Action when TRS is Confirmed

Action when the approach of a TRS is confirmed

  1. Obtain the bearing of the storm center.
  2. Ascertain in which semi-circle the vessel lies.
  3. Take avoiding action.

1. Obtain the bearing of Storm Centre

  1. Face the wind, then the storm center will be within 8 to 12 points on the right hand in NH (on the left hand in SH). – Buys Ballot’s Law
  2. The direction of the swell, indicates roughly the storm center.
  3. The direction of the densest part of the huge bank of clouds also indicates the storm center.

If barometric pressure falls 5 MB below normal, then there is a possibility that the ship is in the well-developed outer storm area. If barometric pressure falls 20 MB or more below normal, then there is a possibility that the ship is near the eye of a well-developed TRS.

2. Ascertain in which semi-circle the vessel lies

Bring the ship in stationery or “heave to” (moving very slowly in one direction) to the position. Carefully monitor and write downwind directions, every after 2 hours.

If wind direction changes clockwise (wind veers), then the vessel is at the Right-hand semicircle (RHSC), and if wind direction changes anti-clockwise (wind backs), then the vessel is at the Left-hand semicircle (LHSC), in both hemispheres.

Veering or backing, once detected, should be continuous while the observer remains stationary, i.e. a veering wind should continue to veer and a backing wind should continue to back.

If the wind veers at first and then backs, or if it backs at first and then veers, the vessel must have passed from one semicircle into another, due to the change of path of the storm.

If the vessel is in the dangerous quadrant:

Proceed as fast as practicable with the wind 1 to 4 points on the stbd bow (port bow in SH) – 1 point for slow vessels (less than 12 knots) and 4 points for fast vessels (more than 12 knots) altering course as the wind veers (backs in SH).

This action should be kept up until the pressure rises back to normal i.e. until the vessel is outside the outer storm area. If there is insufficient sea room, the vessel should heave with the wind on the stbd bow (port bow in SH) until the storm passes over.

If the vessel is in the path of the storm or if in the navigable semi-circle:

Proceed as fast as practicable with the wind about 4 points on the stbd quarter (port quarter in SH), altering course as the wind backs (veers in SH). This action should be kept up until the pressure rises back to normal i.e. until the vessel is outside the outer storm area.

For Advanced Read, check out:

A GUIDE TO EFFECTIVE COMMUNICATION ON SHIP

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