Tropical Update: Tropical Wave to Move Across T&T On Friday, Keeping Our Eyes on Tropical Storm Barry, Invest 93L

Tropical Update:
Tropical Wave 18: A weak tropical wave moved across Trinidad and Tobago this morning, bringing some scattered showers and locally heavy showers to parts of Trinidad. No additional activity forecast as this wave progresses westward.
Tropical Wave 19: A strong tropical wave is located in the Central Atlantic. This wave is presently embedded in the ITCZ. It is not forecast to develop into a tropical cyclone. This wave is forecast to move across the Southern Windwards and the French Antilles, including T&T on Friday into Saturday. Severe weather is possible.
Tropical Wave 20: This wave has now dissipated. This wave branched out into Tropical Wave 20 and Tropical Wave 21 due to differences in speeds from the Northern axis and Southern Axis.
Tropical Wave 21: A tropical wave, dubbed Invest 93L, is being monitored for tropical cyclone formation in the Eastern Atlantic Ocean. This wave is forecast to bring showers and thunderstorms, as well as gusty winds to the Southern Windwards Monday into Tuesday of the upcoming week. Severe weather is likely.
Tropical Storm Barry: A tropical storm located in the Gulf of Mexico is forecast to become a hurricane as it nears the Lousianan Coast over the next 48 hours. Significant rainfall is forecast across already waterlogged Lousisana. No threat to Trinidad, Tobago or the remainder of the Eastern Caribbean.

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 Numbers

Over the last 48 hours, tropical waves have formed and dissipated in the Eastern and Central Atlantic which may bring some confusion of what Tropical Wave number are we on for the season in this tropical update?

A quick synopsis above shows what occurred to each of the tropical waves we were monitoring across the Atlantic.

Tropical Wave 18 moved ahead of the area of inclement weather we were expected, moving across Trinidad and Tobago on the morning of Thursday 11th July 2019.

This area of inclement weather was then attributed to a surface trough that developed behind Tropical Wave 18. However, Tropical Wave 19, which was dropped from the National Hurricane Center’s surface analysis at one point, was analyzed as this surface trough. Now, this Tropical Wave is forecast to move across Trinidad, Tobago and the Windwards over the next 24 hours, bringing locally heavy rainfall and thunderstorms.

Tropical Wave 20 also underwent some shenanigans in the Atlantic. Because of a difference in forward speeds between the Northern area and Southern area of the axis, this wave branched off into two waves – Tropical Wave 20 (the northern section) and Tropical Wave 21 (the southern section). Tropical Wave 20 was located in an area of dense Saharan Dust and brisk easterly trades, which aided in its demise. However, Tropical Wave 21 was embedded within the ITCZ and a fairly large moisture envelope at the time. This, in addition to the vorticity associated with the southern half of TW21, formed a low-pressure center, now dubbed Invest 93L. We’re monitoring this area, albeit a low chance, for tropical cyclone formation over the next 5 days.

Tropical Wave 19

Tropical Wave 19, east of Trinidad, Tobago and the Lesser Antilles. Isolated to scattered showers and locally heavy showers/thunderstorms forecast to begin after midnight tonight, trough Friday lingering through the first half of Saturday. Gusty winds, street flooding, landslides/mudslides, and downed trees all possible through Saturday. Note that much of the heavier showers and thunderstorms are forecast to remain north of Trinidad. Credit: Weathernerds.org
Tropical Wave 19, east of Trinidad, Tobago and the Lesser Antilles. Isolated to scattered showers and locally heavy showers/thunderstorms forecast to begin after midnight tonight, trough Friday lingering through the first half of Saturday. Gusty winds, street flooding, landslides/mudslides, and downed trees all possible through Saturday. Note that much of the heavier showers and thunderstorms are forecast to remain north of Trinidad. Credit: Weathernerds.org

The axis of this wave extends its axis from 14N52W to 06N57W moving west at 10 knots. Scattered showers and thunderstorms are within several hundred kilometers of the axis of this wave as of the 8:00 PM Tropical Update.

This wave is embedded within the ITCZ. It is forecast to bring a surge of moisture across Trinidad, Tobago and the Windwards overnight tonight, through Friday into Saturday, dragging the ITCZ over T&T. Gusty winds are forecast to follow this wave, with moderate seas of waves between 2.0 and 2.5 meters in open waters beginning late Saturday through Tuesday.

On Friday morning through the first half of Saturday, Trinidad and Tobago will see an increase in cloudiness, showers, and thunderstorms. Much of the heaviest activity is forecast to occur on Friday, with moderate to rough seas, street flooding, gusty winds, and landslides. Note that this wave will be similar to Tropical Wave 17, as much of the heaviest showers and thunderstorms move north of T&T.

What To Expect With Tropical Wave 19

 Showers and thunderstorms further east, associated with Tropical Wave 19.
Showers and thunderstorms further east, associated with Tropical Wave 19.

Note: Street/Flash flooding, frequent lightning, gusty winds, landslides/mudslides are all possible beginning Friday through Saturday. In addition, locally heavy showers and thunderstorms may produce isolated areas, up to 60 millimeters of rainfall, across the Windward Islands.

