Real-Time Prediction of the Tropical Cyclogenesis Location over Bay of Bengal Using Global Forecast System (GFS) - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 290

Fig. 6: Observed rainfall and 850 hPa wind analysis (top panel); 24, 48 and 72-hour
rainfall forecast from GFS T382 (middle panel) and GFS T574 (bottom panel) for
heavy rainfall on 23 June 2011 over central India.
with an active monsoon trough, a low pressure area formed over the north
BoB on 21 September, 2011. The vertical wind shear of horizontal wind between
850 and 200 hPa was low to moderate (10-20 knots). There was increase in
lower level relative vorticity and upper level divergence also over the region.
Under these favourable synoptic and environmental conditions, the low pressure
area concentrated into a depression at 0830 hrs IST of 22 September, 2011
over the northwest BoB near lat. 21.5 N and long. 87.5 E. The location and
intensity of depression formed over BoB on 22 September is well captured by
both the analysis of GFS T574L64 and GFS T382 (Fig. 7). The estimated
central pressure was about 998 hPa and the lowest MSLP of 998.2 hPa was
reported by Balasore observatory. The GFS T574 low level (850 hPa) wind
forecast could capture the genesis location of depression formed over BoB on
22 September 2011 (Fig. 8) up to five to six days in advance.