Monitoring Tropical Wave 55 For Development

Tropical Wave 55 Key Messages:
– Tropical Wave 55 has low chances of development over the next 5 days as it moves across the Atlantic Ocean at low latitude.
– Impacts: It is too soon to tell, though it is likely the worst of this system remains north and east of our area (T&T).
– Track: Also, too soon to tell but forecast models suggest a sharp northwestward turn on its approach to the Lesser Antilles.

Tropical Wave 55: Low Chances for Tropical Cyclone Formation

Tropical Weather Outlook as of 8:00 PM Thursday 8th October 2020
Tropical Weather Outlook as of 8:00 PM Thursday 8th October 2020

Over the last 24 hours, we’ve been monitoring a tropical wave in the far Eastern Atlantic, producing tropical-storm-force wind gusts.

The National Hurricane Center, in their 2 PM AST Tropical Weather Outlook, tagged Tropical Wave 55 for tropical cyclone development. However, there is very little model support for tropical cyclone formation at this time.

From the National Hurricane Center’s Tropical Weather Outlook, as of 2:00 AM EST, “A tropical wave located several hundred miles southwest of the Cabo Verde Islands continues to produce disorganized showers and a few thunderstorms. The wave is expected to move generally westward or west-northwestward at about 15 mph. Environmental conditions could be conducive for some gradual development of the system this weekend or early next week while it is located over the tropical Atlantic, well east of the Lesser Antilles. Upper-level winds are forecast to become unfavorable for further development by the middle of next week.”

As of the 2:00 AM EST Tropical Weather Outlook, this system has a low chance, near 0%, of tropical cyclone formation over the next 48 hours and a low chance, 20%, of tropical cyclone formation over the next 5 days.

What We Know

Tropical Wave 55 in the far Eastern Atlantic, producing an area of scattered showers and thunderstorms. (Weathernerds)
Tropical Wave 55 in the far Eastern Atlantic, producing an area of scattered showers and thunderstorms. (Weathernerds)

A tropical wave is along 31W from 15N southward moving west at (15 knots) 27 KM/H, producing scattered showers and thunderstorms. The approximate center of the broad cyclonic turning of this disturbance at 31W, 9N, making it over 3,200 kilometers east-southeast of Trinidad and Tobago.

As of Thursday night, there is no well defined circulation of the system and it is still embedded within the African Monsoon Trough, producing a natural area of vorticity (spin) for this disturbance to take advantage of.

Tropical Wave 55 is located in an area of very favorable upper-level divergence, low-level convergence and abundant moisture, with mostly favorable wind shear ahead of it in the short term.

By next week, wind shear is forecast to increase across the Atlantic and the Lesser Antilles, becoming very strong, up to 60 knots at times. This will limit development and limit thunderstorm and shower formation.

It is still too soon to tell what impacts, if any, this could bring to the Lesser Antilles as models still diverge on whether this wave moves to the northeast, bypassing the region entirely or moving across the Windward Islands.

What We Forecast

Tropical Wave 55: Track

It is too soon to tell. However, the eventual system (whether its a tropical wave, disturbance, or cyclone) may make a sharp northwestward turn before reaching the Lesser Antilles.

Forecast tracks from the EMCWF (EPS/EMCF) ensembles for Tropical Wave 55 as of 12Z Thursday 8th October 2020 (Alan Brammer)
Forecast tracks from the EMCWF (EPS/EMCF) ensembles for Tropical Wave 55 as of 12Z Thursday 8th October 2020 (Alan Brammer)

This tropical wave will move on the periphery of a deep-layered high-pressure system anchored over the subtropics. This high pressure system will gradually weaken into next week, with a trough north of the Lesser Antilles by mid-week. This trough will coincide with the system when it is just east of the Lesser Antilles, allowing the steering flow to move the system poleward (northward).

When looking at the ensemble models, most of these outputs show that the system generally moves to the west-northwest, before taking a sharper turn northwest to the north just east of the Lesser Antilles.

Tropical Wave 55: Intensity

It is too soon to tell. No global models develop this, and their ensembles keep this as a strong tropical wave before upper level winds cause it to weaken later next week.

Dynamical model guidance on systems that have not yet formed has a difficult time showing the eventual track or intensity of undeveloped systems.

In fact, none of the operational models from top global models (EMCWF, GFS, UKMET) shows this system development later next week. Very few ensemble runs of these models bring this system to tropical depression status. It also should be noted that this is a year where models have not performed well in detecting tropical cyclone genesis.

Thankfully, this system is well over 3,200 kilometers away as of Thursday night so there is sufficient time to wait and watch.

The latest model runs of the EMCWF and GFS showing peak wind gusts over the next 10 days east of the Lesser Antilles. (Windy)
The latest model runs of the EMCWF and GFS showing peak wind gusts over the next 10 days east of the Lesser Antilles. (Windy)

Though no operational models develop Tropical Wave 55, they continue to show an area of gusty winds generally staying north and east of the Lesser Antilles.

Less than 30% of the EMCWF ensembles (EPS) bring this system to tropical depression strength over the next 5 days, with none bringing it to tropical storm strength as of Thursday evening model runs.

But this model shows…

Individual model runs are just one possible outcome from a myriad of outcomes. Weather does not always follow what is modeled, and even what may be forecast. Beware of individual model runs being posted on social media.

Always check the National Hurricane Center for the latest information for tropical cyclones and your local meteorological offices for country-specific advisories.

What should I do?

Don’t panic. This system is several days and thousands of kilometers to our east-southeast so we quite a bit of time to wait and watch.

If you are a risk-averse person, now is a good time to check your inclement weather, flood, or hurricane season plan, ensuring your preparedness supplies are not expired, stocked, and in a safe location.

The Office of Disaster Preparedness and Management has put together a comprehensive guide for preparing for the Wet and Hurricane Season.

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