[UPDATED] Showers, Thunderstorms Remain In The Forecast For T&T

What you need to know:
— Several weather features, including Potential Tropical Cyclone Six and two tropical waves (Tropical Wave 31 and 32) are forecast to move across the region this week, producing abundant moisture and instability for showers and thunderstorms.
— Though rainfall is forecast daily across the country, overall heavier rainfall is forecast to favor Trinidad with localized higher amounts across the western half of the island due to heavy afternoon thunderstorms. Light winds and hot temperatures are also forecasted.
— An Adverse Weather Alert is now in effect for Trinidad from 11:00 AM Monday through 6:00 PM Tuesday from the Trinidad and Tobago Meteorological Service. Trinidad and Tobago is not under a direct threat from Potential Tropical Cyclone Six.

The 5-Day Forecast

Moisture associated with Tropical Waves 31 and 32, as well as Potential Tropical Cyclone Six moving across and approaching T&T (SSEC/CIMSS/UW-Madison)
Moisture associated with Tropical Waves 31 and 32, as well as Potential Tropical Cyclone Six moving across and approaching T&T (SSEC/CIMSS/UW-Madison)

Tuesday: Mostly hot and sunny conditions through the morning, with isolated showers and thunderstorms developing across southern Trinidad by the late morning through the afternoon and moving northward across the country. Heavy showers and thunderstorms may favor western coastal Trinidad and along the Northern Range. Scattered showers and thunderstorms associated with a feeder band of Potential Tropical Cyclone Six may affect the country by the evening into the night.

Wednesday: Scattered overnight showers are forecast to give way to a mostly sunny morning, barring the odd shower. Hot conditions with light winds are forecast throughout the day, with isolated heavy showers and thunderstorms developing by the late morning and continuing through the afternoon. Strong thunderstorms are possible across the western half of Trinidad during the afternoon, producing torrential rainfall, gusty winds, and frequent lightning. Isolated showers are possible into the night.

Thursday: Mostly hot and sunny skies until the late morning, where cloudiness is forecast to build across Trinidad. Isolated thunderstorms and heavy showers are possible across western and hilly areas of the island, diminishing by the evening. Increasing cloudiness is forecast overnight.

Friday: Early morning showers are forecast to give way to a partly cloudy day. Cloudiness is forecast to build, mainly across Trinidad by the late morning with isolated thunderstorms and scattered showers through the afternoon. A mostly settled night is forecast.

Friday: Early morning showers are forecast to give way to a partly cloudy day. Cloudiness is forecast to build, mainly across Trinidad by the late morning with isolated thunderstorms and scattered showers through the afternoon. A mostly settled night is forecast.

Marine: Through the remainder of the week, seas are forecast to be slight to moderate with waves up to 1.5 meters in open waters and near calm in sheltered areas, with choppy seas in the vicinity and during heavy showers or thunderstorms.

Temperatures

Through the forecast period, the minimum low for Trinidad and Tobago is forecast to be between 24.0°C and 26.0°C. The maximum high for Trinidad and Tobago is forecast to be between 30.0°C and 34.0°C.

Higher temperatures are possible in urbanized areas like Port of Spain, Scarborough, San Fernando, and Chaguanas. Lower daytime temperatures are possible on days with increased cloud cover.

Forecast Impacts

Forecast impacts due Tropical Wave 31 and Potential Tropical Cyclone Six
Forecast impacts due Tropical Wave 31 and Potential Tropical Cyclone Six

Over the next five days, the main hazards include heavy rainfall, particularly across the western half of Trinidad, with street or flash flooding likely, and a very low to a low chance of riverine flooding. Localized gusty winds and lightning may accompany thunderstorms and heavy to violent showers causing power dips/outages, downed trees, and localized wind damage. In elevated areas, there is also the potential for landslides. With light southerly winds and the potential for strong thunderstorms, funnel clouds, and waterspouts are possible this week, mainly on Wednesday, Friday, and Saturday. If funnel clouds touchdown or waterspouts encounter land, weak tornadoes are possible.

