Tropical Update Overview:
— Area of Disturbed Weather – A surface trough just off the east coast of Florida could form a weak surface low as it moves northward along the southeastern United States coast. This system has a low chance (20%) of development over the next 48 hours and 5 days respectively.
— Tropical Wave 03 – This tropical wave remains devoid of convection in the Caribbean Sea. No threat to T&T.
— Tropical Wave 02 – A weak tropical wave is forecast to traverse the Southern Windwards beginning Tuesday through Wednesday. Increased moisture may fuel heavier showers and thunderstorms across T&T on Tuesday into the first half of Wednesday. No widespread severe weather forecast.
— Impacts to T&T – No direct tropical threats to Trinidad and Tobago are forecast over the next week but locally heavy rainfall is possible on Tuesday into Wednesday, mainly during the intense early morning (12 AM – 4 AM) and afternoon (12 PM – 4 PM) showers and thunderstorms. Street flooding, gusty winds generally between 30-50 KM/H, and occasionally in excess of 55 KM/H are possible. Flash flooding, landslides, and frequent lightning are less likely but possible.
Before we dive into the Tropical Update, a few notes:
- Tropical waves are a normal part of the rainy season.
- Not every tropical wave will form into a tropical cyclone.
- Weaker tropical waves produce 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.
Area of Disturbed Weather
The National Hurricane Center (NHC) is monitoring a tropical disturbance – an area of low pressure that is not forecast to become a tropical cyclone but still will bring locally heavy rainfall, gusty winds, and rough sea conditions to parts of Florida, Georgia, the Carolinas, and the Bahamas over the next few days.
In their special tropical outlook at 5:20 PM, widespread showers and thunderstorms extending across Florida, the Bahamas, and the adjacent Atlantic and Gulf of Mexico waters are associated with an elongated surface trough interacting with an upper-level disturbance.
Although a weak surface low could form along the surface trough just off the east coast of Florida and move northward toward Georgia and South Carolina on Tuesday and Wednesday, the low is not expected to become a tropical cyclone due to strong upper-level winds.
Regardless of development, heavy rainfall could cause flash flooding over portions of southern and central Florida tonight, spreading northward to coastal sections of northeastern Florida, Georgia, and the Carolinas on Tuesday and Wednesday. Gusty winds could also produce rough marine conditions and life-threatening surf and rip currents along the coasts of eastern Florida, Georgia, and the Carolinas through Wednesday.
This tropical disturbance has a low chance of tropical cyclone formation over the next 48 hours and two days respectively.
The next Special Tropical Weather Outlook on this system will be issued by 9 AM EDT Tuesday, or earlier if necessary.
No threat to the Lesser Antilles, including T&T.
Tropical Wave 03
The third tropical wave for the 2020 Atlantic Hurricane Season was added by the National Hurricane Center as of the 4:00 PM Surface Analysis on Sunday.
According to the NHC, this tropical wave is near 80W from 21N southward, moving west at 15 knots. Convection associated to this wave is limited, but the cyclonic curvature is noted on visible satellite imagery.
Near the wave axis, convection has appeared Sunday night across Colombia and Hispanola, with none across the Caribbean Sea.
No threat to the Lesser Antilles, including T&T.
Tropical Wave 02
As of the 4:00 PM Tropical Update, the axis of Tropical Wave 02 is approximately along is along 53W to 57W, from 18N southward, moving westward 12 knots (22 KM/H). Scattered moderate convection from 07N-10N between 53W to 57W is associated with this broad but weak tropical wave.
Following the passage of Tropical Wave 01, it is fair to be on the conservative side of what impacts this wave can bring to T&T – particularly since the overall dynamics have not significantly changed.
Wind shear, one of the chief factors into last week’s lack of rainfall, remains strong across the region. When this wave moves across the region, Tuesday into Wednesday, wind shear is forecast to increase between 50 to 70 knots.
Model guidance from the top global models are now on board with generally wet conditions tomorrow (Tuesday) with periods of showers and isolated thunderstorms, gradually becoming settled by the late afternoon. Showers and thunderstorms are also possible on Wednesday.
Abundant low-level moisture is forecast, supporting cloudiness and isolated to scattered showers, with thunderstorms possible mainly during the late morning through afternoon of Tuesday and the first half of Wednesday. The passage of this tropical wave could bring the onset of the 2020 Wet Season. See below for details.
What does all of this mean for Trinidad and Tobago?
Remainder of Monday: Mostly settled and fair conditions are forecast to continue with the odd isolated shower.
Tuesday: A mostly settled start to Tuesday is forecast, with partly to mostly cloudy skies developing by the mid-morning. This means hot conditions are likely throughout the day, particularly in areas with partly cloudy skies. By the late morning (10 AM) through the mid-afternoon (3 PM), isolated showers of varying intensities are forecast across both islands, with the low chance of an isolated thunderstorm favoring western coastal Trinidad and offshore waters. Conditions are forecast to settle across Trinidad by the evening, with isolated activity favoring Eastern Trinidad and Tobago through the night.
