Chapter 3: Red Sea Trough Flashcards Preview

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Flashcards in Chapter 3: Red Sea Trough Deck (8)
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Rainy season in Middle east:

october to april

  • during this period: cyclones associated with cold upper trough
    • move from west to east over the med. sea 
      • associated with RST sometimes


Red Sea trough:

  • tongue of low pressure
    • extending northward from southern red sea towards eastern mediteranean and levant at lower atmosphere levels
      • RST attains its largest amplitude in low level atm.


Red sea trough origin:

  • sudan monsoon low
    • part of:
      • large scale subtropical/ Equatorial low pressure thermal system 
    • center oscillate from ethiopia - sudan (in summer) to the red sea (winter)


Red sea trough is regarded as extension of:

  • African Monsoon trough
    • large scale subtropical - tropical low pressure thermal synoptic system


The development, intensity and northward extension of RST:

due to:

  • topography
  • thermal forcing factors

over the red sea region


Types of Red Sea trough (first type)

  • Non active:
    • hot dry weather
      • over middle east and vicinity 
    • results from:
      • east south easterly flow at lower atmosphere 
  • Active:
    • major cause of flash floods in Arid southern levant 
    • RST accompanied by upper trough from north over EM
      • trough enhances upward motion and unstable conditions which results in 
        • Development of convective storms
        • (Heavy torrential rain, intense precipitation) heavy showers and thunderstorms E and S part of middle east



  • Most frequent: Oct - Nov
  • second most frequent: April
  • RST shift westward: Sep - Jan
  • RST shift eastward: Feb - May
  • Frequency of occurance negligible: June - Aug


Types of Red Sea trough:

  • Wet:
    • (all months except oct) located east of Dry RST
      • at sea level RST is east of 500 hPa trough 
        • under the inflection point where
          • PVA and upward motion take place 
    • pronounced diurnal variation 
    • northward and westward (over EM) extension of RST more pronounced than dry RST
    • sea level pressure is lower by 3 hPa (except oct)
    • pronounced trough at 500 hpa from black sea towards northern egypt 
      • thermal low at sea level is weakening with height
        • replaced by relatively high pressure aloft
  • Dry:
    • A ridge or zonal flow at 500 hPa accompanies dry RSTs