When observations should be made

Weather observations at sea should be made four times a day as close as practicable to the standard synoptic hours of 0000, 0600, 1200, 1800 UTC. As the observations require some time to complete, they should be commenced a few minutes before these standard hours.

The length of time required to make the observation will depend on the experience of the observer, but it should be arranged that all work is completed as close to the standard hour as possible.

In addition to the four daily observations taken at the standard synoptic hours, ships navigating within Canada and within the 200 SM zone of Canadian and US coastlines are requested to take supplementary observations at the intermediate synoptic hours of 0300, 0900, 1500, and 2100 UTC.

Procedure on single-operator ships 2.2.1

On ships carrying only one radio officer, it may happen that the officer's watch keeping period ends at or slightly before a standard synoptic hour. In such a case to ensure transmission of a message to a coastal station before the radio officer goes off duty, the observing officer should arrange to have their observation completed earlier than usual but not earlier than one hour before a standard synoptic time. The element of the observation denoting the time (

GG

) should be altered accordingly. E.g., if the observation is completed at 0508 UTC, then

GG

should refer to 0500 UTC, i.e.,

GG

=

05

. It is emphasized however, that this procedure should be adopted only in the particular circumstances described, and that the adherence to the standard synoptic hours is most desirable.

When it is impracticable to follow the procedures above (e.g. the radio officer has gone off duty earlier than one hour before the standard synoptic time) an observation should be taken and transmitted at one of the intermediate synoptic hours of 0300, 0900, 1500, or 2100 UTC. For example, if the radio officer is scheduled to complete their watch at

2200 UTC, then the observation should be taken and the message transmitted at 2100 UTC.

When an observation is taken at 0300, 0900, 1500, or 2100 UTC, it is desirable that an observation be taken at the next main standard synoptic time, i.e., 0600, 1200, 1800, or 0000 UTC, in order to ensure its transmission to a coastal station for climatological purposes.

MANMAR — Manual of Marine Weather Observations 2—11

Observations made at any of the standard times 0000, 0600, 1200, or 1800 UTC can be transmitted up to four hours after the time of observation if this arrangement will fit in with the radio officer’s watch hours. An observation received four hours late is much better than receiving no weather message at all. In the southern hemisphere, in the North Atlantic, and in areas where few reports are received from ships, an observation message may be transmitted as much as 12 h after the time of observation.

Non-routine reports 2.2.2

Ships observing officers are encouraged to send

SPREP

and

STORM

reports even if the above conditions were forecast. These reports will aid marine forecasters in verifying their forecasts.

2.2.2.1 Special weather report —

SPREP

It is important that observed, significant changes in weather conditions be entered into the forecast system as soon as possible. Significant weather developments frequently occur between the standard times of observation, therefore it is important to identify those changes and relay special weather reports to the forecast office without delay. A special weather report is identified by the code word

SPREP

. The observation and message format is the same as for a standard observation, except the word

SPREP

and one space will immediately precede the ship’s call sign to assure the immediate attention of the forecaster.

Example:

SPREP D....D YYGGi

_w

A special weather report (

SPREP

) should be sent whenever one or more of the following criteria are met:

Wind

 Mean wind speed doubles to 25 kt or more since the previous main or intermediate synoptic hour.

 Mean wind speed increases to 34 kt (gale force) or more and gale warnings are not in effect.

Visibility

 Prevailing visibility decreases to 0.5 SM or less from 2 SM or more.

Waves

 Combined seas (wind, waves, and swell) become hazardous or increase to 2–3 m (7--10 ft) or more in excess of those forecast.

Ice

 Ice forms on the ship’s superstructure.

2—12 MANMAR — Manual of Marine Weather Observations

2.2.2.1.1 Ships on the Great Lakes

A special weather report (

SPREP

) should be sent whenever one or more of the following criteria are met:

Wind

The wind with a mean speed of 25 kt or more:

 Increases in mean speed by 10 kt, or more, and is sustained for at least 10 min; or,

 changes direction by 90°, or more, and this change is sustained for at least 10 min.

Visibility

 Prevailing visibility decreases to ½ NM or less.

Waves

 Wave height increases by 1.5 m (5 ft) from the height observed at the previous main synoptic hour.

Ice

 Ice forms on the ship superstructure.

Weather

 A funnel cloud (water spout or tornado) is sighted

 Other hazardous weather conditions are encountered but are not mentioned in the latest forecast (MAFOR)

2.2.2.2 Storm report —

STORM

When storm (wind) conditions are encountered at sea, whether forecast or not, a

STORM

report should be issued. The observation and the message format is the same as for a standard observation, except the word

STORM

and one space will immediately precede the ship’s call sign. A

STORM

report should be sent hourly if the storm has not been forecast, or at least every three hours if experiencing storm conditions which have been forecast.

A storm report (

STORM

) should be sent whenever the mean wind speed increases to 48 kt or more.

Example:

STORM D....D YYGGiw

MANMAR — Manual of Marine Weather Observations 2—13

문서에서 Manual of Marine Weather Observations MANMAR (페이지 28-31)