Tropical Update: Several Tropical Waves To Move Across T&T Over Next Week, Possible Tropical Threat May Form in the Gulf of Mexico

Tropical Weather Update:
Tropical Wave 16: This weak tropical wave is forecast to bring a mild surge in moisture across the Lesser Antilles over the next few hours. A slight increase in low to mid-level clouds forecast. No significant rainfall or severe weather expected.
Tropical Wave 17: A tropical wave is located in the Central Atlantic, a several hundred kilometers East of the Lesser Antilles. This wave is forecast to move across Trinidad and Tobago on Tuesday, though an increase in moisture is forecast by late Monday, as the wave brings the ITCZ closer to T&T. On Tuesday, scattered showers and thunderstorms are possible, with locally heavy rainfall forecast. Severe weather is possible, as favorable conditions are in place for thunderstorm development and gusty winds across the Windwards, including Trinidad and Tobago. Specifically, for T&T, we expect much of the inclement weather to occur on Tuesday.
Tropical Wave 18: A strong tropical wave is located in the Eastern Atlantic, with the first wave of the season having a low-pressure center. This wave is presently embedded in the ITCZ. It is not forecast to develop into a tropical cyclone. This wave is forecast to move across the Southern Windwards, including T&T on Saturday, with showers beginning during the latter half of Friday, through late Saturday. Severe weather is possible.
Tropical Wave 19: This tropical wave is located in the far Eastern Atlantic, forecast to move across Trinidad, Tobago and the remainder of the Southern Windwards on Monday into Tuesday of the following week. It is too far out to tell definitive impacts.
AOI: A Mesoscale Convective Vortex over the Central United States is forecast to move into the Northeastern Gulf of Mexico. This is forecast to form an area of broad low pressure, which has a medium chance of becoming the next named tropical cyclone of the 2019 Atlantic Hurricane Season.

Before we dive into the Tropical Updates on the tropical waves, a few notes:

  • Tropical waves are a normal part of the rainy season.
  • Not every tropical wave will form into a tropical cyclone.
  • Tropical waves at the beginning of the Hurricane Season are typically weak, producing more rainfall across Eastern parts of the islands with mostly cloudy conditions and a few showers across Western parts of the islands.
  • Rainfall will be more scattered and intermittent with weaker tropical waves that do not have ITCZ or upper-level support.
  • Saharan Dust may weaken tropical waves.

You can read more about weather associated with Tropical Waves, as well as what to expect as these waves move through the region below.

Tropical Wave 16

Tropical Wave 16, nearing Trinidad, Tobago and the Lesser Antilles. Beyond a slight increase in cloudiness and a few isolated showers, favoring Southern and Eastern Trinidad by the afternoon, little change in weather is forecast Credit: Weathernerds.org
Tropical Wave 16, nearing Trinidad, Tobago and the Lesser Antilles. Beyond a slight increase in cloudiness and a few isolated showers, favoring Southern and Eastern Trinidad by the afternoon, little change in weather is forecast Credit: Weathernerds.org

The axis of this wave extends its axis along 57/58W from 20N southward, moving west at 15 knots as of the 4:00 PM Tropical Update. Isolated showers and thunderstorms are just
inland over northeastern South America, but dry Saharan air is limiting any shower activity at this time along the remainder of the wave. A slight increase in showers is possible tonight into Monday for the Lesser Antilles and Eastern Caribbean.

This wave will bring a minor surge in moisture and cloudiness over the course of today, interrupting mostly sunny skies across the Lesser Antilles. Specifically for Trinidad and Tobago, there is likely to be an increase in isolated showers during the evening, becoming settled by nightfall, with a few brisk, isolated showers into Monday.

Generally, less than 5 millimeters of rainfall is forecast across both islands (T&T), with a few areas across Eastern Trinidad receiving up to 10 millimeters, as there is a the low chance of a thunderstorm or heavy shower.

