Tropical Update Overview:
— There are no systems in the Atlantic, as of 2:00 AM Monday, being officially monitored for tropical cyclone development.
— Tropical Wave 2 – A axis of a weak tropical wave is just east of T&T as of 2:00 AM, forecast to move across the islands this morning. Rainfall, while not significant, is forecast to favor the southern half of Trinidad on Monday.
— Tropical Wave 3 – This weak, low-latitude, tropical wave in the Atlantic is forecast to move across the Windward Islands on Thursday into Friday, bringing potentially heavy rainfall on Friday across T&T.
— 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 on Monday but increased on Friday. A typical wet season pattern is forecast with isolated afternoon showers, with the odd thunderstorm across western coastal Trinidad. The main hazards include 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
As of the 2:00 AM Tropical Update, the 2nd tropical wave for the 2021 Atlantic Hurricane Season is located from 15N, along 60W based on our analysis. The wave axis is moving westward around 10 to 15 knots (18 to 27 KM/H).
Though dry Saharan Dust is keeping the northern half of the wave axis devoid of shower activity, the southern half of the wave, following the wave axis, has isolated thunderstorm activity and scattered showers southeast of Trinidad. This activity is forecast to near the island through the morning, with rainfall favoring the island’s southern half.
The axis of the wave is forecast to move across T&T later this morning, with favorable low-level convergence and low-level confluence. However, moderate to strong wind shear from the west and southwest will keep heavier rainfall offshore eastern Trinidad and thunderstorm activity brief. In addition, a relatively dry mid-level atmosphere may inhibit strong shower or thunderstorm development.
Tropical Wave 3
As of the 2:00 AM Tropical Update, the 3rd tropical wave for the 2021 Atlantic Hurricane Season is located from 14N southward, along 41/42W, based on our analysis. The wave axis is moving westward around 10 to 15 knots (18 to 27 KM/H).
Like Tropical Wave 02, the northern half of the wave axis is engulfed in Saharan Dust, limiting shower or thunderstorm activity. However, across the southern half of the wave, isolated strong showers and thunderstorm activity is present where the wave interacts with the ITCZ.
This wave is forecast to move across the region Thursday into Friday. Scattered showers and isolated thunderstorms will be forecast for Trinidad and Tobago from late Thursday and mainly on 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.
Monday: Periodic showers are forecast from the early morning and forecast to continue into the afternoon, favoring the southern half of Trinidad. Across the northern half of the island and Tobago, while periodic cloudy periods are forecast with brisk showers, no significant rainfall is forecast. Instead, a mostly hazy, breezy, and variably cloudy day. Heavier showers and the odd thunderstorm will favor southern Trinidad and western coastal Trinidad through the afternoon. Again, a few showers may linger overnight, favoring southern Trinidad while the remainder of the country experiences a mostly settled night, barring the brisk, odd shower.
Tuesday: After a few morning showers, a mostly hazy, breezy, and partly cloudy day is forecast across Trinidad and Tobago.
Wednesday: A mostly hazy, breezy, and partly cloudy day is forecast. Temperatures will be hot across Trinidad and Tobago.
Thursday: Initially, a mostly hazy, breezy, and partly cloudy day is forecast. By the afternoon, an increase in cloud cover and isolated showers are likely through the night due to an approaching tropical wave. Though heavier rainfall will stay offshore, showers and the odd thunderstorm will favor Trinidad’s eastern and southern halves from the afternoon through midnight.
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. The highest temperatures for the week may occur on Wednesday and Thursday.
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 48 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 48 hours. T&T may experience heavier rainfall by the end of the week due to the passage of Tropical Wave 03.
- Monday: Less than 25 millimeters across the country. Isolated totals up to 35 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 eastern and southern areas 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, up to 15 millimeters.
- Friday: Between 10-25 millimeters across the country, with higher rainfall totals favoring eastern and offshore eastern areas up to 50 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 Monday, with increased rainfall likely on Friday.