A cold front across the desert

Advertisment
  • Map displaying wind direction and dew point temperatures across the Middle East, forecast for 08:00 UTC Saturday 18 February. Image copyright MeteoGroup.

  • A cold front across the desert
    17.02.2012 12:59

     

    It's not often that mid-latitude cold fronts penetrate across the Middle East but it becomes increasingly possible as the northern hemisphere's winter progresses.

    The accompanying map shows just such a front (dotted line) in its forecast position at 08:00 UTC tomorrow, 18 February, as it moves east and south-east.

    It will produce squally heavy showers in western Iran and eastern Iraq with snow on the Zagros mountains. Farther south, though, the air will become dessicated passing across the Arabian Peninsula, so precipitation is unlikely.

    However, the pressure gradient east of the front will be squeezed, inducing a strong S-SE'ly wind (known locally as the "Kaus" wind) and consequent sandstorms across the UAE and the Empty Quarter. Meanwhile the sinking cold air will help high pressure to build over Saudi Arabia and the Levant which will induce strong N-NW (Shamal) winds and blowing sand over NE Saudi Arabia and the northern Gulf.

    The contrast in air masses either side of the front is stark. Note the high dew point temperatures (numbers and yellow shades) ahead of it, and low dew points (numbers and blue shades) in the colder and much drier airmass following - for example, compare +12 deg C near Abu Dhabi with -12 deg C just west of Riyadh.

    The veer in wind direction is also a clue the front's whereabouts, even without rain as a guide.

    By: Stephen Davenport