Tropical Wave 17

Tropical Wave 17, nearing Trinidad, Tobago and the Lesser Antilles. Isolated to scattered showers and locally heavy showers/thunderstorms forecast to begin overnight Monday, lingering through Tuesday. Gusty winds, street flooding, landslides/mudslides, and downed trees all possible through Tuesday, particularly across Trinidad and Tobago. Credit: Weathernerds.org
Tropical Wave 17, nearing Trinidad, Tobago and the Lesser Antilles. Isolated to scattered showers and locally heavy showers/thunderstorms forecast to begin overnight Monday, lingering through Tuesday. Gusty winds, street flooding, landslides/mudslides, and downed trees all possible through Tuesday, particularly across Trinidad and Tobago. Credit: Weathernerds.org

The axis of this wave extends its axis along 47W from 14N southward, moving west at 15 knots. Scattered showers are from 09N-12N between
45W-51W as of the 4:00 PM Tropical Update.

This wave is embedded within the ITCZ. It is forecast to bring a surge of moisture across Trinidad, Tobago and the Windwards by late Monday into Tuesday, dragging the ITCZ over T&T. Favorable upper-level conditions will support moderate to locally strong convection (thunderstorms).

On Monday afternoon through late Tuesday, Trinidad and Tobago will see an increase in cloudiness, showers, and thunderstorms. Much of the heaviest activity is forecast to occur on Tuesday, with moderate to rough seas, flooding (street and flash flooding), gusty winds and landslides. Note that this wave will be similar to prior inclement weather events for the year as a result of the passage of a tropical wave.

Regardless, an adverse weather advisory (either an alert/watch/warning) may be issued for Trinidad and Tobago from the Trinidad and Tobago Meteorological Service, at models continue to trend towards inclement weather on Tuesday.

What To Expect With Tropical Wave 17

Cloudiness closer to Trinidad, Tobago and Barbados associated with Tropical Wave 16, with showers and thunderstorms further east, associated with Tropical Wave 17.

Note: Street/Flash flooding, frequent lightning, gusty winds, landslides/mudslides are all possible beginning overnight Monday through late Tuesday (8:00 PM). In addition, locally severe thunderstorms may produce isolated areas, up to 50 millimeters of rainfall, across the Windward Islands.

There are still considerable differences between major models with regards to the location of thunderstorms, locally heavy rainfall and gusty winds. Most notably, the GFS shows strong to severe showers and thunderstorms moving across both Trinidad and Tobago, while the EMCWF keeps weaker showers and thunderstorms mainly affecting the Eastern half of T&T. However, given that most other major models are trending towards the EMCWF, the GFS is treated as an outlier presently. Regardless, prepare for inclement weather, particularly during the first half of Tuesday – which both models agree on.

Monday Evening & Night (4:00 PM Monday through 12:00 AM Tuesday): Increasing cloudiness and showers as the evening progresses, with intermittent showers across both islands. Tobago may experience a few heavy showers.

First Half of Tuesday (12:00 AM Tuesday through 12:00 PM Tuesday): Intermittent and scattered, to widespread showers and thunderstorms are likely through the first half of Tuesday. Activity will be similar to previous tropical waves where heavier showers and thunderstorms are isolated and locally heavy rainfall is forecast mainly across Eastern Trinidad.

Second Half of Tuesday (12:00 PM Tuesday through 12:00 AM Wednesday): A few isolated showers and thunderstorms are likely though the early afternoon, favoring Trinidad, becoming more settled as the day progresses. A mild surge of Saharan Dust is likely to begin moving across T&T by the late evening into the night.

Showers and thunderstorms are forecast to become more sparse throughout the day on Tuesday, with severe thunderstorms south of Trinidad, along Coastal Venezuela. Upper-level clouds may produce a partly to mostly cloudy day across Trinidad and Tobago.

