Tropical Update-05

TROPICAL LOW (INVEST-91B) BACK TO LIFE AS THE CONVECTION DEVELOPS-

Yesterday after seeing the insat picture, many might have thought that the system was dead and the convection around it was lost. The low was formed 2 days back, but suddenly the Convection was Lost. According to World Meteorological Organization this period of loss of convection is called "incubation period". During this period, the humidity increases gradually around the Low pressure area. After some time, this will form the convection. The same thing occurred today.

YESTERDAY HIMAWARI PICTURE-(NO PROPER CONVECTION)

LATEST CONDITIONS PICTURE-(DEVELOPING CONVECTION)

CLOUD-LOWER CONVERGENCE:

INFERENCE:

The convergence of clouds make up a crucial role in building good bands. Now we can observe good cloud build up due to heavy convergence. Its likely to increase and will lead to heavy rainfall along Srilankan Coast.

UPPER LEVEL-DIVERGENCE:

INFERENCE-

Upper level divergence will help in proper spread of clouds and their corresponding rain bands. The system associated with good upper-divergence will lead to heavy rainfall around the centre eye wall. The present system (Invest-91B) has a very good diverging air at upper levels. Soon more convection will wrap up leading to heavy rainfall around the center.

THEORY:

INFERENCE:

So for the proper development of Storm, the "lower-converging nature" and "upper-diverging nature" are essential. If they are good, the cloud band around the storm will develop massively and lead to heavy rainfall.

Tropical update-04 a

System Without Clouds-Is it dead??

A low pressure was marked at around 6N , 84E in the Map. The low pressure likely to get intensifited into Well Marked Low and approach Sri Lankan Coast. It is associated good amounts of supporting atmosphere, required for good rainfall.

INFERENCE-

On seeing the above satellite image one can understand that there is no convection around the center. Convection means the presence of clouds. Here there are no clouds and the system seems as if it is dead. But things might improve tomorrow and we can see heavy cloud build up in South-west Bay of Bengal by tomorrow evening. 

Tropical update-04

Heavy Rain On cards To Tamil-Nadu and Kerala

-Says ECMWF

After TN Floods-2015, the state of Tamilnadu bracing for another system (Invest-91B), which is taking shape at South-West Bay of Bengal. Its is associated with high values of Sea Temperatures around 32 degrees, Total Precipitable Water and High Vorticity.

Sea surface Temperature-

INFERENCE:

High Sea surface Temperatures will lead to great amount of Energy which is an essential parameter for the growth of a system. Since May Month is associated with good amounts of Heat, system will contain good rain-bands and moisture flow.

Total Precipitable Water-

INFERENCE:

Precipitable water is the depth of water in a column of the atmosphere, if all the water in that column were precipitated as rain.We can see a High Amounts Of Total Precipitable Water gushing from Equatorial Indian Ocean in the above Map. This entire TPW will pump suitable water vapour into the system now formed and develop good rain bands around the eye-wall. TPW generally gives a well defined structure to the system.

Vorticity-

INFERENCE:

Vorticity is the measure of the Rotating spin around the center of system, which is essential in determining how much strength the system has processed at that time. Now, we have a good vorticity around the system (Invest 91B) , which will lead to good strength and make it moderately windy.

WIND-SHEAR-

INFERENCE:

Wind Shear is the amount of opposition given by wind to the system. Greater the wind shear, weaker the system. Here, the Shear value is less near the east coast of Tamilnadu and Srilanka at present and its likely to decrease further. This will help to keep cyclone to retain its strength all over its journey. Thanks to the Wind Shear.

ECMWF FORECAST REALIZATION-

ECMWF, a leading Weather Forecasting agency tracked the system to be as a minimal cyclone. They also predicted good amounts of rainfall likely over many places of South india, which are closer to the storm Track. At the same a very good news awaits us....Its nothing but "MONSOON ONSET". As the system heads North, The monsoonal Winds will make an entry and tries to fill the "Thermal Void" over North India. Thermal Void is the pressure of Low at the ground level caused due to intense Heat-waves.

CONCLUSION-

Hence i conclude by saying some interesting days on cards to entire South india. I will be tracking ECMWF and GFS models. Whatever it may be, "good rains ahead and it will be a respite to the brewing heat wave but not destructive".

FORECAST BY

B.SAI PRANEETH

(WEATHER OF SOUTH INDIA)