The Adverse Weather Alert
The Trinidad and Tobago Meteorological Service has issued an Adverse Weather Alert as Tropical Wave 29 nears Trinidad and Tobago, interacting with the ITCZ. Heavy showers and thunderstorms are likely, according to the TTMS to after 8:00 PM Saturday 27th July 2019 (tonight) through 12:00 PM Sunday 28th July 2019. Note that due to favorable atmospheric conditions, locally severe thunderstorms are possible, producing heavy rainfall and gusty winds. We (TTWC) went into detail about this system in our earlier updates (today, yesterday, Wednesday).
Note that although this alert has been issued by the TTMS beginning at 8:00 PM, through 12:00 PM tomorrow, showers and thunderstorms are possible likely before this alert begins, as well as through the second half of Sunday, due to favorable conditions in place.
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 and Tobago. Street flooding, flash flooding, particularly across Trinidad where showers and thunderstorms may continue to move across. 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.
Because of the ongoing and forecast adverse weather, the Trinidad and Tobago Meteorological Service has issued the Adverse Weather Alert at 3:00 PM Saturday 27th July 2019, valid from 8:00 PM Saturday until 12:00 PM Sunday according to the Trinidad and Tobago Meteorological Service. As we’ve mentioned above, inclement weather is possible before the alert is in effect and after it expires due to the ITCZ remaining across the region.
Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for July 27-28th, 2019.
“Showers and thunderstorms associated with a tropical wave are continuing over various parts of Trinidad and Tobago. There is a heightened risk for increased, periodic activity overnight and tomorrow. Street/flash flooding and landslips are possible in areas that are usually susceptible, and it is also possible for winds to gust in excess of 50km/hr.” 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 29th tropical wave of the 2019 Atlantic Hurricane Season is still east of Trinidad and Tobago as of 3:00 PM Saturday 27th July 2019.
What to Expect Over Next 24-36 Hours (From the earlier Update)
The Takeaway: Scattered showers and thunderstorms are forecast to move across mainly Southern and Central Trinidad on Saturday, gradually spreading across the northern half of Trinidad and Tobago by Saturday evening into Sunday.
Generally, widespread severe weather is not likely. Localized to scattered severe weather reports are possible, with locally (isolated) heavy rainfall.
Presently, winds are from the northeast at low-levels. This is keeping showers and thunderstorms mainly across Southern Trinidad. As the evening progresses, showers and thunderstorms are forecast to move across Central, Northern Trinidad and Tobago. Street/Flash Flooding and gusty winds possible.
Across parts of Trinidad, mainly across South, this activity may subside by the late evening. Across the remainder of Trinidad, showers and thunderstorms are forecast to continue into Sunday.
Based on the latest model guidance, showers, periods of rain and isolated thunderstorms are forecast to favor Eastern and Southern Trinidad on Saturday, gradually moving across Northern Trinidad and Tobago by the late afternoon into Sunday.
This activity is forecast to persist into Sunday, with slightly more scattered showers across both islands due to favorable atmospheric conditions.
Locally Heavy Rainfall & Flooding: Based on the latest model runs on Saturday morning, from Saturday (2:00 AM) through Monday (2:00 AM), generally, over the 48 hour period, models are in agreement of fewer than 15 millimeters across Western halves of Trinidad and Tobago and between 15-30 millimeters across the Eastern halves of both islands. Isolated rainfall totals up to 50 millimeters are possible across Eastern coastal Trinidad and Tobago. Much of the heaviest showers and thunderstorms are forecast to occur north of Trinidad and Tobago. However, it seems that models are underperforming with regards to rainfall outputs, hence the totals may be below
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.
Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely. As of midnight, through 3:15 PM, over 3200 lightning strikes have occurred near Trinidad and Tobago, with 2031 being dangerous cloud to ground strikes. Note most of these strikes have occurred offshore T&T.
Gusty Winds: Gusty winds, generally between 40 and 50 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 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.
Landslides: Though there is a low chance of 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 29), mostly scattered showers are forecast. Hence, we are likely to see intermittent showers and thunderstorms, interrupting partly cloudy to overcast skies between Saturday and Sunday.