Tropical Update: The Atlantic Is Awakening. No Direct Threats to T&T At This Time.

Tropical Update Overview:
Tropical Wave 39: This tropical wave is located in the Central Atlantic with isolated light showers occurring near the wave axis. This wave is forecast to move across T&T on Saturday. A surge of trade winds and Saharan Dust is forecast to follow the passage of this wave, leading to a dry, dusty and windy Sunday into next week across T&T. No significant weather forecast, beyond localized afternoon showers and downpours.
Central Atlantic Low Pressure – A curious area of low-pressure with a concentrated area of persisting moderate to strong convection in the Central Atlantic. There is some model support for development, particularly as Tropical Wave 40 nears the low-pressure center, though it not highlighted by the National Hurricane Center in their 8 PM Tropical Weather Outlook. Regardless of development, much of the activity associated with this low pressure is forecast to move north and east (at this time) of T&T and the Lesser Antilles by Monday into Tuesday this upcoming week.
Tropical Wave 40: This robust tropical wave is located in the far Eastern Atlantic. As this wave progresses westward, it is forecast to aid in the development of the above-mentioned low-pressure center. This wave is forecast to move across the Lesser Antilles at the end of this upcoming week, with much of the active weather affecting the Leewards, well north of T&T.
— No direct tropical threats forecast for Trinidad and Tobago over the next five days.

Tropical Depression Chantal: After spending just under a day as a minimal tropical storm, Chantal weakened into a tropical depression on Thursday as it meanders in the North Atlantic at minimal strength. No impacts expected to any landmasses. This system is forecast to dissipate over the next 24-36 hours.
Invest 98L: A broad area of low pressure just east of Florida, across the Bahamas, has numerous showers and thunderstorms ongoing, with a broad circulation. This area of low pressure has model support from the top three models for tropical cyclone development. It is forecast to remain just off the Eastern Coast of the United States. However, with King Tides occurring next week, coastal flooding is likely across the region. No threat to T&T & 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 39

Satellite Update from earlier today, showing Tropical Wave 39 at the leading edge of a Saharan Dust and trade wind surge.
Satellite Update from earlier today, showing Tropical Wave 39 at the leading edge of a Saharan Dust and trade wind surge.

Tropical Wave 39 is located in the Central Atlantic Ocean, from 47W to 45W, along 20N to 6N, moving west at approximately 20 knots. This wave is embedded in dry, Saharan air, which is limiting convection near the wave axis. Light showers are ongoing near the axis of the wave, with a surge of Saharan Dust and trade winds following the axis.

Though there is a surge of moisture associated with the wave axis, this wave is not forecast to produce any significant rainfall as it moves across Trinidad, Tobago and the Lesser Antilles on Saturday. However, daytime heating and sea breeze convergence with this elevated moisture may trigger some heavy afternoon downpours, which may trigger street flooding and be accompanied by gusty winds. This activity will be highly isolated. Similar activity may occur on Sunday, but conditions will increasingly become hazy and breezy throughout Sunday.

Central Atlantic Low Pressure System

A 1011 millibar low-pressure area in the Central Atlantic, embedded within the ITCZ, producing a small, concentrated area of showers and thunderstorms. This area of low pressure is forecast to near the Leewards Monday into Tuesday. Credit: Weathernerds.org
A 1011 millibar low-pressure area in the Central Atlantic, embedded within the ITCZ, producing a small, concentrated area of showers and strong convection. This area of low pressure is forecast to near the Leewards Monday into Tuesday. Credit: Weathernerds.org

This area of low-pressure has been producing a concentrated area of showers and strong convection in the Central Atlantic over the last 12 hours. As of 8:00 PM, it is located at approximately 10.1N, 37.0W.

To the north of this low-pressure, dry, dusty air due to a surge in Saharan Dust is present. However, deep, tropical moisture exists across the narrow ITCZ, in which this low-pressure is embedded. Upper-level and low-level dynamics are favorable for convection to flourish, and wind shear is on the decrease.

GEFS (GFS Ensemble Runs) as of Thursday evening for the Central Atlantic Low Pressure System. Credit: Alan Brammer
GEFS (GFS Ensemble Runs) as of Thursday evening for the Central Atlantic Low-Pressure System. Credit: Alan Brammer

Over the next several days, we’ll be monitoring this area of low-pressure closely as there is some model support from the operational GFS and its ensemble runs Thursday evening. However, less than 10% of the EMCWF ensembles show some support for development and the operational runs of the EMCWF and UKMET do not support the development of this system.

