Riverine Flood Warning Orange Level In Effect For Caroni, South Oropouche River Basins

Key Messages:
— A Riverine Flood Alert Yellow Level was upgraded to a Riverine Flood Warning Orange Level in effect from 12:00 PM Wednesday through 6:00 PM Friday for “surrounding areas of smaller rivers and tributaries, particularly in southern Trinidad and lower lying areas near the Caroni river.
— Through Friday, an additional 1 to 2 inches (25 to 50 millimeters) are possible across Trinidad and Tobago with heavier totals across Eastern and Southern halves of Trinidad. There is an elevated threat of street flooding and flash flooding. Note that already between 1-2 inches (25-50 mm) and isolated totals up to 4 inches (100 mm) have fallen across parts Trinidad.
— Seas will remain moderate to occasionally rough, with waves up to 2.5 meters are possible in open waters, occasionally up to and in excess of 3.0 meters and less than 1.0 meter but choppy in sheltered areas.
— Gusty winds in excess of 55 KM/H possible, particularly on Tuesday. Winds of this strength will produce wind damage including downed trees, utility poles and roof damage. Localized power outages possible.
Landslides possible in elevated areas.

The Riverine Flood Warning

As we’ve forecast since Monday, locally heavy rainfall was possible today, Wednesday. Overall rainfall totals were notably heavier than expected, with scattered to widespread showers beginning as early as 2:00 AM Wednesday morning. Between 25-50 millimeters of rainfall has fallen across Trinidad, with isolated totals up to 100 millimeters. This triggered widespread street and flash flooding across parts of Southern Trinidad.

By 10:00 AM Wednesday, with continuing rainfall, major rivers such as the Moruga River, Cipero River, and South Oropouche River were nearing threshold levels, with rising water across much of Debe, Penal and Barrackpore. With more rainfall on the horizon and minor tributaries breaking its banks, the Trinidad and Tobago Meteorological Service has issued a Riverine Flood Alert (Yellow Level) at 12:16 PM Wednesday.

This alert was updated Wednesday night at 9:53 PM to include the Caroni River Basin, maintaining a yellow level alert as the Caroni River was forecast to overtop its banks by dawn Thursday morning.

At 12:21 PM Thursday, the Met Office upgraded the alert to a Riverine Flood Warning (Orange Level) for both the Caroni River Basin from as far west as Bamboo #3 to as far east as Guanapo.

The alert began at 12:00 PM on Wednesday 11th December 2019 and is now extended through 6:00 PM Friday 13th December 2019. Note that although rainfall is continuing, the heaviest showers and thunderstorms have already occurred.

Trinidad and Tobago is NOT under any tropical storm watch or warning.

Based on the latest model guidance and analysis, isolated to scattered showers are forecast to favor Eastern areas, with the Caroni River and the South Oropouche River outside of their banks, the additional flood threat now extends to the Ortoire River which is already overtopped its banks, flooding areas across Mayaro.

Information from the Trinidad and Tobago Meteorological Service concerning the Riverine Flood Alert for 11-13th December 2019.

Isolated light to moderate showers are expected this afternoon with a low (30%) chance of heavy showers or thunderstorms. Run-off from rainfall over the last 24 hours continues to reach some of the smaller watercourses and as a result, impacted areas remain inundated as floodwaters are still slowly on the rise in southern Trinidad. Spring tides are also in effect, which can exacerbate conditions at high tide. The Caroni River is currently at maximum capacity and has overflowed onto its banks and low lying surrounding areas.” according to the Trinidad and Tobago Meteorological Service. This “warning” status takes into account the possibility of the event occurring. This riverine flood event is observed.

The color of the alert indicates the severity of the event and the probability of the event occurring. Currently, the alert level is at Orange. This means that the hazard is observed. Severe impacts are expected, with there may be the loss of a single life or serious injuries. Physical defenses are needed and major losses are possible in confined areas. Income earning may be disrupted for several days. Several communities are affected, with external help needed for recovery.

Image Credit: Trinidad and Tobago Meteorological Service
Image Credit: Trinidad and Tobago Meteorological Service
Image Credit: Trinidad and Tobago Meteorological Service

What We Know

A surface to low-level trough, which is an area of lower than usual pressure at the surface to low-levels of the atmosphere, continues to produce unsettled weather across the Lesser Antilles.

An upper-level jet, which is a narrow area, at upper levels of the atmosphere, where a current of fast-moving winds exists, is providing ample support for broad periods of rain of varying intensities across Trinidad.

A surface to low-level trough affecting the Lesser Antilles, with continuing showers triggering the Riverine Flood Alert. Credit: Weathernerds
A surface to low-level trough affecting the Lesser Antilles, with continuing showers triggering the Riverine Flood Alert. Credit: Weathernerds

Activity associated with this trough is supported by favorable upper-level divergence and very favorable low-level convergence.

The Weather Forecast

Thursday: Brisk, isolated showers are forecast throughout the day affecting both islands, interrupting partly to mostly cloudy and breezy conditions. Heavier showers and isolated thunderstorms are forecast to favor Eastern and Southern Trinidad, as well as eastern coastal waters. As the afternoon into the evening progresses, showers are forecast to be on the decline, interrupting partly to mostly cloudy skies. Gusty winds, up to 50 KM/H possible.

Friday: The unsettled pattern remains mostly unchanged from Thursday, with brisk isolated showers throughout the day bringing the threat of gusty winds. Isolated thunderstorms possible during the afternoon, across Southwestern areas.

Impacts This Upcoming Week

Winds: Sustained surface winds between 20 KM/H and 35 KM/H with gusts up to 50 KM/H are likely in heavy showers or thunderstorms across Trinidad and Tobago throughout the week.

With wind gusts in excess of 50 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.

High Wind Event Precautions
High Wind Event Precautions

Rainfall: Additional Rainfall accumulations are forecast to be scattered totals of 15-25 millimeters. Overall additional totals are expected to be up to 25-50 millimeters in isolated thunderstorms or heavy downpours.

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. The Riverine Flood Warning remains in effect through Friday.

Frequent Lightning: In addition, with forecast thunderstorms, frequent lightning is likely. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.

Landslides: Particularly across Northwestern Trinidad, soils are very saturated with persistent heavy afternoon thunderstorms at the end of the last week. With additional rainfall in the forecast, landslides are possible through Tuesday in landslide-prone and elevated areas.

Hazardous Seas: An increase in strong low-level winds will keep seas at moderate levels, with waves up to 2.5 meters in open waters and even at occasional rough levels, with waves in excess of 2.5 meters, particularly along the Eastern coasts of both islands.

Why I May Not/Will Not See Constant 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.

On Wednesday, widespread rainfall is expected. On Thursday, isolated to scattered activity is possible. On Friday, isolated activity is forecast.

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

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