Forecast: Tropical Wave 32 To Bring Some Showers, Thunderstorms

Over the next five days, two tropical waves are forecast to move across Trinidad and Tobago, with the stronger wave affecting the country today (Wednesday) through Thursday. However, while isolated areas could see locally high rainfall totals, widespread heavy rainfall is not forecast.

What you need to know

Rainfall: Over the next five days, between 10 and 25 millimeters are forecast across Trinidad and Tobago, with areas along eastern Trinidad and coastal areas receiving up to 50 millimeters. In isolated areas across western and eastern coastal Trinidad, locally higher amounts are possible daily.
Saharan Dust: Elevated Saharan Dust concentrations are forecast across T&T, particularly from August 14th.
Hazards: Over the next five days, but particularly Wednesday and Thursday, the main hazards will be localized street/flash flooding and gusty winds exceeding 45 KM/H in heavy showers and isolated thunderstorms. The threat of gusty winds will be elevated on Thursday.
Marine: Seas are forecast to be slight to moderate, with waves in open waters ranging between 1.0 and 1.5 meters, while in sheltered areas, seas are forecast to be near calm, with waves remaining below 0.5 meters.

Latest Alerts

Hazardous Seas Alert Discontinued For T&T

The Trinidad and Tobago Meteorological Service has discontinued the Hazardous Seas Alert for the country on Sunday at 12:04 PM. Over the last four days, northerly long-period swells have…

Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.

The Forecast

Wednesday

Wednesday
6 10 0 1
Partly to mostly cloudy with isolated showers and thunderstorms across both islands, favoring the late morning through afternoon hours. Conditions to settle by nightfall, barring the odd isolated shower or thunderstorm across eastern coastal areas of both islands. Nighttime thunderstorms in the Gulf of Paria are likely, remaining near Venezuela.
Partly to mostly cloudy with isolated showers and thunderstorms across both islands, favoring the late morning through afternoon hours. Conditions to settle by nightfall, barring the odd isolated shower or thunderstorm across eastern coastal areas of both islands. Nighttime thunderstorms in the Gulf of Paria are likely, remaining near Venezuela.
6/10
Thunderstorm Chances
Medium – High

Thursday

Thursday
6 10 0 1
Overnight showers and thunderstorms to continue across T&T throughout the day, interrupting variably cloudy skies. Conditions to become increasingly settled by the evening, barring the odd shower and offshore thunderstorm. Fast-moving and/or isolated intense showers/thunderstorms may produce gusty winds and locally heavy rainfall.
Overnight showers and thunderstorms to continue across T&T throughout the day, interrupting variably cloudy skies. Conditions to become increasingly settled by the evening, barring the odd shower and offshore thunderstorm. Fast-moving and/or isolated intense showers/thunderstorms may produce gusty winds and locally heavy rainfall.
6/10
Thunderstorm Chances
Medium – High

Friday

Friday
4 10 0 1
Partly cloudy, hot and slightly hazy with few early morning, and late morning through afternoon showers. During the afternoon, isolated thunderstorms are possible favoring western coastal areas of Trinidad. A partly cloudy night, barring the odd isolated shower.
Partly cloudy, hot and slightly hazy with few early morning, and late morning through afternoon showers. During the afternoon, isolated thunderstorms are possible favoring western coastal areas of Trinidad. A partly cloudy night, barring the odd isolated shower.
4/10
Thunderstorm Chances
Low – Medium

Saturday

Saturday
5 10 0 1
Early morning fog to give way to mostly sunny, hazy, hot, and slightly breezy with isolated showers from the mid morning through early afternoon, favoring Trinidad. During the late morning through the afternoon, isolated heavy showers and isolated thunderstorms favoring western and hilly areas of Trinidad are possible. A partly cloudy, hazy and foggy (in interior areas of Trinidad) night with a few isolated showers.
Early morning fog to give way to mostly sunny, hazy, hot, and slightly breezy with isolated showers from the mid morning through early afternoon, favoring Trinidad. During the late morning through the afternoon, isolated heavy showers and isolated thunderstorms favoring western and hilly areas of Trinidad are possible. A partly cloudy, hazy and foggy (in interior areas of Trinidad) night with a few isolated showers.
5/10
Thunderstorm Chances
Medium

Sunday

Sunday
5 10 0 1
Partly cloudy with isolated showers throughout the day, and isolated thunderstorms favoring western coastal and hilly areas of both islands during the afternoon. A partly cloudy night with the odd shower.
Partly cloudy with isolated showers throughout the day, and isolated thunderstorms favoring western coastal and hilly areas of both islands during the afternoon. A partly cloudy night with the odd shower.
5/10
Thunderstorm Chances
Medium

