Tornado affects the Mack Pond Area
Antigua and Barbuda Meteorological Services
On Monday 11th April 2005 at approximately 18:30 GMT we observed that the weather conditions showed a change from the pattern that was observed for the day. We noticed unstable conditions mainly to the east and north of the Aerodrome at V.C Bird International Airport.
Within fifteen minutes we received a call from a resident in the All Saints-Mack Pond area of a howling sound emanating from a dark sky with clouds spiraling like that of a tornado. There was also a report of galvanized sheeting removed from the roof of an old outdoor toilet facility. Immediately I conducted a detailed and in depth observation and contacted Deputy Director of the Meteorological Services, Mr. Philbert Mason. Within minutes he journeyed to the All Saints Mack Pond area accompanied by Meteorologist Mr. Ewald Samuel.
They confirmed the presence of a funnel cloud which had touched down as a small tornado in the Mack Pond area.Residents reported structural damages to a church as well as the removal of roofing and galvanized sheeting to an outdoor toilet and bathroom facilities. Forecaster Mr. Llewellyn Dyer who later joined his colleagues, estimated that based upon the damages he observed, the winds may be 40 to 45mph.
From a meteorological stand point we firmly believe that there were several factors that contributed to the phenomenon which occurred yesterday. Firstly the winds came in from the south at light speeds. Secondly the daytime temperature was very hot, 32°C or 90°F. Further, the hilly terrain of the English Harbour and Monks Hill area provided the mechanism for the growth and development of the storm cloud. All of this culminated in an abundance of convective activity specifically in the Mack Pond, All Saints area which assisted in the development of the funnel cloud that eventually touched down as a small tornado. It must also be mentioned that residents as far as the Sweets area reported large diameter size raindrops and gusty winds, apparently from strong down draughts.
Given that the atmosphere was very stable beyond five thousand feet, the occurrence of the tornado was confined to four thousand feet above the surface of the earth. Had the atmosphere been more unstable beyond five thousand feet, I am convinced that we would have seen a more powerful system with the potential to cause tremendous widespread damage to property and loss of lives. Truly we have a lot to be thankful to God for.
In conclusion, the weather phenomenon which occurred on Monday was a microscale¹ feature and went undetected by the forecast models whose scale is synoptic²or at least mesoscale³. It was the weather radar images from Meteo France in Guadeloupe that provided the best guidance in addition to the first hand reports that were given by observers.
¹Micro - scale: The smallest scale of meteorological phenomena that range in size from a few centimeters to a few kilometers. Larger phenomena are classified as mesoscale. It also refers to small scale meteorological phenomena with life spans of less than a few minutes that affect very small areas and are strongly influenced by local conditions of temperature and terrain.
²Synoptic-scale: The scale of the high- and low-pressure systems of the lower atmosphere which typical dimensions range approximately from 1000 to 2500 kilometers (synoptic-scale circulation).
³Mesoscale: The scale of meteorological phenomena that range in size from several kilometers to around 100 kilometers. This includes MCCs, MCSs, and squall lines. Smaller phenomena are classified as micro scale while larger are classified as synoptic-scale.