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Normal to Above Normal Rainfall from September to November: Flooding Potential Remains High
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Key Messages
- High chances exist for normal to above normal rainfall totals during September to November (SON) over Trinidad and Tobago;
- Normal to above normal rainfall in the wet-season means wetter conditions with high rainfall events are possible;
- Enhanced chances for a higher number of extremely wet days (greater than 25.0 mm) during SON.
- September and November have moderate chances for near-normal rainfall;
- October has the highest chance for above-normal rainfall (greater than 200.0 mm at both Piarco and Crown Point stations);
- SON period rainfall totals with the highest chance of occurring range between 400-1073 mm in Trinidad and between 491-963 mm in Tobago;
- Both day and night temperatures are predicted to be mostly average for most of Trinidad and Tobago with low (25%) probabilities for short-duration hot spells in September and October.
- A reasonably moderate chance (60%) exists for short-duration warm spells during the last week of September and the first week of October (maximum temperatures will average around 34.0 oC in Trinidad, and 32.0 oC in Tobago);
Likely Impacts
- Average to Above average rainfall totals during the wet season with enhanced chances for a higher than usual number of wet days suggest a high potential for flooding exist;
- Already soaked grounds and increased water flows, along with wet as usual wet-season conditions, increase the risk of flash and riverine flooding, landslips and landslides;
- Recent increases in surface water ponding can promote mosquito breeding. This will increase the risk for higher incidences of vector-borne diseases, especially during September and October;
- Increased rainfall, mixed with warm and humid conditions tend to promote rapid multiplication of some agricultural pests, diseases and fungal growth.
- Wet season rainfall is associated with high fly and mosquito populations.
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Early Actions & Preparedness
How Should You Respond? Take Early Action!
Health Sector:
- Clear bushes, open drainage systems, and fumigate in and around residences;
- Revisit contingency plans to manage the spike in vector-borne incidences and rainfall-related infections.
Disaster Risk Management Sector:
- Sensitize communities on the forecast and its negative impacts;
- Revisit early warning information dissemination channels;
- Alert communities in low-lying areas (flood-prone) to act early;
- Alert risk residents and communities that are still prone to landslides and slips.
Agriculture & Food Security Sector
- Practice soil moisture conservation like mulching and trenches;
- Clear vegetation from crop beds and drains to ease waterlogged soils.
- Put in place disease control measures.
Water, Drainage and Energy sector
- Implement water harvesting, storage and proper usage;
- Conduct routine de-silting of water channels, canals and reservoirs;
- Remove dry branches, trees and overhangs near electrical wires.
General Public
- Proper preparation especially for persons in at-risk areas;
- Clean drains and surrounding areas of debris, be sand-bag ready;
- Conserve, store and manage water in a safe and adequate manner;
- Be watchful for extreme rainfall events, especially on extremely hot days;
- Take measures to lessen the potential impacts from the expected increased rainfall and warmer than average temperatures.
Figure 1: Category of rainfall likely for September to November (SON) 2022 with the highest chance of occurrence expressed as probabilities represented on the map. Blue areas indicate places with an increased chance for above normal rainfall, brown areas show an increased chance for below normal rainfall, while green areas show an increased chance for near normal rainfall. Normal is defined by the rainfall that was observed in middle one-third of the SON period rainfall totals during the historical period used to produce the outlook.
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- A moderate probability exists for above-normal rainfall totals over large parts of Trinidad during SON;
- Chances are moderate (60%) for a slightly higher number of extremely wet days (> 25.0 mm) for SON; i.e. expect between 6 - 10 extremely wet days in Trinidad and 4-7 in Tobago during the period.
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Figure 2: Percentage of average rainfall totals likely for September to November 2022.
- The pattern for the percentage of average rainfall totals for September to November will be average to above average and range between 116% to 132%, though the lowest percentage of average is expected in small areas in eastern and south-western Trinidad.
