RESPECTED climate change and extreme rainfall specialist Dr Christopher Burgess, in describing the torrential rains which battered the Corporate Area last Friday as “extreme”, says data from automatic weather stations that are privately owned have suggested “at least a 50-to-100-year return period event which is relatively extreme and rare because of the duration” of those showers.

The rains, which began around 4:30 pm on Friday, September 19, caused severe flooding along roadways, immobilising several motorists and commuters and inundating homes. The showers eased sometime after 8:00 pm, leaving debris and devastation.

Wednesday, Dr Burgess — who is a registered professional and civil engineer and who has worked on projects in multiple sectors, namely civil, environmental and coastal engineering — described communities in New Kingston, Cross Roads and Cherry Gardens as the “epicentre of the weather event”.

“There is no doubt that the rainfall was extreme,” he said.

In response to a query from the Jamaica Observer, the Meteorological Services of Jamaica said its recorded rainfall amounts from various stations for the Corporate Area, “during the severe weather event”, showed that for the Kingston College station there was: 39.1 mm of rain in three hours (5:00 pm – 8:00 pm). It said for the Mona Reservoir there was 68 mm of rain in two hours (5:00 pm – 7:00 pm), while for the station in Shortwood Teachers’ College there was 75.6 mm in two hours (5:00 pm – 7:00 pm). The Meteorological Services said its Mico University station (Cross Roads area) went offline during the period of heavy rainfall.

Climate Services Manager Jacqueline Spence-Hemmings said while the Meteorological Service did not have the 30-year mean information for all the stations from which the measurements came for the Observer’s query, what was certain was that the rains were significant.

She explained that the Meteorological Services’ mean rainfall record for the 30-year period between 1971 and 2000 for Mona in the month of September, for example, was 140 mm. She said Friday’s figure for Mona being 68 mm in two hours, when calculated against the 30-year mean rainfall for the month which was 140 mm, the result would be 49 per cent rainfall.

“So you got almost half of a figure that’s expected in a month in about an hour and a half — that’s significant,” she said while noting that the 140 mm for September was based on the old mean as the most recent mean, which is 1991 to 2020, is not yet published.

“A better way to contextualise would be the intensity, to say how much per minute [rainfall there was] but, based on how the data is collected, we don’t have that. But generally, if you got half of what you would expect for a month in one and half hour that’s significant,” she told the Observer.

In the meantime, Dr Burgess said the readings given by the Meteorological Services are lower than those recorded by privately owned stations that are, albeit, in slightly different locations.

“If we take the measurement of the met office then certainly it’s less extreme than I am thinking; it would be in the order of maybe even a five-year event — which the roads should have been capable of taking,” he argued.

On Monday, professor of urban planning and public policy at the University of Technology, Carol Archer said Friday’s deluge which trapped motorists and wrecked homes will “continue” unless there is a complete overhaul of the current rainwater infrastructure and enforcement of existing legislation.

“We have the necessary legislation; what we need is the enforcement, plain and simple. Right now what is happening is the lack of enforcement so persons are still getting away with the [wrong] kinds of development. They will argue that there is no regulation for the Building Code so who is going to enforce rainwater harvesting when there is no regulations? Let’s move on that, let’s get it done, and let’s update,” she said.

In the meantime, the Meteorological Services said Tuesday that a trough is expected to remain across the island over the next few days and should bring scattered afternoon showers and isolated thunderstorms across sections of most parishes this Thursday and Friday.