By Evan Thompson, Contributor
Image from Doppler radar. - File
ON GAINING Independence in 1962, Jamaica became an individual member of the World Meteorological Organisation (WMO) after becoming a signatory to its Convention. The WMO is a specialised agency of the United Nations that, among other things, was created to:
facilitate international co-operation in the establishment of networks of stations and centres that provide meteorological observations and services and
promote the establishment and maintenance of systems for the rapid exchange of meteorological and related information.
The Meteorological Service (Met Office in Jamaica), as we know it today, evolved through this arrangement although it was developed under British colonial rule during the 1940s. This evolution has continued over the years in all aspects of the Service with Jamaica making every effort not to lag too far behind the developed world in the use of state-of-the-art instruments and equipment in performing its functions.
The world has, over the short space of about 40 years, seen the inauguration of the World Weather Watch (WWW), the cornerstone of the WMO; the Global Observing System (GOS) which was set up to co-ordinate data collection throughout the atmosphere and in outer space; the Global Telecommunication System (GTS) which co-ordinates the transfer of meteorological data; and the Global Data-Processing System (GDPS) that carries out weather analysis and prediction to ensure the timely access to forecast products.
Developments in satellite technology followed, along with advancements in Numerical Weather Prediction (NWP) programmes that opened up new dimensions allowing meteorologists to apply their weather-related data to socio-economic fields with greater accuracy.
The Modernisation Programme undertaken by the Government of Jamaica since the early 1990s has also significantly impacted on the operations of the local Met Office. It has provided a catalyst for many of the developmental changes that have taken place within the Service over the past decade. These can be seen in the observation and data collection network, in the transfer of data locally and globally, in the area of data processing, and the application of information particularly with respect to medium- and long-range weather prediction.
Supplementing the work of meteorological observers on the island, the first Automatic Weather Observing Station (AWOS) was introduced in 1994 in Morant Point. Since then, the Service has been inching along, despite the limitations of funding, to develop a network of stations across the island and, so far, stations also now exist in Kingston, Montego Bay, Folly Point (Portland), Negril Point (Westmoreland) and on the Pedro Bank...the first offshore AWOS installed in the English-speaking Caribbean.
Additionally, four low-cost units were acquired through a project with the U.S. National Weather Service and are being monitored by affiliated Ham Radio operators. The AWOS is a data acquisition system comprising different instruments that measure atmospheric pressure, air temperature (current, maximum and minimum), relative humidity, rainfall, wind speed and direction and solar radiation.
It can also be configured to measure soil and grass temperature, surface wetness and ultra-violet radiation. Each instrument has electronic sensors, which are connected electronically to a computerised data acquisition unit that samples and stores the data. This 'intelligent' unit then processes the data and makes the results ready for collection either manually (using a simple data collection unit) or electronically (using a laptop PC).
In the latter part of 1999, the Met Service replaced its ageing, mechanical radar with a new, cutting-edge Doppler Weather Surveillance Radar (DWSR-8500S) that remains the showpiece of the English-speaking Caribbean. Apart from determining precipitation rates and intensities, this device is also capable of discerning the height of cloud bases, cloud tops, the depth of water accumulated on the surface in a period of time, and the total liquid content of cloud cells in each square metre. The Arbitrary Vertical Cross-Section product allows for a slicing of thunderstorm cells for complete analysis and there are also options for flash flood alerting, among other things.
Probably the most interesting of all the radar's capabilities is the Doppler application which equips the device to measure and display movements of wind and wind-related systems. With this feature, the system overshadows the previous mechanical system by being able to estimate wind direction and velocity at a specified height, range and angle. The wind input also makes it possible for the radar to detect horizontal and vertical wind shear, gust fronts, microbursts and mesocyclones by using special colour coding on the display to depict motion towards and away from the radar.
Part 2: Advancing technologies out in the field
Evan Thompson, head, Weather Branch, Meteorological Service
