New Zealand Date/Time:
Fri, May 24, 2013, 1:10:40 PM
Marine Weather Forecasts

How to use them.

Trip Planning

When you plan to go boating, check out the weather outlook first. This covers the next five days, and can help you to avoid going out into major weather events such as gales.
Use the latest forecast as a starting point for your trip. It is the best idea taking into account what’s happening over the horizon. It is averaged over the whole area for the whole day, so you need to monitor your own horizon to be ready for local changes. A barometer helps.

Make sure you get a marine forecast. IF IN DOUBT DON'T GO OUT!

Forecasts for land areas, given in kilometres per hour or ‘k’, are not for you. Marine forecasts are given in knots, and take into account that wind over open sea can blow twice as fast as it can over land.

Coastal and Inshore forecasts consist of the following parts...

Warnings

These are issued and updated whenever the need becomes apparent for gales (average exceeding 33 knots) or storms (average exceeding 47 knots). They are given sequence numbers (e.g. Alpha 42, the A stands for Auckland) that restart at 1 each month.
The Auckland inshore forecast carries a strong wind advisory if the winds are expected to exceed 25 knots, or a squall warning if showers may be accompanied by sudden but brief gales.

Situation

This is a brief description of the key players on today’s weather map; such as lows, highs and fronts, their position and movement. The forecast picks the most likely outcome, but the situation helps you ascertain the alternatives. It also lists the areas affected by warnings.

Forecast Details

Giving wind, sea, swell and weather for the next 24 hours.

Wind

Direction the wind is FROM in degrees true, and speed in knots. This is an average speed over open water. Gusts may be 40 to 50% higher. Terrain effects can swing the breeze and may halve or double the speed.

Sea

Gives the waves formed by the local wind. When wind opposes the tide, waves get steeper.

Swell

Refers to waves rolling in from the ocean, giving the direction they come from. Swells increase in height as they reach shallow water. SIGNIFICANT HEIGHT is given; and that is the average of the top third. The occasional wave (once every 15 minutes or so) is 50% higher and the maximum wave (once a day) can be twice the height mentioned.

Weather

Is included if it drops the visibility to FAIR (below six nautical miles), or POOR (below 3 nautical miles) or FOG (below 1 nautical mile).

Outlook

Covering significant changes in wind weather and swell for the following three days.

Sources of Marine Weather Forecasts Metphone – dial 0900 999 + area number

Inshore Areas:

  • Bay of Islands 0900 999 98
  • Auckland 0900 999 99
  • Coromandel 0900 999 96
  • Coastal Areas
  • Brett 0900 999 60
  • Colville 0900 999 61
  • Raglan 0900 999 75
VHF

Maritime NZ Radio provides forecasts at 0533,0733,1033,1333,1733 and 2133 hours. The forecast is announced on channel 16 and then broadcast on the area working channel.

In the Auckland area, Northern Coastguard channels 20 and 21 give a continuous broadcast of weather and safety information including Nowcasting data.

In Whitianga, eastern coastguard Channel 23 gives a continuous broadcast of weather and safety information.

Other sources of marine forecasts include:
  • National Radio (AM and FM) after the 3am and 5am news.
  • TELETEXT on Television
  • Newspapers, but these will be published many hours earlier.
  • Local radio stations, especially in summer.
  • Private coastal radio stations
  • www.metservice.com
 
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