Tropical Update Overview:
— There are no systems in the Atlantic, as of 8:00 PM Saturday, being officially monitored for tropical cyclone development.
— Tropical Wave 2 – A axis of a weak tropical wave has been reanalyzed east of Trinidad and Tobago. The southern half of the axis is interacting with the ITCZ. This wave is forecast to move across the Windward Islands on Sunday.
— Tropical Wave 3 – Another weak, low-latitude, tropical wave is moving across the Atlantic Ocean. This wave is forecast to move across the region by mid-week with much of the rainfall activity remaining south of Trinidad and Tobago.
— Impacts to T&T – There are no direct tropical threats facing T&T over the next 5 days. Tropical-wave-enhanced rainfall is forecast to be limited. However, a typical wet season pattern is forecast with isolated afternoon showers, with the odd thunderstorm across western coastal Trinidad. The main hazards include highly isolated heavy rainfall, favoring Western Trinidad during the afternoons while across Eastern and Southern Trinidad during other times of day, reducing visibility, and gusty winds up to and in excess of 55 KM/H. Street or flash flooding will be possible in slow-moving showers and thunderstorms. In thunderstorm activity, frequent lightning is possible. Gusty winds may cause power dips/outages, downed trees, and localized wind damage.
Before we dive into the forecast and tropical update, a few notes:
- Tropical waves are a normal part of the rainy season.
- Not every tropical wave will form into a tropical cyclone.
- Weaker tropical waves produce more rainfall across Eastern parts of the islands with mostly cloudy conditions and a few showers across western parts of the islands.
- Rainfall will be more isolated and intermittent with weaker tropical waves that do not have ITCZ or upper-level support.
- Saharan Dust may weaken tropical waves.
Tropical Wave 2
Updated: As of the 2:00 AM Tropical Update, the 2nd tropical wave for the 2021 Atlantic Hurricane Season is located from 15N, along 50W based on our analysis. The wave axis is moving westward around 10 to 15 knots (18 to 27 KM/H).
Much of this wave is surrounded by Saharan Dust, limiting convection. Based on microwave layered precipitable water and water vapor imagery, the wave is in a deep-layered dry environment, hindering deep convection development. However, scattered strong showers and isolated thunderstorms are within 75 nautical miles on either side of the tropical wave from 06N to 08N, and from 06N to 08N between 53W and 55W.
A slight increase in moisture is forecast overnight Saturday into Sunday, which may increase cloudy weather with a few showers mainly across Trinidad on Sunday.
Tropical Wave 3
As of the 2:00 AM Tropical Update, the 3rd tropical wave for the 2021 Atlantic Hurricane Season is located from 13N to 3N, along 36W based on our analysis. The wave axis is moving westward around 10 to 15 knots (18 to 27 KM/H).
Widely scattered moderate to isolated strong showers surrounds the tropical wave, within 420 nautical miles on either side of the tropical wave, from 15N southward.
This wave is forecast to move across the region later next week (sometime between Wednesday through Friday, as models disagree on timing). Scattered showers and isolated thunderstorms will be forecast for Trinidad and Tobago on Thursday and Friday based on the latest model guidance.
At this time, there are no alerts, watches, or warnings issued for T&T from the Trinidad and Tobago Meteorological Service.
Over the next 24 hours, with the approach and passage of Tropical Wave 02, a mostly sunny, hazy, and breezy day is forecast for Trinidad and Tobago interrupted by isolated showers and cloudy periods. However, from the late morning through the afternoon, brisk showers and one or two isolated thunderstorms may impact the southern half of Trinidad and western coastal Trinidad. Cloudy conditions with a few showers are forecast through the evening.
Monday: Periodic showers are forecast from the overnight hours and forecast to continue into the afternoon, favoring Trinidad. These showers and occasional cloudy conditions will interrupt mostly hazy and partly cloudy skies. Like Sunday, heavier showers and the odd thunderstorm will favor southern Trinidad and western coastal Trinidad through the afternoon. A mostly settled evening, with increasingly hazy skies, is forecast.
Tuesday through Wednesday: Mostly hazy and partly cloudy skies are forecast across Trinidad and Tobago, with breezy conditions, interrupted by very brisk isolated showers.
