The Adverse Weather Alert
The Trinidad and Tobago Meteorological Service has issued an Adverse Weather Alert (Yellow Level) as Tropical Wave 35 nears Trinidad and Tobago, interacting with the ITCZ. Heavy showers and thunderstorms are likely, according to the TTMS to after 10:00 AM Wednesday 14th August 2019 through 2:00 PM Thursday 15th August 2019.
Note that due to favorable atmospheric conditions, locally severe thunderstorms are possible, producing heavy rainfall and gusty winds, mainly across Trinidad.
Although this alert has been issued by the TTMS beginning at 10:00 AM tomorrow, through 2:00 PM Tuesday, showers and thunderstorms are possible before this alert begins, particularly by 8:00 AM Wednesday, as well as through the second half of Thursday.
Trinidad and Tobago is NOT under any tropical storm threat, watch or warning.
Based on the latest model guidance, these showers, with isolated heavy showers and thunderstorms may produce severe weather across Trinidad. Street flooding, flash flooding. 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 August 14th-15th, 2019.
“Heavy showers and thunderstorms are likely over Trinidad from 10 AM on Wednesday until 2 PM on Thursday. Street/Flash flooding and gusts up to 65km/h are likely near heavy downpours. There is the possibility of landslides or landslips along hilly areas. This activity is due to the passage of a Tropical Wave interacting with the ITCZ.” 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.
The 35th tropical wave of the 2019 Atlantic Hurricane Season is still east of Trinidad and Tobago as of 5:30 PM Tuesday 13th August 2019.
What to Expect Over Next 24-48 Hours (Ammended from the Previous Update)
The Takeaway: Beginning 8:00 AM Wednesday, showers and thunderstorms are likely to begin (continuing from isolated overnight activity), mainly across Trinidad.
Locally heavy rainfall associated with showers and thunderstorms, gusty winds up to 65 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.
As expected, cloudiness has increased across Trinidad as upper-level clouds from thunderstorms and heavy showers across inland Venezuela move across the area.
As the evening progresses, a few isolated showers are forecast across Southern and Eastern Trinidad, interrupting mostly settled skies.
After midnight, mostly settled conditions are forecast to persist, with increasing showers mainly across the Southern half of Trinidad initially.
On Wednesday, mid-levels across the entire region are forecast to be dry during the early morning period. However, as the day progress, the approaching tropical wave 35 will begin to affect Trinidad and Tobago.
Periods of showers and thunderstorms are forecast to move across T&T, interrupting partly cloudy to overcast skies. In addition, winds are forecast to increase across the region, with sustained winds up to 50 KM/H outside of shower activity. Stronger winds will favor Eastern Trinidad and Tobago, although the alert only extends across Trinidad.
Presently, Tropical Wave 35 is located along 55W, moving westward at 15 knots. Its axis is forecast to move across T&T on Wednesday, with much of the forecast inclement weather expected by the late morning on Wednesday into Thursday.
This wave is forecast to drag the ITCZ across T&T yet again, through the end of the week. Combined with favorable upper-level conditions and increased low-level moisture, periods of showers and thunderstorms are likely.
Lastly, though mostly easterly winds between 20-25 knots (35-45 KM/H) are forecast, light southeasterly winds are forecast across Trinidad during the latter half of Wednesday across Trinidad. Since winds are forecast to move across Trinidad (and Tobago) from the south to southeast, winds across the Northern Range are forced upwards, creating orographic lift. This phenomenon, simply put, aid in the development of showers, or enhance showers and thunderstorms.
With all these features coming together, showers and thunderstorms are forecast to persist across mainly Trinidad throughout the next 24-48 hours, which may dump copious amounts of rainfall.
Based on the latest model guidance, isolated to scattered showers and isolated thunderstorms are forecast to move across both islands, with heavier activity favoring much of Trinidad, beginning on Wednesday.
Locally Heavy Rainfall & Flooding: Based on the latest model runs on Tuesday afternoon, from Wednesday morning (2:00 AM) through Friday morning (2:00 PM), generally, over the 48 hour period, models are in agreement of fewer than 30 millimeters across of Trinidad and Tobago and between 30-50 millimeters across isolated areas of Trinidad and up to 75 millimeters across Eastern and Southern Trinidad.
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, based on the above-mentioned forecast rainfall totals associated with the ITCZ as it moves across the area.
Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely.
Gusty Winds: Gusty winds, generally between 40 and 65 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 65 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.
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, because of winds associated with tropical waves, showers and thunderstorms tend to follow a west-northwest track, generally missing areas across Southwestern Trinidad and even Northwestern Trinidad – though activity due to local climatic effects such as daytime heating may trigger shower and thunderstorm development across these areas. See the below graphic for a simple explanation.
With this tropical wave (Tropical Wave 35), mostly scattered showers are forecast. Hence, we are likely to see intermittent showers and thunderstorms, interrupting partly cloudy to overcast skies between Wednesday and Thursday.