Reputedly, the first snow for over 100 years has fallen on the Sphinx but several photos on the web are actually of a model in Japan! Anyhow, snow certainly fell across Cairo, N Egypt and even deeper snow has fallen over Israel, including Jerusalem and more widely across the Middle East and Turkey. The upper air temperatures across Israel and Egypt are cold, of course, but only -2c or -3c at 850hPa which, in the UK is common and rarely produces snow for us… as a rule of thumb our 850hPa temps need to be at least -5c or lower to deliver much snow to the UK, especially the south away from hills. So why did it snow on the Sphinx when the airmass was not really that cold? BTW check this link for the sphinx in the snow pic http://urbanlegends.about.com/b/2013/12/14/sphinx-in-the-snow-photo.htm
Well, it looks like the snow in Israel and Egypt is what meteorologists call “Lake or Sea Effect snow” and is quite common near the Great Lakes in the USA and across Japan but of course rather more unusual in the warmer Middle East. A deep LOW pressure (Winter Storm Alexa) swept across to the north of Israel dragging in bitterly cold strong N winds across Egypt and Israel and the Middle East as a whole. The air originated from further north over continental Asia, where winter temperatures are extremely cold. The strong wind has crossed the Med (still fairly warm of course) in a wide arc across the warm sea surface which has allowed a good deal of moisture to evaporate, adding humidity and instability to the air mass. A temperature difference of at least 13c is required to produce the greatest evaporation and moisture input required to produce plenty of “sea or lake effect snow”. SST across the Med off Israel is currently over 20c and this air mass had a temp of -3c at 850hPa and around freezing at sea level.
On hitting land the strong wind experiences friction and literally “piles up” against the coast causing convergence and uplift. The uplift, especially pushed up over the heights of Israel, causes cooling in the frigid polar air and, eventually, precipitation in the form of snow. Ingredients for sea effect snow were therefore all met in this case:
- deep polar air mass
- strong winds
- temperature difference of at least 13c between air and water surface
- hills near the sea to encourage uplift
Elsewhere in the region, winter storm Alexa has caused flooding in the Gaza strip http://www.bbc.co.uk/news/world-middle-east-25387020