Tropical Storm Gonzalo May Make Landfall Across Trinidad on Saturday

Tropical Storm Gonzalo Key Messages:
– Watches & Warnings: Tropical Storm Warnings are in effect for Tobago, Grenada, and its dependencies and St. Vincent and the Grenadines. An Adverse Weather Alert (Orange Level) is in effect for Trinidad. A Hazardous Seas Alert (Yellow Level) is in effect for T&T.
– Track: The track of Tropical Storm Gonzalo has shifted south and west, towards Trinidad. The core of Gonzalo is forecast to move across Trinidad, or just north of the island on Saturday. Activity is forecast to begin across Tobago early Saturday, while across Trinidad by mid-morning Saturday. Peak activity is expected late Saturday morning through Saturday afternoon across both islands. Conditions are forecast to settle by nightfall.
– Intensity: Gonzalo is struggling with dry air and may even degenerate into a tropical depression before making landfall or moving across T&T. The main hazard associated with Gonzalo at this point remains heavy rainfall. Across Trinidad and Tobago, wind gusts in excess of 65 KM/H are likely in heavier showers or thunderstorms with wind gusts in excess of 85 KM/H possible.

Key Messages for Tropical Storm Gonzalo as of 11:00 PM Friday 24th July 2020 for Trinidad and Tobago
Key Messages for Tropical Storm Gonzalo as of 11:00 PM Friday 24th July 2020 for Trinidad and Tobago

Rainfall: As of Friday night, direct impacts are forecast, with the overall forecast rainfall totals increased. Generally, between 50-100 millimeters of rainfall forecast Friday through Sunday, with isolated totals in excess of 150 millimeters in areas of persisting heavy rainfall and thunderstorm activity, mainly across Northern, Eastern Trinidad and Tobago.
– Flooding: Street flooding and flash flooding in heavy to violent showers and thunderstorms are likely across both islands. There is a medium chance of riverine flooding across Trinidad.
– Landslides: There is a very high risk of landslides across both islands
– Seas: Seas are forecast to deteriorate on Friday night, with waves up to 2.5 meters, occasionally up to 3.0 meters into Saturday. Mainly on Saturday, forecast to be moderate to rough, with waves up to 3.0 meters, occasionally very rough, up to 4.0-4.5 meters in open waters. In sheltered areas, up to 1.5 meters and choppy.A Hazardous Seas Alert (Yellow Level) is in effect for T&T.

NHC: Gonzalo To Affect T&T on Saturday

Tropical Storm Gonzalo's Official Forecast Track from the National Hurricane Center as of 11:00 PM AST Friday 24th July 2020.
Tropical Storm Gonzalo’s Official Forecast Track from the National Hurricane Center as of 11:00 PM AST Friday 24th July 2020.

The National Hurricane Center, as of 11:00 PM, continues to issue advisories on Tropical Storm Gonzalo, 410 KM East of Trinidad.

At 11:00 PM AST, the center of Tropical Storm Gonzalo was located near latitude 10.0 North, longitude 57.1 West. Gonzalo is moving toward the west near 17 MPH (28 KM/H). A general westward to west-northwestward motion is expected for the next couple of days. On the forecast track, Gonzalo will move across the southern Windward Islands Saturday afternoon or evening and over the eastern Caribbean Sea on Sunday.

Maximum sustained winds are near 40 MPH (65 KM/H) with higher gusts.
Little change in strength is expected before Gonzalo reaches the southern Windward Islands. Weakening is expected after Gonzalo moves over the eastern Caribbean Sea and the system is forecast to dissipate by Sunday night or Monday.

Gonzalo is a small tropical cyclone. Data from the reconnaissance aircraft indicate that tropical-storm-force winds extend outward up to 35 miles (55 KM) from the center. That’s approximately the distance from Sangre Grande to Chaguaramas in Trinidad. The most recent minimum central pressure reported by the Hurricane Hunter plane was 1009 millibars.

Most Likely Arrival Time: the graphic that identifies the time before or after which the onset of tropical-storm-force winds is equally likely. This graphic would be more appropriate for users who are willing to risk not having completed all their preparations before the storm arrives. (NHC)
Most Likely Arrival Time: the graphic that identifies the time before or after which the onset of tropical-storm-force winds is equally likely. This graphic would be more appropriate for users who are willing to risk not having completed all their preparations before the storm arrives. (NHC)

Hazards Affecting Land

WIND: Tropical storm conditions are expected within portions of the Tropical Storm Warning area beginning on Saturday.

RAINFALL: Gonzalo is expected to produce total rain accumulations of 1 to 3 inches (25-75 mm), with isolated maximum amounts of 5 inches (125 mm) in Barbados, the Windward Islands, and Trinidad and Tobago through Sunday night. Gonzalo is also expected to produce total rain accumulations of 1 to 2 inches (25-50 mm) in northeastern Venezuela. Rainfall in Barbados, the Windward Islands, and Trinidad and Tobago could lead to areas of flash flooding.

Watches & Warnings

Tropical Storm Gonzalo Watches & Warnings as of 11:00 PM Friday 24th July 2020.
Tropical Storm Gonzalo Watches & Warnings as of 11:00 PM Friday 24th July 2020.

A Tropical Storm Warning is in effect for:

  • Tobago.
  • St. Vincent and the Grenadines.
  • Grenada and its dependencies.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 24 to 36 hours.

Interests elsewhere in the Windward Islands should monitor the progress of this system.

For Tobago

The Tropical Storm Watch (Orange Alert) For Tobago from the Trinidad and Tobago Meteorological Service as of 11:00 PM Friday 24th July 2020 (TTMS)
The Tropical Storm Watch (Orange Alert) For Tobago from the Trinidad and Tobago Meteorological Service as of 11:00 PM Friday 24th July 2020 (TTMS)

Why No Tropical Storm Warning for Trinidad?