If you see model runs showing a strong tropical storm or even a hurricane over the next several days, or probabilities of formation that does not originate from the National Hurricane Center, this is likely not official information. Follow the information provided by your local meteorological offices, the National Hurricane Center, and other authoritative sources.

Regardless of development, this system is forecast to track just north and east of the Leewards at this time, but it may affect the Leewards – no impacts forecast for Trinidad and Tobago.

Tropical Wave 40

Tropical Wave 40, in the far Eastern Atlantic, is forecast to move across the Lesser Antilles at the end of the upcoming week. This wave, though it doesn't have model support for development, will likely pave the way for more favorable conditions as further tropical waves move off the African Coast. Credit: Weathernerds.org
Tropical Wave 40, in the far Eastern Atlantic, is forecast to move across the Lesser Antilles at the end of the upcoming week. This wave, though it doesn’t have model support for development, will likely pave the way for more favorable conditions as further tropical waves move off the African Coast. Credit: Weathernerds.org

Tropical Wave 40 is located between 17W and 20W, along 20N to 4N in the far eastern Atlantic. Presently, a large area of convection is ongoing mainly east of the wave axis. It is located in a high-moisture environment but strong wind shear.

There is no model support for this system as it moves across the Atlantic. However, as we near the peak of the 2019 Atlantic Hurricane Season, we need to keep a close eye on these waves as they track across the region.

Presently, this wave is being enhanced by a larger scale atmospheric feature called a Convectively-Coupled Kelvin Wave, enhancing convection of the wave.

Although no development is forecast, this large moist area is forecast to moisten the Atlantic as the wave axis progresses westward, paving the way for a more favorable set up as additional Tropical Waves move off the African Coast.

The axis of this wave is forecast to move across the Lesser Antilles at the end of the upcoming week, but much of “active” weather associated with this wave is forecast to affect the Leewards, well north of Trinidad and Tobago. No significant impacts expected from this wave across T&T.

Tropical Depression Chantal

Tropical Depression Chantal continues to weaken in the North Atlantic, with dissipation forecast over the next 24-36 hours. Credit: Weathernerds.org
Tropical Depression Chantal continues to weaken in the North Atlantic, with dissipation forecast over the next 24-36 hours. Credit: Weathernerds.org

At 500 PM AST (2100 UTC), the center of Tropical Depression Chantal was located near latitude 38.1 North, longitude 42.4 West. The depression is moving toward the east-southeast near 22 KM/H, and it is forecast to slow down and make a clockwise loop through the weekend.

Maximum sustained winds are near 55 KM/H with higher gusts. Weakening is expected, and Chantal is forecast to degenerate into a remnant low Friday or Friday night.

The estimated minimum central pressure is 1010 millibars.

Invest 98L

Scattered moderate to strong convection associated with Invest 98L continues across the Bahamas, east of Florida. Credit: Weathernerds.org
Scattered moderate to strong convection associated with Invest 98L continues across the Bahamas, east of Florida. Credit: Weathernerds.org

Satellite and surface observations show that a broad area of low pressure has formed just northwest of Andros Island in the central Bahamas.

This system continues to produce a large area of disorganized showers and thunderstorms that extend eastward over the western Atlantic for a few hundred miles. Environmental conditions are forecast to be conducive for additional development during the next several days, and a tropical depression could form over the weekend or early next week while the system moves near the coast of east-central Florida and then offshore of the southeast United States coast.

Regardless of development, locally heavy rains are possible over portions of the central and northwest Bahamas, and the east-central and southeast Florida peninsula during the next few days.

As of the 8:00 PM Tropical Weather Outlook from the National Hurricane Center, Invest 98L has a low, 30%, chance of tropical cyclone formation over the next 48 hours and a medium, 50%, chance over the next 5 days.

Tropical Cyclone Climatology

Tropical Cyclone Points of Origin during the month of August. 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 August, 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!

Overall, conditions are not favorable for tropical cyclone development at this time due to dominating dry, Saharan air across the Atlantic. However, by the end of August into September, conditions may become more favorable for tropical cyclone development across the Atlantic Basin.

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