What you need to know
— Area of Disturbed Weather: The National Hurricane Center is monitoring an area of disturbed weather east of the Lesser Antilles, with low chances of development over the next seven days. This system is forecast to bring rainfall and locally gusty winds mainly to the northern half of the Lesser Antilles, north of T&T, early to middle of next week.
— Tropical Wave 25: This tropical wave is located approximately 3,000 kilometers east of T&T, along 34W, moving west at 10-15 knots. Scattered moderate to locally strong convection is noted where the wave interacts with the Intertropical Convergence Zone/Monsoon Trough. This wave is forecast to interact with the area of disturbed weather to its west, and track across the Lesser Antilles by Tuesday with much of the heavy rainfall and locally gusty winds staying north of T&T.
— Tropical Wave 26: This tropical wave is located in the far eastern Atlantic Ocean, along 21W, moving west at 10-15 knots. Scattered moderate to locally strong convection is noted where the wave interacts with the Intertropical Convergence Zone/Monsoon Trough. This wave is also forecast to interact with the area of disturbed weather to its west, and track across the Lesser Antilles by next Thursday into Friday with much of the heavy rainfall and locally gusty winds staying north of T&T.
— Hazards for T&T: Both tropical waves and the area of disturbed weather is forecast to track north of T&T. However, on Sunday night through early Tuesday morning, cloudiness, isolated to scattered showers and thunderstorms, are forecast to affect Trinidad and Tobago mainly due to the Intertropical Convergence Zone. Then, due to both tropical waves and the area of disturbed weather, the wind regime across T&T is forecast to be light from the south, to variable, leading to isolated afternoon shower and thunderstorm activity favoring western and hilly areas, as well as the potential for funnel cloud development, particularly Tuesday and Wednesday.
Area of Disturbed Weather
After three weeks of no activity in the Atlantic Basin, the National Hurricane Center (NHC) is now monitoring an area of disturbed weather over the central tropical Atlantic Ocean, which is expected to interact with an approaching tropical wave over the next several days.
According to the NHC, “Some development of this system will be possible while it approaches the Lesser Antilles during the early to middle part of next week and moves generally west-northwestward near the Greater Antilles toward the latter part of the week.”
At 2:00 PM Friday, the NHC gave near 0% development chances over the next 48 hours, and 20% over the next seven days.
Generally, forecast models show fairly moderate wind shear, and a fairly dry environment east of the Lesser Antilles across the forecast path of this area of disturbed weather. However, this area of disturbed weather is forecast to be located in a pocket of deep, tropical moisture which may isolate it from the drier conditions ahead of its movement. As of Friday afternoon, there is some increasing support for slow development of a weak tropical system as it moves mainly across the Leewards and Greater Antilles by the middle of next week.
For Trinidad and Tobago, this system is forecast to remain well north of the country, and as it moves across the Leewards during the middle of next week, the wind regime is forecast to break down across the area. As a result, winds are forecast to become near calm, to southerly/southeasterly which will result in favorable conditions for isolated afternoon shower and thunderstorm development across western and hilly Trinidad, particularly along western coastal areas, and along south-facing slopes of mountain ranges, including the Northern Range, Trinidad and Main Ridge of Tobago.
During the evening, as the Intertropical Convergence Zone remains near/south of T&T, some north/northwestward moving showers and thunderstorms that develop along Venezuela’s northern coastline may also affect particularly southern and southwestern Trinidad through next week.
Tropical Waves 25 & 26
Two tropical waves are located between Trinidad and Tobago and western Africa on Friday afternoon.
The first, Tropical Wave 25, is located approximately 3,000 kilometers east of T&T, along 34W, moving west at 10-15 knots. Scattered moderate to locally strong convection is noted where the wave interacts with the Intertropical Convergence Zone/Monsoon Trough.
Forecast models show that the southern half of this wave axis becomes entangled with the slower-moving area of disturbed weather 1,975 kilometers east of Trinidad and Tobago while the northern half of the wave axis moves across the northern Windwards and Leewards by Tuesday.
The second, Tropical Wave 26, is located in the far eastern Atlantic Ocean, along 21W, moving west at 10-15 knots. This wave is also forecast to interact with the area of disturbed weather to its west and move across the Lesser Antilles in tandem with this tropical disturbance.
Like Tropical Wave 25, Tropical Wave 26 and the tropical disturbance, much of the heavy rainfall and locally gusty winds are forecast to remain north of T&T through next week, with the wind regime across the Windwards affected as mentioned earlier.
Elsewhere across the Atlantic
There are no other areas being monitored for development at this time across the Atlantic Basin, largely due to the generally unfavorable atmospheric conditions, though sea surface temperatures remain near record warmth.
Current high to significant levels of Saharan Dust have led to generally unfavorable conditions in the Atlantic Basin for tropical development and even some cooling of ocean temperatures near 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. This larger area of sinking air has settled across the Atlantic and Eastern Pacific in recent weeks, leading to our general quietness.
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.
Longer-range models show that wind shear is forecast to begin reducing during the first week of August, and the rising branch of the MJO moves across the Lesser Antilles and Main Development Region closer to the Lesser Antilles. Additionally, weaker-than-average trade winds are forecast to return next week, which will allow for the Main Development Region and seas near T&T to warm up once more.
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.
