Making a Case for Heat Advisory Watches and Warnings


Staying hydrated is a must during any heatwave

In the middle of what is traditionally described as the wet or rain season, Grenadians for the first time had to take personal measures to deal with heatwave weather advisories that for some are only heard during the weather segment on USA news networks.

“This weekend is forecast to have lower cloud cover, lighter temperature compared to the last few days. Dress appropriately, stay hydrated by drinking plenty of water, avoid closed spaces, look after the young and old,” was the advisory published by both the Met Office and the National Disaster Management Agency.

Explaining that such an advisory will be issued when temperature occurs for two consecutive days beyond the statistical marker of 31.7 degrees Celsius, Gerard Tamar, Head of the Meteorological Office at the Maurice Bishop International Airport said that these advisories are aimed at warning citizens about the weather condition and the need for them to take personal care.

The heat advisory warnings were preceded by days and nights of high air temperature which had citizens complaining about the humidity. To deal with the high temperature during the months of August and September there was an increase in sales of fans, air conditioners and just about any and everything that will provide a cooler environment.

One of several warnings issued during August.

As the heatwave became the trendy topic of discussion, Tamar and the other forecasters at the Met Office used every available broadcast medium to explain that the heatwave is formed when there is a surge in air temperature and an increase in maximum temperature recorded for the day. 

“What is normally used to determine or call the heatwave is when we have temperatures or the maximum temperature of the day exceeding or reaching the 98 percentile of recorded temperature. In other words, when you look at all the historic data you have and the maximum temperatures, you figure out what is the 98 percentile and anything above that determines a heatwave… It is a statistical call,” he said in an interview. 

“How it works out is that you will notice it is generally hot and with us in Grenada and the Caribbean we find it occurring at this time of the year where we normally call it our heat season and it normally runs from June to September. Coupling with that high humidity is low wind speed, so it seems to be a combination of factors which help exacerbate it,” he said while point out that for Grenada’s statistics the marker is 31.7 degrees Celsius but, on several occasions, it surpasses that reading during the height of the heatwave period.

Heatwave Warning issued by the Authorities

“We have statistical data here at Point Salines going back to 1985, so we have more than the 30-year climatic average. In climatology the average is to go back 30 years. The data is showing we are getting hotter, every valuation of temperature, it is showing we are getting hotter, not only in Grenada or the Caribbean but globally,” said Tamar who explained that the warnings were applicable both night and daytime.

“For us in Grenada what we are seeing or the more telling thing we are seeing is the nighttime temperature is getting hotter more so that with daytime temperature. We are not cooling as much as we used to. The data is showing a steady increase in daytime temperature, but it is more dramatic with the night time temperature,” said Tamar.

“Going back to the 1980s we used to see our highest nighttime temperature getting up to the high 25 point or the low 26 point but like every ten years we seem to be going up, there is a gradual increase, now we are getting nighttime temperature like 27 degrees,” he added. 

In the USA and Europe, citizens are warned about high temperature through advisories that are formatted based on a heat index but there is no heat index formulated for Grenada and the region but a 2021 study funding by the Pan American Health Organisation makes a strong argument for establishing a heat index chart.

Conducted by Public Health Specialist Dr. Lindonna Telesford the 2021 study indicated the direct impact of high temperatures on mortality in Grenada. The study develops the methodology to do heat health studies for the Caribbean and it was one of the initiatives leading up to the development of the Health National Adaptation Plan for Grenada.

Added to the other heat-related illnesses such as dehydration, heat cramps, heat stroke, and accelerated death from respiratory diseases, Dr. Telesford noted increased deaths can be one of the major impacts despite Grenada and its citizens being accustomed to the warm tropical climate.

Heat Index (°C)Increased Relative Risk of Mortality (lag days)Increased Relative Risk of Hospital Admission (lag days)Increased Relative Risk of Emergency Room Visit (lag days)
Heat Index values below 90th percentile352.20 (immediate)1.40 (6)
Heat Index values at or above 90th percentile394.0 (immediate)2.0 (6)1.30 (1), 1.60 (5-6)
415.0 (immediate)2.10 (6)1.35 (1), 1.70 (6)
458.0 (immediate)3.00 (6)1.50 (1), 2.00 (6)

Tamar is in support of the Heat Index chart but admits that it will require the involvement of other stakeholders. “Our heat index is something that we must work upon and the best way to do it is to have a multi sectoral approach to doing it. We provide the raw data, but we will also need other sectors because we will not know how heat affects particular industries,” he said.

