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Hurricanes In The Mediterranean!


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Posted
  • Location: 4 miles north of Durham City
  • Location: 4 miles north of Durham City
    People don't normally use 'The Mediterranean Sea' and 'hurricane' in the same breath. However, on rare occasions the Mediterranean has seen cyclones that resemble tropical storms or hurricanes. Such system occurred in September 1947, September 1969, January 1982, September 1983, and January 1995. Here are some images showing the life cycle of the January 1995 cyclone, which is probably the most outstanding example of these storms.

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

    This is my favourite image: -

    medthur2.gif

    It is interesting to note the hurricane-force sustained winds in such a system. Traditionally, this would not be viewed as a hurricane due to the SST's and air temperature's being a lot colder than that just north of the ITCZ in the Atlantic. Clearly upper-shear must have been minimal to non-existent as well as the small-size of the system suggesting a meso-scale warm-core trough with cold upper-air allowing a good amount of convection to release advected heat from North Africa. Not definite though and other theories could suggest formation. Any thoughts?

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    Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

    Interesting, had a look at wetterzentrale maps for 11th to 20th, certainly a slow-moving cut off upper low that eventually became phased with a trough further north but on the date depicted this low was under thicknesses of 540-546 dm. This would make it marginal to classify as a subtropical low in the Atlantic in late season but looks fairly similar to some of those. Have seen similar appearing lows over Gulf of Mexico in Jan, Feb that drifted northeast in similar fashion.

    It tends to suggest some potential for a weak tropical cyclone in the eastern Med if all factors were conducive, perhaps from mid-November to mid-January. The extent of open water is a little restricted but if waters were particularly warm it could perhaps happen one day if it hasn't already. This would probably be judged a regular low but it does show some tendencies. Probably snowed like mad over northern Greece above a certain elevation.

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    Posted
  • Location: Dorset
  • Location: Dorset

    The article says that the sea temp was 45-50F and the surface temp 60F, to enable the temp differential needed to supply the energy you would need the normal upper air 500 temps of -35C. Sounds like a well substantiated Polar low to me. No evidence of outflow on an enlarged picture either.

    WZ shows the upper cold pool nicely.

    Thre is very little evidence here to suggest anything tropical, we also know that down the eastern med some deep cold upper air can dig in.

    Saying all this the med can we warm enough in summer (maybe September for something sub tropical).

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    Posted
  • Location: Larbert
  • Location: Larbert

    Here's a cold water, deep Atlantic low from Jan 2005( i think). Caused mayhem this system.

    It too had an eye, but is not tropical!

    av-1731.jpg

    Pheww, that was one wild night up in these parts.

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    • 1 month later...
    Posted
  • Location: Western Isles
  • Location: Western Isles
    Here's a cold water, deep Atlantic low from Jan 2005( i think). Caused mayhem this system.

    It too had an eye, but is not tropical!

    av-1731.jpg

    Pheww, that was one wild night up in these parts.

    that little system got down to 942 mb

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    Posted
  • Location: Liphook
  • Location: Liphook

    Actually a paper done by a K.Emanuel suggests that these sort of storms do have a warm core, be it fairly thin sometimes, which would therefore make it tropical.

    Its an immensly complicated set-up to occur but his conclusions were that there these sorts of systems were likely in fact tropical cyclones (or systems very closely related to tropical cyclones) that orginated from cold cored systems, you somtimes see sub tropical cyclones undergo similar transitions. Here is the paper he did:

    http://www.adv-geosci.net/2/217/2005/adgeo-2-217-2005.pdf

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    Posted
  • Location: Dorset
  • Location: Dorset

    Looking at the paper he seems to be saying that as in a PL, it's the temp differential between the 500mb level and sea surface and the associated moisture increase which is driver behind the intensification. Rather than Baroclinic instability.

    This I totally agree with. However a Hurricane does not just rely on the temperature differential. It uses the heat and moisture content of the sea to intensify and expand hence why normally it degrades so quickly as soon as the eye hits land.

    If I am reading him right hes saying that these Cold system storms work in a slightly different way where as the parcel of air they provide actually gives the moisture and the the temp differential the instability.

    Being nit picky this difference is what differentiates a PL to a Hurricane, making it by and large smaller and shorter lived. Which is turn doesn't make the med systems hurricanes.

    BTW I can't pretend to understand the math he uses in this.

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    Posted
  • Location: 4 miles north of Durham City
  • Location: 4 miles north of Durham City
    Actually a paper done by a K.Emanuel suggests that these sort of storms do have a warm core, be it fairly thin sometimes, which would therefore make it tropical.

    Its an immensly complicated set-up to occur but his conclusions were that there these sorts of systems were likely in fact tropical cyclones (or systems very closely related to tropical cyclones) that orginated from cold cored systems, you somtimes see sub tropical cyclones undergo similar transitions. Here is the paper he did:

    http://www.adv-geosci.net/2/217/2005/adgeo-2-217-2005.pdf

    Interesting stuff. Will need to find time to read that properly.

    Its kind of like an enhanced upper-low that is locally intensified by advection of cold upper-air with considerable high humidity and dry-air advection from high pressure belts to the south; the shear conditions being conducive meaning the system will intensify quickly as there is no strong upward mobility to break it although its movement is restricted to inconducive conditions east or west of the 500mb profile.

    His conclusions thus: -

    The climatological potential intensity over the Mediterranean

    Sea is usually only marginal for tropical cyclone formation,

    and the atmosphere is usually far too dry to permit development.

    But when a deep, upper-level cutoff low moves over

    the region, the air mass must ascend and cool to maintain

    balance. Thus the air under such an upper low is unusually

    cold and humid. Its low temperature, in combination with

    the relative warmth of the underlying sea, and its high relative

    humidity provide an ideal incubator for hurricane-like

    development. A simulation with an axisymmetric, nonhydrostatic,

    cloud-resolving model shows rapid development

    under these circumstances. Calculations of potential intensity

    over the Mediterranean using daily re-analysis data are

    underway; these should enable an assessment of the overall

    risk of hurricanes in the Mediterranean region.

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