There are now three tropical waves between Trinidad and Tobago and the African Coast, with the closest wave forecast to move across T&T on Friday afternoon. While the three prior waves have not produced measurable rainfall as they moved near and south of T&T over the past few weeks, this next wave may trigger the official start of the 2023 Wet Season by late Friday into Saturday.
With these early-season tropical waves, showers and thunderstorms tend to be quite spare, and the wind shifts associated with them are quite weak.
Meanwhile, in the North Atlantic near the southeastern United States, the National Hurricane Center is monitoring a front and trough of low pressure for tropical cyclone development, but chances are low.
What you need to know
— Tropical Wave 04: The axis of this wave has been analyzed along 55W, moving west at approximately 15 knots (27 KM/H). Scattered showers have been noted with this wave following the wave axis. It is forecast to begin affecting T&T from Friday, May 26th, 2023, with trailing activity into the upcoming weekend.
— Tropical Wave 05: The axis of this tropical wave is located along 40W, moving west at 15 knots (27 KM/H). No significant showers have been noted with this wave. This wave is forecast to move across T&T by Sunday, May 28th, 2023.
— Tropical Wave 06: The axis of this tropical wave is located along 30W, moving west at 15 knots (27 KM/H). Scattered moderate to isolated strong convection have been noted on either side of the wave axis, mainly where this wave interacts with the Intertropical Convergence Zone (ITCZ). Forecast models indicate this wave is forecast to be near the region by the middle of next week, with a stronger wave approaching by next weekend.
— AOI Near Southeastern US: The NHC is monitoring a frontal system and a trough of low pressure off the coast of the southeastern United States, producing disorganized showers and thunderstorms. While development appears unlikely, gusty winds, heavy rainfall, and dangerous surf and rip currents are forecast for portions of the Carolinas. Development chances remain low.
— Hazards: Rainfall chances are set to increase from Friday afternoon through the weekend as convergence following the passage of TW04 is forecast to support shower and thunderstorm activity. Though widespread severe weather or heavy rainfall is not expected, localized gusty winds and street flooding will be possible in heavy showers and thunderstorms.
— Development Concerns: Elsewhere across the Atlantic, tropical cyclone development is not expected, according to the National Hurricane Center.
Tropical Wave 04
The fourth tropical wave analyzed as of 4:00 PM May 25th, 2023, is along 55W and south of 12N, moving west at 15 knots (27 KM/H). This particular wave has been moving very slowly across the Atlantic Ocean over the last several days, with numerous occasions where it was stationary.
While it was expected to dissipate as it moved across the Atlantic Ocean, the wave axis and its wind field have survived the trek and are forecast to move across Trinidad and Tobago on Friday afternoon, with showers and isolated thunderstorms trailing the wave axis.
Across the wave axis, total precipitable water (a measure of atmospheric moisture) values are near 2.18 inches, but with relative humidity between 300mb to 850mb, around 66%, indicative of a relatively dry atmosphere. Wind shear remains strong, up to 40 knots from the west.
Specifically for T&T, as this tropical wave and associated activity move west, wind shear across Trinidad and Tobago is forecast to improve, with speeds between 10 to 25 knots still from the west. As a result, there is the potential for increased persisting showers/thunderstorms, but overall, stronger showers, thunderstorms, and heavy rainfall are forecast to remain offshore eastern Trinidad and Tobago with isolated heavy showers and thunderstorms along western and hilly areas. Additional details can be found in the weather forecast.
Tropical Wave 05
The fifth tropical wave for 2023 is located along 40W, south of 12N, moving west at 15 knots (27 KM/H). There is no significant convection (showers or thunderstorms) associated with this wave at this time.
Based on forecast models, this wave is forecast to eventually move across the Windwards sometime by Sunday. However, this wave is not forecast to be particularly strong, bringing any major rainfall to the country. In addition, T&T will be on the convergent side of an upper-level trough, suppressing rainfall across the region at the time of this wave’s passage.
Tropical Wave 06
The sixth tropical wave for 2023 has left the African coast with pulsing convection, mainly where the wave interacts with the Intertropical Convergence Zone. As of 4:00 PM, the axis of this tropical wave is located along 30W, moving west at 15 knots (27 KM/H).
Trade winds are forecast to decrease across the Atlantic next week, leading to weaker steering currents for this tropical wave. As a result, this tropical wave is forecast to slow down as it moves across the Atlantic Ocean, with forecast models showing the wave and associated moisture plume reaching across the Windwards by midweek, with another tropical wave by the end of next week, in tandem with a moderate to high concentration surge of Saharan Dust, which could weaken the wave substantially.
Ultimately, there is still abundant time to monitor this wave as it moves across the Atlantic, with eventual impacts still over a week away. Longer range modeling indicates a drop-off in wind shear at the time of the wave’s passage across T&T.
Area of Interest Near SE United States
The National Hurricane Center (NHC) has been monitoring an area of disturbed weather north of the Bahamas and east of Florida for the last several days, giving it a low (10%) chance of tropical cyclone formation over the next 48 hours and seven days as of 2:00 PM Thursday, May 25th, 2023.
In their latest Tropical Weather Outlook, the NHC says, “Disorganized showers and thunderstorms off the coast of the southeastern United States are associated with a front and trough of low pressure. A non-tropical area of low pressure is expected to form along the frontal boundary within the next day or so. The system appears unlikely to become a subtropical or tropical cyclone since it is forecast to remain frontal while moving generally northward and inland over the Carolinas this weekend.”
They added that regardless of development, the system is likely to produce gusty winds and
dangerous surf and rip current conditions along portions of the southeastern United States late this week and into the weekend. In addition, they warn that heavy rainfall is expected in portions of the Carolinas, with hazardous marine conditions expected over the coastal and offshore waters where gale warnings are in effect.
This system poses no threat to Trinidad, Tobago, and the remainder of the Eastern Caribbean.
Not Every Tropical Wave Brings Severe Weather
Tropical waves vary in intensity as it travels westward across the Atlantic. This variability can be on the order of days to 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.
