heat capacity, i.e. it takes the exchange of large quantities of heat to fall (or rise) the temperature. This problem is “solved” when there are only a few water vapour (low humidity), so the first flakes “sacrificed” (melt) to cool the environment, but they do it much more easily in the dry case. In this way, it is possible to snow in positive temperatures. Also, the big intensity of phenomena helps with the above phenomenon, in the humiliation of the level of icing on the surface, from ~500 m, which was planned for that night!

Source: weatheronline

For this reason, there is the map of wet bulb zero level, which, essentially, takes into account the phenomenon of evaporative cooling, and indicates to what extent humiliated the freezing level, after the process is complete cooling of the environment by the fusion of the “raw” flake. Here we see that the freezing level for the dawn of Thursday, is 300 m lower, at only 200 m.

Source: weatheronline

If to these you add in the intensity of the phenomena, have an idea of what to expect on a night like that. So it’s not a coincidence that the GFS predicted about five to six, even temporary, in the entire basin:

Source: Meteociel

Pretty, bored you with the technical. Go to the trek of a 4-hour dream, and in the photos! There is one thing that will surely stay in the minds of all καιρόφιλων who experienced this. The χιονοκαταιγίδες and the χιονοποντές (during the “floods”) the accompanying! There have been times where I counted even a volley of 5 consecutive thunder within 1′. And as in a normal storm, then the thunder starts downpour… that was the same here, only instead of drops falling flakes of immense size, and the snowfall was πυκνότατη! The pictures of the Courts of the Cell, typical!

Some of the discharges as recorded by the national WEATHER service and the blitzortung

Some of the discharges as recorded by the Agis Poulkou (screenshots from the footage that he took, moving with the car in Ag. Stefano). The shocks were visible from the entire basin, and the thunder sounded almost everywhere!

Λάμπινγκ in the Courts…

The first χιονοκύματα reach the end and have left a thin layer of the order of 1-2 cm. snow. A huge feat considering that part of the snow that fell, spent in the humiliation of the temperature from +3.5 to +1.5, and this layer survives to positive temperatures.

But we’re not done yet. Come and other χιονοκύματα. However, I decide to take a walk around the neighborhood. In mind that all the photos are from the center of Athens, in the Hive, and in a region from the Courts (alt. ~120 m) as the ring of Τουρκοβουνίων (~200-250 m) where I met, as you will see, beautiful pictures. The roads have caught a minute χιονοστρώμα that most over was particularly dangerous due to the deviation of the road.

In the Upper Hive, the thickness of the στρωμένου snow is 3-5 cm. local

From here on, climbing up to the regional, the road surface was very slippery. Some of the cars had chains, while others were trying out the “luck” without them. The layered snow, then and the second round of snow later, it arrived in places in the 8-10 cm. here. In some shots it is distinguished, and the Acropolis in the background.

The 2nd χιονοκύμα comes and the lights of the basin disappear at the depth. The snow creates beautiful images…

Return to the Courts, while the wind has acquired a north-east component, bringing enough moisture, with the result that there are alternations with sleet now and abused the layered snow rapidly below 200 m.

The Range of snow

The woods over by the Courts

The Sale white…

Even though the snow is being abused by the humidity with a matter rate, even maintained in the Courts. Trolley buses make a temporary finish there, due to the tilt and non-slip surfacing of the pavement above.

In other areas of the basin, the Maria Di from Argyroupolis, recorded a video (snapshot which we see here), with about five to six has arrived in areas close to the sea!

The centre of Athens temporarily white in the morning. Temple of Olympian Zeus, from the user’s SOOC (via Instagram)

Zappeion also white. Source: Greece Meteogroup (anyone who knows the photographer, let me send a message so as to provide the appropriate credits)

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The Christos Παπασούλης from Chaidari, took the following pictures! About five to six as 13. there. More weather video find in the channel the on youtube.

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The next day, Friday 30/12, again we had a snowfall to a large part of the basin at the beginning of the day and temporary sprinkling of local (and in the Hive). Later, after 11-1130 about, there were periods of rain after midnight/χιονόλυτου made stupa in exacerbations.

One of the χιονοκύματα breakfast, invade the basin…

Beautiful closing of the day by the snowy Penteli through of this camera

The main course was to the north and east of Attica on Friday. Impressive images of dense stoupa and χιονόστρωσης from Pikermi in the afternoon from the George Τζεβελέκο!

Source Athens Astrophotography & Storm Chasing Team

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