10 A globally accepted system that uses latitude and longitude coordinates allows us to locate any place on the earth’s surface. Latitude measures locations on the globe that are north and south of the Equator. The measurements are stated in degrees, minutes and seconds. The highest numerical readings for latitude are ninety degrees north (90°N) and ninety degrees South (90°S). The Equator is zero degrees (0°). The Equator divides maps of the earth into Northern and Southern hemispheres. When lines of latitude are shown on a map, a globe or graphic of the earth they are displayed as parallel with the Equator and are equidistant. One degree of latitude is equivalent to 70 miles. Longitude measures locations east and west of the Prime Meridian. In 1884 it was agreed that the Prime Meridian identified a location in Greenwich, London, England. You should note that the most widely used meridian in more modern times is the IERS Reference Meridian. The International Reference Meridian (IERS) was devised from the Greenwich Meridian but it is slightly different. The difference between both is because of variations between astronomical and geodetic coordinates. Those differences are important in this age of satellite imagery. Lines of longitude are also stated in degrees, minutes and seconds. Longitude is measured in degrees that extend both east and west of the Prime Meridian to a maximum of one hundred and eighty degrees east and west (180°E or °W). The International Date line is at 180 degrees. The Prime Meridian is zero (0°) degrees. It divides maps of the world into the Eastern and the Western hemisphere. On a map, the lines of longitude meet at the North and South Poles. At the Equator one degree of longitude is equivalent to about 70 miles but only at the Equator. That distance becomes smaller and smaller until the longitude lines meet at the Poles on a map or a globe. Lines of longitude are known as meridians and not parallels. It is the intersection of the values for latitude and longitude that give a unique position for a specific location. The locations of storms or hurricanes are given in terms of latitude or longitude for the centre of the system, e.g. seventeen degrees North and sixty degrees West. (17°N 60°W). That information makes it possible to track the movement of the system on a map or follow it on technology-created schematics. When you know the location of your country (a CARICAD member state for example) in latitude and longitude you can get the earliest indication of the proximity of your country to likely effects from the storm. Additionally, you will get a clearer picture by examining the predicted, projected path of the system as given in weather reports. Remember that the centre of the hurricane could be anywhere in the “cone of uncertainty’ and there is about a thirty per cent chance that the system will also travel outside the cone. You must be mindful that a hurricane can be hundreds of miles across and hurricane conditions might extend for a hundred miles or more from the centre. Continues on next page
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