A rare "Medicane"
--a hybrid storm with characteristics of both a tropical storm and an extratropical storm--formed over the South Central Mediterranean Sea on Friday and moved over the island of Malta, bringing them tropical storm-like conditions. Winds at the Luqa, Malta Airport
looked suspiciously like what one would observe with a tropical storm passing overhead--a double peak with a near-calm in between, with the pressure falling to 984 mb during the calm. Winds peaked in Malta at 47 mph, gusting to 66 mph, at 6:37 pm local time, and the island was lashed with flooding rains. At least one funnel cloud was also observed. A Personal Weather Station (PWS) on the north coast of Malta
recorded sustained winds of 69 mph, gusting to 96 mph, with a minimum pressure of 979 mb. Lampedusa e Linosa, Italy
, an island between Malta and Tunisa: sustained at 53 mph, gusting to 84 mph. A PWS on Linosa Island
recorded a minimum pressure of 982 mb and wind gust to 61 mph. As of late Friday night, the storm was moving northwards along the east coast of Sicily, Italy, bringing them heavy rain and strong winds.Figure 1.
Radar image of the November 7, 2014 Medicane as the storm passed along the east coast of Sicily, Italy. Sure looks like an eyewall is trying to form. Image credit: Protezionecivile Italy
. Other radar images are available from girovaghi.it.Figure 2.
MODIS satellite image of the November 7, 2014 "Medicane" near Malta in the Mediterranean. Image credit: NASA.Figure 3.
Wind damage at Calatabiano along the east coast of Sicily, Italy, from the November 7, 2014 Medicane. Photo credit: Cosimo Manitta.Is it a hurricane?
Today's Medicane, which has been dubbed "Qendresa I" by the Free University of Berlin, derived part of its energy from last weekend's Nor'easter that brought early snows to portions of the Eastern U.S., according to TWC's Stu Ostro. So, it got its start from a non-tropical storm, but has definitely acquired characteristics of a tropical storm, making it a hybrid. The NHC does not have responsibility for naming storms in the Mediterranean. If they were responsible, there is a good chance that they would have named this Medicane, labeling it a subtropical storm. A radar loop
out of the the Malta Airport Metoffice
showed the storm appeared to be forming a banded eye-type structure typical of a tropical storm approaching hurricane strength as the storm moved over the island.Figure 4.
Sea Surface Temperatures (SSTs) near Malta are about 23°C (73°F), which is warm enough to support a subtropical storm, but probably not a tropical storm. Ocean temperatures are cooler on the east side of Sicily, about 21°C (70°F.) The coldest waters I've seen an Atlantic tropical storm form in were 22°C during Hurricane Epsilon
of 2005. Cool air aloft can offset cold SSTs and create the instability needed to create a Medicane. Image credit: U.S. Navy.Hurricanes may begin forming in the Mediterranean by 2100
According to research published by Gaertner et al. (2007)
, an increase in ocean temperatures of 3°C in the Mediterranean by the end of the century could lead to hurricanes forming there. Miguel Angel Gaertner of the University of Castilla-La Mancha in Toledo, Spain, ran 9 different climate models with resolutions of about 50 km and found that some (but not all) of the models simulated hurricanes in the Mediterranean in September by the end of the century, when ocean temperature could reach 30°C.
Though the Mediterranean may start seeing hurricanes by the end of the century, these storms should be rare and relatively short-lived for three reasons:
1) The Mediterranean is quite far north and is subject to strong wind shear from jet stream activity.
2) The waters are shallow, and have relatively low heat content. There is no deep warm water current like the Gulf Stream.
3) The Mediterranean has a lot of large islands and peninsulas poking into it, increasing the chances that a tropical storm would weaken when it encountered land.Figure 5.
The Medicane of January 1995 (dubbed "Celeno") emerged off of the Libyan coast into the central Mediterranean Sea toward the Ionian shoreline of Greece on 13 January as a compact low-pressure area, the precursor low maintained winds reaching up to 108 km/h (67 mph) as it traversed the Ionian Sea, while the German research ship Meteor noted winds of 135 km/h (84 mph). Celeno intensified over waters that were just 16°C (61°F), far below the 26°C threshold usually needed to sustain a tropical storm.Figure 6.
Hybrid subtropical storm of October 8, 1996, off the coast of Italy. According to Reale and Atlas (2001), the storm had characteristics similar to a hurricane, but formed over water of 21.5°C. "The maximum damage due to wind occurred over the Aeolian Islands, at 38.5°N, 15°E, to the northeast of Sicily: assistance for disaster relief was required. Unfortunately, no weather station data were available, but the media reported sheds, roofs and harbor devices destroyed, and houses and electric lines damaged, due to "extremely strong westerly wind." The perfect agreement between the observations at Ustica, the storm scale, the eye-like feature position and the damages over the Aeolian Island reasonably suggest that the hurricane-level intensity of 32 m/s (72 mph) was reached over the Aeolian Islands." A similar hybrid low affected Algeria on 9 - 10 November 2001. This storm produced upwards of 270 mm (10.6") of rain, winds of 33 m/s (74 mph), and killed 737 people near Algiers, mostly from flooding and mud slides. Image credit: Dundee satellite receiving station.References
Wikipedia has an excellent "Medicane"
Gaertner, M. A., D. Jacob, V. Gil, M. Dominguez, E. Padorno, E. Sanchez, and M. Castro (2007), Tropical cyclones over the Mediterranean Sea in climate change simulations,
, Geophys. Res. Lett., 34, L14711, doi:10.1029/2007GL029977.
Reale, O., and R. Atlas. 2001: Tropical Cyclone-Like Vortices in the Extratropics: Observational Evidence and Synoptic Analysis
, Weather and Forecasting, 16, No. 1, pp. 7-34.Video 1.
Heavy flooding in Malta on November 7, 2014 from the "Medicane." Thanks go to wunderground member barbamz for posting this video in my blog comments, as well as many of the other links.