MED: (Sub)Tropical Depression over the central Mediterranean Sea

[DanieleItalyRm]

TropicalDisturbance or TD developed over central Mediterranean sea?
https://it.sat24.com/it/it
http://www.sierrapapa.it/rapid_thunders ... seviri.htm
http://www.weatheronline.co.uk/weather/ ... remium.htm

[Vince_and_Grace_fan]

Some of the earlier CMC runs developed it partially, but the newest one not anymore. Now it's non-tropical and associated with an upper level low, but if it can maintain itself until it reach the central Mediterranean Sea, I think some development is possible. Also a subtropical or tropical cyclone maybe can form on the next week too.

[DanieleItalyRm]

However, it is not an extratropical system. Convection near the center and outflow are obvious. I think it's at least subtropical

[Alyono]

Think this is too weak to be classified. It's a heavy rain threat for Italy, however

[Vince_and_Grace_fan]

However, it is not an extratropical system. Convection near the center and outflow are obvious. I think it's at least subtropical

It's a mesoscale convctive system triggered by the upper level low over it. These system often has some weak circulation at the surface and upper level outflow on the divergent part of the upper level low, but the convection is mostly not too organized and sustained that it to be classified. In late summer and in autumn often form such systems over the Mediteranean Sea but they very rarely develop into a real subtropical or tropical cyclone.
Also the 'classical' Mediterranean cyclones stand betwen the extratropical and subtropical cyclone, and sometimes it has subtropical or tropical-like vorticies in their core, but these are not true subtropical or tropical cyclones, especially what form in winter. And it is possible that a front-less, well-defined warm core cyclone develop in winter, when the SST's are too cold (around 15 Celsius or more less) that is rather related to polar lows.

[Alyono]

However, it is not an extratropical system. Convection near the center and outflow are obvious. I think it's at least subtropical

It's a mesoscale convctive system triggered by the upper level low over it. These system often has some weak circulation at the surface and upper level outflow on the divergent part of the upper level low, but the convection is mostly not too organized and sustained that it to be classified. In late summer and in autumn often form such systems over the Mediteranean Sea but they very rarely develop into a real subtropical or tropical cyclone.
Also the 'classical' Mediterranean cyclones stand betwen the extratropical and subtropical cyclone, and sometimes it has subtropical or tropical-like vorticies in their core, but these are not true subtropical or tropical cyclones, especially what form in winter. And it is possible that a front-less, well-defined warm core cyclone develop in winter, when the SST's are too cold (around 15 Celsius or more less) that is rather related to polar lows.

They're tropical. Remember, it is not the SST that matters. It is the difference between the SST and the tropopause. In those Med TCs, there are unusually cold tropopause temperatures. Similar to Alex last year by the Azores in January

[Sciencerocks]

Looks like a tropical cyclone! Loop the satellite below and what you'll see is outflow at the upper levels with convection near the center of the system.

I'd say 25-30knts

http://www.weatheronline.co.uk/weather/ ... remium.htm

[Dean_175]

ASCAT shows max winds of only 10-15kt-- though there is a closed surface circulation. Convection seems shallow and sparse- even for a medicane.

[Vince_and_Grace_fan]

They're tropical. Remember, it is not the SST that matters. It is the difference between the SST and the tropopause. In those Med TCs, there are unusually cold tropopause temperatures. Similar to Alex last year by the Azores in January

But then every polar low could be tropical cyclone because the temperature gradient is big in their case. I think the SST matters, if it too cold, pure tropical cyclones are not possible. But indeed it is hard to tell a limit in the water temperature when it still supports tropical cyclone's formation or not anymore because the instability cames from the temperature difference between the sea and the upper troposphere as you said. I think there is around 18-20 Celsius, the cooler water possibly don't ensure enough latent heat sources. I think the height of the tropopause is also important. Winter medicanes usually form when a strong cold break reach the Sea, but in this case the tropopause is much lower than in autumn (and the air temperature is quite low too).
Alex also formed in the middle part of the ocean (south of the Mediterranean Sea) where the SST's were around 22-23 Celsius, and most of the Atlantic (sub)tropical cyclones that transitioned from extratropical lows formed at least over 20-21 Celsius water. Of course these cyclones later often go over cooler water where it can maintain itself for a while.

[Sciencerocks]

This was a tropical cyclone...

Convection near the core
Outflow at the upper levels

This was no polar low. Polar lows don't have warm cores and if you believe that anything over 23c water is a polar low then so was all tropical cyclones that have formed northeast of the azores.

[Vince_and_Grace_fan]

This was a tropical cyclone...

Convection near the core
Outflow at the upper levels

This was no polar low. Polar lows don't have warm cores and if you believe that anything over 23c water is a polar low then so was all tropical cyclones that have formed northeast of the azores.

I didn't speak about this cyclone, I spoke only about the medicanes which form in winter over around 15 Celsius SST. And polar lows also have warm core, but this is shallow due to the low tropopause and the upper level cold air. In autumn real subtropical or tropical cyclone can form over the Mediterranean Sea, and I follow them as well (the report from a 2007 October cyclone will came out within a few days). http://zivipotty.hu/tcr.html

Also this cyclone wasn't tropical (but it was close to it), the convection wasn't organized and sustained enough and the circulation was weak and elongated. The NHC never classify a cyclone like this tropical.

[Dean_175]

It is almost a true medicane (Mediterranean tropical-like cyclone or whatever you would prefer to call them), but it is not well defined enough and there is not much convection(though it has increased some east of the center in the past 6 hours ).

[Alyono]

This was a tropical cyclone...

