Tropical Update: Tropical Wave 35, ITCZ To Bring Heavy Rainfall To T&T Wednesday & Thursday

Tropical Update:
Tropical Wave 34: This tropical wave is located in the Central Caribbean Sea, well west of Trinidad and Tobago. It has brought the ITCZ across T&T over the last 12-18 hours. The ITCZ is forecast to drift southward over the next 12-18 hours, bringing some showers and thunderstorms to the Southern half of Trinidad. No further impacts from this wave forecast.
Tropical Wave 35: This tropical wave is located in the Central Atlantic, forecast to move across Trinidad and Tobago Wednesday into Thursday. Favorable mid- and upper-level conditions are forecast to aid in the development of moderate to strong convection. Severe weather and locally heavy rainfall are likely.
The ITCZ: Between TW35 and TW36, the ITCZ and a surface trough are forecast to move across Trinidad and Tobago, keeping showers and isolated thunderstorms in the forecast for the region, keeping a rainy week and weekend on tap for mainly Trinidad.
Tropical Wave 36: This tropical wave is located in the Eastern Atlantic, forecast to move across T&T on Saturday into Sunday. There is a significant model difference on potential impacts of this wave between the GFS and EMCWF. However, locally heavy rainfall is possible.
— No tropical cyclone formation expected for the next 5 days across the North Atlantic.

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 isolated 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 the weather associated with Tropical Waves, as well as what to expect as these waves move through the region below.

Tropical Wave 34

The ITCZ present across Trinidad and Tobago, as it was dragged north by Tropical Wave 34, bringing showers and thunderstorms on Monday across the islands. Credit: Weathernerds.org
The ITCZ present across Trinidad and Tobago, as it was dragged north by Tropical Wave 34, bringing showers and thunderstorms on Monday across the islands. Credit: Weathernerds.org

Tropical Wave 34 is located in the Central Caribbean Sea, along 71W, moving west at approximately 15 knots. This wave is embedded in dry, Saharan air, which is limiting convection near the wave axis.

Though this tropical wave moved across the islands over the weekend, much of the showers and thunderstorms resulted from the ITCZ on Monday as it lingered across T&T.

The ITCZ is forecast to drift southward overnight, through Tuesday. This will keep showers and isolated thunderstorms in the forecast for the southern half of Trinidad on Tuesday. Street/flash flooding, gusty winds possible.

Tropical Wave 35

Tropical Wave 35, along 45W to 47W. This wave is moving across the Central Atlantic Ocean, with the northern portion of the wave axis located in dry, Saharan air. This wave is forecast to bring locally heavy rainfall, street/flash flooding and inclement weather T&T by Wednesday into Thursday. Credit: Weathernerds.org
Tropical Wave 35, along 45W to 47W. This wave is moving across the Central Atlantic Ocean, with the northern portion of the wave axis located in dry, Saharan air. This wave is forecast to bring locally heavy rainfall, street/flash flooding and inclement weather T&T by Wednesday into Thursday. Credit: Weathernerds.org

Tropical Wave 35 is located in the Central Atlantic, along 47W to the north and 45W to the south, extending from 22N southward, moving west at approximately 10-15 knots. The wave is well depicted in model guidance, at the 700 millibar level and TPW imagery shows abundant moisture in the wave’s environment. However, dry Saharan air is limiting convection north of 10N, with isolated moderate convection near the southern portion of the wave axis.

This tropical wave is forecast to begin affecting Trinidad, Tobago, and the Southern Windwards by Wednesday into Thursday. Street/flash flooding and gusty winds possible.

What to Expect?

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 mainly on Wednesday and also on Thursday.

Locally Heavy Rainfall & Flooding: Based on the latest model runs on Monday afternoon, from Wednesday morning (2:00 AM) through Friday morning (2:00 AM), generally, over the 48 hour period, we forecast up to 40 millimeters across of the Western halves of Trinidad and Tobago and between 30-50 millimeters across isolated areas of Trinidad and up to 70 millimeters across Eastern and Southern Trinidad.

There is some difference in the leading models for precipitation output, with the GFS trending to higher rainfall accumulations while the EMCWF is notably drier.

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 over the 24-48 hours period.

Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely.

Gusty Winds: Gusty winds, generally between 40 and 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.

High Wind Event Precautions
High Wind Event Precautions

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?

Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.
Tropical waves typically have fair weather ahead of the wave axis, though other features in the area such as surface troughs, increased atmospheric moisture, and local climatic effects, to name a few, may trigger showers and the odd thunderstorm. Following the passage of the wave, much of the active weather typically associated with a tropical wave occurs.

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 Tropical Wave 35, scattered activity is forecast. Hence, we are likely to see showers and thunderstorms, interrupting partly cloudy to overcast skies Wednesday into Thursday.

The ITCZ & A Surface Trough

Following the passage of Tropical Wave 35, the ITCZ is forecast to linger through Friday into Saturday, with a surface trough embedded, is forecast to move across T&T.

Periods of showers and thunderstorms are forecast to linger across Trinidad and Tobago through the end of the week into the weekend. This activity is forecast to remain fairly intermittent, with partly to mostly cloudy periods being interrupted.

Note that as with all heavy showers and thunderstorms, gusty winds and street/flash flooding is possible.

Tropical Wave 36

Tropical Wave 36 in the far Eastern Atlantic is along 30/32W. This wave is forecast to move across the Lesser Antilles by the end of the upcoming weekend. No tropical development expected. Credit: Weathernerds.org

Tropical Wave 36 is located in the far Eastern Atlantic, along 30/32W, 2-12N. This tropical wave is forecast to move across the Lesser Antilles by the end of the upcoming weekend.

There are still significant differences between leading models for possible precipitation accumulations. The EMCWF is notably drier than the GFS model but both models indicate showers and thunderstorms possible beginning Saturday through Monday of next week, interacting with the ITCZ. Additional updates will be posted in a future tropical update.

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of August. 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 August, 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!

Overall, conditions are not favorable for tropical cyclone development at this time due to dominating dry, Saharan air across the Atlantic. However, by the end of August into September, conditions may become more favorable for tropical cyclone development across the Atlantic Basin.

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

2019 Atlantic Hurricane Season Names

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