The Adverse Weather Alert
The Trinidad and Tobago Meteorological Service has issued an Adverse Weather Alert as Tropical Wave 21 nears Trinidad and Tobago, interacting with the ITCZ. Heavy showers and thunderstorms are likely to after 2:00 AM Monday 15th July 2019 (tomorrow) through 12:00 PM Monday 15th 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 Tropical Update.
Note that although this alert has been issued by the TTMS beginning at 2:00 AM, through 12:00 PM tomorrow, showers and thunderstorms are possible before this alert begins, as well as through Tuesday and into Wednesday, 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 intermittent showers, with isolated heavy showers and thunderstorms may produce severe weather across Trinidad and Tobago. Street flooding, flash flooding, particularly across Northeastern 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 forecast adverse weather, the Trinidad and Tobago Meteorological Service has issued the Adverse Weather Alert at 4:00 PM Sunday 14th July 2019, valid from 2:00 AM Monday until 12:00 PM Monday 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 15th, 2019.
“Intermittent showers and thunderstorms are likely over Tobago, and to a lesser extent Northern Trinidad from early morning until midday on Monday 15th July 2019. Street/flash flooding, landslides/landslips and gusty winds in excess of 45km/hr are possible.” 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 21st tropical wave of the 2019 Atlantic Hurricane Season is still east of Trinidad and Tobago as of 4:30 PM Sunday 14th July 2019.
What to Expect Over Next 24-48 Hours (From the earlier Update)
The Takeaway: As we have been repeatedly forecasting, increased cloudiness and showers during the second half of Sunday persisting into Monday, with thunderstorms possible Monday into Tuesday, generally interrupting overcast to mostly cloudy skies.
Street/Flash flooding, gusty winds up to 60 KM/H, landslides and downed trees/utility poles possible.
The heaviest activity is forecast to remain across the Eastern and Northern halves of Trinidad, Tobago, and north of T&T. Showery spells will interrupt partly cloudy skies throughout the next 72 hours.
Generally, increasing cloudiness is forecast to begin late Sunday, with isolated showers occurring through Sunday night into Monday morning. A few isolated thunderstorms and locally heavy showers are possible during the latter half of Sunday. Street/Flash Flooding and gusty winds possible.
On Monday, during the late morning through the afternoon, scattered showers and isolated thunderstorms are possible across parts of Trinidad and northeastern Venezuela. The latter activity will likely cause mostly cloudy skies across the southern half of Trinidad. This activity will be directly associated with Tropical Wave 21 and is forecast to subside by the late afternoon into the evening.
However, as Tropical Wave 21 progresses westward, the ITCZ is forecast to remain across the Eastern and Northern halves of Trinidad and Tobago through Tuesday. This will facilitate scattered to possibly widespread showers across the aforementioned areas. The heaviest rainfall is likely across Eastern parts of Trinidad and Tobago.
Based on the latest model guidance, this activity is likely to linger into Wednesday with intermittent showers across both islands. An adverse weather alert may be issued for Trinidad and Tobago from the Trinidad and Tobago Meteorological Service, particularly for Monday into Tuesday.
Note: Street/Flash flooding, frequent lightning, gusty winds, landslides/mudslides are all possible beginning Sunday evening through Tuesday evening. In addition, locally heavy showers and thunderstorms may produce isolated areas, in excess of 100 millimeters of rainfall, across the Windward Islands, particularly Eastern areas of Trinidad and Tobago and north of T&T.
Locally Heavy Rainfall & Flooding: Based on the latest model runs on Sunday, from Sunday (2:00 PM) through Wednesday (2:00 PM), generally, over the 72 hour period, models are in agreement of fewer than 30 millimeters across Western halves of Trinidad and Tobago and between 30-50 millimeters across the Eastern halves of both islands. Isolated rainfall totals up to 75 millimeters are possible across Eastern coastal Trinidad and Tobago. As mentioned above, much of the heaviest showers and thunderstorms are forecast to move north of Trinidad and Tobago, particularly between Tobago and Barbados.
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. Thunderstorms are likely to begin on Monday through Tuesday.
Gusty Winds: Gusty winds, generally up to 60 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 60 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.
Across parts of Tobago, Grenada, St. Vincent and the Grenadines and Barbados, winds may gust up to 65 KM/H at times, particularly in the vicinity of heavy showers and thunderstorms.
Landslides: In landslide-prone areas, particularly in areas that receive heavy rainfall, landslides and/or mudflows may occur. These landslides, in addition to gusty winds, may down trees, utility poles and impede traffic on roadways.
What’s Causing This Inclement Weather?
The axis of Tropical Wave 21 is nearing T&T presently, forecast to bring additional showers, scattered thunderstorms and the ITCZ across the region. A deep surge in tropical moisture associated with this wave is moving across T&T presently and is forecast to persist over the next 24-48 hours.
These favorable conditions are forecast to remain in place throughout the next 2 days, with upper level divergent and low-level convergence aiding in the development of showers and thunderstorms with the passage of the wave axis. The Intertropical Convergence Zone, or the ITCZ, is also shifting across T&T as a result of this tropical wave.