Models showed from Oct 1 that Matthew would avoid Ja, says US meteorologistSaturday, October 22, 2016
BY VERNON DAVIDSON Executive editor – publications email@example.com
An American meteorologist and blogger at Weather Underground has said that it became clear to him from as early as Saturday night, October 1, that Hurricane Matthew would not have hit Jamaica, even as local forecasters were warning the country to prepare for some effects from the cyclone.
However, he admitted that there was some difficulty in predicting Matthew’s final path in relation to Jamaica, given the unusually sharp right turn it made in the central Caribbean.
"Forecasters knew as far back as Wednesday, September 28 that Matthew was likely to make a sharp right turn in the central Caribbean and head northward toward Jamaica and Haiti around Sat-Sun October 1-2," Bob Henson wrote in an e-mailed response to a
Jamaica Observer query.
"This part of the forecast was fairly clear. However, it was more difficult to tell exactly when that right turn would take place, and exactly how sharp it would be, since the steering currents driving Matthew were fairly weak," he explained.
Henson said that on Thursday, September 29 and Friday, September 30, computer models were trending a bit further west with Matthew’s track, which meant that Jamaica was at some risk of a direct hit.
"By Saturday, the models had shifted further east, reducing the risk to Jamaica. Once Matthew had started its sharp right turn to the north on Saturday night, it was then apparent that the hurricane was too far east to move toward Jamaica," Henson said.
Jamaica’s National Meteorological Service, in its bulletin number 12 issued at 11:00 pm on October 1, had advised that it was maintaining a hurricane warning for the island as Matthew turned toward the north-northwest.
"Matthew began to move toward the north-northwest at 11 km/h (7 mph). This general motion is expected to continue on Sunday, followed by a turn toward the north on Monday. On the forecast track, the centre of Matthew will approach Jamaica and south-western Haiti on Monday," the Met Service said in the bulletin.
According to the Met Service, it had expected that by Monday, October 3, Jamaica would have been affected by "dangerously high water or a combination of dangerously high water and exceptionally high waves, even though winds expected may be less than hurricane force" as well as average winds of 118 kilometres per hour or higher.
Twenty-four hours later, the Met Service’s bulletin number 19A advised that it was maintaining the hurricane warning as Matthew had strengthened slightly and had begun to move northward towards Jamaica as a "powerful category four hurricane".
Noting that Matthew was moving at near seven kilometres per hour, or five miles per hour, the Met Service said that that general motion was expected to continue through Monday, October 3.
"On the forecast track, the centre of Matthew will approach Jamaica and southwestern Haiti on Monday," the Met Service said, adding that outbreaks of showers and thunderstorms were expected to continue on Sunday night and the following day as Matthew approached Jamaica.
It said further that Matthew was expected to produce excessive rainfall, especially over eastern parishes, with the greatest accumulations likely over higher elevations of Portland and St Thomas, and that the rain could "produce extensive flooding and trigger dangerous landslides".
However, by the Monday evening (October 3) the Met Service downgraded the hurricane watch to a tropical storm warning, saying that the island was then expected to be outside the range of hurricane-force winds associated with Matthew, but was likely to experience tropical storm conditions.
The downgrade from a hurricane warning came after Jamaicans spent five days preparing for the cyclone that at one point grew to Category Five strength as it slow-marched across the central Caribbean.
Then, on Tuesday, October 4, the forecasters discontinued the tropical storm warning, saying that Jamaica was no longer faced with the threat of tropical storm-force winds as Matthew continued to move away and weather conditions improved.
However, the Met Service said that while Matthew was no longer considered a threat to Jamaica, the island could continue to experience isolated showers and thunderstorms, especially over eastern parishes.
By then, irate Jamaicans, many of whom had rushed to stock up on emergency supplies, hurled criticism at the Met Service, accusing it of making errors in its forecasts.
Among them was Montego Bay journalist and former parliamentarian Lloyd B Smith, who said he had grown increasingly concerned about weather forecasts as presented by local meteorologists, particularly in the electronic media.
"Based on my own experience, they have been wrong on numerous occasions. Indeed, a common joke among my colleagues and I is that whatever they say should be taken with a grain of salt, or one should expect the opposite outcome," Smith wrote in a letter to the editor of the Observer published on October 5.
"This latest episode with respect to Hurricane Matthew has seriously put a dent in their credibility in the eyes of John Public. This is a most dangerous scenario as the next time round when the island is threatened by a hurricane, many Jamaicans may totally ignore their forecasts," Smith said.
He recommended that a probe be launched into the Met Service’s modus operandi "in order to ascertain if there are any flaws or grey areas as to how they go about gathering data and interpreting these for the public".
Added Smith: "Forecasting the weather may not necessarily be the most exact science, however, citizens need to rely on their word, especially against the backdrop of climate change, which makes weather patterns very unpredictable. It should not be a case that one cannot tell for certainty whether or not the Met Office’s predictions will hold true. This could be a matter of life and death."
Two attempts by the Sunday Observer to get an explanation from the Met Service were not successful as the meteorologist to whom we were referred could not be contacted.
However, Henson pointed out that uncertainty is an occupational hazard among meteorologists.
"Every weather forecast has some uncertainty in it, which is why you see the ‘cone of uncertainty’ in the maps," Henson told the Sunday Observer in reference to the graphics published by the National Oceanic and Atmospheric Administration in the United States.
"You can see that the cone gets wider as the forecast ‘lead time’ gets longer," he said. "We are more confident about a forecast six hours from now than six days from now. This is largely because tiny errors in our ability to observe the atmosphere turn into bigger errors over time in the computer models that show us how the atmosphere is most likely to behave over the next few days. The science behind this is often referred to as ‘chaos theory’.
"In the case of Matthew, I think the forecast was especially difficult because of the hurricane’s unusually sharp right-hand turn. It’s more common for a hurricane to approach Jamaica from the east or east-southeast on a fairly direct path that doesn’t have such a sharp turn embedded in it," added Henson.