Tropical Weather Update:
— Tropical Wave 22: This tropical wave moved across T&T during the first half of this week, producing street and flash flooding across T&T mainly on Wednesday. No further impacts forecast.
— Tropical Wave 23: This tropical wave is forecast to move across T&T and the Lesser Antilles today, producing a few showers and possible thunderstorms across Western Trinidad and mainly north of Trinidad and Tobago. No significant rainfall forecast.
— Tropical Wave 24: A weak tropical wave is located in the Eastern Atlantic, well north of the usual tropical wave position. This wave is forecast to move across the Lesser Antilles late this weekend with minimal effects. No significant rainfall forecast.
— Tropical Wave 25: This tropical wave is located in the far Eastern Atlantic, forecast to move across Trinidad, Tobago and the remainder of the Southern Windwards on Sunday into Tuesday, with severe weather possible, particularly on Monday. Heavy showers and thunderstorms are forecast to produce heavy rainfall on Monday, over a 24 hour period.
— No Tropical Cyclone Formation Forecast over 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 22
The axis of this tropical wave now extends along 70-72W, from 26N to 9N across the Central Caribbean Sea. Moisture trailing this tropical wave, in combination with favorable low-level convergence triggered heavy showers and thunderstorms across Trinidad and Tobago on Wednesday.
Parts of Trinidad experienced violent rainfall rates in excess of 100 millimeters per hour. San Fernando picked up 60 millimeters of rainfall between 11:45 AM and 12:45 PM, triggering widespread street and flash flooding between 3-4 feet of water.
For more details, see the below updates from Wednesday
Tropical Wave 23
The axis of this wave extends its axis along 25N to 5N, over 2,200 kilometers in length, between 55W and 58W, moving west at 15 knots. A surge of moisture is associated with this wave, with much of the showers and thunderstorms near the northern axis of the wave, northeast of the Leewards.
With this increase in moisture, and at times favorable low-level convergence and upper-level divergence, scattered showers and isolated thunderstorms are possible, mainly north of Trinidad and Tobago.
Across T&T however, by the late morning through the afternoon, daytime heating, sea breeze convergence, and shallow cloud patches may move across the island, triggering brisk isolated showers with the low to medium chance of a thunderstorm, favoring Western parts of Trinidad.
Wind shear is minimal, with a moderate CAP in place (stable layer in the atmosphere that inhibits shower and thunderstorm development). Hence, any heavy showers or thunderstorms to occur will favor the mid- to late afternoon as daytime heating will aid in eroding said CAP.
Street/Flash flooding possible during heavy showers, thunderstorms and prolonged moderate to heavy showers. Gusty winds are also possible in the vicinity of heavy showers or thunderstorms. The likelihood of landslides is low, but with heavy showers possible across the Northern Range, landslides are within the realm of possibility.
Tropical Wave 24
This tropical wave is not the traditional African Easterly Wave. It formed from a mid-level trough, off the northwestern coast of Africa. The axis of Tropical Wave 23 wave extends along 28N to 30N from 41W to 43W, well northeast of the Lesser Antilles, moving southwest fairly rapidly at 25 to 30 knots as of the 9:00 AM Tropical Update. No significant surge of moisture or convection is noted with this tropical wave. It is forecast to move across the Lesser Antilles late Saturday into Sunday.
This wave is not forecast to be a significant rainmaker but it will increase moisture and overall favorable conditions for the following tropical wave, Tropical Wave 25, which is forecast to be our next notable rain event.
Tropical Wave 24
The axis of Tropical Wave 25 wave extends along 26-27W, south of 20N and is moving westward at 15 knots as of the 9:00 AM Tropical Update. This wave is forecast to begin affecting Trinidad, Tobago and the Windwards by late Sunday (July 21st).
Model guidance, although we’re still about 3-4 days away, is forecasting inclement weather across Trinidad and Tobago, particularly on Monday, with scattered thunderstorms and possibly scattered to widespread showers.
With regards to development, none of the top three models for tropical cyclogenesis support development at this time, keeping this a strong tropical wave as it moves across the Atlantic.
Daily rainfall totals beginning Monday next week, through Friday are forecast to be between 10-30 millimeters, with totals on the upper end of this range favoring Eastern Trinidad. Note that locally higher amounts may be possible resulting from persistent heavy showers and thunderstorms.
Favorable upper-level conditions on the western side of an upper-level anti-cyclone (upper level low) centered just east of Tobago, may provide the platform for thunderstorm development.
Confidence is increasing for inclement weather on Monday 22nd July 2019 as global models continue to trend towards higher rainfall accumulation over the last 12-18 hours. We’ll continue to monitor this over the weekend with subsequent updates in the daily tropical update.
What We Forecast For Tropical Wave 25
The Takeaway: Severe Weather is possible across both islands. Beginning Sunday night, an increase in cloudiness is forecast, with a few isolated showers. After midnight Sunday into Monday, showers and thunderstorms are forecast to begin.
Peak thunderstorm activity is likely during the late morning through the afternoon, with heavy showers and thunderstorms forecast across both islands.
Conditions are forecast to become more settled by the late evening on Monday, with an additional round of showers and isolated thunderstorms on Tuesday as the hind leg of this wave affects T&T.
An Adverse Weather Alert may be issued by the Trinidad and Tobago Meteorological Service for this event.
Locally Heavy Rainfall & Flooding: Based on the latest model runs on Thursday morning, from Sunday night (8:00 PM) through Tuesday afternoon (2:00 PM), models are in agreement of heavy rainfall across both islands. Based on our analysis, generally of fewer than 30 millimeters across most areas on both islands. Rainfall totals of up to 50 millimeters are possible eastern halves of both islands Trinidad and Tobago.
Recent guidance from the United States GFS model has been outputting totals up to 100 millimeters within a 24 hour period on Monday, and 120 millimeters over the above 42-hour period. If these totals verify, severe flash flooding and possible riverine flooding may occur.
Regardless, a heavy rainfall event is forecast. 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. We’re also monitoring this event as riverine flooding may also occur, for the first time for 2019. Riverine flooding is more severe and prolonged than street and flash flooding.
Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely. Thunderstorms are likely on Monday.
Gusty Winds: Gusty winds, generally up to 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.
Landslides: 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.
Tropical Cyclone Climatology
Tropical Cyclone Points of Origin during the month of July. 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 July, 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!
There are NO tropical cyclone threats to the Eastern Caribbean, including Trinidad and Tobago at this time in the latest Tropical Update.