Tuesday, March 20, 2012

The dust storm from the West Asian Region moved into Pakistan and Western India on Tuesday, and moved NE later. 

The reason for this directional movement is the 
1)  The eastwards movement of M-5. As mentioned in Vagaries' weekly forecast put up on Sunday, M-5 is moving away and is expected to fizzle out by Wednesday. This system has attracted the winds from the SW, and unfortunately, it was laden with sand/dust from the Middle East.

2) The pressure gradient from the Northern Kashmir region to Southern Sindh/Gujarat was steep. There was a marked difference in pressures. This allowed the isobars to be closely concentrated (see Thai map above). And such concentric closely formed isobars are bound to generate very strong winds along its axis. 

Kashmir region was gushed by winds between 50-60 kmph on Tuesday. The winds were in fact SW, and attracted much sand and warm air from the Arabian Sea. So much so, that the day's high in Srinagar was 21c, 6c above normal, and the low was 15.7c, 12c above normal !! With some rain of-course.

This caused the dust to cover an area from Gujarat to Kashmir, including Delhi.Now, in the evening, it is concentrated in the NW regions.

Parts of Sindh and Karachi was  swept by winds upto 35 kmph and blowing dust and sand. Sukkar too was windy and dusty, with the day temperature dropping to 30c. Nawabshah dropped from 40c on Monday to 31c on Tuesday ! 

Dust will clear by Wednesday from Pakistan and Northern India.
As M-5 moves away, and the pressure gradient "flattens", actually, the West blowing winds will "move" eastwards towards the U.P. Plains and Southern Nepal. But without much of dusty conditions.

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