What you need to know
No areas are being monitored for tropical development in the Atlantic Basin at this time. We’re monitoring two tropical waves east of the Lesser Antilles, set to move across T&T this week.
— Tropical Wave 22: This tropical wave is just east of Barbados and Trinidad and Tobago, along 57W, moving west at 15-20 knots. There is no significant shower or thunderstorm activity associated with this wave at this time, but it is forecast to increase convergence across T&T tonight, and bring the ITCZ across the country on Tuesday and Wednesday.
— Tropical Wave 23: This wave is located along 35W, moving west at 15 knots, and is forecast to move across T&T and the Lesser Antilles on Thursday, producing showers and thunderstorms across T&T. Scattered showers are noted where the wave interacts with the ITCZ/Monsoon Trough in the Atlantic.
— Hazards for T&T: From early Tuesday morning through Friday morning, cloudiness, isolated to scattered showers and thunderstorms, are forecast to affect Trinidad and Tobago as Tropical Waves 22 and 23 interact with the Intertropical Convergence Zone.
Tropical Waves 22 and 23
Two weak tropical waves are analyzed at 57W (Tropical Wave 22) and 35W (Tropical Wave 23), east of Trinidad and Tobago.
Tropical Wave 22 is forecast to move across Trinidad and Tobago tomorrow, Tuesday, July 16th, 2024. However, convergence ahead of the wave axis will increase cloudiness with isolated shower and thunderstorm activity tonight, favoring Trinidad. The wave axis should clear T&T by tomorrow afternoon, with low-level winds remaining light but now coming from the south to the southeast. As a result, with an unstable airmass and southerly winds, isolated late morning through afternoon showers and thunderstorm activity will likely intensify as it moves from the south to the north, particularly along south-facing slopes of the Northern Range and along western coastal Trinidad.
This pattern of light southerly winds to near-calm winds is forecast to hold through the week as Tropical Wave 22 brings the Intertropical Convergence Zone (ITCZ) across T&T on Tuesday night into Wednesday. The ITCZ, in addition to trailing convergence from Tropical Wave 22, will produce variably cloudy conditions with isolated to scattered showers and thunderstorms, particularly on Wednesday.
Then, Tropical Wave 23 is forecast to move across T&T on Thursday, interacting with the ITCZ. It will bring more cloudy skies, isolated to scattered showers and thunderstorms, particularly during the early morning and again from the late morning through the afternoon.
This wave is forecast to clear the region by Thursday night, with the ITCZ shifting southward on Friday. However, trailing convergence and moisture from the southeast are still forecast to produce some isolated shower/thunderstorm activity.
Elsewhere across the Atlantic
Forecast models show the next tropical wave will move across T&T by July 25th, but top models and the National Hurricane Center show no tropical cyclone development is expected across the Atlantic Basin over the next seven days. Longer-range modeling shows no development is likely through the end of July.
Meanwhile, the tropical Atlantic is experiencing its most significant outbreak of Saharan dust in over two years.
According to hurricane specialist Michael Lowry, the ongoing outbreak has at least temporarily turned off the tropics and has likely contributed to some cooling of Atlantic waters – especially closer to Africa. The dry, dust-laden air from the deserts of North Africa usually peaks in late June and July and is an anticipated part of the seasonal cycle. In 2023 Saharan dust was largely a no-show, with the lowest coverage of dust over the tropical Atlantic in at least 20 years (since satellites began measuring dust).
Another reason is likely the Madden-Julian Oscillation, or MJO, which circles the globe roughly every month or two. The MJO generally leads to rising or sinking air across large portions of the globe. The rising branch promotes hurricane activity by encouraging stormier conditions in the tropics and reducing storm-busting wind shear—which we saw in June, which produced Tropical Storms Arlene and Chris and Hurricane Beryl. The sinking branch of the MJO generally leads to mostly quiet tropical conditions, though development does happen from time to time.
While conditions remain quiet for now, the background conditions are becoming increasingly favorable as we move into the peak of the Atlantic Hurricane Season from late August with warmer ocean temperatures, lower overall wind shear, and stronger tropical waves that roll off the African coast.
Not Every Tropical Wave Brings Severe Weather
Tropical waves vary in intensity as they travel westward across the Atlantic. This variability can be in the order of days or as short term as hours. Sometimes, you may see satellite imagery that shows heavy thunderstorms and deep convective activity east of Trinidad and Tobago during the late night and early morning, but by daybreak – nothing.
This is due to diurnal (daily) variations in convective showers whereby convection peaks overnight and wanes during the day for already occurring convective systems (i.e., not triggered by daytime heating).
Activity can be enhanced by its proximity to upper-level troughs and the ITCZ but can also be degraded by hostile upper-level conditions and Saharan Dust.
