A common Mediterranean hurricane

A hurricane-like storm, known as "Medicine", appears in the Mediterranean about once a year. Although it is weaker and rarer than its tropical counterpart, which is now mercilessly hitting the world, it can cause a lot of damage and even cost human lives. Although Madikane has not yet hit Israel's shores, according to estimates, these storms will become more powerful and dangerous due to climate change

By Dor Sandler, Angle - news agency for science and the environment

In recent days, the devastating consequences of Hurricane Florence on the eastern coast of the United States are becoming clear. About a million Americans were forced to evacuate their homes, and after about two days of heavy rains and winds of up to 150 km/h, at least 20 people were reported dead and about a million homes and businesses were left without power. At the same time, Typhoon Mangot, almost twice the size of Florence, hit the Philippines and China, killing dozens of people as a result of mudslides, floods and extreme winds. Thousands of flights were canceled over these two hubs, and the full extent of the damage has yet to be clarified.

These two storms are the most severe in their region (Florence in the Atlantic Ocean and Mangote in the Pacific Ocean) within the 2018 hurricane season (June to November). While each region gives storms their own name, such as hurricane or typhoon, the meteorological phenomenon is the same - a system of strong winds (over 119 km/h) that move around a low pressure center in the atmosphere, and are accompanied by heavy rains that originate from evaporation from the sea. These storms often form in tropical areas near the equator, but the question arises - is such a thing also possible here in the Mediterranean?

The hurricane's dangerous little brother

Meteorologist Dr. Baruch Ziv from Tel Aviv University recalls: "When I was a forecaster in the Air Force in 1971, on one of my shifts I saw that in Cyprus there were reports of a southerly wind of 80 km/h, heavy rain and a steep drop in pressure. It was extreme, I was afraid it might be a mistake. In the next observation the rain and wind continued in full force. It was very strange. Barometric depressions in the Mediterranean have a typical diameter of 1,000 km, and this depression was undersized, about the size of Cyprus. It was a new and scary thing."

The scientific community has since been able to give a name to this rare phenomenon - "Medicane". This is an expression derived from a combination of "hurricane" and "Mediterranean". These storms, which are similar in structure to the known tropical storms, are much rarer and luckily also weaker. In an American-Spanish study published about a year ago in the Journal of Climate, a pair of scientists characterized these storms. They found that the medicaines appear with a frequency of about 1.5 storms per year on average, mainly in the fall and winter months. This while a typical hurricane season includes about 6 hurricanes in the Atlantic Ocean alone. In addition, the Medicain storms are even rarer in the eastern Mediterranean compared to the entire basin, and so far no storm has yet been recorded that managed to reach the shores of Israel.

According to Ziv, hurricanes and Medicaid have a lot in common - a diameter that reaches up to about 500 km, a cloud spiral structure and an "eye of the storm" in the center. Near the ground, the Madicane can produce wind gusts at a speed of tens of kilometers per hour. In some cases, the winds may even reach 100 km/h or more, similar to a category 1 hurricane (the lowest). In addition, the Medici brings with it heavy rains that can accumulate to about 100 mm per day.

The Medici is formed through a mechanism that resembles that of its big brother from the Atlantic Ocean: cold air in the atmosphere encourages instability and the rise of air. A relatively high sea surface temperature accelerates this rise, allowing the Mediterranean to become a source of moisture and energy for the storm. However, Ziv explains, there are several question marks regarding the conditions that enable the formation of Medicane. The Mediterranean does not contain warm currents like those that naturally exist in the oceans and feed hurricanes, which require a water temperature of at least 26 degrees Celsius. Medicians, on the other hand, settle for lower temperatures (15-23 degrees), which exist in the Mediterranean Sea in autumn and early winter thanks to its significant warming in summer. Also, the Mediterranean Sea is relatively small and surrounded by land, so it is not entirely clear how the storm gathers enough moisture. This is compared to hurricanes that bring in moist air from a range of a thousand kilometers or more.

600 dead in Algeria

Although the average Medicain is weaker than the storms that grab headlines around the world, its damage potential could be significant. Flooding is a major side effect of Medicaid, both due to flooding from sea level rise at the center of the storm and flash flooding from extreme rain. Added to this are mudslides and strong gusts of wind that can cause damage to buildings and infrastructure at costs of tens of millions of dollars. In an article published by a group of researchers from Greece about a year ago, the consequences of about 63 medicares that occurred between 1969 and 2014 were examined. Areas such as southern Italy, northern Tunisia, Sicily, Sardinia, and the Balearic Islands (Spain) are at the highest risk, due to their proximity to centers of storm formation on the western side of the sea. The deadliest medicaine on record occurred in 2001, killing over 600 people in Algeria and causing $250 million worth of damage. In the eastern Mediterranean, on the other hand, only three hurricanes from Deccan (in Greece and Cyprus) that led to deaths were recorded in recent decades.

The future of the Medicians, like that of many extreme weather events, does not bode well. In the same American-Spanish study, the researchers examined the change that may apply to the McCains by the year 2100, as they are represented in computer models of the atmosphere. In a world warming as a result of the greenhouse gases emitted by humanity, the storms may become more energetic and violent. While the total number of storms is probably not expected to change, it was found that the likelihood of the formation of extreme medicaines (with winds of over 150 km/h, such as Hurricane Florence) will double by the end of this century. The chance is still low, with an estimate of one extreme storm every 30 years, but in light of the pictures from the USA and Asia last weekend, there is no doubt that this is too much.

More of the topic in Hayadan:

• Global warming has contributed to the number and intensity of hurricanes
• An Israeli study published in Nature: the strength of a hurricane can be predicted by lightning activity
• "A cynical and cunning effort has been made by certain sectors and stakeholders to attack climate science"