Tropical Update: Dorian A Strong Category 4 Hurricane, Monitoring Two Areas for Tropical Development

Tropical Update Overview:
Tropical Wave 41: This tropical wave is located in the Central Atlantic, forecast to move across the Lesser Antilles on overnight into Sunday. No significant change in the weather forecast, beyond localized showers and afternoon downpours. This increase in moisture may bring localized and brief street flooding.
Tropical Wave 42 – This tropical wave is moving into the Central Atlantic. This wave is forecast to move across the Lesser Antilles by Tuesday. An increase in low-level moisture, combined with the ITCZ across the area is forecast to bring increased showers and thunderstorms to Trinidad and Tobago, particularly on Tuesday. Street/flash flooding, gusty winds during heavy showers and thunderstorms are possible, which may trigger downed trees, utility poles and lines, as well as possible wind damage.
Hurricane Dorian: Hurricane Dorian continues to strengthen as it moves across the Southwestern Atlantic. Based on the latest advisory from the National Hurricane Center, Dorian is forecast to remain a high-end Category 4 Hurricane as it moves across the Northwestern Bahamas, skirting along the Eastern Florida Coast and moving along the Southeastern United States coast as a powerful hurricane.
Tropical Wave 43 – This tropical wave, just moving off the coast of Africa, is being monitored for tropical development as it moves west to west-northwestward. Presently, it has a medium chance of tropical cyclone formation as it moves into the Atlantic. This system, based on present modelling, poses no direct threat to the Lesser Antilles.
Gulf of Mexico Trough – This area of low-pressure is being monitored for tropical development as it moves westward across the Gulf of Mexico. Presently, it has a low chance of tropical cyclone formation over the next 5 days.
— No direct tropical threats forecast for Trinidad and Tobago over the next five days.

Before we dive into the Tropical Update, a few notes:

  • Tropical waves are a normal part of the rainy season.
  • Not every tropical wave will form into a tropical cyclone.
  • Weaker tropical waves produce 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 41

A weak tropical wave located at 56W, east of Trinidad and Tobago. Most of the showers and thunderstorms associated with this wave are along the north of the wave axis, well north of the Lesser Antilles. Credit: Weathernerds.org
A weak tropical wave located at 56W, east of Trinidad and Tobago. Most of the showers and thunderstorms associated with this wave are along the north of the wave axis, well north of the Lesser Antilles. Credit: Weathernerds.org

Tropical Wave 41 is located in the Central Atlantic Ocean, at 56W, along 24N southward, moving west at approximately 10 knots. Scattered moderate to strong showers are from 20N to 22N between 54W and 57W. Isolated moderate to locally strong showers are elsewhere from 20N to 30N between 50W and 60W.

Though there is a mild 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 into Sunday.

However, this tropical wave is forecast to weaken the high pressure dominating the region, slackening winds across the islands. Daytime heating and sea breeze convergence with this elevated moisture may cause some heavy afternoon downpours, which may trigger street flooding and be accompanied by gusty winds. This activity will be highly isolated, particularly on Sunday.

Tropical Wave 42

A tropical wave is located in the Central Atlantic along 35/36W. This wave is forecast to move across the Lesser Antilles next Tuesday, bringing showers and thunderstorms to Trinidad and Tobago. Credit: Weathernerds.org
A tropical wave is located in the Central Atlantic along 35/36W. This wave is forecast to move across the Lesser Antilles next Tuesday, bringing showers and thunderstorms to Trinidad and Tobago. Credit: Weathernerds.org

A Tropical Wave is located in the Central Atlantic, located at 35/36W, along 19N southward, moving westward at 20 knots. This wave is forecast to move across the Lesser Antilles beginning late Monday through Tuesday, also bringing the ITCZ across the region on Wednesday.

Based on the latest modeling, showers and thunderstorms are likely across Trinidad and Tobago on Tuesday. No widespread or significant rainfall is expected, however, 10-20 millimeters of rainfall is forecast, with isolated downpours producing up to 50 millimeters in localized areas.

As with all heavy showers and thunderstorms across Trinidad and Tobago, there is the threat of gusty winds, street/flash flooding and the lower chance of landslides. Wind damage, including downed trees, utility poles, and power lines are also possible, particularly on Tuesday.

