TROPICAL REVIOLVING STORMS

ORIGIN -               Tropical Ocean Areas               (7° - 15° North/South)

Generally Western & Equatorial Sides of Anticyclones

Exceptions – North West Australia

                            West Central America

And NOT in South Atlantic.

Tropical Depression                                            Force < 7

Tropical Storm                                                        Force 8/9

Severe Tropical Storm                                           Force 10/11

Hurricane, Typhoon, Cyclone,                            Force 12 +

Hurricanes-               West North Atlantic

                            East North Pacific

                            South Pacific

Typhoon -               West North Pacific

Cyclone -               Indian Ocean

                            Bay of Bengal

                            Arabian Sea

SEASON – Late Summer – Early Autumn in their hemisphere

                            July – October in North.

                            December – March in South

                            N. Indian Ocean: May – December (SW then NE Monsoon)

DIRECTION & SPEED - N. Hemisphere              

Origin                             275° ± 30°               10 increasing to 15 knots

Lat 20°/25°                             Recurve               15 increasing to 25 knots

Lat 30°                            N.E’ly               25 knots

Lat < 20°              Force 6/7               200 miles from centre

                            Force 8              100 miles

                            Hurricane               < 75 miles

SIGNS

Long Low Swell extending from storm centre. (Up to 1000 miles)

Check Barograph Trace

Corrected Barometer -               3 mb/hPa below normal  (Suspicious)

5 mb/hPa               (No Doubt, Consider Avoiding Action)

Change in Wind Direction & Strength (Trades)

Extensive Cirrus cloud  / Altocumulus

If suspicious inform all vessels & shore authorities

AVOIDANCE

1.       Bearing of Storm Centre (Face wind centre 100°/120° on right in Northern H. Left in Southern H.)

2.     Determine Path (2 bearing 2/3 hours apart)

3.     Navigable or Dangerous Semi-Circle?

Dangerous – Vessel pushed on to path

                            On side of curvature

                            Increased wind speed

ACTION

In Northern Hemisphere:               Falling Barometer,

Wind Veering

V/l in Dangerous Semi Circle

Put Wind on Starboard Bow 10°/45°, Max Speed

                                                                      Falling Barometer,

Wind Steady / Backing

V/l in Navigable Semi Circle

Put Wind on Starboard Quarter, Turning to PORT

In Southern Hemisphere:               Falling Barometer,

Wind Backing

V/l in Dangerous Semi Circle

Put Wind on Port Bow 10°/45°, Max Speed

                                                                      Falling Barometer,

Wind Steady / Veering

V/l in Navigable Semi Circle

Put Wind on Port Quarter, Turning to STARBOARD

If in harbour proceed to SEA as quickly as possible