Winds

Sustained surface winds up to 25 KM/H are forecast. In shower activity, gusts up to and in excess of 45 KM/H are possible. With wind gusts in excess of 45 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.

Rainfall

Over the next five days, overall higher rainfall is forecast to favor much of Trinidad, with accumulations between 25 and 75 millimeters. However, localized totals up to and in excess of 150 millimeters are possible in prolonged heavy showers or isolated thunderstorm activity.

  • Tuesday: Between 10-25 millimeters of rainfall across the country and isolated areas receiving between 25-75 millimeters, with highly isolated higher totals. Heavier rainfall to favor the western and northern halves of Trinidad.
  • Wednesday: Between 5-15 millimeters of rainfall across the country with isolated areas in excess of 40 millimeters. Heavier rainfall to favor the western half of Trinidad and along south-facing slopes of the Northern Range.
  • Thursday: Less than 5 millimeters across the country. In isolated heavy showers or thunderstorms across western, southwestern and hilly areas of Trinidad, totals may reach and exceed 25 millimeters.
  • Friday: Between 5-15 millimeters of rainfall across the country and isolated areas receiving up to 50 millimeters, with highly isolated higher totals. Heavier rainfall to favor southern and western areas of Trinidad.
  • Saturday: Between 10-20 millimeters of rainfall across the country and isolated areas receiving in excess of 25 millimeters, with highly isolated higher totals. Heavier rainfall to favor Trinidad.

As mentioned earlier, all types of flooding are on the table through the next five days, with high to very high chances for street flooding and flash flooding, and very low to low chances for riverine flooding, mainly across the South Oropouche River Basin.

Other Adverse Weather Impacts

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.

Landslides: Landslides and fallen trees are possible through the forecast period, particularly in areas where heavy thunderstorms or persisting rains occur.

Tornadic Activity: With light southerly winds and the potential for strong thunderstorms, funnel clouds, and waterspouts are possible this week, mainly on Tuesday, Friday, and Saturday. If funnel clouds touchdown or waterspouts encounter land, weak tornadoes are possible.

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.

Through the next five days, isolated to scattered showers and thunderstorms are forecast.

Forecast - Isolated, Scattered, Widespread - What do they mean?

Forecast Discussion

Infrared satellite imagery showing scattered showers east of Trinidad and Tobago associated with a feeder band from Potential Tropical Cyclone Six. (Weathernerds)

Tropical Waves: At 12Z Tuesday 10th August 2021, the axis of Tropical Wave 31, associated with Potential Tropical Cyclone Six, is along 61W, south of 24N, moving westward at 15 knots (28 KM/H). A second wave, Tropical Wave 32, is along 41W from 21N southward and moving west at 10-15 knots (18-27 KM/H), forecast to move across the region from Thursday night into Friday. A third wave, Tropical Wave 33, is along 22W from 21N southward and moving west at 10-15 knots (18-27 KM/H), forecast to move across the region from Saturday night into Sunday.

This week’s forecast remains a mix of light winds, high atmospheric moisture, and instability due to the passages of two tropical waves and two tropical disturbances slackening the pressure gradient.

Potential Tropical Cyclone Six continues to move well north of T&T, now in the Caribbean Sea, and has slackened the pressure gradient, keeping winds light, and allowing for sea breeze convergence, daytime heating, and orographic effects to act as the chief rainmakers across the country. Convergence associated with the disturbance will allow for showers and thunderstorms additionally.

Now that this system is north of the country, a southerly to southeasterly wind regime will still be in place today (Tuesday) though the low to mid-levels of the atmosphere will not be conducive for widespread rainfall. Still, light winds, high temperatures, and orographic effects are forecast to dominate, triggering highly isolated afternoon showers and thunderstorms.

On Wednesday, a similar setup to Tuesday is forecast as Tropical Wave 31 now moves westward, with light winds but abundant moisture and instability will allow for strong thunderstorms to develop during the afternoon while a high-pressure system briefly rebuilds across the region and remains through much of Thursday.

Moisture ahead of Tropical Wave 32 is forecast to begin moving across the region late Thursday into Friday, with increasing cloudiness and showers with winds shifting to the southeast and south on Friday.

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