Khamsin


Khamsin, chamsin or hamsin, more commonly known in Egypt as khamaseen , is a dry, hot, sandy local wind affecting Egypt and Israel; similar winds, blowing in other parts of North Africa, the Arabian Peninsula and the entire Mediterranean basin, have different local names, such as bad-i-sad-o-bist roz in Iran and Afghanistan, haboob in the Sudan, aajej in southern Morocco, ghibli in Tunis, harmattan in the western Maghreb, africo in Italy, sirocco which blows in winter over much of the Middle East, and simoom.
From the Arabic word for "fifty", these dry, sand-filled windstorms blow sporadically in Egypt over a fifty-day period in spring, hence the name. The term is also used in the southern Levant, where the phenomenon takes a partly different form and blows both during spring and autumn.
When the storm passes over an area, lasting for several hours, it carries great quantities of sand and dust from the deserts, with a speed up to 140 kilometers per hour, and the humidity in that area drops below 5%. Even in winter, the temperatures rise above 45° C due to the storm. The sand storms are reported to have seriously impeded both Napoleon's military campaigns in Egypt as well as Allied-German fighting in North Africa in World War II.
In the southern Levant it takes the shape of an oppressive weather front with hot temperatures, large quantities of dust impeding visibility, but no strong winds except during the night. In the Book of Exodus of the Hebrew Bible, the ruah kadim or "east wind" is the cause of the parting of the Red Sea.

Causes and history

Khamsin can be triggered by extratropical cyclones that move eastwards along the southern parts of the Mediterranean or along the North African coast from February to June.
In Egypt, the khamsin usually arrives in April but occasionally can occur between March and May, carrying great quantities of sand and dust from the deserts, with a speed up to 140 kilometers per hour, and a rise of temperatures as much as 20 °C in two hours. It is believed to blow "at intervals for about 50 days", although it rarely occurs "more than once a week and lasts for just a few hours at a time." A 19th-century account of the khamsin in Egypt reports that
These winds, though they seldom cause the thermometer of Fahrenheit to rise above 95° in Lower Egypt, or in Upper Egypt 105°, are dreadfully oppressive, even to the natives. When the plague visits Egypt, it is generally in the spring; and the disease is most severe in the period of the khamáseen.
The same account relates that Muslims in Egypt "calculate the period of ... to commence on the day immediately following the Coptic festival of Easter Sunday, and to terminate on the Day of Pentecost ; an interval of forty-nine days." This period roughly coincides with the Jewish Counting of the Omer, which also lasts for an interval of 49 days, between the springtime feasts of Passover and Shavuot, the Jewish origins of Easter and Pentecost.
During Napoleon's 1798 Egyptian Campaign, the French soldiers had a hard time with the khamsin: when the storm appeared "as a blood tint in the distant sky", the Ottomans went to take cover, while the French "did not react until it was too late, then choked and fainted in the blinding, suffocating walls of dust." During the North African Campaign in World War II, "Allied and German troops were several times forced to halt in mid-battle because of sandstorms caused by the khamsin... Grains of sand whirled by the wind blinded the soldiers and created electrical disturbances that rendered compasses useless."
In Israel, the khamsin is known more formally as sharav.

Cultural references