Tropical Revolving Storm

TRS

Tropical Revolving Storm is a small area of very low pressure, around which wind of gale force (8) Or more blow spirally inwards. 

Anticlockwise in northern hemisphere and clockwise in southern hemisphere. 

Origine

This originate in latitudes between 5° & 20° and travel between W & WNW in the northern hemisphere and W & WSW in southern hemisphere, at a speed of about 12 knots. 

They curve away from the equator 

• Curve to N and then recurve to NE in the NH. 
• Curve to S and then recurve to SE in the SH. 

Structure

Eye or Vortex :- calm central area of low pressure, diameter 4 to 30 miles average 10 miles. 

Eye wall :- an inner ring of hurricane🌪 force, diameter 4 to 30 miles. 

Outer Storm Area :- area of surrounding the eye wall, diameter 50 to 800 miles. 

Warning signs of approaching TRS 

1. Swell :- swell can be experienced as much as 1000 miles away. Swell approaches from the direction of storm centre. It is the first indication of approaching TRS. 

2. Atmospheric Pressure :- Falls steadily, the presence of TRS is confirmed if the vessel is in area where TRS generally originate, or it is the time of the year within the season when TRS occurs or barometric pressure is 5 mb below normal. A pressure drop of 20 mb is sufficient to cause a well developed TRS. 

3. Weather :- 

• Unusually clear visibility may occur. 
• Sometimes peculiar dark red or copper colour of sky is seen at sunset before a TRS
• Increase of wind force as the pressure falls. 
• Frequently lightning may be seen. 
• Succession of squalls, with or without rain. 

4. Storm warning