Adverse Weather Alert In Effect For T&T As ITCZ Affects the Region

Key Messages:
— An Adverse Weather Alert Yellow Level goes into effect at 6:00 AM Wednesday through 6:00 PM Thursday.
— Between 0.5 to 2.5 inches (12.5 to 62.5 millimeters) of rainfall fell across T&T on Tuesday, with the heaviest rainfall occurring across Eastern Trinidad and Tobago.
— Through Friday, an additional 2 to 4 inches (50 to 100 millimeters) are possible across Trinidad and Tobago with isolated totals up to 5 inches (125 millimeters) across Eastern, Northern Trinidad and Tobago. There is an elevated threat of street flooding and flash flooding by the late week. There is the low chance of riverine flooding in the event of rainfall totals between 100-125 mm materializing, particularly across Northern and Eastern Trinidad.
— Seas will remain moderate, with waves between 1.5 meters and 2.0 meters are possible in open waters and choppy in sheltered areas. Swells are forecast to persist through Wednesday.
— 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 Adverse Weather Alert

The Trinidad and Tobago Meteorological Service has issued the Adverse Weather Alert (Yellow Level) at 5:00 PM Tuesday as the ITCZ is forecast to continue affecting Trinidad, Tobago, and the Southern Windwards. The alert goes into effect from 6:00 AM Wednesday 9th October 2019 through 6:00 PM Thursday 10th October 2019. The ITCZ is forecast to remain in the area through Friday.

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

Based on the latest model guidance and analysis, these showers, with scattered heavy showers and thunderstorms, are forecast to produce possible severe weather across Trinidad and Tobago. This activity is forecast to begin mainly after midnight tonight through Friday, with periods of cloudiness, though the Adverse Weather Alert begins at 6:00 AM Wednesday 9th October 2019 and ends at 6:00 PM Thursday 10th October 2019.

Information from the Trinidad and Tobago Meteorological Service concerning the Adverse Weather Alert for October 9th-10th, 2019.

The Inter-Tropical Convergence Zone will affect Trinidad and Tobago with periods of showers and/or rain and isolated thunderstorms. The main impacts will include saturated soils, possibility of landslips and/or landslides in addition to gusty winds, electrical discharges, street and/or flash flooding. ” 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 alert 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.

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

What We Know

 The ITCZ continuing to affect T&T, bringing periods of showers and thunderstorms as forecast, triggering the Adverse Weather Alert. Credit: Weathernerds
The ITCZ continuing to affect T&T, bringing periods of showers and thunderstorms as forecast, triggering the Adverse Weather Alert. Credit: Weathernerds

The ITCZ is now located directly across Trinidad and Tobago.

T&T is located in an area of favorable upper-level divergence and low-level convergence, though showers have subsided for the night. Moisture remains abundant, though at the 500 millibar level, relative humidity values are very low, likely due to Saharan Dust still across our region.

Wind shear remains low to light, forecast to remain low over the next 48 hours.

Mostly settled but cloudy skies are ongoing across T&T as of 5:30 PM.

Impacts From The ITCZ

5:00 PM Tuesday 8th October 2019 Trinidad and Tobago Impact Assessment for the ITCZ across Trinidad and Tobago. Note that this will be continually updated.

Weather

The forecast remains generally unchanged from Monday evening’s and Tuesday post.

Tuesday (until midnight); The ITCZ. Mostly settled with a few isolated showers, increasing in coverage near midnight.

Wednesday (until midnight): The ITCZ. Similar conditions to Tuesday are forecast. Isolated to scattered showers and possible thunderstorms are likely to develop after midnight, favoring Northern and Eastern Trinidad as well as Tobago, gradually spreading across both islands. Periods of showers and possible thunderstorms are likely across both islands, with heavier showers and thunderstorms now favoring the Western and Northern halves of Trinidad throughout the day. Conditions are forecast to become settled into the night, with a few lingering showers.

Thursday (until midnight): The ITCZ and a low-level trough. Essentially the same forecast as the previous. Periods of showers and thunderstorms forecast, interrupting partly cloudy to mostly cloudy skies. Conditions become settled by the late evening with a few lingering showers. Elevated threat for flooding.

Friday (until midnight): The ITCZ, upper and low-level trough. Periods of showers and thunderstorms for the 4th day in a row, interrupting partly cloudy to mostly cloudy skies. Conditions become settled by the late evening with a few lingering showers. Elevated threat of flooding.

Wind

Peak sustained surface winds of 25 KM/H to 45 KM/H with gusts in excess of 55 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago, during heavy shower or thunderstorm activity.

With wind gusts in excess of 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, bringing down utility poles and lines.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Through Friday, an additional 2 to 4 inches (50 to 100 millimeters) are possible across Trinidad and Tobago with isolated totals up to 5 inches (125 millimeters) across Eastern, Northern Trinidad and Tobago.

Between 0.5 to 2.5 inches (12.5 to 62.5 millimeters) of rainfall fell across T&T on Tuesday, with the heaviest rainfall occurring across Eastern Trinidad and Tobago.

There is an elevated threat of street flooding and flash flooding by the late week. There is a very low chance of riverine flooding in the event of rainfall totals between 100-125 mm materializing, particularly across Northern and Eastern Trinidad.

Thunderstorms and Lightning

With thunderstorms, locally severe wind (in excess of 55 KM/H), violent rainfall rates (in excess of 50 millimeters per hour) and lightning are all possible.

Gusty winds and lightning pose a threat to our power grid, causing localized power outages. Lightning may also strike trees, homes or utility poles causing damage to property. Lightning can also be deadly to persons outside during a thunderstorm.

Seas and Surf

Long-period swells are forecast to continue through Wednesday, with seas moderate in open waters with waves between 1.5 to 2.0 meters. In sheltered areas, seas are near 1.0 meters, but choppy, particularly during heavier showers or thunderstorms.

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