Mediterranean tropical cyclone

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A Mediterranean subtropical cyclone on January 15, 1995

Mediterranean tropical cyclones are an extremely rare weather phenomenon. These systems are a subject of some debate within meteorological circles whether they closely fit the definition of tropical cyclones, subtropical cyclones, or polar lows. Their origins are typically non-tropical, and develop over open waters under strong, initially cold-core cyclones, similar to subtropical cyclones in the Atlantic Basin. ^[1] Sea surface temperatures in late-August and early-September are quite high over the basin, though research indicates water temperatures of 20 °C/68 °F are normally required for development. ^[2] Cold air aloft appears to be the main trigger for instability in the development of these systems.

1 Possible Tropical Cyclones
2 See also
3 References
4 External links

[edit] Possible Tropical Cyclones

Meteorological literature documents hurricane-like systems formed in the Mediterranean Sea in September 1947, September 1969, January 1982, and September 1983. ^[3] To the right is an image of the September 30, 1983 system.

[edit] January 14-18, 1995

In the middle of January of 1995, a cold front moved across the Mediterranean Sea. A frontal wave developed along it on the 13th, and developed a low-level circulation the next day to the west of Greece. Convection built and organized around the center as it moved to the southwest, and by the 15th it resembled a tropical storm. It continued to organize, and developed an eye later that day. Though water temperatures were only 16 °C (61 °F), the storm was characterized by well-defined outflow, an eye, an upper level anticyclone, and a ship report of 135 km/h, 37.5 m/s (73 kt, 84 mph) winds, equivalent in strength to a Category 1 hurricane. The system continued to the southwest and quickly weakened, making landfall on northern Libya as a convectionless vortex on the 17th. It dissipated the next day. ^[4]

[edit] October 4-6, 1996

On October 4, 1996, a small vortex was first observed between Sicily and Tunisia. It moved to the north-northeast, and quickly organized due to warm water temperatures. The system may have tried to develop a warm core, but only limited shallow convection was seen within its circulation. It passed over Sicily on the night of the 4th and crossed southern Italy on the 5th. By the 6th, it entered the Adriatic Sea and dissipated. The storm dropped heavy rainfall and produced gusts of up to 105 km/h, 29 m/s (55 kt, 65 mph), causing heavy damage in its short path. ^[5]

[edit] October 6-10, 1996

As the previous system was at its peak, a frontal wave extended through the western Mediterranean. It developed into a frontal low on October 6, and strengthened and became better organized as it moved eastward over warm waters. With little upper level shear, a warm core, an organized vertical structure, and an eyewall, the system was possibly a hurricane late on the 7th just before hitting Sardinia. Over land it lost its eye structure, but quickly reorganized and acquired an eye early on the 8th after crossing Sardinia. The storm retained its organization for a day before hitting northern Sicily on the 10th and weakening. Damage information is unknown. The development of a hurricane in the central Mediterranean Sea was well-predicted by computer models in the days prior to the storm's genesis. ^[6]

[edit] March 27-28, 1999

A deep cyclone cutoff in the Gulf of Lyons on March 26. Winds at Portbou, Spain increased to 150 km/h, 41.6 m/s (81 kt, 93 mph) by the evening of March 26. The pressure of the cyclone fell to 998 hPa by midnight. By the morning of March 27, it was no longer connected to its occluded front and satellite imagery briefly revealed an eye feature, though convection around it was shallow. Water temperatures under the system were a mere 15°C (59°F) since temperatures at the 500 hPa level were quite cold; -28°C (-18°F). ^[7] Soon afterwards, the system weakened as it approached northern Italy.