Graham P Davis wrote:

On 19 Nov 2013 08:56:12 GMT
"Norman" wrote:

wrote:

http://www.bbc.co.uk/news/world-europe-24996292

That's a new one !

Keith (Southend)
http://www.southendweather.net
"Weather Home & Abroad"

I haven't been following this one carefully but, from what I have
seen, I think the event was a fairly straightforward cut-off low.
These happen from time to time in the Mediterranean. I'm not sure if
use of the word "cyclone" is intended to imply a tropical type of
event or if it is used merely as an alternative to "depression".
Although tropical-type systems do occur in the Mediterranean on rare
occasions I don't think this was one of them but, as I say, I haven't
been following it closely so I am open to correction if I am wrong.

A fairly good reference to tropical-type lows in the Mediterranean
can be found at


http://en.wikipedia.org/wiki/User:At...opical_cyclone

The event of Jan 1995 was particularly interesting.


Current one is nothing like a tropical storm. A quick dash through the
satellite pictures suggest it's a trough (instant occlusion?) linked to
frontal wave to the south that has caused the trouble.

The 1995 example is said to be a probable polar low and, given a sea
temperature of 16C, I don't think it qualifies as a tropical storm.


I think the jury is still out on the Jan 1995 event. Certainly there are
similarities to a polar low but there are also difference. These "Medicane"
events do seem to develop from cold-cored cut-off lows. However, they have much
deeper convection around the centre than is normally found in a polar low. With
time, the latent heat released in this deep convection seems to result in a
relatively small warm core developing, something that isn't found in a polar
low. It is this warm core development that transforms the feature into
something closely related to a tropical cyclone.

This paper by Kerry Emanuel is worth a read

http://hal.archives-ouvertes.fr/docs...2-217-2005.pdf

Some notes on the Jan 1995 event, prepared by Jack Beven, one of the
forecasters at the National Hurricane Center, can be found at

http://www.mindspring.com/~jbeven/intr0008.htm

It seems that these events in the Mediterranean do not fit comfortably into any
of the common definitions. The indtroduction of a separate category of
"Medicane" is therefore probably quite appropriate.


--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.