Hurricane Dorian

Hurricane Dorian is forecast to continue strengthening as it moves across the Southwestern Atlantic. It is forecast to maintain its strength as a high-end Category Four Hurricane as it moves across the Northwestern Bahamas, nearing Eastern Florida. Credit: Tropical Tidbits
Hurricane Dorian is forecast to continue strengthening as it moves across the Southwestern Atlantic. It is forecast to maintain its strength as a high-end Category Four Hurricane as it moves across the Northwestern Bahamas, nearing Eastern Florida. Credit: Tropical Tidbits

At 2:00 PM, the distinct eye of Hurricane Dorian was located near latitude 26.1 North, longitude 73.9 West. Dorian is moving toward the west near 13 KM/H, and a slower westward motion should continue into early next week.

On this track, the core of Dorian should move over the Atlantic well north of the southeastern and central Bahamas today, be near or over the northwestern Bahamas on Sunday, and move near the Florida east coast late Monday through Tuesday.

Data from an Air Force reconnaissance plane indicate that the maximum sustained winds are near 240 KM/H with higher gusts to 305 KM/H. Dorian is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in intensity are likely, but Dorian is expected to remain a powerful hurricane during the next few days.

Hurricane-force winds extend outward up to 45 kilometers from the center and tropical-storm-force winds extend outward up to 185 kilometers. The minimum central pressure reported by a reconnaissance plane was 945 millibars.

For the latest, see the updated advisories from the National Hurricane Center.

Tropical Wave 43

 Tropical Wave 43 is located in the Far Eastern Atlantic at 21/22W. This wave is being monitored for tropical cyclone formation over the next 5 days as it moves into the Central Atlantic. Credit: Weathernerds.org
Tropical Wave 43 is located in the Far Eastern Atlantic at 21/22W. This wave is being monitored for tropical cyclone formation over the next 5 days as it moves into the Central Atlantic. Credit: Weathernerds.org

A Tropical Wave is located in the far Eastern Atlantic, located at 21/22W, along 20N southward, moving westward at 10-15 knots. Isolated moderate to locally strong showers are from 11N to 22N from the Cabo Verde Islands eastward.

Based on the latest tropical outlook from the National Hurricane Center, this tropical wave has a low, 20%, chance of tropical cyclone formation over the next 48 hours and a medium, 60% chance of tropical cyclone formation over the next 5 days.

Of the top three models for tropical cyclone development, the EMCWF and GFS are the most enthusiastic for development, showing this system attaining a weak tropical storm strength over the next 48-72 hours, and possibly making a run at hurricane strength over the next 5 days. The UKMET model does not develop this tropical wave, at this time.

Environmental conditions are forecast to be conducive for development of this disturbance during the next few days and a tropical depression could form next week while the system moves across the eastern tropical Atlantic Ocean. Heavy rainfall is possible over portions of the southern Cabo Verde Islands during the next couple of days, and interests on those islands should monitor the progress of this system.

This system is forecast to move west-northwest to the northwest into the Central Atlantic Ocean, staying well away from any landmasses, once it clears the Cabo Verde islands. Depending on the strength of this system in the Central Atlantic Ocean, some long period swells may be generated and propagated to the Caribbean Islands.

Gulf of Mexico Trough

 A broad area of low pressure located over the southeastern Gulf of Mexico is producing limited shower and thunderstorm activity. Some gradual development of this system is possible during the next few days while it moves slowly westward across the southern and southwestern Gulf of Mexico. Credit: National Hurricane Center
A broad area of low pressure located over the southeastern Gulf of Mexico is producing limited shower and thunderstorm activity. Some gradual development of this system is possible during the next few days while it moves slowly westward across the southern and southwestern Gulf of Mexico. Credit: National Hurricane Center

A surface trough is along 27N85W, to a 1010 millibar Yucatan Channel low-pressure center, southeastward into the NW corner of the Caribbean Sea, to 19N84W and 16N83W. Widely scattered moderate to isolated strong showers are in the Gulf of Mexico from 90W eastward.

Based on the latest tropical outlook from the National Hurricane Center, this surface trough has a low, 20%, chance of tropical cyclone formation over the next 48 hours and a low, 30% chance of tropical cyclone formation over the next 5 days.

Of the top three models for tropical cyclone development, the EMCWF and GFS are the most enthusiastic for development. However, the GFS brings this system to a weak tropical storm strength as it nears the Western Mexican Coast, while the EMCWF keeps this system as a Tropical Depression. The UKMET does not develop this system, based on runs on Saturday afternoon

Regardless, this system may bring some locally heavy rainfall to parts of Western Mexico by late next week.

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 have become slightly more favorable for tropical cyclone development though dominating dry, Saharan air remains across the Atlantic.

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