Marine Forecast

Seas Forecast: Moderate Seas, Reduced Visibility

While no hazardous marine events are forecast over the next seven days, marine interests, particularly small craft operators, will need to exercise caution from this weekend due to a…

Temperatures

Wednesday

Low: 24-26°C

High: 29-33°C

Thursday

Low: 24-26°C

High: 30-34°C

Friday

Low: 25-27°C

High: 31-35°C

Saturday

Low: 25-27°C

High: 32-35°C

Sunday

Low: 25-27°C

High: 31-34°C

Over the next five days, maximum high temperatures are forecast to be hot, ranging from 30°C to 35°C, with higher temperatures across urbanized areas of Trinidad, particularly after Thursday, where in built-up areas, maximum high temperatures are likely to exceed 34°C. Minimum lows are forecast to remain mild, ranging between 24°C and 27°C in Trinidad and Tobago, trending marginally cooler in interior areas. The heat index will generally be above 30°C through the forecast period and higher than 35°C from Friday.

Forecast Impacts

Flooding

Flooding
6 10 0 1
Overall, five-day rainfall accumulations between 10 and 50 millimeters of rainfall are forecast with higher totals possible along western coastal Trinidad and eastern areas of Trinidad. Note that daily, with the potential for isolated, western coastal, heat-driven thunderstorms, downpours along western Trinidad could exceed 25 millimeters of rainfall accumulations. As a result, there is a medium to high chance of street/flash flooding, given activity is forecast to be relatively slow-moving, resulting in highly isolated areas of high rainfall accumulations.
Overall, five-day rainfall accumulations between 10 and 50 millimeters of rainfall are forecast with higher totals possible along western coastal Trinidad and eastern areas of Trinidad. Note that daily, with the potential for isolated, western coastal, heat-driven thunderstorms, downpours along western Trinidad could exceed 25 millimeters of rainfall accumulations. As a result, there is a medium to high chance of street/flash flooding, given activity is forecast to be relatively slow-moving, resulting in highly isolated areas of high rainfall accumulations.
6/10
Likelihood
Medium – High

Forecast Rainfall Totals

  • Wednesday: Between 5 and 15 millimeters across T&T, with totals up to 25 millimeters favoring the northern and eastern halves of Trinidad, as well as Tobago. In highly isolated downpours favoring the western half of Trinidad, local rainfall totals could exceed 25 millimeters.
  • Thursday: Between 5 and 10 millimeters across T&T, with isolated totals up to 20 millimeters. In highly isolated downpours, favoring but not limited to the western half of Trinidad, local rainfall totals will exceed 25 millimeters.
  • Friday: Less than 5 millimeters of rainfall across T&T, with isolated rainfall amounts up to 25 millimeters favoring western coastal Trinidad.
  • Saturday: Between 0 and 5 millimeters of rain across T&T, with isolated totals nearing 15 millimeters across eastern and western coastal areas of both islands. In thunderstorm activity, locally higher totals are possible.
  • Sunday: Between 5 and 15 millimeters of rain across T&T, with isolated totals exceeding 15 millimeters across eastern coastal Trinidad, as well as northern and western areas of both islands. In thunderstorm activity, locally higher totals are possible.

Understanding Rainfall Rates

Understanding Rainfall Accumulations

Putting the rainfall forecast into context, rainfall rates in excess of 50 millimeters per hour or areas that receive in excess of 25 millimeters within an hour tend to trigger street flooding across the country or flash flooding in northern Trinidad. For riverine flooding to occur, a large area of the country (not just in highly localized areas of western coastal Trinidad) would have to record upwards of 75 millimeters within 24 hours, and rainfall would have to fall across major rivers’ catchment areas.

Strong Thunderstorms

Strong Thunderstorms
5 10 0 1
In a low to moderate wind shear environment with light southeasterly low-level winds, at times near calm, with favorable mid to upper-level conditions, particularly Wednesday and Friday, there is the potential for isolated strong thunderstorms with the potential for funnel clouds, particularly on Wednesday, particularly along western coastal areas of Trinidad. However, this strong thunderstorm potential is highest in offshore northeastern areas.
In a low to moderate wind shear environment with light southeasterly low-level winds, at times near calm, with favorable mid to upper-level conditions, particularly Wednesday and Friday, there is the potential for isolated strong thunderstorms with the potential for funnel clouds, particularly on Wednesday, particularly along western coastal areas of Trinidad. However, this strong thunderstorm potential is highest in offshore northeastern areas.
5/10
Likelihood
Medium
What is a strong or severe thunderstorm?

