TTMS To Launch Sub-Seasonal To Seasonal Forecasts

A first look at 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. (Trinidad and Tobago Meteorological Service)

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. This information was presented in 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 millimeters and 25 millimeters.

They will also be forecasting the total rainfall amounts in week three and week four and the percent chance of both weeks being either wet or dry. The TTMS expects to roll out these forecasts beginning in 2021, being issued every Friday afternoon on their website.

The TTMS’ extended forecast will be generated from several global ensemble prediction systems including the EMCWF VarEPS, the NCEP CFSvs2, the IRI SubX and the NOAA WMO-RCC GFS models.

This sub-seasonal forecast may lead to more awareness in the short term for the public when very wet conditions are possible, allowing for community warnings and preparedness activities to initiate ahead of inclement or severe weather. These extended forecasts can give disaster management officials ample time to preposition disaster response materials. In the event of extremely dry weather, officials can use these forecast to adjust water allocations, inform loss scenarios and update energy supply scenarios.

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

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

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