Thursday: An increase in isolated showers and cloudiness is forecast after midnight, with few showers continuing throughout the day across both islands. Heavier showers are forecast to favor western coastal areas, as well as southern Trinidad. Through the evening and into the night, showers are forecast to increase coverage across the country, with heavier rainfall favoring eastern and southern areas of both islands. Note that the GFS model indicates heavier rainfall, though it mostly stays east of Trinidad.
Friday: Isolated to scattered showers with mostly cloudy to cloudy skies are forecast across Trinidad and Tobago. Isolated thunderstorm activity is also expected throughout the day, with heavier rainfall favoring eastern and southern areas of both islands, though overall higher totals are forecast to remain offshore.
Through the forecast period, Saharan Dust concentrations will be variable, with seas remaining moderate in open waters and less than 1.0 meters to near calm in sheltered areas. In heavy showers or thunderstorms, sheltered seas may become choppy.
Across both islands, overnight lows are forecast to be mild, with daytime highs warm.
The minimum low for Trinidad is forecast to be 23.0°C to 25.0°C. In Tobago, a minimum low between 24.0°C to 26.0°C is forecast. The maximum high for Trinidad and Tobago is forecast to be between 30.0°C and 33.0°C, higher across Trinidad. Temperatures may record higher in urban and built-up areas, particularly between 9:00 AM and 3:00 PM. The maximum heat index in Trinidad is forecast to be between 35.0°C and 40.0°C while across Tobago between 33.0°C and 36.0°C.
On days with increased cloud cover, such as Thursday and Friday, maximum high temperatures may be lower.
Temperatures in cities, such as Port of Spain, tend to be much higher than surrounding locations due to a phenomenon called the Urban Heat Island Effect. There are several causes, but the main instigator for this phenomenon tends to be increased dark surfaces such as roads and pavement in cities, absorbing solar radiation more than surrounding areas.
The main hazards through the next 72 hours would be localized heavy rainfall and gusty winds, particularly in moderate to heavy showers or thunderstorms, bringing the risk of street flooding or flash flooding.
Sustained surface winds up to 35 KM/H. In shower activity, gusts up to and in excess of 55 KM/H are possible.
With wind gusts in excess of 55 KM/H, whole trees are expected to be in motion, and there may be some inconvenience when walking against the wind gusts. Light outdoor objects may topple or become airborne such as garbage cans, potted plants, loose galvanize or construction material and other outdoor furniture. Tents may jump. Older/weaker trees may fall, bringing down utility poles and lines.
No significant rainfall is forecast for T&T through the next several days. T&T may experience heavier rainfall by the end of the week due to the passage of Tropical Wave 03.
- Sunday: Less than 5 millimeters across the country. Isolated totals up to 15 millimeters favoring eastern and southern Trinidad, as well as western coastal areas.
- Monday: Less than 5 millimeters across the country. Isolated totals up to 20 millimeters favoring eastern and southern Trinidad, as well as western coastal areas.
- Tuesday: Little to no rainfall across the country. GFS, as the outlier, showing showers persisting across southern Trinidad. 0-10 millimeters possible across the southern half of Trinidad.
- Wednesday: Little to no rainfall across the country. Isolated totals, favoring southern and southwestern Trinidad less than 5 millimeters.
- Thursday: Between 5-10 millimeters, favoring eastern halves of Trinidad and Tobago. Heavier rainfall to remain offshore.
- Friday: Between 5-20 millimeters across the country, with higher rainfall totals favoring eastern and offshore eastern areas up to 35 millimeters.
Generally, with heavy showers and thunderstorm activity, street flooding, particularly in flood-prone areas or areas with poor drainage, is possible as well as flash flooding in areas where more prolonged heavy rainfall may occur.
Lightning: Lightning is possible in thunderstorm activity. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.
Why I May Not/Will Not See Rainfall?
A frequent complaint is the forecast is wrong because I didn’t experience any rainfall. Scattered showers mean that you, individually, may experience some showers intermittently throughout the day and there is a higher chance for this activity than isolated activity. Widespread showers mean that nearly all persons and areas may experience rainfall.
Brisk, isolated to scattered rainfall is forecast on Sunday and Monday, with increased rainfall likely on Friday.