Specialised Meteorological Centre

Darwin RSMC - FAQ

What is the ACCESS Model?

Why can't I see the charts?

All charts are currently only available through Registered User Access, so you require a user-name and password to access them. Access for meteorological organisations can be arranged by contacting Darwin RSMC. For other users please refer to the Registered User Services page for access details.

What is RadioFax?

Many of the black and white charts on the RSMC web page are broadcast over a HF radio facsimile service now called VMC and VMW. This replaced AXI and AXM, which was operated by the Royal Australian Navy on 1 July 2002. More details are available in the RadioFax Guide and A Guide to Marine Radio Services pages.

For general information about Radio Fax Services(pdf version)

Can you explain the different types of charts?

The following discusses weather charts available on the Darwin RSMC web page -

  • Analyses (ANAL) are drawn from weather observations taken at a particular nominal time (0000, 0600, 1200, 1800 UTC) and therefore describe the weather pattern as it occurs. Computer generated charts are usually only for 0000 and 1200 UTC.
  • Prognoses (PROG) depict forecast patterns at selcted times, usually at +12, +24, +36 and +48 hours from the analysis time.
  • Isobars connect points of equal surface pressure and are represented by numbered solid lines.
  • Streamlines represent the wind flow direction and are represented by arrowed lines.
  • Isotachs represent points of equal wind speed and are drawn using dashed lines. All wind speeds are 10-minute averages.
  • Wind Barbs indicate the strength and direction from which the wind is blowing.
  • Mean Sea Level Pressure (MSLP) Analysis & Prognosis -
    These charts represent surface pressure fields. lsobars are used to connect points of equal mean Sea level pressure and are represented by numbered solid lines.
  • Gradient Level Wind Analysis -
    This chart is a combination of a pressure (isobar) analysis poleward of latitude 35, and a streamline analysis between 35N and 35S.
    The gradient level lies 1000 metres above the earth's surface and is chosen as the level most representative of the lower atmosphere. The wind at the gradient level, whilst being representative of the surface wind, is less likely to be. modified by topographic and surface friction effects.
    Also included on these charts are tropical cyclone positions, including information on their names, maximum wind speeds, central pressures and speeds and directions of movement.
  • Upper Wind Analysis & Prognosis -
    The standard upper level charts are 850, 700, 500 and 250 hPa. These charts represent the wind flow at the these levels as either winds barbs or as fixed length vectors with isotach contours.
  • Sea Surface Temperature (SST) Analysis -
    This chart is produced every Tuesday and depicts the distribution of sea surface temperatures. Isotherms join points of equal temperature and are depicted by numbered solid lines. Values represent the mean sea surface temperature for the preceding week based on ship and satellite-derived observations.
  • Current Warning Summary -
    The Current Warnings Summary is a relay service providing a summary of current tropical cyclone warnings and gale/storm warnings that have been issued by those meteorological agencies operating within the area 70E-180, 25N-25S.
    The Darwin office does not modify these warnings from other agencies but collates them into a unified bulletin. Occasionally an advisory message will be appended to a Current Warnings Summary if there exists an unwarned system for which the Darwin office feels a warning is appropriate.