“The heat index is something that have to be derived because what a heat index will tell you is that a particular temperature you can expect this and at a particular temperature you can expect that, so therefore you will have to offer guidance on what to expect,” he said while recalling that several years ago the local Met Office used one that it got from an American source.

“We used it for a while and then we figured that it was not working exactly for us because our conditions are different, but the discussion last year was to see how we could generate one locally and that approach should be explored,” he said. 

The study further shows that one of the groups of citizens who are susceptible to the negative side effects of heat waves are outdoor workers such as construction workers and market vendors.

“What the study shows is that some of the workers will experience health consequences if they fail to prepare themselves for working outdoors. These include wearing the appropriate clothes and consuming water. Failure to drink water can lead to serious medical problems, even death,” said Telesford.

The findings and recommendations of the study are integral for developing adaptation measures for the new health plan being developed by the Government. “These recommendations required the National Disaster Management Agency to lead the way for adapting to climate change effects especially when it comes to coping with heatwaves,” she explains.

Increase in Water Consumption?

As the heatwave days increase and more and more citizens began applying the dos of drinking plenty water as advised, data from two sources shows that over the past five years, there have been increase water use and possible consumption. 

Finding ways to “cool down” during the heat

Where it is very clear based on data from the MET office that temperatures have been increasing in the last ten years there is no data to show that there is an increase in the consumption of water because of the steady rise in the temperature and citizens are consuming water to ensure that they do not become dehydrated.

Data from the National Water and Sewage Authority and Central Statistical Office show that for the past five years water has been on the increase. Data from the National Water and Sewage Authority shows the increase in residential consumption. 

Residential water consumption for the period January 2018 to June 2023 in gallons:

  • 2018 – 1250003474.96
  • 2019 – 1281569468.05
  • 2020 – 1343601209.13
  • 2021-  1326524391.59
  • 2022 – 1325395854.86
  • 2023 –  688362388.97

“The figures here are telling, we are seeing an increase in consumption for each year since 2018 and though this year we are experiencing the heatwave, what the data is showing is our customers are using more and more water,” said Jamila Lewis, Communications supervisor at NAWASA.

Fans and Air Conditioned units were in high demand. 

Data from central statistics also show that the importation of bottled water has been increasing even when there was no heat advisory.

Grenlec, the main supplier or distributor of electricity, reported increased usage of power during the past 12 months, and many believe that the continuous need for the use of cooling systems such as air conditioners and other cooling systems is responsible for that increase. 

“Despite the challenges, 2022 witnessed growth in kWh unit sales across all sectors. Notably, each month set a new record for the highest consumption (excluding Grenlec’s own-use) for the respective month on record. It is noteworthy that gross generation increased by 8.2% compared to 2021, rebounding from the contraction of 7.7% in 2020 and the marginal growth of 2.8% in 2021,” said Benedict Brathwaite, the Chairman of Grenlec in the 2022 annual report.

Sales growth was consistently higher in each month and quarter of the year compared to 2021. In 2022, kWh sales were 9.48% higher than in 2021. The commercial sector, which constitutes 55% of total consumption, grew by 14.05% (15.47M kWh) over 2021. 

Customer Categories2022 GWh2021 GWh% Change
Industrial & Street Light10.8910.721.57%

Despite the increase in water and electricity to assist with a cooler environment, the heat wave is causing heat related illnesses that are seeing medication for heat related illness disappear from shelves. Pharmacists are experiencing an increase in over-the-counter medication for heat related illness such as rash.

“The heatwave is causing many to have rash over their body and we are recording an increase with medications for rash,” said one pharmacist who often recommends that they visit a doctor instead of purchasing over the counter medication. 

Despite high temperatures both day and night Grenada, according to the Chief Medical Officer, has not recorded any deaths directly linked to the heatwave. However, going forward policy makers should consider the benefits of issuing not just heat advisories but heat watches.

From scientific research, there is no doubt that heatwave will be become seasonal and like hurricane and therefore Just like when a hurricane or storm is approaching and citizens are put on notice with various levels of advisories such as tropical wave, tropical depressing following by storm watch and warnings so too consideration should be given for issuing heat watches, warning and excessive heat advisories.

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