Saturday, June 4, 2011

Update on the Arabian Sea Low!


in an unexpected turn in the Tropical Weather system, the previous forecasted low pressure has vanished and the tropical wave has produced another band of thunderstorms in a region of SST over 28C which lacks presence of a lower convergence. This system has strong vortex system at the base,mid level.

Various models confirm that the the forecasted low shall be a Warm Core Low as the warm moist air influxes in the system at lower levels due to torrential heating during spring season.

Low-Mid level vorticity ( Vertical Vorticity) is favorable for upward lifting of parcel of air carrying moisture which is lifted adiabatically and the energy of the parcel is released at the upper level favoring where the system is having a weak upper air divergence ( Outflow of air aloft releasing heat of parcel)

CIMSS models indicate a bare 5-10kt upper air divergence around the system located 730km SW of Mumbai. The area has a wind shear of around 20kt+ and the tendency of wind shear in 24hrs IS INCREASING.
Convection is weakly organized around the geometric center as depicted by higher cloud top temperature of -30C. Typically strong lows ( Depressions) have Cloud Top Temp over -50C.
The 850mb plots are showing developing LLC ( Low level cyclonic circulation) in the region which is a primary step for development of surface lows. The precipitation & surface pressure map shows a formation of 1000mb region by 5th June which shall intensify then. Precipitation map shows formation of weak rain bands in the region after 48hrs. Overall as per the 00z,4th June GFS shows unorganized shape of system.

The GFS Cyclone Prediction maps show the system travelling WNW and expected to make a landfall in coastal Oman on by or on 11th June 2011. The system shall get chance of intensifying in Northern Arabian Sea as the Mid level wind shears have relaxed nature and the upper level winds are forecasted to be weak. The TPW-Precipitable Water shows 60mm+ precipitable water ( Good Moisture content) in the region!

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