Gusty winds up to 55 KM/H, street flooding is possible in heavy to violent showers and isolated thunderstorms. Seas to remain moderate, with waves up to 2 meters in open waters, but may become choppy during heavy showers and thunderstorms.
This axis of Tropical Wave 02 to move across T&T overnight, with winds shifting between east-southeast to the east-northeast, returning to east-southeast throughout the day into Wednesday.
Wednesday: After midnight, isolated showers are possible, favoring Eastern Trinidad and Tobago. By the early to mid-morning (4 AM – 8 AM), heavier showers and an isolated thunderstorm are possible, continuing to favor the eastern half of Trinidad and Tobago, gradually moving westward. Variably cloudy skies (meaning sunshine may be mixed in) are forecast through the mid-afternoon (3 PM) with periods of rain, showers of varying intensities, and isolated thunderstorms favoring Trinidad, lesser so Tobago. Conditions are forecast to settle by the late afternoon into the evening, becoming increasingly hazy due to the surge of Saharan Dust that follows.
That said, there is still the chance of this wave becoming another “dry” tropical wave as it moves across the region. The European model (EMCWF) in mostly in line with our forecast, bringing early morning showers and isolated thunderstorms across Trinidad and Tobago, becoming settled by the evening.
However, the US model (GFS) keeps activity just offshore Trinidad, with showers affecting Tobago, with a few showers gradually moving across Trinidad but generally a hot and sunny day across Trinidad with cloudy conditions across Tobago – both becoming settled by the evening.
As abundant low-level moisture is still forecast for much of Wednesday, with southeasterly winds – a likely scenario if showers do not move across Trinidad would be sea-breeze convergence, daytime heating, and orographic effects will trigger showers and isolated thunderstorms during the late morning through the afternoon. There may be the occasional enhancement from gust fronts as wind shear causes activity east of Trinidad and Tobago to dissipate, generating said gust fronts.
Confidence in the current forecast is at medium – which will increase by tomorrow as conditions become finalized. The axis of this wave will be west of T&T by the late afternoon.
There is the medium chance, presently, of locally heavy rainfall, particularly during heavy to violent showers and thunderstorms on Wednesday, with gusty winds up to 60 KM/H. Seas to remain moderate, with waves up to 2 meters in open waters, but may become choppy during heavy showers and thunderstorms. Street/flash flooding and landslides are possible.
Thursday: As quickly as the tropical wave came, its influence will leave. A high-pressure system is forecast to regain dominance across the region. This is forecast to allow for mostly sunny, breezy, and hot conditions throughout the day. Low-level cloud patches will traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 55 KM/H. Afternoon showers are possible, mainly across hilly, southern, and western areas of Trinidad, as low-level moisture is forecast to move in from the southeast across the island, with mostly dry conditions across Tobago. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers. Note that a surge of Saharan Dust is forecast to move across the region by late Wednesday into early Thursday.
Friday: In contrast to yesterday, while a high-pressure system would continue to dominate across the Lesser Antilles, allowing for mostly sunny, breezy, and hot conditions throughout the day across Tobago – conditions across Trinidad would be wetter. A surge of moisture is forecast to move in from the southeast, with a partly to a mostly cloudy day. However, by the late morning (10 AM) through the mid-afternoon (3 PM), isolated showers and even an isolated thunderstorm are possible, favoring hilly areas, southern and western halves of Trinidad. Gusty winds up to 55 KM/H and street flooding are possible. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers.
Saturday: A high-pressure system remains dominant across Trinidad and Tobago, allowing for mostly sunny, breezy, and hot conditions throughout the day. Partly to mostly cloudy conditions are forecast by the late morning through the mid-afternoon, with isolated showers possible favoring southern and western halves of Trinidad, as well as hilly areas. Low-level cloud patches will also traverse T&T, bringing brisk isolated showers, accompanied by gusty winds up to 55 KM/H. Mostly settled conditions are forecast during the evening into the night, with the odd isolated showers.
Impacts This Upcoming Week
Winds: Sustained surface winds between 25 KM/H and 45 KM/H with gusts up to 60 KM/H are likely in heavy showers or thunderstorms across Trinidad and Tobago, particularly Tuesday into Wednesday.
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, bringing down utility poles and lines.
Rainfall: Throughout the week, no to trace daily rainfall accumulations are forecast, less than 5 millimeters. On Tuesday into Wednesday, isolated totals between 5-15 millimeters, with in excess of 15-20 millimeters in isolated thunderstorms or heavy/violent downpours.
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.
Frequent Lightning: In addition, with forecast thunderstorms, frequent lightning is likely. Lightning can cause power outages, voltage dips, damage to life and property, particularly during cloud-to-ground lightning strikes.
Why I May Not/Will Not See Constant Rainfall?
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. Widespread showers mean that nearly all persons and areas may experience rainfall.
This week, isolated to scattered activity is forecast.
Tropical Cyclone Climatology
Tropical Cyclone Points of Origin during the month of May. Though much of the points of origin are west or north of T&T as we move into the first month of the Hurricane Season, we still need to pay attention to some of these waves and the ITCZ, which have historically brought major flooding events to T&T, hence all low-pressure systems in the Atlantic should be closely monitored, as we do in the Tropical Update.