Tropical Storm Gonzalo Key Messages:
– Watches & Warnings: A Hurricane Watch is in effect for Barbados.
– Track: Tropical Storm Gonzalo is forecast to move across the region on Saturday, with the center of circulation remaining north of Tobago.
– Intensity: This tropical storm is expected to strengthen into a hurricane on Thursday, then slightly weakening to a strong tropical storm as it moves north of T&T on Saturday with sustained winds of between 110 KM/H to 130 KM/H and gusts to 140 KM/H to 160 KM/H. Across T&T, wind gusts in excess of 65 KM/H are likely in heavier showers or thunderstorms.
Rainfall: As of Wednesday night, much of the active weather is forecast to remain north of Trinidad and Tobago. Slight adjustments in the track may have significant changes in the rainfall forecast. Isolated heavy rainfall will still be possible across T&T. Generally, less than 25 millimeters of rainfall forecast Friday through Sunday, with isolated totals in excess of 75 millimeters in areas of persisting heavy rainfall and thunderstorm activity, mainly across Northern, Eastern Trinidad and Tobago. There is an elevated threat of street flooding and flash flooding as showers and thunderstorms associated with tropical systems can produce violent rainfall rates. As of Tuesday morning, there is a negligible threat of riverine flooding.
– Between late Friday and Sunday, seas are forecast to remain moderate with waves up to 2.0 meters in open waters east of T&T, occasionally up to 2.5 meters, and near 1.0 meter in sheltered areas. On Saturday, seas are forecast to be moderate to rough, with waves up to 2.5 meters, occasionally up to 3.0 meters in open waters. In sheltered areas, up to 1.5 meters and choppy.
NHC: Tropical Storm Gonzalo to Strengthen Into A Hurricane On Thursday
The National Hurricane Center, as of 11:00 PM, continues to issue advisories on Tropical Storm Gonzalo, 1,685 KM east of the Windward Islands. Tropical Depression Seven strengthened into Gonzalo on Wednesday morning.
At 11:00 PM AST, the center of Tropical Storm Gonzalo was located near latitude 9.9 North, longitude 45.9 West. Gonzalo is moving toward the west near 12 MPH (19 KM/H). A general westward motion at a faster forward speed is expected during the next few days. On the forecast track, the center of Gonzalo would approach the Windward Islands late Friday and Saturday.
Maximum sustained winds have increased to near 60 MPH (95 KM/H), with higher gusts. Further strengthening is forecast during the next couple of days, and Gonzalo is expected to become a hurricane on Thursday. Tropical-storm-force winds extend outward up to 35 miles (55 kilometers) from the center. The estimated minimum central pressure is 998 millibars.
Watches & Warnings
The government of Barbados has issued a Hurricane Watch for Barbados.
This means that hurricane conditions (sustained winds of 74 MPH or greater) are possible within your area. Because it may not be safe to prepare for a hurricane once winds reach tropical storm force, The NHC issues hurricane watches 48 hours before it anticipates tropical storm-force winds.
There are no alerts, watches, or warnings in effect for the remainder of the Southern Windwards as of 11:00 PM Wednesday 22nd July 2020.
What We Know
Tropical Storm Gonzalo continues to produce a compact area of strong convection in the Central Atlantic, well east of Trinidad and Tobago. It is located in an area with little to no vertical wind shear, favorable upper-level divergence and low-level convergence, and a well-defined circulation.
A series of earlier microwave passes over Gonzalo reveal a small eye feature beneath a relatively ragged, Central Dense Overcast with associated -75.5C cloud tops. Based on the evidence of the small eye and a blend of the subjective and objective satellite intensity estimates, the initial intensity is raised to 50 knots by the National Hurricane Center.
This tropical cyclone, previously INVEST 99L and Tropical Depression Seven, was spawned by the interaction of the ITCZ, Tropical Wave 26, and the African Monsoon Trough, which has extended into the Atlantic, producing a natural area of vorticity (spin) for this tropical cyclone to take advantage of.
Tropical Wave 26 is now well west of the low-pressure center as it continues to ward off dry Saharan air to the north and west of the system.
Tropical Storm Gonzalo will be traversing warmer waters, with sea surface temperatures between 29°C and 30°C over the next 48 to 72 hours, allowing for strengthening. Gonzalo has broken the current record for the earliest 7th named storm formation in the Atlantic, edging out Gert on July 24th, 2005.
This tropical storm is forecast to bring adverse weather to the Southern Windwards, including T&T on Saturday, with tropical storm and hurricane conditions generally remaining north of T&T.
What We Forecast
Well North of Tobago, south of Barbados on Saturday 25th July 2020.
Based on present model guidance, the core (i.e. where the heaviest showers and thunderstorms may occur) is forecast to track well north of Tobago and south of Barbados on Saturday. Models continue to trend northward, which is expected of a stronger tropical cyclone.
