Accra, Dec 15th, GNA - Ghana and her neighbours in the West African sub-region are experiencing some variations in their weather systems. These variations are the effects of the global weather phenomenon, La Nina.

The Senior Forecaster and Deputy Officer in Charge, Ghana Meteorological Agency, Kotoka International Airport, Torgbui Gbebie Fiamekor I, told the Ghana News Agency in an interview, that the effect of La Nina on the sub-region and Ghana in particular, was erratic rainfall which was typically heavy. This was because the sea was relatively warmer than normal, resulting in more evaporation which led to cloud development and rainfall. The Senior Forecaster said the La Nina period would last till February 2011, which meant that part of the dry season would come under its influence.

"There is the probability that the dry season may not be severe because of the changes in the atmosphere", he said. Torgbui Fiamekor explained in meteorological terms that the sub-tropical high pressure systems over North Africa which steered the cold air from the Mediteranian down to Ghana were very weak. "Currently, the sun is directly over the southern hemisphere, which is now experiencing summer, and on the other hand, the angle of inclination of the sun's rays is very small, resulting in less heating taking place over the northern hemisphere which is now experiencing winter." He said this implied that the northern hemisphere was very cold, adding, "this cold causes high pressure build up. The intensification of these high pressures at this time steer the cold air mass from Europe to Africa."

Torgbui Fiamekor I said this year, the sea was warmer than normal, resulting in more moisture than usual. According to him, with the high pressure being too weak to steer the dry wind flow from the Sahara, the dry atmosphere that typified the harmattan season was absent, whilst the moisture being generated from the sea resulted in cloud formation and ultimately, rainfall. "That is why we have a relatively weak harmattan season, as well as heavy rainfall from time to time."

He said although dry air had invaded Northern Ghana, extending to northern Brong Ahafo and the northern part of the Volta Region, the condition was not that severe; "just a mild haze because of the weak sub-tropical high pressure over north Africa."

Torgbui Fiamekor I said the typical effects of the harmattan such as the dry winds and dust could however intensify at the later part of the dry season, specifically from January to February, when the effect of the La Nina was weak and the high pressures had intensified. 15-12-10