The World Meteorological Organisation
The World Meteorological Organisation co-ordinates global scientific activity to allow increasingly prompt and accurate weather information and other services for public, private and commercial use, including international airline and shipping industries.
Within the United Nations, the Geneva based 185 Member Organisation provides the authoritative scientific voice on the state and behaviour of the earth's atmosphere and climate.
The purposes of the WMO are to facilitate international co-operation in the establishment of networks of stations for making meteorological, hydrological and other observations. Promote the rapid exchange of this information and standardise the format within which the information is broadcast
The World Meteorological Congress, which is the supreme body of the WMO, meets every four years. It determines policies, approves the programme and budget and adopts regulations.
Members are grouped into 6 regional associations (Africa, Asia, South America, North and Central America, South West Pacific and Europe). These groups meet every four years to co - ordinate meteorological and operational hydrological activities within their region and to examine questions referred to them by the council
WMO has eight technical commissions responsible for: aeronautical meteorology; agricultural meteorology; atmospheric sciences; basic systems; climatology; hydrology; instruments and methods of observation; and marine meteorology. Each commission meets every four years.
The Safety Of Life at Sea (SOLAS) convention requires that the United Kingdom provide Marine Safety Information (MSI), including gale warnings, storm warnings and weather bulletins suitable for shipping for its area of responsibility as defined in the Global Maritime Distress and Safety System regulations.
This area includes the waters around the British Isles, North West Europe and the High seas of the North Atlantic (Metarea 1).
The Information is broadcast via Inmarsat and, when in coastal waters the NAVTEX service on 518 kHz. MSI is also broadcast on VHF, MF and HF SSB HM Coastguard broadcasts.
In the United Kingdom, the Met. Office initiates warnings as required, and prepares the routine forecasts for transmission.
Storm Warnings
Storm Warnings are issued for the High Seas area of the North Atlantic when winds are expected to reach Force 10 or above.
Gale Warnings are issued for the U.K. Shipping Forecast areas when winds are expected to reach at least Force 8 or gusts reaching 43 knots. Gale warnings remain in force until amended or cancelled, and will be re issued if the gale persists for more than 24 hours.
Gale warnings are transmitted in the following form: -
“Gale warning issued 1 May 0500UTC. Malin, Hebrides, southwesterly gale Force 8, imminent. “
‘Imminent’ means within 6 hours of the warning being issued.
‘Soon’ means between 6 and 12 hours of the warning being issued.
‘Later’ means more than 12 hours of the warning being issued.
Strong wind warnings are issued for the ‘Coastal strip’ (waters up to 5 miles off shore) whenever winds of Force 6 or above are forecast. These warnings automatically expire 12 hours after issue.
Radio
Shipping Forecast
The shipping forecast is prepared 4 times a day for broadcast via the BBC Radio 4 transmitters on 198kHz at: -
0048, 0535, 1201, 1754 local time.
The bulletin consists of: Summary of gale warnings in force
General synopsis
Area forecasts
Coastal weather reports (0048 and 0535 only)
The synopsis will cover the next 24 hours, and the forecast for the next 24 hours will be given in a fixed rotation including details of wind direction and force, weather, visibility and superstructure icing.
Shipping Forecast Broadcast Times
0535 on 198kHz LW and 92.4 - 94.6MHz FM
1201 on 198kHz LW
1754 on 198kHz LW (Mon - Fri)
0048 on 198kHz LW and 92.4 - 94.6MHz FM
Gale warnings are issued as separate messages and are broadcast on Radio 4 at the first available programme junction following receipt at the BBC. If this does not coincide with a news bulletin, the warning will be repeated after the next news bulletin.
A brief 24-hour forecast for the inshore waters is broadcast after the main shipping forecast at 0053 and 0539. The inshore waters are divided into 9 areas defined by prominent headlands or geographical names. The inshore forecast contains details of wind direction and force, visibility and weather.
The MCA provide a comprehensive VHF and MF service for shipping, which includes the broadcast of gale warnings and strong wind warnings, those parts of the shipping forecast for the area covered by the station and the relevant part of the inshore forecast.
The forecast bulletins are transmitted twice daily by the area Maritime Rescue Co-ordination Centre. (MRCC) Details of times of transmission can be found in the A.L.R.S.
Warnings are transmitted on receipt and repeated in the next routine broadcast. The order of transmission would normally be as follows;
Inshore waters forecast
Strong wind warnings
Gale warnings
Shipping forecast for the relevant area
Navigation warnings
Naval exercise warnings
Any other messages on hand
Navtex
Navtex is an International automated direct printing service, broadcast on 518kHz for the promulgation of navigational and meteorological warnings and other urgent messages for shipping.
It fulfils an integral role in the GMDSS and is also a component of the World Wide Navigational Warning Service. It has been developed to provide a low cost, simple means of receiving marine safety information on board ships at sea in coastal waters.
