As of the 8 PM Tropical Weather Outlook by the National Hurricane Center, A low-pressure trough associated with a tropical wave over the tropical central Atlantic Ocean is producing disorganized showers and thunderstorms. Although this system is close to dry air, some slow development is possible over the next few days while the system moves westward at 27 KM/H to 32 KM/H.

The National Hurricane Center gives this wave a low (10%) chance of developing into a tropical cyclone in the next 48 hours and a low (20%) chance of developing into a tropical cyclone over the next 5 days.

This tropical wave has dry Saharan air well to the west and east of the wave axis, quelling development at this time. However, scattered moderate to isolated strong convection (showers) are within 333 Kilometers east of the wave and 222 kilometers west of the wave axis between 9° – 10°N. This wave may possibly acquire more convection Sunday through Tuesday and a low pressure forming along it.

Currently, this tropical wave as an elongated area of vorticity – or spin in the atmosphere – with is integral to tropical development but vorticity will need to become less elongated for any organized tropical system.
Additionally, this tropical wave is located in an area with dry Saharan air to its north, east and west of the wave. This will keep convection minimal and possibly quell any development as the dry air becomes entrained into convective activity.
Lastly, this wave is currently located in an area with strong wind shear, which also inhibits the development of any convective development.

However, surprisingly, this tropical wave or low-pressure trough has received consistent model support from both the EMCWF and GFS from the Saturday model runs. We’ve also seen the UKMET model show some development of this wave over the next 72 hours to 96 hours. These are the top three leading models for tropical development and it is cause for concern with all three showing some sort of development.

Model guidance shows this tropical wave eventually moving west to west-northwest bringing an organized tropical system into the Central Lesser Antilles Tuesday into Wednesday next week.

Regardless of development, a strong tropical wave will be reaching the Lesser Antilles Islands between Tuesday, July 18th and Wednesday, July 19th, 2017. This will bring moderate to heavy showers, gusty winds, street/flash flooding. IF it organizes further or becomes a tropical depression/tropical storm, there is the possibility of landslides and downed trees which may bring down utility poles and cause power outages.

Now, what is expected for Trinidad and Tobago as a result of this tropical wave? At this time, 4 days out, it is difficult to say. The longer this wave takes to develop, the further westward it may travel. This may put the southern edge of the wave axis across parts of Tobago and Northern Trinidad. If this scenario occurs, the usual moderate to heavy rainfall with isolated thundershowers associated with the passage of a tropical wave is possible. Street/flash flooding and gusty winds would be possible as well as the possible landslide in elevated areas. These events may bring downed trees and utility poles.

NOTE: This is nothing out of the ordinary as these impacts are always possible during the rainy season when a tropical wave moves over the area.

IF it organizes, much of the activity should remain well to the north of Trinidad and Tobago. This area of disturbed weather is still 2180 Kilometers east of Trinidad and Tobago as of the 8 PM National Hurricane Center’s Tropical Weather Outlook. Again, this system is still 4 days away. Much can change in that time frame. Trinidad and Tobago, Grenada, St. Vincent and the Grenadines, St. Lucia and Barbados should remain alerted and informed of what may be to come early next week.

Over the next coming days, you may begin to see model runs showing a tropical cyclone of varying intensities moving into the Lesser Antilles. Please do not use model forecasts as fact as models are meant to be used as guidance in conjunction with other meteorological data. This tropical wave still has to survive the 4-day trek across the Atlantic.

More reading on long range weather models: https://weather.com/…/forecast-models-tropics-case-study-20…

For more information on the definitions of a tropical disturbance, and invest, a tropical storm and much more, see our explainer here: https://goo.gl/PUQMKW

Trinidad and Tobago Meteorological Service: http://www.metoffice.gov.tt/forecast

National Hurricane Center: http://www.nhc.noaa.gov/

Again, Trinidad and Tobago remains under no bulletin, watch or warning from the Trinidad and Tobago Meteorological Service as of 10 PM 15th July 2017.

Disclaimer: This is not an official forecast from the Trinidad and Tobago Meteorological Service. When making decisions, please consult the Trinidad and Tobago Meteorological Service and the National Hurricane Center for all official forecasts, bulletins, watches, and warnings.