Possible Impacts to Trinidad and Tobago

Locally Heavy Rainfall & Flooding: Based on the 12Z and 18Z model runs on Thursday, from Friday (2:00 AM) through Sunday (2:00 AM), generally, over the 48 hour period, models are in agreement of fewer than 20 millimeters across Western halves of Trinidad and Tobago and between 20-40 millimeters across the Eastern halves of both islands. Isolated rainfall totals up to 50 millimeters are possible across Eastern coastal Trinidad and Tobago.

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.

Frequent Lightning: In addition, with thunderstorms, frequent lightning is likely.

Gusty Winds: Gusty winds, generally up to 50 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 50 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.

High Wind Event Precautions
High Wind Event Precautions

Landslides: In landslide-prone areas, particularly in areas that receive heavy rainfall, landslides and/or mudflows may occur. These landslides, in addition to gusty winds, may down trees, utility poles and impede traffic on roadways.

Tropical Wave 21

The axis of Tropical Wave 21 wave extends along 33W, south of 14N and is moving westward at 10 knots as of the 8:00 PM Tropical Update. A 1010 millibar low pressure is embedded on the wave axis near 08N33W. Scattered moderate to isolated strong convection is from 08N-11N between 32W-36W. Scattered showers are elsewhere within 180 nautical miles of the wave axis.

This area of low pressure is being monitored for tropical cyclone development, with low chances of 10% at this time for tropical cyclone formation. Regardless of development, heavy rainfall and gusty winds are possible Monday into Tuesday of the upcoming week.

Tropical Storm Barry Becoming More Organized in the Gulf of Mexico, May Become the First Hurricane of the 2019 Hurricane Season.

Forecast Cone for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.
Forecast Cone for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.
Key Messages for Tropical Storm Barry from the National Hurricane Center as of 5:00 PM AST.
Key Messages for Tropical Storm Barry from the National Hurricane Center as of 5:00 PM AST.

At 7:00 PM CDT (0000 UTC), the center of Tropical Storm Barry was located near latitude 27.8 North, longitude 89.3 West. Barry has moved little over the past few hours, but a motion toward the west near 3 MPH (5 KMH) is expected to resume later tonight.

A turn toward the northwest is expected on Friday, followed by a turn toward the north on Saturday. On the forecast track, the center of Barry will be near or over the central or southeastern coast of Louisiana Friday night or Saturday and then move inland into the lower Mississippi Valley on Sunday.

Maximum sustained winds have increased to near 45 MPH (75 KMH) with higher gusts. Strengthening is expected during the next day or two, and Barry could become a hurricane late Friday or early Saturday when the center is near the Louisiana coast. Weakening is expected after Barry moves inland.

Tropical-storm-force winds extend outward up to 140 miles (220 KM) from the center. The minimum central pressure estimated by data from NOAA and Air Force reconnaissance aircraft is 1001 millibars (29.56 inches).

 Watches and Warnings for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.
Watches and Warnings for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.

Several tropical storm, hurricane, storm surge, and flood watches and warnings are posted from as far as Western Louisiana to the Mississippi coast.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. A warning is typically issued 36 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. Preparations to protect life and property should be rushed to completion.

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

A Storm Surge Warning means there is a danger of life-threatening inundation from rising water moving inland from the coastline during the next 36 hours in the indicated locations. For a depiction of areas at risk please see the National Weather Service Storm Surge Watch/Warning Graphic available at hurricanes.gov. This is a life-threatening situation. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other dangerous conditions. Promptly follow evacuation and other instructions from local officials.

A Storm Surge Watch means there is a possibility of life-threatening inundation from rising water moving inland from the coastline in the indicated locations during the next 48 hours.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds conditions that make outside preparations difficult or dangerous.

A Tropical Storm Watch means that tropical storm conditions are possible within the watch area generally within 48 hours.

Interests elsewhere along the Gulf Coast from the Upper Texas Coast to the Florida Panhandle should monitor the progress of this system.

For storm information specific to your area, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office.

Rainfall accumulation forecast for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.
Rainfall accumulation forecast for Tropical Storm Barry from the National Hurricane Center as of 8:00 PM AST.

Barry poses a significant heavy rainfall threat, with already waterlogged areas under threat from the heaviest rainfall accumulations. Parts of eastern Lousiana may see totals upwards of 15-20 inches (400-500 millimeters) of rainfall.

In addition, this cyclone is forecast to near hurricane strength as it nears landfall across the Louisiana coast. Intensity forecasts presently call for a Category 1 hurricane at landfall. However, as indicated above, this cyclone is mostly a heavy rainfall threat above all else.

Earliest reasonable arrival time of tropical storm force winds for Tropical Storm Barry from the National Hurricane Center as of 5:00 PM AST.
Earliest reasonable arrival time of tropical storm force winds for Tropical Storm Barry from the National Hurricane Center as of 5:00 PM AST.

For more details on the system, the latest information can be found at the National Hurricane Center and subsequent tropical updates.

This system is NO threat to Trinidad, Tobago, and the Eastern Caribbean.

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!

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