Tropical Wave 07 Key Messages:
– Regardless of tropical cyclone development, locally heavy rainfall and gusty winds are possible across parts of Trinidad and Tobago.
– Overall, less than 1 inch (25 mm) are forecast across Trinidad and Tobago. Isolated totals up to 2.5 inches (63.5 mm) are possible across Trinidad and Tobago, with heavier rainfall favoring eastern and northern areas of both islands beginning early Thursday through late Friday. There is an elevated threat of street flooding and flash flooding. As of Wednesday night, there is a negligible threat of riverine flooding.
– Seas are forecast to remain slight, becoming moderate into Friday with waves up to 1.5 meters in open waters east of T&T and near calm in sheltered areas. Note that in heavy showers or thunderstorms, seas may become locally rough and choppy.
— Gusty winds in excess of 65 KM/H are possible. Winds of this strength will produce wind damage including downed trees, utility poles, and roof damage. Localized power outages possible.
— Development chances are low over the next 48 hours and next 5 days as of 7:00 PM AST Wednesday, at 10% respectively. While the wave is well defined, development is not expected due to unfavorable upper-level conditions and dry Saharan Dust.
Chances for Tropical Cyclone Development: Low
We’ve been monitoring this tropical wave throughout the day today as it became increasingly organized, producing sustained winds up to 34 knots (63 KM/H).
The National Hurricane Center, in their 8 PM EST (7 PM Local Time) Tropical Weather Outlook, has now tagged Tropical Wave 07 for tropical cyclone development. There is no model support for development of this system into a tropical cyclone.
Regardless of development, it is forecast to bring locally heavy rainfall and gusty winds to T&T on Thursday into Friday, favoring eastern offshore areas, eastern and northern Trinidad as well as Tobago.
From the National Hurricane Center’s Tropical Weather Outlook, as of 8:00 PM EST, “A well-defined tropical wave is located about 425 miles east of the Windward Islands, producing disorganized showers and thunderstorms. Although further development is not expected due to dry air and adverse upper-level winds, some areas of heavy rain and gusty winds are possible across portions of the Windward Islands on Thursday and Thursday night while the wave moves westward at 15 to 20 mph.”
What We Know
A tropical wave is along 54W/55W from 13N southward moving west at 24 KM/H to 32 KM/H. Scattered moderate and isolated strong convection is noted from 10N-12N between 54W-56W, with additional deep convection inland over French Guiana and Suriname.
The approximate center of circulation for this tropical disturbance is at 10.3°N and 54.2°W. This is approximately 750 kilometers east of Trinidad and Tobago.
The latest scatterometer data showers that this wave contains near gale force winds, with sustained winds between 18 knots to 34 knots (33-63 KM/H) on both sides of the wave axis from 9N-13N.
The wave is forecast to cross the Windward Islands on Thursday into Friday. Regardless of development, locally heavy rainfall and gusty winds are possible, favoring Eastern Trinidad and Tobago.
Based on our counts, this is the 7th tropical wave of the 2020 Atlantic Hurricane Season.
As of the 8:00 PM EST Tropical Weather Outlook, this system has a low chance, 10%, of tropical cyclone formation over the next 48 hours and a low chance, 10%, of tropical cyclone formation over the next 5 days.
However, upper-level convergence (not favorable for thunderstorm development) and Saharan Dust surrounding the wave axis will limit development of this system. Conditions remain unfavorable for development, with moderate to strong shear of 20 – 30 knots over the next several days, but warm sea surface temperatures between 28°C and 29°C and a fairly supportive moisture envelope continue.
What We Forecast
Based on present model guidance, the core (i.e. where the heaviest showers and thunderstorms may occur) is forecast to track across Trinidad and Tobago on Thursday afternoon based on the EMCWF (European) while the GFS (US) takes the core further north.
The UKMET (UK) and other top models, like the ICON (German) and ARPEGE (French), have similar outputs to the EMCWF.
This system is then forecast to move into the Caribbean Sea by late Friday.
Regardless of any development, the primary threat from this system will be locally heavy rainfall and gusty winds between Thursday and early Friday across T&T.
There are no top models that support tropical cyclone development (GFS, EMCWF, and UKMET), as of Wednesday night.
However, these models do bring winds between 40-55 KM/H and gusts in excess of 65 KM/H to Trinidad and Tobago particularly during those heavier showers and thunderstorms.
Hence, as of Wednesday night, we continue to expect an organized tropical wave to traverse the region on Thursday into Friday, bringing locally heavy rainfall, gusty winds, and agitated seas to T&T, with more adverse effects affecting Eastern areas. This will be due to favorable upper-level conditions are expected as the tropical wave passes across the area. As a result, this is likely to enhance scattered deep convective activity.
Impacts From Tropical Wave 07
As we keep reiterating, much of the worst weather associated with this system will remain offshore and mainly affect Eastern and Northern Trinidad, as well as Tobago
Peak sustained surface winds of 25 KM/H to 55 KM/H with gusts in excess of 65 KM/H are possible in heavy showers or thunderstorms across Trinidad and Tobago. These peak sustained winds are forecast to occur late Thursday in particular.
With wind gusts in excess of 65 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. Localized power outages expected.
Overall rainfall accumulations remain low, but isolated totals may be high. Overall, less than 1 inch (25 mm) are forecast across Trinidad and Tobago. Isolated totals up to 2.5 inches (63.5 mm) are possible across Trinidad and Tobago, with heavier rainfall favoring eastern and northern areas of both islands beginning early Thursday through late Friday.
Thunderstorms and Lightning
With thunderstorms, locally severe wind (in excess of 65 KM/H), violent rainfall rates (in excess of 50 millimeters per hour) and lightning are all possible.
Gusty winds and lightning pose a threat to our power grid, causing localized power outages. Lightning may also strike trees, homes, or utility poles, causing damage to property. Lightning can also be deadly to persons outside during a thunderstorm.
Seas and Surf
waves up to 1.5 meters in open waters east of T&T and near calm in sheltered areas. Note that in heavy showers or thunderstorms, seas may become locally rough and choppy.
But this model shows…
Individual model runs are just one possible outcome from a myriad of outcomes. Weather does not always follow what is modeled, and even what may be forecast. Beware of individual model runs being posted on social media.
Always check the National Hurricane Center for the latest information for tropical cyclones and your local meteorological offices for country-specific advisories.
What should I do?
Firstly, don’t panic. This is likely to be just another tropical wave, with isolated to scattered showers and isolated thunderstorms. No alerts (as of Wednesday night) are in effect by the Trinidad and Tobago Meteorological Service, so the overall threat to T&T this wave poses is low at this time.
An important note: if this system organizes further, a short-notice tropical storm watch or warning may be issued for parts of the Southern Windwards, including Trinidad and Tobago. This is an unlikely scenario at this time. Regardless of if a warning is issued or not, be prepared.
Secondly, if you are a risk-averse person, now is a good time to check your inclement weather, flood or hurricane season plan, ensuring your preparedness supplies are not expired, stocked and in a safe location.
The Office of Disaster Preparedness and Management has put together a comprehensive guide for preparing for the Wet and Hurricane Season.