Halloween Surprise: Rare Tropical Storm Forms in Mediterranean Sea

https://www.wunderground.com/news/medicane-tropical-storm-mediterranean-sea-31oct2016

A tropical storm formed Halloween weekend, not in the typical Atlantic or Pacific, but in the Mediterranean Sea.

This rather strange sequence of events began as an area of low-pressure dropped southward from southern Europe and became temporarily left behind by the jet stream over the central Mediterranean Sea south of the Italian coast.

(MORE: The 35 Strangest Weather Events I've Seen in My Lifetime)

By Saturday, Oct. 29, a non-tropical low pressure center formed east of Malta, a group of islands between Sicily and the coast of Libya over the weekend. 

RGB composite satellite image of the Mediterranean storm as it was making the transition to a subtropical storm on October 30, 2016, at 12:00 UTC.
(NERC Satellite Receiving Station, University of Dundee)

The next day, thunderstorms became more clustered near the low-pressure center to warm the mid levels of the atmosphere sufficiently to morph the system into a subtropical storm. 

A subtropical storm displays features of both tropical and non-tropical systems, including a broad wind field, no cold or warm fronts, and generally low-topped thunderstorms displaced from the center of the system.