By Sarah Haddon, Meteorologist
The MetService team produces both coastal and recreational marine forecasts. Part of these forecasts includes the state of the sea and the swell. But what is the difference?
Firstly, it is important to understand how a wave is described. Figure one shows the different characteristics of a wave.
New Zealand lies mid-way between the tropics and the Southern Ocean, and our day-to-day weather can arrive from either direction. On a longer time scale (weeks to months), tropical weather is influenced by the state of the El Nino-Southern Oscillation (ENSO). The ENSO climate pattern affects wind flows, rainfall distribution and sea temperatures right across the tropics, from equatorial South America to Indonesia. It also has some effect on New Zealand’s climate (winds, temperatures and rainfall patterns), although generally to a lesser degree than in the tropics.
Besides the coastal waters, the MetService forecasting team produces marine forecasts for a number of smaller areas where there is a lot of recreational boating activity. These forecasts are routinely issued four times every day; they are monitored continually and updated more frequently if conditions warrant it.
The recreational forecasts are written for high-use recreational areas: Bay of Islands, Auckland, Coromandel, Bay of Plenty, Hawke Bay, Kapiti, Mana, Wellington, and Christchurch.
MetService's forecasting team produces marine forecasts for New Zealand coastal waters. These forecasts are routinely issued four times every day; they are monitored continually and updated more frequently if conditions warrant it.
Forecasts for coastal waters cover the area from the coastline to 60 nautical miles (about 100km) out to sea. The New Zealand coast is divided into 18 areas, as shown in figure 1:
Talking temperatures, 2014 will be remembered for being somewhat back-to-front. With a cooler than usual start and finish to the year for much of the country, the middle months of 2014 were very mild.
Weather balloons have been released for decades around New Zealand to record data throughout the lower layers of the atmosphere. They have been used to measure everything from the base of low cloud to atmospheric wind and temperature profiles. One of the first people to use weather balloons was French Meteorologist Léon Teisserenc de Bort. He released hundreds of weather balloons from his observatory in Trappes, France. His experiments lead to the discovery of the tropopause and the stratosphere.
The development of modern radar started in 1886, when German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. In 1904, another German, Huelsmeyer, was the first to build a simple ship detection device, successfully detecting a ship in dense fog. In the pre-war period (the 1930s), many nations were working on radar devices. A major advance occurred once systems were developed that allowed short ‘pulses’ of radio energy to be generated, allowing the range of the object to be determined by timing the pulses.