When we think about cyclone everyone has a common view, cyclone is equal to devastation. Once there is a news of cyclone, most of us are glued to television to know about the progress of cyclone due to its effect on all walks of our life including our basic needs like food and shelter. Watching the growth of a cyclone is like watching the growth of a child very closely, as both of them has growing stages. A cyclone is a rotating air mass around a low pressure. They have different structures like the eye, eye wall and rain bands (Fig. 1.).
The eye of the cyclone is the calm region, eye wall will have strong winds and heavy rainfall and the rain bands have more thunder storm activities. Once we move from the eye wall to the outer region of a cyclone we will experience less intense rainfall and wind speed.
Fig. 1. Structure of a cyclone
Image source: https://www.weather.gov/jetstream/tc_structure
Nowadays, most of us knows how a cyclone will look like when we see them from above, thanks to the satellite science that gives us a bird's eye view of the cyclones. The satellite picture of cyclone Fani is given in Fig. 2.
Fig. 2. Cyclone Fani, 2019
Image source: https://disasters.nasa.gov/cyclone-fani-2019
Currently, in the Bay of Bengal we have an active cyclone Nivar. So, I thought this would be the right time to know how to observe the cyclones from satellite and radar images and also through other sources. Lets begin to observe the cyclone....
Fig.3. INSAT 3D Infrared and cloud brightness temperature image,
Image source: India Meteorological Department
In Fig.3. you can see a dense cloud mass in the left hand side image and in the right hand side image you are seeing cloud brightness temperature along with cloud mass. The higher the clouds lower the temperature of the clouds. As it is a night time, visible image is not available. The dense clouds you are seeing is the cyclone Nivar in the Bay of Bengal.
There are also other products available with colored images for easy interpretation as shown in the images below in Fig.4. where the same infrared and cloud top temperature are enhanced.
Fig. 4. Meteosat 8 Satellite images of infrared and cloud top temperature. The dense clouds you are seeing is Cyclone Nivar.
Image source: https://meteologix.com/
Not only satellites, radars are also used efficiently in cyclone tracking. Here we are going to see the wind and cloud component in radar images (Fig. 5)
Fig. 5. Radar image showing wind (Blue indicates wind moving towards the radar and yellow, orange means wind moving away from the radar) and cloud component (Cloud height is shown and their spatial extension in east, west and north, south direction, when the color goes up in the scale above yellow convective cloud development ie., thunderstorm).
Image source: India Meteorological Department
If you wonder how it will be to view every movement of a cyclone in animation, you have that option too....
Fig. 6. Cyclone Nivar (anticlockwise rotating mass)
Image source: earth.nullschool.net
Now, some of us might be enthusiastic to know the forecast path of the cyclone. This will be available with most of the national meteorological service providers websites. For cyclone Nivar the forecast path can be seen below (Fig. 7) as given by India Meteorological Department.
In the image you can see the change of black dot depression to the red colour cyclone. 22/21, 25 KT, D means the position of the depression (D) at 06 UTC on 22/11/2020. Similarly, you can see the forecast position on different days and time. Some of you might be wondering why a green color cone is shown, this is the cone of uncertainty. That means the possible path of the cyclone as they are model predicted.
Fig. 7. Cyclone Nivar Observed and forecast path.
You can see interactive track of cyclone in the link https://ddgmui.imd.gov.in/dwr_img/ GIS/cyclone.html.
I hope now, you know to observe the cyclone using different openly available sources. Do read the identifying clouds in weather satellite image blog to improve your understanding and keep observing the growth of the cyclone. Observe them closely so that you can understand them. A good observer will become a good forecaster.
Be alert and Stay tuned to know more about the cyclones!
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