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Figure 3: Risk of the SON 2022 being extremely drier than normal (within the lowest 10% on record).
- The risk of extremely drier than normal conditions is low (3-28%) over both islands;
- A moderate (60%) chance of dryness is likely to occur in the last week of September and during the first week of October 2022.
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Figure 4: Outlook of possible rainfall accumulated totals for September to November 2022.
The largest rainfall accumulated totals for SON are likely to be as high as 1073 mm in areas such as North Oropouche Valencia, Sangre Grande and Plum Mitan in Northeast and east Trinidad; and near 687 mm in the Belle Garden, Goodwood, Mount St George and environs in southeast Tobago.
Figure 5: Outlook of possible rainfall totals for September 2022.
- September rainfall with the highest chance of occurring ranges from about 111-270 mm in Trinidad and 149-264 mm in Tobago.
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Figure 6: Outlook of possible rainfall totals for October 2022.
- October’s rainfall with the highest chance of occurring ranges from about 115-377 mm in Trinidad and 184-335 mm in Tobago.
Figure 7: Category of rainfall likely for December to February (DJF) 2022/23 with the highest chance of occurrence expressed as probabilities represented on the map. Blue areas indicate places with an increased chance for above-normal rainfall, brown areas show an increased chance for below-normal rainfall, while green areas show an increased chance for near-normal rainfall. Normal is defined by the rainfall that was observed in the middle one-third of the DJF seasons during the historical period used to produce the outlook.
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- High chances for December to February (DJF) rainfall totals to be mostly near normal with patches of above normal rainfall over certain parts of Trinidad and Tobago;
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The Temperature Outlook Favours as Normal to Above Normal Temperatures for September to November 2022
- Both daytime and night temperatures are likely to be near normal over the majority of both islands with the exemption of north-western Trinidad and south-western Tobago;
- Chances of warmer than average days are highest in Trinidad where there is a 55% chance of warmer than average days in north-western areas; while there is a 55% chance for southwestern Tobago;
- Chances of warmer than average nights are higher in north-western Trinidad where there is a 50% chance; while south-western Tobago has a 40% chance of warmer than average temperatures;
- A reasonably moderate chance (60%) exists for short-duration warm spells during the last week of September and the first week of October (maximum temperatures will average around 34.0 oC in Trinidad, and 32.0 oC in Tobago);
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Figure 8: The map shows the colour-coded category (below-normal, above-normal, and near-normal) of maximum and maximum temperatures that is most likely to occur across Trinidad and Tobago for the September to November (SON) period 2022. The colour-coded bar-graph with the numbers to the right gives the likelihood for each forecast category to occur
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Climatic Influencers and Context of the Outlook
- Currently, sea surface temperatures (SSTs) in waters surrounding Trinidad and Tobago and further east of the islands are mostly warmer than average. Climate models surveyed mostly favour these conditions to persist during the SON period.
- La Niña is favoured during SON 2022 and continues into the first quarter of 2023. La Niña conditions generally have been associated with the enhancement of local rainfall, but not always.
- The North Atlantic Oscillation (NAO) maintains a slightly negative phase throughout September and will possibly continue through October. The overall influence should be a small positive impact on local rainfall.
- Models indicate that the Madden Julian Oscillation (MJO) signal was in a positive phase during the first part of September and will eventually change into a rainfall-neutral phase at the end of September and continue into October. This will have little influence on October’s rainfall.
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Disclaimer: This information is provided with the understanding that the Trinidad and Tobago Meteorological Service makes no warranties, either expressed or implied, concerning the accuracy, completeness, reliability, or suitability of the assessment or outlook contained in this document. This Outlook provides possible temperature and rainfall conditions over the next 3-6 months and is part of a suite of early warning climate forecasts designed for contingency planners which should not be used in isolation but used along with daily weather and shorter-range forecasts and warnings available from the TTMS. The information may be used freely by the public with appropriate acknowledgement of its source but shall not be modified in content and then presented as original material.
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