There is the question, given the significant changes in track, why is Trinidad not under a tropical storm warning? Tropical Storm Gonzalo is barely hanging onto a its tropical storm classification. Though the chances for experiencing tropical-storm-force winds have increased, overall weakening of this system is anticipated and it may even reach tropical depression status before landfall. If that occurs, all Tropical Storm Warnings will be dropped, as tropical-storm-force winds impacting land are the criteria for one of these warnings to be issues.

As we continue to reiterate, the main hazard for Trinidad continues to be, as it always has been: heavy, flooding rainfall. The change in track did not significantly change the rainfall impact.

What We Know

Tropical Storm Gonzalo in the Central Atlantic, producing a concentrated area of strong convection near the center of circulation as of Friday afternoon, in the southeastern quadrant of the storm. (Weathernerds)
Tropical Storm Gonzalo in the Central Atlantic, producing a concentrated area of strong convection near the center of circulation as of Friday afternoon, in the southeastern quadrant of the storm. (Weathernerds)

Tropical Storm Gonzalo continues to produce a compact area of moderate to strong convection just east of Trinidad.

After ingesting a hefty portion of dry high statically stable air (Saharan Dust) over the last 48 hours, Gonzalo has struggled to maintain its intensity, gradually weakening as it moved westward.

Convection continues to wane and restrengthen over the last several hours, with pop up showers and thunderstorms near the system’s center.

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 T&T on Saturday with tropical storm conditions possible across both islands, though this system may weaken to a tropical depression before moving across T&T. Regardless, heavy rainfall remains the main hazard.

What We Forecast

Track

Across North Trinidad, or just south of Tobago. Models continue to trend further south.

Early-cycle track guidance from top models, showing Tropical Storm Gonzalo moving across Trinidad and Tobago as of 00Z Saturday 25th July 2020. (NCAR)
Early-cycle track guidance from top models, showing Tropical Storm Gonzalo moving across Trinidad and Tobago as of 00Z Saturday 25th July 2020. (NCAR)

Based on present model guidance, the core (i.e. where the heaviest showers and thunderstorms may occur) is forecast to move across Trinidad and Tobago on Saturday by the late morning. It then affects Grenada, St. Vincent and the Grenadines Saturday night.

Models, and the official forecast, have moved southward and westward on Friday.

Zoomed version of the National Hurricane Center's track for Tropical Storm Gonzalo, as it moves across Trinidad and Tobago this weekend.
Zoomed version of the National Hurricane Center’s track for Tropical Storm Gonzalo, as it moves across Trinidad and Tobago this weekend.

Gonzalo continues moving generally westward or 270/15 kt. The system is not expected to gain much latitude as it should continue moving westward to west-northwestward within the low-level easterly flow. The track guidance continues to trend southward and the NHC track forecast has again been shifted in that direction. The new track lies to the south of the consensus aids, closest to the GFS and UKMET ensemble means.

Intensity

Intensity guidance for Tropical Storm Gonzalo as of  00Z Saturday 25th July 2020 (NCAR)
Intensity guidance for Tropical Storm Gonzalo as of 00Z Saturday 25th July 2020 (NCAR)

Although there has been a recent increase in deep convection in association with Gonzalo, data from an Air Force Reserve Hurricane Hunter aircraft continues to show that the tropical cyclone is poorly organized. The aircraft has not yet found winds to support tropical storm strength, however, the advisory intensity will remain a possibly generous 35 knots until the aircraft completes its mission overnight. There is also some possibility that this recent convective burst could result in some short-term re-organization.

However, with the system losing organization over the past day or so, it is becoming less likely that the small cyclone will be able to significantly recover due to the nearby dry mid-level environment. The updated NHC intensity forecast no longer calls for any re-strengthening, and Gonzalo could even become a tropical depression before reaching the Windward Islands. After that time, dry air and Gonzalo’s close proximity to the coast of Venezuela are likely to cause the system to weaken and degenerate into a trough of low pressure. The NHC forecast now calls for dissipation by 60 hours, but this could occur sooner.

Gonzalo’s small size makes it susceptible to short-term changes in intensity that cannot be reflected in the official forecast.

Impacts From Tropical Storm Gonzalo

For Trinidad and Tobago, the main hazard is heavy rainfall causing flooding and landslides, with gusty winds also a localized concern, as well as rough seas.

Wind

Across Trinidad and Tobago, wind gusts in excess of 65 KM/H are likely in heavier showers or thunderstorms with wind gusts in excess of 85 KM/H and tropical storm conditions possible.

With wind gusts in excess of 85 KM/H, it will be hazardous to be outdoors. Whole trees are expected to be in motion, with tree damage likely. 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. Power outages expected, with damage to trees, power lines and small structures possible.

High Wind Event Precautions
High Wind Event Precautions

Rainfall

Overall rainfall accumulations have increased over the three-day period between Friday through Sunday across T&T, with isolated totals high. Heavy rainfall will be possible across T&T. Generally, between 50-100 millimeters of rainfall forecast Friday through Sunday, with isolated totals in excess of 150 millimeters in areas of persisting heavy rainfall and thunderstorm activity, mainly across Northern, Eastern Trinidad and Tobago.

Street flooding and flash flooding in heavy to violent showers and thunderstorms are likely across both islands. There is a medium chance of riverine flooding across Trinidad. There is a very high risk of landslides across both islands

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

Seas, mainly on Saturday, forecast to be moderate to rough, with waves up to 3.0 meters, occasionally up to 4.0-4.5 meters in open waters. In sheltered areas, up to 1.5 meters and choppy. A Hazardous Seas Alert is in effect

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