The Adverse Weather Alert
The Trinidad and Tobago Meteorological Service has issued the Adverse Weather Alert (Yellow Level) as the ITCZ remains across Trinidad and Tobago through much of the week. However, the alert goes into effect from 11:00 AM Tuesday 17th September 2019 through 8:00 PM Wednesday 18th September 2019.
Note that due to favorable atmospheric conditions, locally severe thunderstorms are possible, producing heavy rainfall and gusty winds. Heavier rainfall totals are likely across Tobago as well as Northern and Eastern Trinidad.
Trinidad and Tobago is NOT under any tropical storm threat, watch or warning.
Based on the latest model guidance and analysis, these showers, with isolated heavy showers and thunderstorms, may produce severe weather across Trinidad. This activity is forecast to begin by the late morning on Tuesday and continue into late Thursday, though the Adverse Weather Alert ends at 8:00 PM Wednesday.
Regardless, street flooding, flash flooding and even riverine flooding by Thursday are possible. Gusty winds are likely in the vicinity and during heavy showers or thunderstorms. These gusty winds and heavy rainfall will be capable of triggering landslides in landslide-prone areas, as well as downing trees and utility poles. See below for more details on what impacts to expect.
Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for September 17th-18th, 2019.
“There is a medium chance (65%) chance of intense showers and/or thunderstorms developing by late morning on the Tuesday (17th September 2019) and a high chance (80%) during predawn hours of Wednesday (18th September 2019). This activity will be intermittent with some settled periods but in the event of heavy downpours, street/flash flooding and gusty winds can be expected. The possibility of landslides/landslips is also heightened during the period.” according to the Trinidad and Tobago Meteorological Service. This “alert” status takes into account the possibility of the event occurring. This adverse weather event is likely.
The color of the watch indicates the severity of the event and the probability of the event occurring. Currently, the alert level is at Yellow. This means that the hazard is possible to be aware of the impacts of Street/Flash Flooding and Gusty Winds in your area. Areas prone to landslides should also be aware of the hazard and impacts.
What to Expect Over Next 48-72 Hours
The Takeaway: Intermittent showers are forecast overnight, interrupting partly cloudy skies. Increased showers are forecast mainly by the late morning on Tuesday with intermittent thunderstorm activity. Intermittent showers and thunderstorms are forecast throughout Tuesday and again on Wednesday.
Locally heavy rainfall associated with showers and thunderstorms, gusty winds up to 55 KM/H and landslides possible.
Generally, widespread severe weather is not likely. Localized to scattered severe weather reports are possible, with landslides across the Northern Range and street/flash flooding across Southern and Eastern Trinidad possible through Thursday.
The axis of Tropical Wave 47 is well west of Trinidad and Tobago, but the active weather follows this wave axis, forecast to move across the Lesser Antilles over the next 12 hours.
Favorable atmospheric dynamics will be present across Trinidad and Tobago through Thursday and into Friday due to the ITCZ remaining across the region all week. Favorable upper-level and low-level conditions, increased low-level moisture and low wind shear will result in intermittent periods of showers and thunderstorms throughout the week, although the alert extends only through Wednesday.
Based on the latest model guidance, showers and thunderstorms are forecast to move across both islands, with heavier activity favoring Tuesday through Wednesday.
Locally Heavy Rainfall & Flooding: Based on the latest model runs on Monday evening, from Monday afternoon (2:00 PM) through Friday morning (2:00 AM), generally, over the next several days, models are in agreement of widespread totals of 50 millimeters of rainfall across of Trinidad and Tobago. Up to 100 millimeters are possible in isolated areas across both islands.
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. By late Wednesday, the threat of riverine flooding will be elevated.
Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely. This may cause fires, power outages or destroy utility poles and trees if struck.
Gusty Winds: Gusty winds, generally between 40 and 55 KM/H are possible Gusty winds are most likely prior to, in the vicinity of, or occur during heavy showers or thunderstorms. With wind gusts up to 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.
Landslides: Heavy showers across the Northern Range may trigger landslides in landslide-prone areas. Particularly in areas that receive heavy rainfall, landslides and/or mudflows may occur across both islands. These landslides, in addition to gusty winds, may down trees, utility poles and impede traffic on roadways. The threat of landslides will be elevated by Wednesday into Thursday with saturated soils.
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.
Generally, over the next several days, isolated to scattered activity is forecast. Showers and thunderstorms may become more widespread between Tuesday and Wednesday, particularly on Wednesday morning through the afternoon across Trinidad, during the Adverse Weather Alert.