Thursday, April 18, 2024

Reasons for heavy rainfall over UAE and parts of Oman 

Clarification of some doubts, Vagaries briefly explains the reasons behind the recent heavy rains and thunderstorms which lashed UAE and Oman. 

The main reason - a strong trough in the jet stream (strong Western Disturbance, as we call these systems over India) which was strong enough to generate a low-pressure system near the surface close to the warm waters of the Persian Gulf. 
This system had typical characteristics which are seen in weather systems in the midlatitudes, and so strong thunderstorms and rainbands formed near the boundary between winds from opposite directions (see below image from National Center for Meteorology, UAE).

Also, this event was well forecasted by various Global weather forecast models well in advance, therefore signifying that the natural processes were most likely governing this weather system. 

Such high-intensity extreme rainfall in this part of the world is rare but not unheard of.

Clarification on some confusion on common meteorological features over the Arabian Sea:

  • A high-pressure system (anticyclone) is present in the lower levels of the atmosphere over the Arabian Sea, usually from March to May-end, till Monsoon onset. 

  • The presence of this high pressure causes some southerly winds over the Oman coast, but does not give such extreme rainfall. 
  • This high pressure is seen every year, but we do not see such rain events every year. 

The observed heavy rainfall event was due to the trough in the Jet stream as explained above.

Impacts on the western parts of India:

  • The variation in the location and intensity of this high pressure also affects the weather for the west coast of India, by sometimes delaying the sea breeze or even setting in the sea breeze early.
 High pressures create sinking air or subsidence and are often associated with clear skies and dry weather. Such high pressure areas have caused heatwave like conditions with very dry weather and low humidity for Mumbai during February end and early March in the past years.

  • There was no strong high pressure over western Maharashtra across the first few kilometers of the atmosphere, otherwise we wouldn't have witnessed thunderstorms developing over the Ghats and Madhya Maharashtra regions.
  • Explained by Vagarian Shreyas



Paresh said...

Thanks for the great explanation, Shreyas! Much appreciated.

Shreyas Dhavale said...

Thanks a lot, Paresh!

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