Given how rare these types of thunderstorms are in our region – we classify a severe or strong thunderstorm as one that produces any of the following:

  • Damaging wind gusts exceeding 55 KM/H;
  • Frequent lightning (more than 30 cloud-to-ground strikes within a 10-minute period);
  • Hail (of any size);
  • Rainfall of more than 50 millimeters or more within an hour or exceeding 75 millimeters or more within three hours;
  • The sighting of a funnel cloud or touchdown of a waterspout/tornado associated with the thunderstorm.

Gusty Winds

Gusty Winds
5 10 0 1
Outside of Thursday, through the forecast period, winds are forecast to be gentle to light through the forecast period, with sustained winds reaching as high as 25 KM/H and gusts may reach as high as 45 KM/H in occasional gusts associated with isolated heavy showers or thunderstorms. On Wednesday night through Thursday afternoon, particularly in heavy showers and isolated thunderstorms, winds could gust in excess of 45 KM/H.
Outside of Thursday, through the forecast period, winds are forecast to be gentle to light through the forecast period, with sustained winds reaching as high as 25 KM/H and gusts may reach as high as 45 KM/H in occasional gusts associated with isolated heavy showers or thunderstorms. On Wednesday night through Thursday afternoon, particularly in heavy showers and isolated thunderstorms, winds could gust in excess of 45 KM/H.
5/10
Likelihood
Medium

Possible impacts include localized wind damage to trees, power lines, and small structures. Small potted plants may blow over with light outdoor objects becoming airborne in stronger gusts. Tents may jump.

Other Hazards

Saharan Dust Forecast

Major Saharan Dust Surge Now Moving Across T&T

Air quality monitoring stations across Trinidad and Tobago are detecting a major surge of Saharan Dust moving in from the east as forecast. Air quality is quickly dropping across Tobago and…

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.

During the forecast period, isolated to scattered rainfall is forecast, with isolated activity favoring Friday into Saturday.

Forecast Discussion

Tropical Update

Tropical Update: All Eyes On Invest 94L

The remnants of Tropical Storm Sean and an active tropical disturbance, Invest 94L, are forecast to bring rainfall to the Lesser Antilles over the next five days. The National Hurricane Center…

On Wednesday into Thursday, Tropical Wave 32 is forecast to move across Trinidad and Tobago. While the strongest convection (heavier showers, stronger thunderstorms) is forecast to remain north of T&T, there is the potential for isolated strong convection across the country. Favorable mid to upper-level conditions with deep tropical moisture are forecast to prevail across the Windwards, including T&T, with light southerly to southeasterly and, at times, near calm winds.

While showers and thunderstorms are likely to also move in from the east associated with TW32, local climatic effects such as orographic precipitation (influence of the terrain), daytime heating, and sea breeze convergence are likely to act as triggers for additional showers and thunderstorms, or further intensify existing activity. With light winds, where westerly winds could dominate along western Trinidad on Wednesday, there is the potential for funnel clouds.

Additionally, on Thursday, low-level winds are forecast to increase as TW32 moves west, which can make it to the surface in heavy showers or thunderstorms. The ECMWF model has been fairly persistent in the development of a mesoscale convective system well east of T&T on Thursday morning and moving across the country by the afternoon. While confidence is not particularly high, the potential is there, and the good news about these types of systems is we’ll be able to see it develop on both radar and satellite imagery before it affects land, providing ample heads-up.

By Friday and into Saturday, mid to upper-level conditions remain favorable due to a favorably positioned upper-level trough, but moisture begins to decrease as the ITCZ, which has been north/near T&T in days prior, drifts south as a high-pressure ridge regains dominace. Still, with isolated afternoon thunderstorms as a result of daytime heating and sea breeze convergence, convection could take advantage of these conditions and develop into isolated strong thunderstorms in the Gulf of Paria. However, model guidance suggests thunderstorms and showers are likely to remain non-severe.

Tropical Wave 33 is forecast to move across T&T by Sunday, but with already present mild concentrations of Saharan Dust at this time and a moderate to high-concentration surge on TW33’s heels, forecast models are not too enthusiastic about significant rainfall on Sunday. Still, an increase in cloudiness with isolated showers remains in the forecast.

To note for north of T&T: As a result of favorable mid to upper-level conditions, cool mid-level temperatures, ample instability, and likely thunderstorms, forecast models show the potential for strong/severe thunderstorms north and east of T&T, to the Leewards on Thursday into Friday, with an elevated potential for hail. Pay attention to the latest information coming out of your local meteorological offices.

Total
0
Shares
Related Posts
Total
0
Share