Convection near the core
Outflow at the upper levels

This was no polar low. Polar lows don't have warm cores and if you believe that anything over 23c water is a polar low then so was all tropical cyclones that have formed northeast of the azores.

I didn't speak about this cyclone, I spoke only about the medicanes which form in winter over around 15 Celsius SST. And polar lows also have warm core, but this is shallow due to the low tropopause and the upper level cold air. In autumn real subtropical or tropical cyclone can form over the Mediterranean Sea, and I follow them as well (the report from a 2007 October cyclone will came out within a few days). http://zivipotty.hu/tcr.html

Also this cyclone wasn't tropical (but it was close to it), the convection wasn't organized and sustained enough and the circulation was weak and elongated. The NHC never classify a cyclone like this tropical.

The January 1995 storm was clearly a hurricane

[BYG Jacob]

A medicane!? Awesome!

[Vince_and_Grace_fan]

The January 1995 storm was clearly a hurricane

Yes, the biggest question is the well-defined, sustained and front-less winter tropical-like cyclones like the 1995's one or the 1982's one (on the picture below), which are indeed look more tropical than a polar low. They possiby can be tropical, but I doubt that the NHC would ever classify a similar cyclone in the Atlantic over such cold water (but the similar autumn medicanes are tropical for sure). However the less-defined lows are clearly not tropical in my oppinion. It would be great if the medicanes would get more attention and measurements, perhaps Recon, that would help a lot to their classification (for example how deep is their warm core).

[Vince_and_Grace_fan]

And back to this cyclone, the Meteocenter WRF again show some development from tomorrow as it move around Greece (firstly toward SE, then NE).

[Alyono]

The January 1995 storm was clearly a hurricane

Yes, the bigest question is the well-defined, sustained and front-less winter tropical-like cyclones like the 1995's one or the 1982's one (on the picture below), which are indeed look more tropical than a polar low. They possiby can be tropical, but I doubt that the NHC would ever classify a similar cyclone in the Atlantic over such cold water (but the similar autumn medicanes are tropical for sure). However the less-defined lows are clearly not tropical in my oppinion.
It would be great if the medicanes would get more attention and measurements, perhaps Recon, that would help a lot to their classification (for example how deep is their warm core).

That cyclone would be named as would 1995. Look stronger than Alex

[DanieleItalyRm]

They're tropical. Remember, it is not the SST that matters. It is the difference between the SST and the tropopause. In those Med TCs, there are unusually cold tropopause temperatures. Similar to Alex last year by the Azores in January

But then every polar low could be tropical cyclone because the temperature gradient is big in their case. I think the SST matters, if it too cold, pure tropical cyclones are not possible. But indeed it is hard to tell a limit in the water temperature when it still supports tropical cyclone's formation or not anymore because the instability cames from the temperature difference between the sea and the upper troposphere as you said. I think there is around 18-20 Celsius, the cooler water possibly don't ensure enough latent heat sources. I think the height of the tropopause is also important. Winter medicanes usually form when a strong cold break reach the Sea, but in this case the tropopause is much lower than in autumn (and the air temperature is quite low too).
Alex also formed in the middle part of the ocean (south of the Mediterranean Sea) where the SST's were around 22-23 Celsius, and most of the Atlantic (sub)tropical cyclones that transitioned from extratropical lows formed at least over 20-21 Celsius water. Of course these cyclones later often go over cooler water where it can maintain itself for a while.

This was a tropical cyclone...
Convection near the core
Outflow at the upper levels
This was no polar low. Polar lows don't have warm cores and if you believe that anything over 23c water is a polar low then so was all tropical cyclones that have formed northeast of the azores.

That cyclone would be named as would 1995. Look stronger than Alex

Comparing Medicanes to Polar lows is an obsolete thought of 80-90s. There is no polar low identical to a tropical cyclone. None. Medicanes are just like tropical cyclones. Even Medicane in January 1982 and 1995 have intense central convection, outflow, band typical of a tropical cyclone, and hurricane characteristics. Medicanes are tropical cyclones just like Karl nov.1980, Vince oct.2005, Grace oct.2009, Alex jan.2016, Arlene apr.2017. All of these tropical cyclones were initially extratropical, later becoming tropical with tropical transition, over 18-22°C sea surface, just like Medicanes.

I do not think that 16-17 ° C of central Mediterranean temperature in January are different from 19-20°C of Karl November 1980 developed. These are still temperate sea surface temperatures and non polar (average terrestrial temperature 15°C). Alex Jan.2016 intensified in Hurricane just on 19°C sea surface. A meteorological natural phenomena does not meet net temperature limits.

HURRICANE ALEX DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL

Remarkably, Alex has undergone the transformation into a hurricane.
A distinct eye is present, embedded within a fairly symmetric mass
of deep convection. Water vapor imagery shows that the upper-level
trough is now west of the cyclone, with divergent flow over the
center - indicative of a tropical transition. It is very unusual to
have a hurricane over waters that are near 20 deg C, but the
upper-tropospheric temperatures are estimated to be around -60 deg
C, which is significantly colder than the tropical mean. The
resulting instability is likely the main factor contributing to the
tropical transition and intensification of Alex.[/b]

The Medicane of October 1996 (23-24°C sea surface) just like Vince oct.05 or Grace oct.06. Sea surface temperature is more high than Grance and Alex jan.2016


The Medicane season does not match that of the Atlantic Tropical cyclones but is the same as that of tropical cyclones
of the Subtropical Atlantic. The Mediterranean sea is only a geographic part of the Subtropical Atlantic.

Disturbance south of Sicily, yesterday, 5-6 otober, 26c Sea surface, probably 1008 hpa: