Visual Storm (Cyclone) Warning Signals for Indian Sea Ports

by OldSailor on November 10, 2010

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When storm (cyclone) warnings are given by news channels, they mostly report only the storm warning signal numbers hoisted in sea ports. What those signal numbers imply are not known to the common man listening/viewing the news.

Here I have brought out some details of Visual Storm (Cyclone) Warning Signals for Indian Sea Ports. Before going through the details, let me give you first some information on cyclone warning system in India.

  • The India Meteorological Department (IMD) is responsible to provide tropical cyclone warnings.
  • Tropical cyclone warnings are provided by three Area Cyclone Warning Centres (ACWCs) located at Kolkata, Chennai and Mumbai in addition to three Cyclone Warning Centres at Bhubaneswar, Visakhapatnam and Ahmedabad.
  • The entire cyclone warning work is coordinated by the Deputy Director General of Meteorology (Weather Forecasting) at Pune and Deputy Director General of Meteorology (Services) at New Delhi.
  • Tracking of tropical cyclones is done by integrating data collected from:
    • conventional surface and upper air observations from inland and island stations, coastal Automatic Weather Station (AWS), ships and buoy observations.
    • cyclone detection radar including Doppler Weather Radar.
    • satellite cloud pictures from the Geostationary Satellite (INSAT 3A & Kalpana1).
  • Classifications of cyclonic disturbances for the north Indian Ocean region (Weather system and Maximum wind speed):
    • Low pressure area: Wind speed less than 17 knots (31 km/hour)
    • Depression: Wind speed between 17 and 27 knots (32 and 51 km/hour)
    • Deep Depression: Wind speed between 28 and 33 knots (52 and 61 km/hour)
    • Cyclonic storm: Wind speed between 34 and 47 knots (62 and 88 km/hour)
    • Severe cyclonic storm: Wind speed between 48 and 63 knots (89 and 118 km/hour)
    • Very severe cyclonic storm: Wind speed between 64 and 119 knots (119 and 221 km/hour)
    • Super cyclonic storm: Wind speed 120 knots (222 km/hour) and above

Visual Storm (Cyclone) Warning Signals:

The storm warning signals (both day and night signals) are hoisted prominently on masts in ports. Day signals are in the form of cones and cylinders. Night signals are in the form of red and white lamps. In addition to hoisting signals, most of the ports have arrangements to disseminate information and warnings received by them to  ships  in harbour and to ships leaving/entering harbour.

Signal Number One:

Distant Cautionary Signal Number One
1. Implies that there is a region of squally weather in which a storm may be forming (well marked ) low or depression with surface winds up to 61 km/hour (33 knots) 2. Day and Night signals shown below are hoisted to indicate that ships may be exposed to danger after leaving harbour.
Day Signal Night Signal

16a_Day_DCS_1

3b_Night_DCS_1

Signal Number Two:

Distant Warning Signal Number Two
1. Implies that a storm has formed (cyclonic storm with surface winds 62-88 km/hour (34-47 knots)) 2. Day and Night signals shown below are hoisted to indicate that ships may be exposed to danger after leaving harbour.
Day Signal Night Signal
10a_Day_DWS_2 2b_Night_DWS_2

Signal Number Three:

Local Cautionary Signal Number Three
1. Implies that the port is threatened by squally weather (cyclonic circulation with surface winds 40-51 km/hour (22-27 knots) or squalls due Nor’Westers) 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
3a_Day_LCS_3 5b_Night_LCS_3

Signal Number Four:

Local Warning Signal Number Four
1. Implies that the port is threatened by a storm, but it does not appear that the danger is as yet sufficiently great to justify extreme measures of precaution (cyclonic circulation with surface winds 52-61 km/hour (28-33 knots)) 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
2a_Day_LWS_4 4b_Night_LWS_4

Signal Number Five:

Danger Signal Number Five
1.Implies that the port will experience severe weather from a storm of slight or moderate intensity that is expected to cross the coast keeping the port to the left of its course (to the east of the port in the case of Mangla) (cyclonic storm with surface winds 62-88 km/hour (34-47 knots)) 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
17a_Day_DS_5 16b_Night_DS_5

Signal Number Six:

Danger Signal Number Six
1. Implies that the port will experience severe weather from a cyclone expected to move keeping the port to the right of its track. 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
18a_Day_DS_6 17b_Night_DS_6

Signal Number Seven:

Danger Signal Number Seven
1. Implies that the port will experience severe weather from a cyclone expected to move over or close to the port. 2. Day and Night signals shown below are also hoisted when a storm is expected to skirt the coast without (actually) crossing it.
Day Signal Night Signal
19a_Day_DS_7 18b_Night_DS_7

Signal Number Eight:

Great Danger Signal Number Eight
1. Implies that the port will experience severe weather from a severe cyclone expected to move keeping the port to the left of its track. 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
20a_Day_GDS_8 19b_Night_GDS_8

Signal Number Nine:

Great Danger Signal Number Nine
1. Implies that the port will experience severe weather from a severe cyclone expected to move keeping the port to the right of its track. 2. Day and Night signals shown below are hoisted to indicate that the port itself and the ships in harbour are in danger.
Day Signal Night Signal
21a_Day_GDS_9 20b_Night_GDS_9

Signal Number Ten:

Great Danger Signal Number Ten
1. Implies that the port will experience severe weather from a severe cyclone expected to move over or close to the port. 2. Day and Night signals shown below are also hoisted when a storm is expected to skirt the coast without (actually) crossing it.
Day Signal Night Signal
22a_Day_GDS_10 21b_Night_GDS_10

Failure of communication:

Day and Night signals shown below are hoisted to indicate that communications with the meteorological warning centre have broken down, and the local office considers that there is a danger of bad weather.
Day Signal Night Signal
23a_Day_FoC_11 7b_Night_FoC_11

Source: Tropical Cyclone Operational Plan for the Bay of Bengal and the Arabian Sea (TCP 21, Edition 2010 of World Meteorological Organization)

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{ 2 comments… read them below or add one }

Dayalan Bernard October 31, 2012 at 12:03 PM

Very useful and reliable information available in this portal. Thanks.

AMIT RAVIKIRAN MHAISEKAR September 11, 2013 at 9:43 AM

Dear Sir, Marine Buzz is a very informative and right website for various marine related issues and information.Dear sir,kindly let me know what are the standard dimensions of the Visual Storm (Cyclone) Warning Signals for Indian Sea Ports.Dimension means height,width.Also what should be the diameter of a anchor ball.Kindly reply the query eagerly waiting for reply.Thanks and Regard.

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