Friday, November 20, 2015

Arabian Sea Low

 [a] The formation of LOW in the SE Arabian Sea is evident from gradient wind analysis chart.
Mid-Level Atmospheric Shear also supports this.  Western parts of TN ie Kumari, Nellai, Virudunagar, Theni, Dindigul will be experiencing rainfall

Reference Background from CIMSS: Using the gridded atmospheric motion vector output u and v AMV components are averaged over a mid troposphere layer (400, 500, and 600 hPa) and a lower layer (700, 775, 850, and 925 hPa). The difference in these averaged components is used to compute the speed shear between the lower and mid layers. The contours show the vector magnitude shear (absolute value). The streamlines indicate the direction of the shear.

In the case when a tropical cyclone (TC) is present, the analyses are modified in the storm region by a procedure which removes the storm circulation within a prescribed radii. This allows a more representative depiction of the environmental shear acting on the storm.

Uses: The presence/lack of atmospheric wind shear is vital to hindering/supporting TC development. A low shear environment is favorable for tropical cyclone development, while a high shear environment will deter a immature TC region from (further) developing or destroy an already mature TC. Shear values below 10 m/s (20 kts) are considered low enough for tropical cyclogenesis. 
20.11.2015: (upto 0430 hrs IST)
HVF Avadi reported 119.0mm ,KVK Kattukuppam 90.0mm, Puzal 26.0mm,Ponamalle 45.0mm and Chembarambakkam 50.0mm

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