Friday 21 September, 2018

Met Office: High chance of heavy rainfall, heat spells in September

Photo: Flooding in the Caparo area in June 2017.

Photo: Flooding in the Caparo area in June 2017.

Citizens in Trinidad are being warned of wetter-than-normal conditions from September to October, along with higher-than-normal temperatures. 

In an update, the Trinidad and Tobago Meteorological Service said most of Trinidad experienced a wetter than average August and the outlook for September to November shows increased chances for the continuation of wetter than usual conditions, with an increased potential for flooding.

The Met Office said Sangre Grande and surrounding areas are estimated to have the largest rainfall with accumulated totals of approximately 1067.0mm (3.5 feet), while areas near Cedros and Icacos in the southwest are likely to receive the least amount.

North-eastern Tobago in areas near Mount Saint George is favoured to receive the highest accumulated rainfall totals, while the smallest totals are likely in the vicinity of Canaan and Bon Accord.

 

Likely impacts: Heavy flooding

In Trinidad, October and November typically have increased frequency in prolonged rainfall that can lead to flooding, while September and October are part of the peak of the hurricane season. 

Citizens are being warned of the following:

- Flooding potential associated with heavy rainfall days is enhanced for flood-prone areas

- Wetter than usual conditions are likely to reduce water stress in areas where this exists. Drier than usual conditions are likely to worsen existing water stress conditions

- Increased potential for heat stress in the vulnerable population and small livestock during September and October, especially in areas with drier than usual conditions. Cooling needs will be greater in most areas.

- Existing surface wetness is likely to become enhanced. This increases landslip and landslide potential in areas so prone.

The Met Office said however that most of Tobago experienced drier than usual conditions during June, July and August. An outlook for near to below average rainfall in the coming three months, suggests improvement in rainfall deficit are less likely to occur during the period.


(Photo: Category of rainfall most likely for December 2018 to February 2019 (DJF) with the highest chance of occurrence expressed as probabilities and colour coded on the map. Blues indicate that it is more likely for above normal rainfall to occur than for below normal or near normal. Browns indicate it is more likely for below normal rainfall; while greens indicate it is more likely for near-normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the DJF period rainfall totals during the historical period used to produce the outlook.)

 

Met Office: September the hottest month?

The Met Office projected that the peak of the second local heat season is likely to take place in September with some of the warmest days.

The Met Office said there is a 70-80 percent chance of at least seven hot-spell days from September to November 2018 where temperatures may exceed 33.9 degrees Celsius in Trinidad and 32.2 degrees Celsius in Tobago.

The Met Office added that chances for this to occur are greater than 40 percent for all of Trinidad. Tobago has the most likely chance for near normal to below normal accumulated rainfall totals (high confidence). 

"In most years, September to October is the second heat season in Trinidad and Tobago, with September often the hottest month. Warmer than average daily temperatures are likely during September to October and there is a greater than 70 percent chance for September to November days and nights to be warmer than average with September and October days and nights likely to be the warmest."

Implications

The Met Office said these high temperatures can aid more intense showers, which will increase the risk for flash floods on hot days, especially in the cities and built-up areas. 

A risk of flash and riverine flooding, landslips and landslides on heavy rainfall days and prolonged wet spells remains relatively high, as well as an increase in recharge rates at water reservoirs associated with wetter than usual conditions. Slower than usual recharge rates may occur at water reservoirs in areas with drier than usual conditions.

The Met Office said an increase in surface water ponding can promote mosquito breeding, leading to higher risk for spikes in vector-borne diseases. 

"Increased rainfall, mixed with warm and humid conditions tend to promote rapid multiplication of some agricultural pests, diseases and fungal growth," the Met Office said, adding that increased rainfall could lead to reduced traffic flows, disruptions in localized travel, longer travelling times and increased disruption of outdoor activities.

The Met Office warned that excessive heat on hot spell days could lead to increased heat stress in the vulnerable population and small livestock until October.

Advice

The Met Office advised the following:

- Continue de-silting and cleaning of drainage systems, canals, drains, outlets and river mouths;

- Clean and clear choked surface drains to allow fast drainage and to reduce flash flood.

- Continue efforts to prevent waste from entering drains and water courses in order to reduce flooding;

- Implement anti-litter activities to raise awareness on the impacts of poor solid waste management.

- Clear bushes, open drainage systems, fumigate in and around residences;

- Revisit contingency plans to manage spike in vector-borne disease incidences.

- Sensitize communities on the forecast and its negative impacts;

- Revisit early warning information dissemination channels;

- Alert communities and citizens in flood and landslide-prone areas to act early.

- Put in place disease control measures; Ready pumps for clearing waterlogged drainage;

- Clear or clean poorly maintained and choked surface drains to prevent waterlogging;

- Initiate contingency planning for the likely drier than usual start to the upcoming dry season.

- Conduct routine de-silting of reservoirs and riverine flooding channels;

- Remove dry branches, trees and overhang near electrical wires, especially in landslip prone areas.

- Harvest excess rainfall now and revisit contingency plans for drier than usual DJF.

- Continue proper preparation especially for persons in at-risk areas. Stock up on emergency supplies for 3-7 days;

- Clean drains and canals; Conserve, store and manage water in a safe and adequate manner;

- Take measures to lessen impacts from flooding. Be sand-bag ready;

- Be vigilant and visit the Met. Service website at www.metoffice.gov.tt regularly to keep up to date with local weather changes and follow them on social media.

 

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