The special equipment consists of a dedicated receiver tuned to 518kHz connected to a continuous feed printer. The receiver is left switched on continuously and may be programmed to accept relevant station messages. Some types of safety messages cannot be rejected by the receiver including navigational and meteorological warnings along with search and rescue information.
The U.K.Navtex service is provided by the M.C.A. to meet its obligation to provide marine safety information at sea. It includes the twice daily broadcast of the 24-hour Area forecast, an outlook for the next 24 hours and an extended outlook to identify hazards in the next 36 hours. Gale warnings are broadcast on receipt from the Met. Office and repeated in the next four hourly routine broadcast.
There are three U.K. Navtex transmission stations; Cullercoats (G),
Niton (S) and Portpatrick (O). Details of broadcast information and transmission times are available in the Admiralty List of Radio Signals Volume 3.
Radio - Facsimile Broadcasts for Shipping
The receipt of graphical meteorological information has continued in the form of HF Radio facsimile broadcasts. There are a number of different types of chart broadcast, which include:
Surface Charts
1. Surface Analysis with observations.
These charts give a picture of existing conditions at the preceding synoptic hour. The isobaric patterns enable the observer to visualise the general weather and conditions likely to be encountered.
The isobar spacing varies from country to country. The U.K. uses
4 hPa as the standard, but other countries use 5 hPa and 8 hPa spacing. The symbols used for fronts are those agreed by IMO.
If observations are included the information is shown as a standard station model.
2. Surface Prognosis.
These extend the synoptic period to give a forecast of the weather. This forecast is based on a computer model of the atmosphere. Forecasts are made for different periods of time, 12 hrs, 24 hrs, 48 hrs, 72 hrs, 96 hrs and 120 hrs are the most common periods.
3. Change of Pressure Charts.
These charts show isallobars, lines joining stations with equal change of pressure, and can be used for extrapolation.
Sea Charts
1. Sea surface temperature analysis.
These normally use isotherms in degrees Celsius. These could be used as an aid to fog forecasting, cargo care and locating ocean currents. One of the most common applications is in tracking shoals of fish which prefer the sea temperature to lie in a certain range.
2. Wave charts.
Wave charts are of most value when used with synoptic charts to indicate general area of heavy weather. Isopleths of wave heights are shown and the direction of wave trains is indicated by arrows. The isopleths are of "significant wave height". This is defined as the mean height contours of the third highest seas. If waves vary from 2 to 8 metres, they can be divided into thirds, (2-4, 4-6, 6-8). The mean of the upper third will be 7 metres.
3. Ice and Iceberg Information.
These charts the amounts of each type of ice and the boundaries of bergs, packs and leads. The charts are based on observations as far as possible, but meteorological, climatic and oceanographic data are also used. They are often combined with sea temperature charts.
4. Ice accretion charts
These charts show areas where ice accretion is likely to occur and the rate at which ice will accumulate.
Other Meteorological Charts
1. Constant pressure analysis and prognosis
Charts are made for 850, 700, 500, 300, 200 and 100 hPa. The charts show the height of the surfaces upon which the pressure has some fixed value. The contour lines shown on the chart approximate to streamlines of motion at that level.
2. Layer thickness charts
The most common chart is the 500 / 1000 hPa thickness chart.
3. Wind plotting for upper levels.
2 and 3 can be used in forecasting the movement of pressure systems.
4. Environmental lapse rates
5. Tephigrams for selected stations.
4 and 5 are used for forecasting atmospheric stability etc. The data for these is collected by radiosonde at airports and from some ships.
6. Satellite images
These show the distribution of clouds as seen from satellite. The images may be from polar or geostationary satellites and they can be in the visible or IR part of the electromagnetic spectrum. They can be used to identify the position of depressions, anticyclones, fronts, TRS etc. They are particularly useful for areas where surface observations are sparse.
7. Nephanalysis
This chart is a pictorial representation of the satellite cloud picture and shows areas of cloud and cloud types.
Definitions
Gale: Winds of at least Beaufort force 8 (34 - 40 knots) or gusts reaching 43-51 knots.
Severe Gale: Winds of force 9 (41 - 47 knots) or gusts
reaching 52 - 60 knots.
Storm: Winds of force 10 (48 - 55 knots) or gusts reaching 61-68
knots.
Violent Storm: Winds of force 11 (56 - 63 knots) or gusts of 69
knots or more.
Hurricane force: Winds of force 12 (64 knots or more). Note the term " hurricane " on its own is only used to define a true tropical cyclone.
Imminent: Expected within 6 hours of time of issue.
Soon: Expected within 6 - 12 hours of time of issue.
Later: Expected more than 12 hours from time of issue.
Visibility
Fog: Visibility less than 1000m.
Poor: Visibility between 1000m and 2 n.miles.
Moderate; Visibility between 2 and 5 n.miles.
Good: Visibility more than 5n.miles.
Movement of pressure systems
Slowly: Moving at less than 15kts
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dariusz.lipinski