MED: XANDRA - Tropical Storm over the Tyrrhenian Sea

[DanieleItalyRm]

In the past days we had a hot for the period (23-27°C), and a lot of sand from the Sahara in high cuota, wind very hot; rained sand, as sometimes happens here.

This system increase over Tyrrhenian sea on 2 Dicember, convection in the center, warm core, outflow band! (Xandra name of university fu Berlin) 994 hpa

[DanieleItalyRm]

[DanieleItalyRm]

[Alyono]

sure looks interesting. No frontal structures anywhere near it

[DanieleItalyRm]

Incredible in this momento. .

[DanieleItalyRm]

[somethingfunny]

Ummmm wow. This looks even more legit than the thing that hit Malta and Sicily last month. What the heck is going on in the Mediterranean this year??

[somethingfunny]

Rome is currently reporting 59 degrees F and rain, ESE wind at 20mph, and a pressure of 1001 mb. The center is not too far to the northwest of Rome but I'm unfamiliar with Italian geography.

[DanieleItalyRm]

In my city, Rome, impressive rapid passage of cumulonimbus this morning, with low base (600 m ca.) rain and moderate wind (60 km/h gust), 1000 Hpa.
BuT the cyclone rapidly weakened approx the Latium coast, and the center storm landfall 100 km North West of Rome. The webcams of those places showed very intensive wind and precipitation. This storm have a 150 km in diameter and 994 Hpa in the center; I believe that wind of Tropical Storm intensity (40-45 kt) in 20-50 km around the center. Indeed the radar shows that the part most intense of this storm it was over the sea, west of the eye.

[NDG]

Impressive when you take into effect that SSTs in that area are only in the mid to upper 60s! As if the Mediterranean has its own Micro-climate.

[DanieleItalyRm]

Thanks, I would like other opinions from the Storm2k users,
Many Thanks,
Daniele

[somethingfunny]

Was there any damage?

[bahamaswx]

Wow that thing looked impressive at landfall.

[euro6208]

so people over there thinking they are just experiencing another strong low pressure or any non tropical system when in fact they are experiencing a true hurricane?

[DanieleItalyRm]

Hi guys, the Latium coast was stricken by the part less intense, East from the eye (75-87 Km/H | 40-47 kt wind).
However The part most intense was in the open sea, 30 km from the coast. This most intense zona was evident in the radar, map wind and in top cloud; I suppose 85-102 km/H | 46-54 kt wind in this part. The landfall rapidly weakening the storm. This storm is very tiny, like tropical storm Marco in 2008; Marco had a very Little zone with tropical storm intensity (12-20 km from the center);
Ladispoli, like the landfall, report 993.9 Hpa.
I suppose in this case it was at Least tropical storm t.25/t.3.0 intensity and 993 hpa.
Im sorry that sab noaa stopped the track of the Mediterranean tropical cyclone in November 2011.. they were latest hope ...

https://www.youtube.com/watch?v=zarGzCWJe0o

[AJC3]

The traditional low end SST threshold of 26-27C (79-81F) assumes a barotropic atmosphere typical of the deep tropics. Generally, in absence of cold core TUTT cells or troughs that show some reflection down into the mid levels, this type of atmosphere features 500MB temperatures of -4C to -6C. Since instability is a function of temperatures both at the surface and aloft, obviously traditional SST thresholds for TC formation will almost never apply to "medicanes", given their formation north in the range between 30-37N, coupled with their geneses from strong cold core mid level troughs or closed lows.

I think a decent rule of thumb here might be to look for a temperature difference of no less than 30C between SST/near surface air mass and 500MB when looking at true TC processes (i.e latent heat feedback from convection). In other words, when your SSTs drop to, say...20C, as long as 500MB temps have cooled to at least -10C or lower, and in absence of a significant intrusion of a dry and/or cool (polar) air mass at the time, the local atmosphere, would still support TC formation, at least thermodynamically.

A couple more things to consider are, 1) Incipient disturbances, and 2) Basin areal extent as it relates to the size of these features. Since tropical waves do not exist at 30-37N, this area must rely on advection of some lower-end synoptic or mesoscale feature into the region (e.g. a cutoff 500MB low) ...be it from the north, south or west. I think the relative infrequency of these features is in part due to the lack of frequency of these features having sufficiently limited spatial/areal extent. This also explains why these features are small...by necessity. Larger scale features would suffer some disruption of inflow, and also incorporate continental air into their circulations. Finally (captain obvious speaking here), smaller basin size means a smaller area of formation, less space to roam, and shorter lifespans. No surprise there, right?

Of course, there are other considerations, such as the presence of dry air aloft leading to the air mass having an unfavorable low mean PWAT...etc.

In any event, those are some of my initial thoughts on "Medicanes". I should probably read up on a journal paper or two about the subject before spouting off any more.

[CrazyC83]

That definitely looks subtropical in nature.

[NDG]

The traditional low end SST threshold of 26-27C (79-81F) assumes a barotropic atmosphere typical of the deep tropics. Generally, in absence of cold core TUTT cells or troughs that show some reflection down into the mid levels, this type of atmosphere features 500MB temperatures of -4C to -6C. Since instability is a function of temperatures both at the surface and aloft, obviously traditional SST thresholds for TC formation will almost never apply to "medicanes", given their formation north in the range between 30-37N, coupled with their geneses from strong cold core mid level troughs or closed lows.

I think a decent rule of thumb here might be to look for a temperature difference of no less than 30C between SST/near surface air mass and 500MB when looking at true TC processes (i.e latent heat feedback from convection). In other words, when your SSTs drop to, say...20C, as long as 500MB temps have cooled to at least -10C or lower, and in absence of a significant intrusion of a dry and/or cool (polar) air mass at the time, the local atmosphere, would still support TC formation, at least thermodynamically.

A couple more things to consider are, 1) Incipient disturbances, and 2) Basin areal extent as it relates to the size of these features. Since tropical waves do not exist at 30-37N, this area must rely on advection of some lower-end synoptic or mesoscale feature into the region (e.g. a cutoff 500MB low)...be it from the north, south or west. I think the relative infrequency of these features is in part due to the lack of frequency of these features having sufficiently limited spatial/areal extent. This also explains why these features are small...by necessity. Larger scale features would suffer some disruption of inflow, and also incorporate continental air into their circulations. Finally (captain obvious speaking here), smaller basin size means a smaller area of formation, less space to roam, and shorter lifespans. No surprise there, right?

Of course, there are other considerations, such as the presence of dry air aloft leading to the air mass having an unfavorable low mean PWAT...etc.

In any event, those are some of my initial thoughts on "Medicanes". I should probably read up on a journal paper or two about the subject before spouting off any more.

Very good explanation, it makes sense to me now.

[DanieleItalyRm]

The traditional low end SST.... threshold of
any more.

Many Thanks for the explanation.
I think as you..
I think this explanation is good also for These cyclones, right?
Chris jun 2012 sea surface 21-22°C
Grace October 2009 sea surface 21°C
Vince October 2005 sea surface 23°C
Karl October 1980 sea surface 19-20°C

All these cyclones have occurred over 30-40¤Latitude.
All initially not tropical. In these cases an Extratropical cyclone become in subtropical and subsequently in a tropical cyclone (Tropical transition).
Are only occurred 2-3000 km to west, over sub-atlantic, instead ' at east, over Mediterranean.
Moreover, naturals phenomena not have a geografic limits, and the Mediterranean Sea is only a part of the Subtropical-Atlantic.

[CrazyC83]

I would say based on all that data a peak intensity around 50 kt seems reasonable.