A first look at what the 3-week and 4-week sub-seasonal forecasts from the Trinidad and Tobago Meteorological Service. Note that this is not an actual forecast, but was used for demonstrative purposes only. Image courtesy Trinidad and Tobago Meteorological Service (TTMS).

The Trinidad and Tobago Meteorological Service (TTMS) will begin issuing an interactive sub-seasonal to season forecast, covering the 3-week and 4-week time frame for Trinidad and Tobago.

Confirmation came during the TTMS’ National Climate Outlook Forum XI.

Presently, the TTMS issues weather forecasts up to three days for the public, up to ten days for some stakeholders, and for their seasonal outlook, climate forecasts up to three months.

With the sub-seasonal forecast, the TTMS will not be attempting to give day-to-day detail, which is challenging to forecast outside of the 7-10-day period.  Instead, the service will be issuing the percent chance of exceeding rainfall totals of 10 millimetres and 25 millimetres.  They also will be forecasting the total rainfall amounts in week three and week four, and the percentage chance of both weeks being either wet or dry.  

The TTMS expects to roll out these forecasts beginning in 2021.  They will be issued every Friday afternoon on their website.

The TTMS anticipates the chief users of these forecasts’ will be the agricultural sector, as farmers tend to use forecasts and seasonal outlooks most to support operational decisions such as irrigation, spraying, and harvesting.  Forecasts at the sub-seasonal levels can help inform farmers’ strategic decisions regarding crop-planting choices, scheduling irrigation, and pesticide or fertilizer application.

The forecasts on the three to four-week time frames also can be applied to the health sector. These sub-seasonal forecasts can be used for planning if there are favourable conditions for the development of disease vectors or an extreme hot spell, particularly for a possible increase in hospital admissions or preparing awareness messages.