Tropical Update Overview:
— Tropical Wave 41 – An active tropical wave interacting with the ITCZ has produced an area of low pressure now being monitored for development in the Central Atlantic. Based on present model guidance, much of the active weather associated with this system will move north of T&T on Sunday through Monday.
— Tropical Wave 42 – This tropical wave in the far Eastern Atlantic is also being monitored for development. However, the northern axis of the wave is moving faster than the southern axis, which will linger near the Cabo Verde Islands over the next few days. No impacts anticipated for T&T based on present model guidance.
— Tropical Wave 43 – A tropical wave that is still over Western Africa has been picked up by the top models for tropical development, showing tropical development likely later next week, and potentially a threat to the Lesser Antilles by late next week. It is far too soon to tell what impacts, if any this may bring to T&T.
— Impacts to T&T – Through Sunday, a dry mid- and upper-level atmosphere will limit deep convective activity. However, following the passage of Tropical Wave 41 and its possible low-level circulation, a southerly flow may bring moisture and instability across T&T and the Windwards. This may fuel isolated areas of heavy rainfall late Sunday through Tuesday. Showers and thunderstorms may reduce visibility and produce gusty winds up to and in excess of 55 KM/H. Street or flash flooding will be possible in slow-moving showers and thunderstorms. In thunderstorm activity, frequent lightning is also possible. Gusty winds may cause power dips/outages, downed trees, and localized wind damage.
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
As of the 8:00 PM Tropical Update, the 41st tropical wave for the 2020 Atlantic Hurricane Season is located from 18N, along 45W based on our analysis. The wave axis is moving westward around 15 knots (27 KM/H) with scattered moderate convection mainly along the ITCZ and surrounding the low-pressure center near 12N.
The axis of this tropical wave has moved ahead of the low-pressure center, with the wave forecast to move across the Lesser Antilles late Saturday through Sunday, mainly affecting the northern Windward and the Leeward Islands. The low-pressure center is forecast to follow late Sunday into Monday, generally moving across the Leewards.
As of the 12Z and 18Z runs of the top-performing models for tropical development, none of the operational models bring this system as a tropical storm across the region. The EMCWF (EPS) Ensemble models show less than 45 % of the members bringing winds of tropical depression (25 knots) strength and none showing tropical-storm strength. The GFS (GEFS) ensembles show a more organized tropical system moving across the northernmost Leewards on Monday, potentially at tropical storm strength.
Regardless of formation, the strongest winds and heaviest rainfall is forecast to remain well north of Trinidad and Tobago on Sunday through Monday. The system is forecast to bring southerly winds to move across T&T late Sunday through Tuesday, advecting moisture and instability across the islands. This may fuel isolated showers and thunderstorms, as low to mid-level conditions may be favorable, but surface convergence appears to be unfavorable.
According to the National Hurricane Center’s tropical weather outlook at 8:00 PM, “ Showers and thunderstorms associated with a tropical wave over the central tropical Atlantic have gradually become a little better organized during the day. Additional development of this system is possible during the next several days while it moves westward at about 15 mph.“
Chances of tropical cyclone development remain low over the next 48 hours and 5 days at 20% and 30% respectively, as this system moves across the region.
Tropical Wave 42
As of the 8:00 PM Tropical Update, the 42nd tropical wave for the 2020 Atlantic Hurricane Season is located from 23N southward and elongated along 18W to 30W, based on our analysis. It is moving west at 15 to 20 knots and is approaching the Cabo Verde Islands. To the north and west, an associated northern vorticity trough is analyzed from 25N27W to 14N25W. Scattered moderate and isolated strong convection is noted from 08N-18N between 15W-25W. Although conditions are not favorable for development over the next couple of days, they are forecast to become more conducive over the weekend and into early next week as this wave moves into the central and later western tropical Atlantic.
Models show moisture associated with this wave moving across the region mid-week next week, with any active weather remaining north of T&T and the Windward Islands.
As of the 12Z and 18Z runs of the top-performing models for tropical development, none of the operational models bring this system as a tropical storm strength at this time. The EMCWF (EPS) Ensemble models show up to 70 % of the members bringing winds of tropical depression (25 knots) strength and none showing tropical-storm strength. The GFS (GEFS) ensembles show nearly half the members bringing an organized tropical cyclone into the Central Atlantic. This system is forecast to remain well out to sea, away from the Lesser Antilles and T&T.
According to the National Hurricane Center’s tropical weather outlook at 8:00 PM, “A tropical wave located over the eastern Atlantic Ocean just west of the Cabo Verde Islands is producing disorganized shower and thunderstorm activity. The northern part of this wave, which is expected to move rapidly westward over the central Atlantic during the next few days, is forecast to remain too far to the north and in an unfavorable environment for development to occur. However, the southern part of the wave is expected to be nearly stationary south of the Cabo Verde Islands for the next several days, and some development of this system is possible early next week when it begins to move slowly westward over the eastern and central tropical Atlantic.”
Chances of tropical cyclone development remain low over the next 48 hours and 5 days at near 0% and 30% respectively, as this system moves across the region.
Tropical Wave 43
As of the 8:00 PM Tropical Update, the 43rd tropical wave for the 2020 Atlantic Hurricane Season analyzed from 20N southward, along 5W. The wave axis is moving westward around 15 knots (28 KM/H).
As of the 12Z and 18Z runs of the top-performing models for tropical development, both the GFS and EMCWF show support for development later next week near the Lesser Antilles. The EMCWF (EPS) Ensemble models show up to 75 % of the members bringing winds of tropical depression (25 knots) strength and less and 10% showing tropical-storm strength. The GFS (GEFS) ensembles show nearly half the members bringing an organized tropical cyclone into the Central Atlantic.
This tropical wave is over 10 days away from the Lesser Antilles, but top-performing long-range models are already showing the potential for an organized tropical cyclone nearing the Lesser Antilles, particularly the Leeward Islands.
As of the National Hurricane Center’s tropical weather outlook at 8:00 PM, this tropical wave is not tagged officially for tropical cyclone formation. It is still too early to tell what impacts if any this may bring to T&T but given that we’re heading into the peak of the hurricane season, each tropical wave should be closely monitored.
Tropical Cyclone Climatology
Tropical Cyclone Points of Origin during the last week of August into the first week of September.