MED: Subtropical Depression near Corsica/Sardinia

[DanieleItalyRm]

Noaa added Mediterranean Sea basin:
http://www.ssd.noaa.gov/PS/TROP/floaters.html

Today A Low circulation has acquired some tropical characteristics between France and Corsica, over 25-26°C sea surface.
Tomorrow it moved to SE over 28°C sea surface of the Tyrrhenian Sea.
however not have a strong low pressure supported and I THink not exceed tropical depressione intensity:

[DanieleItalyRm]

[AJC3]

Noaa added Mediterranean Sea basin:
http://www.ssd.noaa.gov/PS/TROP/floaters.html

Today A Low circulation has acquired some tropical characteristics between France and Corsica, over 25-26°C sea surface.
Tomorrow it moved to SE over 28°C sea surface of the Tyrrhenian Sea.

However not have a strong low pressure supported and I Think not exceed tropical depression intensity:

The upper air sounding from 08/11 at 1200 UTC from Ajaccio, Corsica...

http://weather.uwyo.edu/cgi-bin/soundin ... STNM=07761

...showed a 500MB temperature of -10.7C. From an environmental perspective, this easily falls within the >= 30C threshold (an unofficial approximation, of course) which was identified as the temperature difference between the SST/near surface air mass and 500MB needed to support warm-core tropical cyclone convective processes (i.e. "medcane" development) at that high latitude. See...

viewtopic.php?f=31&t=116987&p=2429573#p2429573

[DanieleItalyRm]

iF this easily falls within the >= 30C threshold which was identified as the temperature difference between the SST/near surface air mass and 500MB needed to support warm-core tropical cyclone convective processes,
what to be missing? a small vorticity perhaps? or much high initial pressure?
almost always these tropical systems be started from extratropical cyclones (cut-off) to below 1000 hPa.

[AJC3]

iF this easily falls within the >= 30C threshold which was identified as the temperature difference between the SST/near surface air mass and 500MB needed to support warm-core tropical cyclone convective processes,
what to be missing? a small vorticity perhaps? or much high initial pressure?
almost always these tropical systems be started from extratropical cyclones (cut-off) to below 1000 hPa.

It could be one or a combination of several factors. Were conditions favorable for a long enough period of time? Perhaps there was some interaction with the islands of Corsica and Sardinia? Was there any sort of dry air in the vicinity? It seems the system was moving and may not have been clear of land interaction for it to sufficiently develop.

[DanieleItalyRm]

Thanks. I think low vorticity and especially dry air intrusion has a major negative effect in this case for a tropical center convection development:

[DanieleItalyRm]

The depressione produced floods and waterspouts over Italian coasts.
Calabria flash floods: https://m.youtube.com/watch?v=0TNFJ0aIhwQ

sea tornado civitavecchia (Roma) italy: http://www.youreporter.it/video_Tromba_ ... 10_08_2015

[Hammy]

That looks pretty bad, hopefully there won't be too much damage.