Possible Impacts to Trinidad and Tobago

Locally Heavy Rainfall & Flooding: Based on the 0Z and 12Z Sunday model runs, from Monday (2:00 PM) through Wednesday (2:00 AM), generally, over the 36 hour period, models are in agreement of less than 20 millimeters across Western halves of Trinidad and Tobago and between 20-40 millimeters across the Eastern halves of both islands. Isolated rainfall totals up to 60 millimeters are possible across Eastern coastal Trinidad and Tobago. As mentioned above, there is still some uncertainty regarding the severity of showers.

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 forecast to occur mainly after 10:00 PM Monday.

Gusty Winds: Gusty winds, generally up to 60 KM/H are likely. 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.

High Wind Event Precautions
High Wind Event Precautions

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.

Tropical Wave 18 & 19

Tropical Wave 18, embedded within the ITCZ and a low-pressure center located at 8N, along 30W, producing scattered showers near the axis of the wave. This wave is forecast to move across the Lesser Antilles by late Friday through Saturday, bringing another round of possible inclement weather to the islands. A weak Tropical Wave 19 follows. Credit: Weathernerds.org

The axis of Tropical Wave 18 wave extends its axis along 29W, south of 12N and is moving westward at 15-20 knots as of the 4:00 PM Tropical Update. A 1012 millibar (mb) low is near 08N along the wave. Scattered moderate showers are from 04N-08N between 26W-38W. This is the first tropical wave for the 2019 Atlantic Hurricane Season that has a low-center associated with the wave axis – which is worth mentioning as tropical waves are becoming slightly stronger as we progress further into the hurricane season.

To be clear: This wave is NOT forecast to develop. This wave has NO model support for development with no closed low-pressure center moving across the Lesser Antilles. What models are continuing to show is some circulation (vorticity) moving across T&T on Friday 12th July into Saturday 13th July 2019.

This wave is forecast to weaken as it moves westward, losing its low-pressure center. Tropical Wave 18 and Tropical Wave 19 are forecast to move across Trinidad and Tobago back-to-back, with the former forecast Friday into Saturday and the latter Sunday into Monday.

Tropical Wave 19’s axis is along 22W from 04N-17N, moving W at 15-20 kt. Scattered showers are from 08N-11N between 18W-23W as of the 4:00 PM Tropical Update.

Rainfall totals from both waves, based on present analysis, are forecast to be between 20-50 millimeters across Western halves of Trinidad and Tobago, 50-100 millimeters across Eastern halves of T&T and isolated totals up to 150 millimeters, making this a potential flooding threat. In addition, there is the threat of gusty winds.

Because of the long range of these waves, there is considerable uncertainty in the exact timing of showers, thunderstorms and locations which may receive heavier rainfall totals. Expect additional details in a subsequent tropical update.

Potential Tropical Threat in The NE Gulf of Mexico

A trough of low pressure over the southeastern United States is forecast to move southward toward the northeastern Gulf of Mexico, where a broad low-pressure area will likely form in a few days. Thereafter, upper-level winds support gradual development, and a tropical depression could form late week while the low meanders near the northeastern Gulf of Mexico coast through Friday. Interests along the northern Gulf Coast and Florida peninsula should monitor the progress of this system.

For more details on the system and its formation, the latest information can be found at the National Hurricane Center.

If this system forms, it will be of NO threat to Trinidad, Tobago, and the Eastern Caribbean.

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of July. This month, the attention goes to tropical waves moving across the Atlantic, particularly as they near the Lesser Antilles, as well as low-pressure systems in the Gulf of Mexico and troughs Southeast of the United States.

In July, we turn our eyes to East of the Lesser Antilles, the Southeastern areas of the United States and the Gulf of Mexico for the formation of tropical cyclones in the Atlantic Basin, historically. However, tropical cyclones can form in the Atlantic Basin, without regard for the location once conditions support development. Stay updated with the latest tropical update!

There are NO tropical cyclone threats to the Eastern Caribbean, including Trinidad and Tobago at this time in the latest Tropical Update.

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