Given the small radii of circulation, slight track adjustments northward would result in minimal impacts to T&T, while track adjustments southward would mean widespread heavy showers, thunderstorms and gusty winds to the islands.
Gonzalo is on the south side of a low- to a mid-level tropospheric ridge, and this feature should steer the storm generally westward at a faster forward speed for the next few days. After that time, a move toward the west-northwest is expected. The NHC track forecast is nudged a bit to the north of the previous one and is close to the various consensus aids.
Scenario 1: A well-organized tropical storm/borderline Category 1 Hurricane north of Tobago – the current NHC forecast
Two days later since Tropical Depression Seven formed, now Tropical Storm Gonzalo and models still continue to grapple with the intensity of this system.
Gonzalo should remain in an environment of relatively low shear, although the impacts of dry, stable air and large-scale subsidence could hamper further intensification in a few days.
It’s worth noting that the ECMWF Ensemble model is showing a pretty significant low- to mid-level easterly surge that spreads just to the north of the cyclone’s forecast track and over the northeastern Caribbean in a couple of days. This predicted event could possibly curtail strengthening at that time. On the other hand, with the exception of the ECMWF, the global models now show the cyclone maintaining tropical storm strength while moving into the eastern Caribbean.
However, global models have underperformed on compact systems like Tropical Storm Gonzalo as these systems do have the ability to fluctuate in strength much more rapidly than larger tropical cyclones.
Hence, a strong tropical storm moving north of Tobago, with sustained winds of between 110 KM/H to 130 KM/H and gusts to 140 KM/H to 160 KM/H is the likely scenario. There may be slight adjustments to this intensity forecast over the next 2-3 days, as small systems are difficult to forecast.
In this scenario, Tobago may experience tropical storm conditions, while across Trinidad, wind gusts in excess of 65 KM/H become likely, particularly near showers and thunderstorms.
Scenario 2 (still unlikely): Gonzalo rapidly intensifies into a hurricane, moving slower and across the French Antilles.
Statistical-dynamical models and some of the hurricane regional models showing the system becoming a hurricane within the next few days. With compact systems like Tropical Storm Gonzalo, these outcomes are possible.
Generally, the stronger (intensity) a tropical cyclone is east of the Lesser Antilles, the further north it recurves. This intensity depends on how much organization the storm can attain over the next 24 hours. The SHIPS model does show above average indicators for rapid intensification.
As mentioned, just north of Tropical Storm Gonzalo, a surge of trade winds and dry Saharan air will serve as a detriment to the cyclone,.
In this scenario, little to no impacts are expected across T&T. In fact, winds may calm across the islands, allowing for near-record high temperatures with locally heavy showers and thunderstorms possible – but due to localized climatic features.
Impacts From Tropical Storm Gonzalo
As we keep reiterating, much of the worst weather associated with this system will remain offshore and north of Trinidad and Tobago, as of Wednesday night, This can change over the coming week.
Tobago may experience tropical storm conditions, while across Trinidad, wind gusts in excess of 65 KM/H become likely, particularly near showers and thunderstorms.
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 relatively low during the three-day period between Friday through Sunday across T&T, but isolated totals may be high. Isolated heavy rainfall will still be possible across T&T. Generally, less than 25 millimeters of rainfall forecast Friday through Sunday, with isolated totals in excess of 75 millimeters in areas of persisting heavy rainfall and thunderstorm activity, mainly across Northern, Eastern Trinidad and Tobago.
Thunderstorms and Lightning
With thunderstorms, locally severe wind (in excess of 55 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
On Saturday, seas are forecast to be moderate to rough, with waves up to 2.5 meters, occasionally up to 3.0 meters in open waters. In sheltered areas, up to 1.5 meters 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. No alerts (as of Wednesday night) are in effect by the Trinidad and Tobago Meteorological Service.
An important note: if this system organizes further, tropical storm watches or warnings may be issued for parts of the Southern Windwards later this week. 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.
Tropical Storm Gonzalo is still two to three days away, so a lot can change. Tropical storm watches may be issued 48 hours in advance if tropical-storm-force winds are possible, while tropical storm warnings would be issued 36 hours ahead of expected tropical-storm-force winds. Given that strongest winds are forecast to remain north of T&T, do not wait until a watch or warning is issued. You should continue to monitor updates from official and trusted sources.
If you live in a flood-prone area, it is always recommended to prepare sandbags and ensure watercourses and guttering on your property are cleared. Secure loose objects outdoors and trim larger trees. You can request assistance from your local city, borough, or regional corporation. If your roof is not secured, consider securing your roof with hurricane straps. A hurricane strap costs between $8 to $10. It takes about 50 straps to secure the roof of an average three-bedroom house. Most straps are available in your neighbourhood hardware and are made with galvanized steel.
The Office of Disaster Preparedness and Management has put together a comprehensive guide for preparing for the Wet and Hurricane Season.